Category 6™

Guillermo Gathers Steam in NE Pacific; Invest 94L Clings to Life

By: Bob Henson , 5:54 PM GMT on July 31, 2015

Hurricane Guillermo is stepping up its game in the Northeast Pacific, as it moves along a steady west-northwest course that could bring it near the Hawaiian Islands next week. Guillermo was upgraded to hurricane status by the National Hurricane Center at 5:00 am EDT Friday, and in the NHC’s 11:00 am EDT advisory, Guillermo was located at 12.4°N, 132.7°W, with top sustained winds at 90 mph. Visible and infrared satellite imagery shows a healthy tropical cyclone, with extensive upper-level outflow, a distinct convective core, and a small eye beginning to take shape. Guillermo is successfully fending off an expanse of dry air to its north and maintaining an envelope of rich moisture.


Figure 1. A GOES West infrared satellite image of Hurricane Guillermo from 1630 GMT (12:30 pm EDT) on Friday, July 31. Image credit: NOAA/NESDIS.

Guillermo is in a quite favorable environment to intensify further, with warm sea-surface temperatures and low wind shear. SSTs are around 28-29°C (82-84°F) along Guillermo’s path for the next day or so, which is 1-2°C above the climatological norm (see Figure 2). The oceanic heat content--the amount of energy in the uppermost part of the ocean--is rather low ahead of Guillermo, which could spell trouble for a slow-moving system churning up cooler water from below (see Figure 3). However, Guillermo is moving briskly (about 17 mph), and that pace is expected to continue for the next couple of days.


Figure 2. Departures from average sea-surface temperature over the Northeast Pacific for the week ending July 27, 2015. Image credit: NOAA National Hurricane Center.

It is still too soon to know how much of a threat Guillermo will pose to the Hawaiian Islands. The steering flow around Guillermo will be fairly stable over the next several days, keeping it on a track headed almost directly toward the islands. The NHC’s latest outlook places Guillermo located about a day away from the Big Island by early Wednesday morning. The most recent track models are in some disagreement over whether Guillermo will be picked up by a strong band of upper-level westerlies around this point, taking it well northeast of Hawaii; continue on its west-northwest track; or arc further westward, a path that could take it south of the islands. The disagreement is evident within the 1200 GMT Friday runs of the 20-member GFS ensemble (see Figure 3). As for intensity, Guillermo is likely to peak over the weekend, with NHC bringing the hurricane to low-end Category 3 strength (peak sustained winds of 115 mph) by Saturday. The unusually warm waters fostered by El Niño would keep Guillermo traveling over SSTs of at least 27°C (the rough threshold for sustaining a tropical cyclone) all the way to Hawaii. However, wind shear is expected to steadily increase as Giuillermo gains latitude and approaches the belt of upper-level westerlies noted above. Given its current track and intensity, and the increased climatological risk of hurricanes affecting Hawaii during El Niño, we will need to keep a close eye on Guillermo over the next few days. Twice-daily hurricane-hunter flights to monitor Guillermo have been slated beginning on Saturday, with the NOAA Gulfstream IV aircraft tentatively scheduled to sample the large-scale environment around Guillermo on Monday.


Figure 3. Projections for the track of Hurricane Guillermo produced on Friday morning by the 20-member GFS ensemble. The operational run is shown in white. Ensemble runs are produced by running the models at lower resolution than the operational run and varying the initial atmospheric conditions slightly to generate an "ensemble" of twenty potential weather situations, illustrating a range of possible outcomes.


Invest 94L shows little sign of strengthening
Invest 94L is still identifiable, but not very impressive, in the central North Atlantic. The loosely organized system was located around 12.5°N, 32.2°W at 8:00 am EDT Friday, moving west at about 15 mph. The circulation around 94L is highly elongated, with upper-level outflow evident but dry air invading the storm, leaving it with only weak shower and thunderstorm activity. The SHIPS statistical model brings 94L to moderate tropical-storm strength in the next several days, but none of the most reliable dynamical models for tropical cyclone formation indicate any substantial development of 94L, and NHC has lowered its five-day odds of development from 30% to 10%. Even if 94L managed to get a new lease on life in the central Atlantic, it would face largely hostile conditions as it continued west into the very high wind shear present across the Caribbean.


Figure 4. Infrared satellite image of Invest 94L (located at center left). Image credit: NOAA/NESDIS.


Soudelor a potential threat to Japan next week
Tropical Storm Soudelor should begin flexing its muscle over the next couple of days in the Northwest Pacific. Hindered over the last day by a tropical upper tropospheric trough (TUTT) to its north, Soudelor will soon escape the TUTT’s influence and likely launch into several days of significant strengthening. Soudelor’s peak winds were about 40 mph at 8:00 am EDT Friday, but the outlook issued by the Joint Typhoon Warning Center brings Soudelor’s winds to typhoon strength by Saturday and Category 4 strength (140 mph) by Monday. Track and intensity forecasts are increasingly uncertain beyond that point, as wind shear will be on the increase and water temperatures along Soudelor’s path will be cooler. It appears there is a good chance Soudelor will move far enough west to pose a potential threat to Japan later in the week.

Another off-season system pops up in the South Pacific
While our attention is focused on the peak season for tropical development in the Northern Hemisphere, Invest 91SH is defying seasonal expectations. The system was located at 7.8°S and 167.9°E at 8:00 am EDT Friday, moving slowly south-southeast with peak winds of around 23 mph. The 0600 GMT Friday run of the U.S. Navy’s version of the GFDN model brings Invest 91SH to tropical storm strength over the weekend before a weakening trend is projected to set in, well before the system approaches the islands of Vanuatu. A tropical storm in this basin in early August would be very unusual, as the official South Pacific season runs from November to April, but El Niño does tend to increase activity in the South Pacific. If 91SH does develop, it will be named Tuni and classified as the first South Pacific cyclone in the 2015-16 season. Another off-season system, Tropical Cyclone Raquel, formed at the end of June and intensified to Category 1 strength in early July, bringing at least one fatality and extensive damage to agriculture in the Solomon Islands. Raquel is the only tropical cyclone recorded to date in the South Pacific during July.

I’ll have another update by Monday at the latest. Wunderblogger Steve Gregory added a new post on Friday afternoon. We’re also pleased to welcome Dr. Phil Klotzbach (@philklotzbach) as a WU blogger. Phil worked with Dr. Bill Gray for many years on the Colorado State University seasonal hurricane forecasting project, and he is now lead author on those forecasts. In his first Weather Underground post, Phil weighs in on the multiple ways in which El Niño tends to inhibit Atlantic hurricanes.

Have a great weekend!

Bob


Hurricane

What to Expect from El Niño: How Much Snow Back East?

By: Bob Henson , 3:43 PM GMT on July 30, 2015

Some of the impacts from El Niño across the United States are fairly straightforward: hurricane suppression in the Atlantic, for example. Then there’s snowfall in the Northeast, where El Niño is just one of several big factors at work. We touched on the complexities of this topic in Tuesday’s roundup post on typical El Niño impacts during North American winter. (Jeff Masters posted an update earlier today on tropical activity in the Atlantic and Pacific, including an area of interest being tracked in the eastern Atlantic.)

Two main elements to watch in the upcoming winter are:

Temperature. Strong El Niños tend to spread above-average winter readings from the Midwest across the Northeast. With temperatures often borderline along the big East Coast cities during heavy snow, this outcome would push the region toward more rain and less snow, all else being equal. That said, it’s entirely possible for a northeastern winter to average on the milder-than-usual side while still featuring a few periods that are cold enough for big snow. The blockbuster El Niño events of 1982-83 and 1997-98 brought temperatures across the entire Midwest and Northeast well above average, yet the snowstorm of February 10-12, 1983, pummeled big cities along the East Coast with widespread 1-to-2-foot amounts (see Figure 1). The most destructive winter weather event of 1997-98 was actually a multi-day ice storm in early January 1998 that paralyzed Montreal and parts of far northern New York and New England for days (see Figure 2).

The North Atlantic Oscillation. This semicyclic atmospheric pattern describes whether the flow from eastern North America to Europe is a strong, west-to-east channel (a positive NAO) or a more wavy, variable path (a negative NAO). See Figure 3 below. Heavy snow becomes more likely along the eastern seaboard when a negative NAO is present, as the more-variable polar jet stream allows storm systems to dig more sharply along and near the coast before heading poleward as nor’easters. Since the NAO doesn’t have a strong oceanic connection like El Niño does, it varies much more from week to week and month to month.


Figure 1. Snowfall map for the February 10-12, 1983, snow event (the “Megapolitan storm”), which arrived during one of the two strongest El Niño events since 1950. This storm was rated as 6.25 (“crippling”) on the Northeastern Snowfall Impact Scale. Image credit: NOAA National Centers for Environmental information.



Figure 2. A pedestrian walks past fallen branches and trees in Ottawa, Canada, on January 8, 1998. Arriving in the midst of a very strong El Niño event, this ice storm paralyzed much of southeastern Canada and the far northeast United States. Image credit: Dave Chan/AFP/Getty Images.


Figure 3. On average, the surface pressure near Iceland is relatively low (L), while the pressure near the Azores Island is relatively high (H). During a negative phase of the North Atlantic Oscillation (left), this pressure difference weakens. During a positive phase of the NAO (right), the difference becomes even stronger than usual. The variation in pressure patterns influences the strength and location of the jet stream and the path of storms across the North Atlantic. Image credit: climate.gov, adapted from AIRMAP by Ned Gardiner and David Herring, NOAA.


Uncharted territory
The powerful El Niño now taking shape will face off this winter with a recent tendency toward cold and snow across the northeast U.S. During the northern winter of 2015, eastern North America was the only large, populous land mass on Earth that saw temperatures much below average (see Figure 4 below). Over the better part of a decade, winter storms and intense cold have buffeted the northeast U.S. and southeast Canada more often than one might expect in a warming climate. For the NOAA-defined Northeast region, three of the last six winters have seen December-through-February temperatures running below the 20th-century average. Since 2009, Boston has experienced its snowiest winter on record (2014-15) and its eighth snowiest (2010-11), while Washington’s Dulles International Airport has scored its third, fourth, sixth, and ninth biggest one-day snowfalls of the last 53 years.


Figure 4. Eastern North America was the only major region on the globe with temperatures well below average for the period December 2014 – February 2015. Image credit: NOAA National Centers for Environmental Information.


There’s been spirited debate among weather and climate scientists over exactly what’s happening and why. Some researchers, including Jennifer Francis of Rutgers University, have analyzed evidence for a weaker, more variable polar jet stream, possibly associated with Arctic sea ice loss. Others, such as Dennis Hartmann of the University of Washington, emphasize the role of warmth across parts of the tropical Pacific in generating an atmospheric “bridge” that extends to the cold, snowy Northeast. Given that the processes at work aren’t universally agreed on, and we’re still months away from winter, there’s no single diagnosis on what lies in store for the Northeast, but I checked in with several experts to see what they’ll be looking for with the upcoming El Niño. 


According to Francis, we may be wise to expect the unexpected this time around. “In many ways, we are sailing in uncharted waters, because humans have never experienced a strong El Nino in combination with such a warm Arctic and low sea-ice cover,” Francis told me. Another wrinkle: the Pacific Decadal Oscillation, which was in a predominately negative mode from the late 1990s into the early 2010s, has turned strongly positive over the last few months. Positive PDO regimes tend to favor El Niño over La Niña and generally boost global temperatures.

Should the plentiful supply of North Pacific tropical cyclones continue into this fall, said Francis, “it may lead to episodic injections of tropical energy into midlatitudes, which tends to throw large kinks into the jet stream that create highly amplified, persistent ridge/trough patterns like the Ridiculously Resilient Ridge/Terribly Tenacious Trough configuration that has dominated the past two years and caused a variety of extreme weather.” She added: “Recent research suggests that large ridges are intensified by the abnormally warm Arctic, making them even stronger and more persistent. Will this pattern continue into fall/winter 2015? Like I said, we have no chart for the path ahead.”

The Siberian connection
For more than a decade, Judah Cohen (Atmospheric and Environmental Research) and colleagues have been predicting U.S. winter weather based on the state of Siberian snow cover in the autumn. Cohen's hypothesis is that heavier-than-normal autumn snowpack in Siberia can trigger atmospheric waves that disrupt the polar vortex over a period of weeks, leading to a negative NAO tendency by wintertime. The resulting U.S. winter outlooks for Jan-Feb-Mar successfully anticipated the very mild readings of early 2012 and the widespread eastern cold of early 2013 and 2015. (For more background, see this Capital Weather Gang interview with Cohen from last December.)

Cohen pointed to the winters of 2002-03 and 2009-10 as good examples of snowmaking teamwork between moderate El Niño events and a negative NAO, reflected on both sides of the North Atlantic. The snowy winter of 2002-2003 included the “President’s Day II” storm, which plastered East Coast cities from Washington to Boston with 15” to 30” of accumulation, and 2009-10 brought the infamous Snowmageddon as well as several other major winter storms. In both of these cases, Cohen added, the El Niño warming was focused toward the central Pacific, a state known as El Niño Modoki. During the stronger, more classic El Niño of 1997-98, the NAO also tended negative, but mild weather dominated the Northeast, and it wasn’t an especially snowy winter.

“For now, I see little reason to anticipate or favor one NAO phase over the other for this upcoming winter,” Cohen told me. However, he did note that Siberian snow cover tends to run above average during El Niño events. Also, the relative lack of of late-summer/autumn sea ice in recent years over the adjacent Barents and Kara Seas may be allowing extra oceanic moisture to contribute to heavier autumn snows in Siberia, which suggests an enhanced likelihood of negative NAO periods.

Overall, says Cohen, “I have always felt and continue to believe that the relationship between ENSO and winters in the northeastern U.S. is relatively weak and the phase of the NAO is more important. But that may not be true when El Nino is in record-strong territory, especially if the NAO is relatively weak.”


A bridge from the western Pacific to the eastern U.S.
UW’s Dennis Hartmann questions the idea that Arctic sea ice loss is playing the lead role in the recent cold across eastern North America. “This would be remarkable given the small area of the Arctic Ocean and its presence at the tail end of the atmospheric and oceanic chain moving energy from the tropics toward the poles,” wrote Hartmann in Geophysical Research Letters earlier this year. In that paper, Hartmann pointed to another player on the field: the North Pacific Mode. You can think of the NPM as a third sibling in the family that includes the El Niño/Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Each of these explains a portion of the multi-year ups and downs in sea-surface temperature and favored weather patterns across the midlatitude North Pacific, which in turn helps shape weather downstream across the United States. ENSO varies most on timescales of a year or two, while the PDO and NPM are most influential on decade-plus timescales. The NPM is a pattern of warming along the U.S. West Coast and into the North Pacific, with a timescale similar to the Pacific Decadal Oscillation but a different spatial fingerprint. See Figures 5 and 6 for more about the nature of all three siblings.


Figure 5. The three EOFs (empirical orthogonal functions) that represent the bulk of monthly variation in sea-surface temperature (SST) over the ocean area from 30°S to 65°N and 120°E to 105°W. EOF1 is related to the El Niño-Southern Oscillation (ENSO), EOF2 to the Pacific Decadal Oscillation (PDO), and EOF3 to the North Pacific Mode (NPM). The period examined is from January 1900 to July 2014, with positive values in red and negative values in blue. Image credit: American Geophysical Union, with permission, from “Pacific sea surface temperature and the winter of 2014,” Dennis Hartmann, doi:10.1002/2015GL063083.


Figure 6. Time series showing the trends over time in the EOFs depicted in Figure 5 above, expressed here as principal components (PCs) over the Pacific Ocean from 30°N northward. PC1 represents the El Niño-Southern Oscillation (ENSO), PC2 the Pacific Decadal Oscillation (PDO), and PC3 the North Pacific Mode (NPM). The NPM is often strongly positive during the build-up to an El Niño event. The time period shown is from January 1979 to January 2015. Image credit: American Geophysical Union, with permission, from “Pacific sea surface temperature and the winter of 2014,” Dennis Hartmann, doi:10.1002/2015GL063083.


In his 2015 GRL paper, Hartmann linked a positive NPM to to the resilient Western ridge and tenacious Eastern trough of 2013-14. According to Hartmann, the NPM has remained positive throughout 2015 after its big positive jump in 2013 and 2014 (see Figure 6). “It appears the NPM anomalies are controlled by the SST gradient along the equator, especially by the warm conditions west of the dateline and slightly north of the equator,” said Hartmann. Even as the tropical Pacific has gradually shifted into an El Niño configuration over the last year-plus, the patch of unusually warm water identified by Hartmann and colleagues has remained fairly stable. However, said Hartmann, “I expect a large El Niño will dominate and wipe out or reverse the NPM. I don't see a collaboration developing.” Moreover, like Francis and Cohen, Hartmann opted not to offer any prediction on whether the East Coast will see big snow this winter in tandem with the upcoming big El Niño.

Watch for an upcoming post from Jeff Masters that will take a global look at potential El Niño impacts. Meanwhile, I'll have a full update on the tropics by midday Friday.

Bob Henson


El Niño

Little Change to 94L; Hawaii Watching Guillermo; TC 2 Kills 27 in Myanmar/Bangladesh

By: Jeff Masters , 1:10 PM GMT on July 30, 2015

A strong tropical wave that pushed off the coast of Africa on Wednesday (Invest 94L) was located a few hundred miles southwest of the Cape Verde Islands on Thursday morning, and was headed west at 15 mph. 94L does have conditions that favor some slow development over the next few days. Satellite images show that 94L has a decent amount of spin, but only a modest area of heavy thunderstorms that have not increased in organization this morning. Wind shear off the coast of Africa is moderate, 10 - 20 knots, ocean temperatures are a warm 28°C, and the atmosphere is reasonably moist. The 8 am Thursday run of the SHIPS model predicted that wind shear would remain moderate over 94L for the next five days, but ocean temperatures beneath it would cool to 26°C by Sunday, at which time 94L will encounter an increasingly dry and stable airmass courtesy of the Saharan AIr Layer (SAL). The SAL is dominating most of the tropical Atlantic, from the coast of Africa into the Central Caribbean, making 94L's long-term survival questionable. If 94L does manage to make it to the Caribbean, the high wind shear that has dominated the region all summer will likely tear the storm apart. The Thursday morning ensemble runs of the GFS and European models--done by running the models at lower resolution and varying the initial atmospheric conditions slightly to generate an "ensemble" of twenty potential weather situations (fifty for the European model)--do have a number of their 20 - 50 runs that develop 94L into a tropical depression, but none of these solutions have the storm that develops making it as far west as the Lesser Antilles Islands. The operational high-resolution versions of our three top models for predicting genesis of tropical cyclones--the GFS, European, and UKMET models--have one model, the European model, that does show possible development of 94L into a tropical depression by Sunday. In their 8 am Thursday Atlantic Tropical Weather Outlook., NHC gave 94L 2-day and 5-day odds of development of 10% and 30%, respectively.


Figure 1. Latest satellite image of Invest 94L near the Cape Verde Islands.

Hawaii should watch Guillermo
In the Eastern Pacific, Tropical Storm Guillermo has formed, and is something Hawaii should watch. Both the GFS and European models show Guillermo (or its remnants) getting within 500 miles of the islands by Tuesday, though the storm should be weakening at that time due to dry, stable air and cooler ocean temperatures.


Figure 2. Tropical Cyclone Two in the Bay of Bengal as seen at 05 UTC July 30, 2015, from the MODIS instrument on NASA's Terra satellite. JTWC gave top winds of 40 mph to the system, which made landfall over Bangladesh. Image credit: NASA.

Bay of Bengal's Tropical Cyclone Two kills 27
Tropical Cyclone Two made landfall near Chittagong, Bangladesh, on Thursday morning, bringing heavy rains and deadly landslides to portions of Bangladesh and Myanmar. At least 27 people have been killed in Bangladesh and Myanmar from the storm, according to an article by TWC's Nick Wiltgen. The coastal city of Chittagong reported 879 millimeters (34.61 inches) of rain in just a four-day period July 24 through 27 from the storm.

This may be my last post for a week, as I plan on taking some vacation time and turning the blog over to Bob Henson. He will have the latest installment in our "what to expect from El Niño" series--on how El Niño might affect winter weather in the Eastern U.S.--late this morning.

Jeff Masters

Hurricane

Invest 94L Off the Coast of Africa May Slowly Develop

By: Jeff Masters , 3:29 PM GMT on July 29, 2015

The first African tropical wave worthy of being classified by NHC as an area of interest (an "Invest") has emerged from the coast of Africa, and lies a few hundred miles southeast of the Cape Verde Islands. Invest 94L has conditions that favor some slow development over the next few days. Satellite images show that 94L has a decent amount of spin and a small but growing area of heavy thunderstorms. Wind shear off the coast of Africa is moderate, 10 - 20 knots, ocean temperatures are a warm 28°C, and the atmosphere is reasonably moist. These conditions should allow for some slow development as the system heads west at 15 mph the next two days. However, 94L faces a rugged path ahead of it. The 8 am Wednesday run of the SHIPS model predicted that wind shear would remain moderate over 94L this week, but a massive area of dry, dusty air from the Saharan AIr Layer (SAL) is dominating most of the tropical Atlantic, from the coast of Africa into the Central Caribbean. As 94L moves into the Central Atlantic this weekend, the storm will encounter increasingly dry, stable air, making development difficult. If 94L does manage to make it to the Caribbean, the high wind shear that has dominated the region all summer will likely tear the storm apart. The ensemble runs of the GFS and European models--done by running the models at lower resolution and varying the initial atmospheric conditions slightly to generate an "ensemble" of twenty potential weather situations (fifty for the European model)--do have a number of their 20 - 50 runs that develop 94L into a tropical depression, but none of these solutions have the storm that develops making it as far west as the Lesser Antilles Islands. The operational high-resolution versions of our three top models for predicting genesis of tropical cyclones--the GFS, European, and UKMET models--show only weak development of 94L over the next few days. In their 8 am Wednesday Atlantic Tropical Weather Outlook., NHC gave 94L 2-day and 5-day odds of development of 0% and 20%, respectively.


Figure 1. Invest 94L between the coast of Africa and the Cape Verde Islands as seen by the MODIS instrument on NASA's Aqua satellite on Wednesday morning, July 29, 2015. Image credit: NASA.


Figure 2. Saharan Air Layer (SAL) analysis for 8 am EDT Wednesday, July 29, 2015, from the University of Wisconsin CIMSS shows plenty of dry air dominating the tropical Atlantic.

Hawaii should watch Invest 91E
In the Eastern Pacific, Tropical Depression Eight-E is encountering dry, stable air and should dissipate well before reaching the Hawaiian Islands. Hawaii should be more concerned with Invest 91E, which both the GFS and European models show getting within 500 miles of the islands by next Wednesday. In their 5 am PDT Wednesday Tropical Weather Outlook, NHC gave 91E 2-day and 5-day development odds of 60% and 90%, respectively.

In the Western Pacific, all looks to be quiet until at least Saturday, when the European model predicts a new tropical depression will form about 1500 miles east of the Philippines' Luzon Island.


Figure 3. Tropical Cyclone Two in the Bay of Bengal as seen at 05 UTC July 29, 2015, from the MODIS instrument on NASA's Terra satellite. JTWC gave top winds of 40 mph to the system, which was expected to move slowly onshore over Bangladesh. Image credit: NASA.

Bay of Bengal's Tropical Cyclone Two generating heavy rains
The Indian Meteorological Department (IMD) and Joint Typhoon Warning Center are issuing advisories on Tropical Cyclone Two in the Indian Ocean's Bay of Bengal, which is bringing heavy rains to portions of India, Bangladesh, and Myanmar. Tropical cyclones embedded within India's monsoon rarely grow into strong tropical storms, but can be prodigious rain makers. India's monsoon has been 12% below normal in rainfall as of July 22, so the country could use more rainfall--though perhaps not in the concentrated manner a monsoon tropical storm typically delivers, causing dangerous flooding rains. Tropical Cyclone Two is expected to move slowly onshore over Bangladesh and weaken over the next few days.

Jeff Masters

Hurricane

What to Expect from El Niño: North America

By: Bob Henson , 3:16 PM GMT on July 28, 2015

We’re now well into the ramp-up phase of what promises to be one of the top three El Niño events of the last 60-plus years. Sea-surface temperatures (SSTs) in the Niño3.4 region--an area straddling the eastern tropical Pacific--are the most widely accepted index for the oceanic evolution of El Niño. NOAA announced in its weekly ENSO update on Monday (see PDF) that Niño3.4 SSTs were running 1.6°C degrees above the seasonal average for the week ending Monday. While this is down slightly from a peak of 1.7°C the week before, Michelle L’Heureux reminds us in NOAA’s ENSO Blog that minor weekly variations aren’t worth getting too worked up about. The latest value still keeps the current El Niño in the “strong” category (Niño3.4 SSTs at least 1.5°C above average). Unusually warm waters now extend from the South America coast westward to the International Date Line in a classic El Niño signature (see Figure 1), with widespread above-average SSTs at least partially related to El Niño extending northward across much of the northeast Pacific. For much of 2014, the atmosphere failed to respond to several brief warmings of the eastern tropical Pacific, but now both ocean and air are locked into the synchrony that builds and sustains the strongest El Niño events. Westerly winds bursts continue to kick up across the tropical Pacific, pushing warm water downward and eastward in the form of lumbering, downwelling Kelvin waves that push toward the shores of South America, where they act to suppress the normal upwelling of cooler water.


Figure 1. Sea surface temperatures for the week ending July 22 were more than 1°C above average from the eastern tropical Pacific northward through much of the northeast Pacific, with pockets of 2 - 4°C above average evident near the equator. Image credit: NOAA National Centers for Environmental Information.


Figure 2. Precipitation departures from average for the period November through March for the five events characterized as “strong” (SSTs in the Niño3.4 region of at least 1.5°C above average for at least three overlapping three-month periods). The final two events, 1982-83 and 1997-98, are characterized by Jan Null as “very strong,” with SST departures of more than 2.0°C above average. Image credit: Jan Null, Golden Gate Weather Services, from data and graphics generated by NOAA/ESRL/PSD and CIRES-CU.



The only El Niño events in NOAA's 1950-2015 database comparable in strength to the one now developing occurred in 1982-83 and 1997-98. A single pair of cases is a thin framework on which to build any projections of what El Niño may bring across North America this winter. However, three other episodes since 1950 are rated as “strong” (Niño3.4 readings topping the SST threshold of +1.5°C for at least three overlapping three-month periods). Many of the far-flung atmospheric responses to El Niño become more reliable the stronger the event, so it’s wise to look especially closely at these cases, rather than simply averaging across all El Niño events.

Later this week, Jeff Masters will take a look at the global consequences of El Niño for weather and climate. In today’s post, we’ll focus on North America, which has some of the world’s clearest tie-ins to El Niño--not surprisingly, since we’re located just north of the oceanic heart of the phenomenon.

Drought-easing rains for California? Likely, but not certain
Some of the keenest interest in El Niño lies with Californians, who are suffering through Year 4 of an extreme drought that’s left Sierra snowpack in tatters and pushed statewide average temperatures far above anything on record over the last few months. The state needs a very wet winter just to get soil moisture back to near-normal levels, and a good deal more than that to bring California’s reservoirs and groundwater close to their long-term average. "It takes years to get into a drought of this severity, and it will likely take many more big storms, and years, to crawl out of it," said NASA’s Jay Famiglietti at an American Geophysical Union talk last December.

Like other strong El Niño events, this one will almost certainly last just one winter. But at least for the coming wet season, it holds encouraging odds of well-above average precipitation for California. During a strong El Niño, the subtropical jet stream is energized across the southern U.S., while the polar jet stream tends to stay north of its usual winter position or else consolidate with the subtropical jet. This gives warm, wet Pacific systems a better chance to push northeast into California. During 1997-98, downtown San Francisco scored its largest number of days with measurable rain (119) and its second wettest rainfall season (47.22”) since records began in 1849, coming in behind only 1861-62 (49.27”). The 1982-83 event was the fifth wettest in San Francisco annals, with a wet-season total of 38.17”. In downtown Los Angeles, the 1982-83 and 1997-98 seasons came in as fifth and sixth wettest, respectively, with 31.25” and 31.01”. Records began in L.A. in 1877.

Californians will need to be patient, as the biggest drenchings from a strong El Niño can take till the midwinter peak of the wet season to arrive (December can actually be drier than average). The 1997-98 season didn’t produce much more than sporadic storms until January in northern California and February over the state as a whole. The story was similar in 1982-83, which brought California its biggest storms after New Year's. This was before regular monitoring of El Niño, so scientists and the public didn't even know that a wet winter was in the cards. Jack Williams, who founded the USA TODAY weather section when the newspaper debuted in 1982, has said he doesn't recall writing a single article about El Niño in the winter of 1982-83. Things were different in 1997-98, when ocean monitoring systems caught the development of El Niño months ahead of its U.S. impact and word spread widely through traditional media and the burgeoning World Wide Web (and via Chris Farley in a brief but unforgettable “Saturday Night Live” skit).

With hopes for drought relief running so high in California, it can’t be stressed enough that El Niño shifts the odds but doesn’t guarantee the roll of the meteorological dice in any particular winter. On the plus side, the heavy rains that often accompany a strong El Niño don’t necessarily translate into major flooding damage. That threat hinges largely on the timing, intensity, and location of individual storm systems, which can cause problems during La Niña or El Niño alike.


Figure 3. A luxury home in the Orange County suburb of Laguna Niguel slips down a hillside eroded by heavy El Nino generated rains earlier on March 19, 1998. Two homes and seven condominiums were destroyed in the slide. Image credit: Vince Bucci/AFP/Getty Images.


Milder and drier a good bet for Pacific Northwest, Northern Plains, western Canada
The altering of the polar and subtropical jet stream tracks fostered by El Niño can leave a big chunk of North America in the lurch, with relatively tranquil weather that tends to be warmer and drier than average. Unusually mild weather can overspread most of Canada---1998 was the nation’s warmest year on record, though 2014 didn’t pan out that way)---and the mildness often extends across the northern tier of US states from Washington to the Great Lakes. (The winter of 1997-98 was the second warmest in U.S. history.) It won’t necessarily be bone-dry in normally damp places like Washington or British Columbia, but anything less than average precipitation wouldn’t be good news for that region, which has seen wildfires taking advantage of a warm winter with little snowpack followed by a very dry spring. Cliff Mass (University of Washington) does cite one potential benefit to the Pacific Northwest this winter: “Big windstorms avoid strong El Niño years. Similar to vampires and garlic.”

Rockies snowfall: The south usually wins out
Thanks to the jet-shifting effects noted above, snowfall tends to be below average in the Northern Rockies and above average in the Southern Rockies during strong El Niños. The north-south split extends to Colorado, where northern resorts such as Steamboat Springs typically lose out to areas like the San Juan and Sangre de Cristo ranges across the southern part of the state. Along the populous Front Range from Denver to Fort Collins, El Niño hikes the odds of a big snowstorm, especially in the spring and autumn. About half of Boulder’s 12” – 14” storms occur during El Niño, and the odds of a 20” or greater storm are quadrupled during El Niño as opposed to La Niña. See this UCAR writeup for more detail.

Rainy and cool across the Gulf Coast
According to NOAA, the single most reliable El Niño outcome in the United States, occurring in more than 80% of El Niño events over the last century, is the tendency for wet wintertime conditions along and near the Gulf Coast, thanks to the juiced-up subtropical jet stream. (The same upper-level jet also tends to suppress Atlantic hurricane activity by fostering subsidence and stable air and boosting the upper-level wind shear that inhibits tropical cyclone formation). Severe weather is often associated with El Niño during the winter months across the southeast fringes of the nation, a finding reinforced in a 2015 study led by John Allen (International Research Institute for Climate and Society) that we discussed in a March post. The study found that the risk of tornadoes across south Texas and Florida is roughly doubled during El Niño. Florida's worst outbreak on record occurred on February 22-23, 1998, during the intense 1997-98 El Niño. A total of 12 tornadoes killed 42 people, mainly in a swath running along Interstate 4 through central Florida.


Figure 4. A resident of a Kissimmee, Florida, residential complex picks up some of her belongings from what is left of her home after a tornado leveled her house and ripped through the neighborhood on February 23, 1998. Image credit: Roberto Schmidt/AFP/Getty Images.


A dry pocket in the Midwest
One fairly localized but distinct product of El Niño is a tendency for drier-than-usual winters across the lower Midwest, especially in the Ohio Valley. A typical winter brings a stream of low-pressure centers approaching the lower Midwest from either the southwest or northwest. The split stream favored by El Niño tends to push these lows either well north or well south of the Ohio Valley, leaving the area with better-than-usual odds of relatively mild temperatures and light precipitation during the core of winter.

What about the Northeast US?
Some of the bigger snowstorms on record for the mid-Atlantic and Northeast have accompanied El Niño events, but the influence of El Niño is highly conditional on other factors. The blockbuster El Niño events of 1982-83 and 1997-98 pushed temperatures across the entire Midwest and Northeast well above average, yet the ”Megapolitan” snowstorm of February 10-12, 1983, pummeled big cities along the East Coast with widespread 1-to-2-foot amounts. The most destructive winter weather event of 1997-98 was actually a multiday ice storm that paralyzed Montreal and parts of far northern New York and New England for days. And the infamous Snowmageddon of 2009-10 (see Figure 5) occurred during a moderate El Niño. One crucial element is the state of the North Atlantic Oscillation (NAO), a semi-cyclic atmospheric pattern that describes whether the flow from eastern North America to Europe is a strong, west-to-east channel (a positive NAO) or a more wavy, variable path (a negative NAO). Heavy snow during El Niño becomes much more likely along the eastern seaboard when a negative NAO predominates. Winter hasn’t been especially kind to the northeast U.S. and eastern Canada over the last few years, with frequent negative NAO periods leading to major winter storms and intense cold buffeting the region more than one might expect in a warming climate. In a follow-up post to this one, we took a closer look at the imminent face-off between a powerhouse El Niño and the recurrent tendency over the last few years toward cold and snow in parts of the Northeast.


Figure 5. Walkers struggle through the snow in front of the U.S. Capitol Building on February 6, 2010, in Washington, DC. The blizzard that came to be known as Snowmageddon dumped 20” to 35” of accumulations from the Washington area into southern New Jersey, paralyzing the region and snapping power lines. Image credit: Mandel Ngan/AFP/Getty Images.


Villain or welcome guest?
When all is said and done, a strong El Niño can actually be a net benefit to the US economy. A detailed analysis by climatologist Stanley Changnon, published in 2004 in the Bulletin of the American Meteorological Society, estimated that U.S. weather associated with the big 1997-98 El Niño event led to direct losses of about $4 billion but direct gains of around $19 billion. Moreover, Changnon reckoned that hundreds more lives were saved by the lack of intense winter cold than were taken by El Niño-related storminess. Seth Borenstein and Frank Bajak make a good case in an AP story that the United States is one of the largest beneficaries of El Niño relative to other parts of the globe.

Based on NOAA data and analyses, Jan Null (Golden Gate Weather Services) has created an handy graphical guide to U.S. temperature and precipitation effects from weak, moderate, strong, and very strong El Niño and La Niña events, including composites as well as individual Nov-Mar seasons. Looking these over will give you a good sense of where El Niño’s fingerprints are crystal clear or on the muddy side. You’ll also find helpful writeups on NOAA’s ENSO Blog outlining typical U.S. El Niño impacts, including entries by Mike Halpert (June 2014) and Tom Di Liberto (June 2015).

Bob Henson

El Niño

Quiet in the Atlantic; Two Disturbances for Hawaii to Watch

By: Jeff Masters , 3:29 PM GMT on July 27, 2015

The tropics have fallen silent the past two days, with no named storms anywhere on the planet. It's not unusual to see a quiet period for tropical cyclones in July, which lies before the climatological peak months of August, September, and October in the Northern Hemisphere (a tropical cyclone is the generic term for all tropical depressions, tropical storms, and hurricanes/typhoons). The tropical cyclone-free period will likely be short lived, though, as Invest 90E, located in the Eastern Pacific about 1,050 miles southwest of the southern tip of Mexico's Baja Peninsula on Monday morning, may develop into a tropical depression by Wednesday. This system is something residents of Hawaii should keep an eye on. Satellite loops show the disturbance has good degree of spin, but heavy thunderstorm activity is limited due to dry air and moderate wind shear of 10 - 20 knots. The system is on a trajectory that will likely take it within 300 miles of Hawaii this weekend, but the latest SHIPS model forecast shows that late this week 90E will encounter higher wind shear, cooler ocean temperatures, and drier, more stable air. These conditions should cause significant weakening as 90E approaches Hawaii. In their 8 am EDT Tropical Weather Outlook, NHC gave 90E 2-day and 5-day odds of development of 40% and 70%, respectively. Hawaii should also watch a tropical wave located several hundred miles south of the southern tip of the Baja California peninsula. This wave was moving westwards, and should arrive in the vicinity of Hawaii by Tuesday next week. In their 8 am EDT Tropical Weather Outlook, NHC gave this disturbance 2-day and 5-day odds of development of 0% and 40%, respectively.


Figure 1. Tropical Depression Two in the Bay of Bengal as seen on Monday afternoon, July 27, 2015, from the MODIS instrument on NASA's Aqua satellite. The Indian Meteorological Department (IMD) gave top winds of 30 mph to the system, which was nearly stationary. Image credit: NASA.

In the Indian Ocean's Bay of Bengal, the Indian Meteorological Department (IMD) is issuing advisories on Tropical Depression 2, which is bringing heavy rains to portions of India and Bangladesh along the coast of the Bay of Bengal. Tropical depressions embedded within India's monsoon rarely grow into strong tropical storms, but can be prodigious rain makers. India's monsoon has been 12% below normal in rainfall as of July 22, so the country could use more rainfall--though perhaps not in the concentrated manner a monsoon tropical depression typically delivers, causing dangerous flooding rains. The Joint Typhoon Warning Center (JTWC) is not classifying this system as a tropical depression yet.

In the Western Pacific, all looks to be quiet until at least this Saturday, when both the European and GFS models predict a new tropical depression could form about 500 miles east of the Philippines.


Figure 2. Saharan Air Layer (SAL) analysis for 8 am EDT Monday, July 27, 2015, from the University of Wisconsin CIMSS shows plenty of dry air dominating the tropical Atlantic. Two tropical waves over the Eastern Atlantic were apparent, with no signs of development.

African tropical wave-watching season has begun
In the Atlantic, it's the time of year when we need to start watching the regular procession of tropical waves coming off the coast of Africa. About 85% of all major hurricanes in the Atlantic get their start as an African tropical wave, so these potential trouble-makers are important to track and monitor. We do have several solid tropical waves with decent spin and moisture that have pushed off the coast of Africa over the past few days, but these tropical waves face a rugged path ahead of them if they want to develop into tropical depressions. Wind shear off the coast of Africa is not prohibitive--a moderate 10 - 20 knots--but a massive area of dry, dusty air--a Saharan AIr Layer (SAL) outbreak common for this time of year--is dominating most of the tropical Atlantic, from the coast of Africa into the Central Caribbean. This dry air will make it difficult for any tropical waves to spin up into tropical depressions over the Eastern Atlantic. If something does manage to form, it will likely be short-lived, if it attempts to move very far west. High wind shear of 20 - 40 knots dominates the Caribbean, and is expected to stay strong for at least the next five days. The ensemble runs of the GFS and European models--done by running the models at lower resolution and varying the initial atmospheric conditions slightly to generate an "ensemble" of twenty potential weather situations (fifty for the European model)--do have a few of their 20 - 50 runs that develop a tropical depression from one of these African tropical waves later this week. However, none of these solutions have the storm that develops making it as far west as the Lesser Antilles Islands, and the operational high-resolution versions of our three top models for predicting genesis of tropical cyclones--the GFS, European, and UKMET models--do not show anything developing this week. NHC did not highlight any suspected areas of development over the next five days in their 8 am Monday Atlantic Tropical Weather Outlook.


Figure 3. Latest radar image out of Tampa, Florida.

Heavy rains in Florida from Gulf of Mexico low
A low pressure system has formed in the Gulf of Mexico off the coast of Florida, and will drift toward the Florida coast today, bringing 1 - 3" of rain with a few high spots of 3 - 5" over Central Florida over the next few days. The Tampa radar is estimating that this low has already brought 6+ inches of rain to the coast near Tampa, Fort Myers, and Naples. High wind shear of 20 - 30 knots is keeping this system from developing. While a number of members of the GFS and European ensemble model forecast do show this system developing, none of the operational versions of our reliable models for predicting genesis of tropical cyclones show development over the next five days. We should keep an eye on this system over the next few days, but I am not expecting it to develop.

Wunderblogger Steve Gregory will be providing updates by about 4 pm EDT on Monday, Wednesday, and Friday this week.

Jeff Masters

Hurricane

Record Ocean Temperatures Threaten Hawaii's Coral Reefs

By: Jeff Masters , 7:34 PM GMT on July 24, 2015

Record warm sea surface temperatures in Hawaii's waters threaten to bring a second consecutive year of record coral bleaching to their precious coral reefs this summer. According to NOAA, ocean temperatures in the waters near and to the south of the Hawaiian Islands were 1 - 2°C (1.8 - 3.6°F) above average in June, which was the warmest these waters have been since record keeping began over a century ago. With the waters surrounding Hawaii expected to warm to their highest values of the summer by September, and likely remain 1 - 2°C above average, NOAA's Coral Reef Watch has placed the islands under a Coral Bleach Watch, and their experimental coral bleaching forecast gives a 50 - 90% chance that Hawaii will experience "Level 2" thermal stress this summer--the highest category of danger, likely to result in widespread coral bleaching and mortality. The record warm ocean temperatures are due to a strong El Niño event that is pushing large amounts of record-warm water into the Central Pacific, in combination with the steady rise in ocean temperatures due to global warming. Mass coral die-offs commonly occur during strong El Niño events; the United Nations Environmental Program found that 16% of the worlds coral reefs were effectively lost during a nine-month coral bleaching episode associated with the 1997 - 1998 record-strength El Niño event. With this year's El Niño event likely to be almost as strong as the 1997 - 1998 one, coral reefs are going to take a beating again.


Figure 1. NOAA's experimental coral bleaching forecast gives a 50 - 90% chance that Hawaii will experience Satellite Bleaching Alert Level 2 thermal stress this summer--the highest category of danger, likely to result in widespread coral bleaching and mortality. El Niño conditions have produced an extremely warm band of water from the central equatorial Pacific to the South American coast, and Level 2 thermal stress has already been reached in the Gilbert, Phoenix, and Northern Line Islands in Kiribati, as well as in Micronesia, the Howland and Baker Islands, and to the east in the Galápagos.


Figure 2. Unusually warm waters are also in place along the northern coast of Cuba and in the Bahamas, and NOAA's experimental coral bleaching forecast gives about a 70% chance coral reefs in these waters will experience Satellite Bleaching Alert Level 2 thermal stress this summer--the highest category of danger, likely to result in widespread coral bleaching and mortality.

Second consecutive year of severe coral bleaching in Hawaii
Hawaii's reefs are already reeling from their worst coral bleaching event in recorded history in 2014, when record warm ocean temperatures caused 50 - 70% of the corals sampled in Northeast Oahu's Kāneʻohe Bay to bleach. When the sea surface temperature is 1°C warmer than the highest monthly mean temperature corals usually experience, coral polyps will expel the symbiotic algae that live in their tissues, exposing the white skeleton underneath, resulting in a white "bleached" appearance. Death can result if the stress is high and long-lived. In Hawaii's waters, corals cannot tolerate water temperatures above 83°F (28.3°C) for multi-week periods without suffering bleaching. Corals typically recover from mild bleaching, gradually recovering their color by repopulating their algae. However, if the bleaching is severe or prolonged, individual polyps or whole colonies will die. With Hawaii likely to undergo a second consecutive year of record warm waters and coral bleaching in 2015, widespread mortality in many of Hawaii's coral reefs is possible, particularly around the Big Island.


Figure 3. During June 2015, the ocean areas near and to the south of Hawaii were at their warmest levels since record keeping began in 1880. Image credit: National Centers for Environmental Information (NCEI) .

Could a hurricane help?
When hurricanes and tropical storms churn the waters, they upwell large amounts of cooler waters from the depths that can cool the surface waters, potentially reducing the thermal stress on coral reefs. The heavy rains from the storm can also potentially cause cooling. This occurred in the Virgin Islands in 2010, when Hurricane Earl and Hurricane Otto helped relieve a potentially dangerous coral bleaching episode (Figure 4.) So, should Hawaii hope for a hurricane this September to help save its coral reefs? Well, be careful what you wish for. Hurricanes cause damage to reefs. Following Tropical Storm Iselle, which hit the Big Island of Hawaii on August 7, 2014, with 60 mph winds, researchers at the University of Hawaii, Hilo documented that one coral reef on the Big Island (the Wai`ōpae tide pools) suffered physical damage from pounding waves that broke up to 18% of the coral colonies of one species of coral with long slender branches--cauliflower coral. Other corals suffered lesser damage, 0 - 10% breakage. In addition, these corals were subjected to sewage contamination due to damage of cesspools and septic tanks.


Figure 4. Mean daily temperatures (on left Y-axis) with standard error collected at reef-depth (26'-58') monitoring sites on St. John US Virgin Islands, and total daily rainfall (on right Y-axis) from August through October 2010 from Newfound, Haulover, Tektite, Yawzi and Mennebeck Reefs in the Virgin Islands. Image credit: Rafe Boulon, Resource Management Chief, Virgin Islands National Park.

Long term outlook for world's coral reefs: bleak
The large amount of carbon dioxide humans have put into the air in recent decades has done more than just raise Earth's global temperature--it has also increased the acidity of the oceans, since carbon dioxide dissolves in sea water to form carbonic acid. The oceans are acidifying faster than at any time in the past 300 million years. Corals have trouble growing in acidic sea water, and the combined effects of increasing ocean temperatures, increasing acidity, pollution, and overfishing have reduced coral reefs globally by 19 percent between 1950 - 2008. Another 35 percent could disappear in the next 40 years, even without the impact of climate change, according to a report released in October 2010 by the World Meteorological Organization and the Convention on Biological Diversity.

Coral expert J.E.N. Veron, former chief scientist of the Australian Institute of Marine Science, had this to say in an excellent interview he did with Yale Environment 360 in 2010: "the science is clear: Unless we change the way we live, the Earth's coral reefs will be utterly destroyed within our children's lifetimes...Reefs are the ocean's canaries and we must hear their call. This call is not just for themselves, for the other great ecosystems of the ocean stand behind reefs like a row of dominoes. If coral reefs fail, the rest will follow in rapid succession, and the Sixth Mass Extinction will be upon us--and will be of our making."


Figure 5. An example of coral bleaching that occurred during the record-strength 1997-1998 El Niño event. Image credit: Craig Quirolo, Reef Relief/Marine Photobank, in Climate, Carbon and Coral Reefs

Jeff Masters

Climate Change

Fewer but Stronger Global Tropical Cyclones Due to Ocean Warming

By: JeffMasters, 3:36 PM GMT on July 23, 2015

Global ocean temperatures hit their warmest levels in recorded history last month. Since hurricanes are heat engines which extract heat energy from the oceans and convert it to the kinetic energy of the storms' winds, we should be concerned about the potential for hurricanes to be stronger as a result of global warming. Indeed, the observed 0.3°C (0.5°F) warming of Earth's oceans over the past 30 years has made more energy available to hurricanes, says a new study published in May in Nature Climate Change by Florida State hurricane scientist James Elsner and the deputy director of the National Typhoon Center in South Korea, Namyoung Kang. The researchers found that this extra heat energy has led to a change in both the frequency and intensity of global tropical storms and hurricanes. Using a new mathematical framework to categorize all global tropical cyclones with wind speeds of at least 39 mph over the past 30 years, the authors showed that the observed warming of Earth's oceans during that time period has led to an average increase in wind speed of about 3 mph (1.3 m/s) for each storm--but there were 6.1 fewer named storms globally each year because of the warmer oceans. A typical year has about 85 named storms globally, so this represents about a 7% decrease in the number of storms.


Figure 1. One of the most spectacular images ever captured of a tropical cyclone from space: Category 5 Super Typhoon Maysak as seen from the International Space Station at approximately 6 pm EDT Tuesday March 31, 2015 (just after dawn local time.) At the time, Mayask had top winds of 160 mph as estimated by the Joint Typhoon Warning Center, and a central pressure of 905 mb, as estimated by the Japan Meteorological Agency. Image has been brightened and flipped 180 degrees. Image credit: Terry W. Virts.

Why fewer storms, but the strongest ones getting stronger?
More moisture is evaporated from a warmer ocean surface, resulting in water vapor concentrating in the lower atmosphere. Since moist air is less dense than dry air, this creates greater instability, leading to stronger updrafts in developing storms and more intense tropical storms and hurricanes. However, this low-level moisture is not effectively transported to high altitudes, resulting in warmer and drier conditions aloft and stronger high pressure in the middle and the upper troposphere. This high pressure aloft forces thunderstorm activity to concentrate in time and space, resulting in fewer tropical cyclones--but the increased moisture at low levels allows more efficient intensification once a tropical storm is spawned. "Thus tropical cyclone intensity increases at the expense of tropical cyclone frequency", the authors wrote. In an interview at sciencedaily.com, Kang said, "In a warmer year, stronger but fewer tropical cyclones are likely to occur. In a colder year, on the other hand, weaker but more tropical cyclones." Many climate models also predict fewer but more intense tropical cyclones in a future warmer climate--for example, Knutson, T. R. et al., 2010, "Tropical cyclones and climate change", which projected intensity increases of 2 - 11% by 2100. The "official word" on climate, the 2013 IPCC report, predicts that there is a greater than 50% chance (more likely than not) that we will see a human-caused increase in intense hurricanes by 2100 in some regions. The 2014 U.S. National Climate Assessment found that "the intensity, frequency, and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5) hurricanes, have all increased since the early 1980s. The relative contributions of human and natural causes to these increases are still uncertain. Hurricane-associated storm intensity and rainfall rates are projected to increase as the climate continues to warm.”

Impacts
While it is good news that warming of the oceans may potentially lead to fewer hurricanes, this will probably not decrease the total amount of hurricane damage if the strongest storms get stronger. Damage done by a hurricane increases by somewhere between the second and third power of the wind speed, so just a 10 mph increase in winds can cause a major escalation in damage. According to Pielke et al., 2008, over the past century, Category 3 - 5 hurricanes accounted for 85% of U.S. hurricane damage, despite representing only 24% of U.S. landfalling storms. Category 4 and 5 hurricanes made up only 6% of all U.S. landfalls, but accounted for 48% of all U.S. damage (if normalized to account for increases in U.S. population and wealth.) This study also found that hurricane damages in the U.S. were doubling every ten years without the effect of climate change, due to the increases in wealth and population. If we add in an increase in the frequency of the strongest storms, combined with storm surges that will be riding inland on top of ever-increasing sea levels due to global warming, the damage math for coastal regions gets very impressive for the coming decades.

References
Nam-Young Kang, James B. Elsner, "Trade-off between intensity and frequency of global tropical cyclones", Nature Climate Change, 2015; DOI: 10.1038/nclimate2646

Pielke, R.A, et al., 2008, "Normalized Hurricane Damage in the United States: 1900 - 2005," Natural Hazards Review, DOI:10.1061/ASCE1527-6988(2008)9:1(29)

Hurricanes and Climate Change: Huge Dangers, Huge Unknowns, my 2013 blog post

The Atlantic remains quiet
High wind shear and dry, sinking air continue to dominate the tropical Atlantic, and none of the reliable models for predicting tropical storm formation show a tropical depression or tropical storm forming over the next five days. However, the models are showing that the remains of an old cold front extending from Florida's Gulf Coast to the waters offshore of North Carolina could serve as the focus of the development of a low pressure area capable of transforming into a tropical storm, early next week. Anything that does form along this front would move northeastwards, out into the open Atlantic, and not be a significant threat to any land areas.

Jeff Masters

Hurricane Climate Change

Weather Underground Takes Over The Weather Channel in New Weeknight Series

By: Jeff Masters , 1:25 PM GMT on July 22, 2015

It's been three years since Weather Underground (WU) became part of The Weather Company (AKA The Weather Channel, TWC). A key goal of mine for the merger--to make both Weather Underground and The Weather Channel better--has shown steady progress over the past few years, and takes an even larger step in that direction beginning on August 24, with the launch of the "Weather Underground" live cable TV show airing weekdays from 6-8 p.m. ET on The Weather Channel. The new show will appeal to everyone’s inner weather geek, featuring unique insights into the science behind weather and forecasting. I flew down to Atlanta last week to tape some segments for the new show, including what should be a pretty amusing series of promos (Part 1 embedded below). TWC is really making an impressive effort on this, complete with a custom set built to look like an underground bar, an original theme song of Seattle-grunge type music, and state-of-the art 3D visual presentations. Both Bob Henson and I will be appearing via Skype (and occasionally live in the studio) during some of the shows, but the show will also tap into the expertise of other severe weather experts, through forecast debates, deep dives into atmospheric science and live storm coverage. Each show will aim to promote a unique feature of the Weather Underground web site, like the latest blog post by Bob or myself, WunderPhotos, or personal weather stations. Breaking weather events will be the main focus, but climate change stories will also be featured.

WU’s unique community of personal weather station owners and fans will play an integral role in the show’s live, interactive experience--fans will be able to submit questions via #WUTV across social media, report current conditions in their area, contribute to the creation of show segments, access behind-the-scenes live-stream video via wunderground.com and participate in weather roundtables live on air.


Video 1. I give Mike Bettes a tough grilling during his interview for host of the new Weather Underground TV show. This is Part 1 of what may be up to an 8-part series.

After a lengthy interview process last week, it was decided that the show would be hosted by Mike Bettes, an Emmy Award-winning meteorologist and storm tracker. You can see part of the interview in the video clip above. Not shown is the part that almost blew it for him (which will be aired in a later installment of this series.) You see, Weather Underground's origin came as an educational project at the University of Michigan, where I was a Ph.D. student in the early 1990s. It turns out that Michigan has a pretty notorious rivalry with a certain Big Ten school based in Columbus, Ohio. Here's the transcript of this portion of the interview:

Me: "Mike, when we launch the show, we want to make sure we've selected a host that's fully qualified for the role. Do you mind if we go over your resume?"

Mike: "Not a problem!"

Me: "It says here that you graduated from Ohio State University."

Mike: "Yes sir. I got my degree in Atmospheric Science from the Ohio State University. Go Bucks!"

Me (skeptically): "Hmmm…and that's an accredited university??"

Mike (incredulously): "Well…yeah, of course!"

Mr. Bettes really did graduate from Ohio State, and has gone on to do some excellent coverage of landfalling hurricanes and severe weather outbreaks since he began working at TWC in 2003--including such events as the 2011 Joplin tornado and the 2013 El Reno tornado. I am very excited to see this new Weather Underground show launch, and think it will be a great dive deep into the science of meteorology for all weather enthusiasts.

Jeff Masters

Wunderground News

What the Weekend Rains Did to Southern California—and What a Real Hurricane Could Do

By: Bob Henson , 3:07 PM GMT on July 21, 2015

The maxim “be careful what you wish for” comes to mind when pondering last weekend’s amazing rain across Southern California. After three years of fierce drought, some of the heaviest midsummer rains on record struck the region, facilitated by the remnants of former Hurricane Dolores. The spirit-boosting effects of the rain were accompanied by some rare disruptions, including a bridge collapse along Interstate 10 in far southeast California and the first rained-out pro baseball game at Anaheim’s Angel Stadium since 1995. As unusual as the rain was, there could be even more to come in the next several months, as an already-strong El Niño event continues to gather steam. Records for Southern California from the past century show that the risk of impact from Pacific tropical storms and hurricanes is greater during El Niño years. History also tells us that we can’t rule out the possibility of a full-blown hurricane coming ashore: this apparently happened in 1858, long before the region was densely populated.


Figure 1. Emergency crews respond after a pickup truck crashed into the collapse of an elevated section of Interstate 10 on Sunday, July 19, 2015, in Desert Center, Calif. The bridge, which carries the eastbound interstate about 15 feet above a normally dry wash, snapped and ended up in the flooding water below, the California Highway Patrol said, blocking all traffic headed toward Arizona. Image credit: Chief Geoff Pemberton/CAL FIRE/Riverside County Fire, via AP.

A century’s worth of July rain in one weekend
As the circulation around ex-hurricane Dolores stalled southwest of San Diego over the weekend (see Figure 3), the flow around it contributed to a channel of rich moisture flowing northward across much of Arizona and Southern California. Dewpoints rose to sultry Southern levels as high as the upper 60s in Los Angeles and the low 70s in San Diego. Very light rain had been in the forecast along the southern CA coast, but the amount of instability proved greater than expected, and intense thunderstorms developed on Saturday afternoon and evening. Much of western San Diego County picked up an inch or more of rain on Saturday, with another 0.50” – 1.00” widespread on Sunday and some lighter amounts on Monday. San Diego’s Lindbergh Field measured a whopping 1.69” on Saturday and Sunday—more rain than in any other July in San Diego records that go back to 1850 (the runner-up was 1.29” in July 1865). Midsummer is typically bone-dry in San Diego, with June through August racking up a combined average of just 0.14”. Amazingly, the past weekend produced more rain in San Diego than the previous 100 Julys combined (1915 – 2014). This was also more rain than the year’s wet-season months of January, February, and March managed to cough up. Downtown Los Angeles notched 0.38” over the weekend, its greatest monthly total for any July in records going back to 1877 (the previous record was 0.24” in July 1886). In that entire 139-year period, the station recorded a total of 1.17” of July rain, with close to a third of it falling this year.


Figure 2. More than 20,000 intracloud and cloud-to-ground lightning flashes occurred in southern California from Friday, July 17, through Sunday, July 19. Image credit: NWS/San Diego.


Figure 3. This satellite image tweeted by the NWS San Diego office on Sunday morning, July 19, shows the remnants of Dolores (lower left) and a displaced cluster of thunderstorms north of Los Angeles (near top of image). Image credit: NWS/San Diego.

Chris Landsea, science and operations officer at NOAA’s National Hurricane Center, points out the absence of the usual July circulation patterns that shove Northeast Pacific hurricanes westward before they can influence the United States so strongly. “Typically in July you have a strong subtropical ridge centered over Mexico and a quick westward steering induced by the ridge,” Landsea told me. “This year, that ridge is much weaker.” Although Dolores did not reach Southern California, it edged further north than almost any other Northeast Pacific system on record for July (see Figure 4 below).

SoCal’s natural, but imperfect, buffer against hurricanes
The ocean circulation that keeps California’s coastal climate naturally air-conditioned also helps protect the state from direct hurricane landfalls. Prevailing sea-surface temperatures (SSTs) are far too cool to support a tropical cyclone, even as far south as San Diego. Hundreds of miles further south, though, summer and autumn SSTs are more than warm enough to make the Northeast Pacific (also called the Eastern North Pacific) fertile ground for hurricane formation. This is especially true during El Niño, which typically pushes SSTs above average across the Northeast Pacific hurricane genesis region. El Niño also provides favorable dynamics for development, as rising motion and weak upper winds tend to predominate across the Northeast Pacific. Heavy rains often result when moisture streams into the western U.S. from tropical cyclones in this region. Sometimes the remnants of tropical systems move bodily into Southern California from the Pacific, but a more dangerous approach can be from the southeast, via the extremely warm waters of the Gulf of California, where SSTs can soar above 29°C (84°F). One can also envision a strong hurricane developing west of Mexico and moving north quickly enough to maintain some of its power into southern California.


Figure 4. Tracks of the 223 tropical cyclones in the NOAA Historical Hurricanes database that occurred in July (1950 – 2013) across the Northeast Pacific. Dolores was tracked by the National Hurricane Center until it became a remnant low late on Saturday, July 18, near latitude 25.6°N, a location near the top of the tracks shown here. Tropical cyclones are more likely to affect the southwest U.S. in August, September, and October than in July. Image credit: NOAA.

California’s tropical cyclone history
A roundup published in 1997 by the Los Angeles (Oxnard) office of the National Weather Service summarized the seven years of the 20th century in which at least two tropical cyclones affected Southern California: 1921, 1939, 1972, 1977, 1982, 1983, and 1997. The office stated that six of those seven were classified as El Niño years. Most of these occurred with El Niño conditions taking hold during the autumn, with 1921 being the La Niña outlier. In addition, the highest winds ever recorded with a tropical cyclone in the Southwest U.S. were from Hurricane Kathleen, which delivered sustained winds of 57 mph at Yuma, Arizona, on September 10, 1976—another El Niño-onset year. Torrential rains over far southeast California (as much as 14.76” at Mount San Gorgonio—see PDF) and related flooding ripped out parts of I-8 and other roads and damaged or destroyed hundreds of homes, inflicting an estimated $160 million in damage.


Figure 5. Tracks and intensities of Hurricanes Kathleen (tracking through California and Nevada as an extratropical system) and Nora (paralleling the Colorado River as a tropical storm and tropical depression). Image credit: NOAA.

The region got a startle in September 1997 when Category 5 Hurricane Linda became the most powerful storm ever recorded in the Northeast Pacific. At one point, some computer models predicted that a weakening Linda would recurve into or near southern California, and long-range forecasts from the National Hurricane Center briefly depicted this scenario. The Oxnard NWS office addressed the potential in public statements and forecast discussions, according to the NHC report on Linda. “Some of these products specifically mentioned the uncertainties in forecasting Linda and asked the media not to overdramatize the storm,” the report noted. Only a few days later, fast-moving Hurricane Nora entered the United States with tropical-storm-force winds near the CA/AZ border after cruising north along the east side of Baja California. “The threat to the southwestern United States was unusual and required an unprecedented coordination between the NHC and offices in the NWS Western Region,” said the the NHC’s report on Nora. Heavy rains over the U.S. Southwest were much less than during Kathleen, but damage may have topped $100 million.

The big ones: 1939 and 1858
The most ominous precedents for the megalopolis from San Diego to Los Angeles are the 1858 San Diego hurricane mentioned above and a deadly 1939 system that struck Long Beach as a tropical storm. The 1939 cyclone appears to have reached minimal Category 1 strength on the day before before its northward track brought it into San Pedro, CA (just west of Long Beach) on September 25, bringing an intense week-long heat wave to a dramatic end. Remnants of three other cyclones had affected southern California earlier in the month, as noted in the NWS summary, and moisture surging into the area ahead of the September 25 storm helped trigger heavy rains the day before landfall. In addition, modern flood control devices were not yet in place. The storm gave Los Angeles its 24-hour rainfall record for September with 5.24”, and Mount Wilson picked up 11.60”. An estimated 45 deaths occurred during the storm, including some at sea. Wind damage was minimal, although windows were reportedly blown out across Long Beach. The storm cost an estimated $2 million in 1939 dollars; such a storm would probably cause hundreds of millions in damage today, given the growth in population and wealth across the area.

Less is known about the 1858 San Diego hurricane, although independent researcher Michael Chenoweth teamed up with Chris Landsea to put together the first detailed analysis of the storm, published in the November 2004 issue of the Bulletin of the American Meteorological Society. Chenoweth and Landsea drew on daily weather reports collected by U.S. Army medical staff, as well as California newspaper accounts and U.S. Coast Survey notebooks. On October 13, 1858, the Daily Alta California reprinted coverage from the San Diego Herald that included this account:

“About 11 o’clock A.M. of Saturday, 2d instant, a terrific gale sprung up from the S.S.E. and continued with perfect fury until about 5 P.M., when it somewhat abated, and rain commenced to fall. It blew with such violence, and the air was filled with such dense clouds of dust, that it was impossible to see across the Plaza, and it was with the greatest difficulty that pedestrians could walk the streets. The damage to property was considerable; houses were unroofed and blown down, trees uprooted, and fences destroyed. It is said to have been the severest gale ever witnessed in San Diego.”

Based on the reported leveling of trees and complete destruction of some homes, comparable to F1/F2 damage on the original Fujita tornado damage scale, Chenoweth and Landsea concluded that sustained winds on the order of 50 to 68 knots (57 – 78 mph) appear to have occurred. “We assume that the more substantial buildings were only unroofed, and weaker structures completely destroyed,” they wrote. “The F2 damage was probably done by the higher gusts during the hurricane, accompanied with structural weakening due to the [four hours] of high winds. The account of ships being driven ashore, the visually estimated winds, and structural damages from winds are all consistent with a category-1 hurricane impact in San Diego.”

What would happen this time?
San Diego County’s population in 1860 was a mere 4324, compared to more than 3.2 million today. To the north, there are some 3 million people in Orange County and about 10 million in Los Angeles County. The massive growth in population and wealth would clearly make a reprise of the 1858 hurricane a much more serious affair, inflicting at least a few hundreds of millions in damage, according to Landsea. Although wind damage is an obvious concern, the region already experiences howling gales as a result of Santa Ana and gap-wind events, where gusts can top 60 mph. A prolonged Santa Ana might produce wind damage comparable to a tropical-storm landfall, says Landsea. His bigger concern is inland flooding: “If you got a direct hit by a hurricane, some of the coastal mountains could see 10” or even 15” of rain. The rainfall-produced flooding would be severe. Wind impact would be more secondary.” Unlike much of the Gulf and Atlantic coastline, storm surge would be a relatively minor problem, thanks to the steep topography along most of the Southern California Coast.

The National Hurricane Center has never issued official advisories for any land areas in California (or Arizona). That could change if a storm like Linda targeted the coast. “We’d be looking at tropical storm watches or warnings and perhaps hurricane watches or warnings. We’d also have the same type of coordination with local offices that we now have in the Eastern and Southern Regions [of the NWS]. All this is in place. We know we will again someday have a tropical storm or hurricane in this area.”

This 2012 NASA interview with researcher Bill Patzert discusses the California hurricane risk in more detail. See also this 2011 article by NHC director Rick Knabb, who lists San Diego as the nation’s second-most-overdue hurricane strike.

Bob Henson


Video 1. A short video documentary with newspaper clips and 16-mm film of the 1939 tropical storm as it approached Newport Beach, CA.

Hurricane

June 2015: Earth's Warmest June on Record

By: Jeff Masters , 4:10 PM GMT on July 20, 2015

June 2015 was Earth's warmest June since global record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Monday. NASA also rated June 2015 as the warmest June on record. June 2015's warmth makes the year-to-date period (January - June) the warmest such period on record, according to both NOAA and NASA. A potent El Niño event in the Eastern Pacific that crossed the threshold into the "strong" category in early July continues to intensify, and strong El Niño events release a large amount of heat to the atmosphere, typically boosting global temperatures by at least 0.1°C. This extra bump in temperature, when combined with the long-term warming of the planet due to human-caused emissions of heat-trapping gases like carbon dioxide, makes it likely that 2015 will be Earth's second consecutive warmest year on record. Four of the six warmest months in recorded history (for departure from average) have occurred this year, according to NOAA:

NOAA's top ten warmest global monthly departures from average
1) 0.90°C, Mar 2015
1) 0.90°C, Feb 2015
3) 0.89°C, Jan 2007
4) 0.88°C, June 2015
5) 0.87°C, Feb 1998
6) 0.86°C, May 2015
7) 0.85°C, Mar 2010
8) 0.84°C, Dec 2014
9) 0.83°C, Nov 2013
9) 0.83°C, Apr 2010


Figure 1. Departure of temperature from average for the globe for 12-month periods ending in June each year, starting in 1880 and ending in 2015. There is no evidence of a long term slow-down in global warming. Image credit: NOAA.

For the oceans, the June global sea surface temperature was 0.74°C (1.33°F) above the 20th century average, the highest for June on record, and tied with September 2014 as the highest monthly departure from average for any month. Nine of the ten highest monthly departures from average have occurred since May 2014. Global land temperatures during June 2015 were also the warmest on record. Global satellite-measured temperatures in June 2015 for the lowest 8 km of the atmosphere were the 3rd warmest in the 37-year record, according to the University of Alabama Huntsville (UAH). The lowest 8 km of the atmosphere heats up dramatically in response to moderate to strong El Niño events, with a time lag of several months--as occurred during the El Niño events of 1998 and 2010. Thus, we should see Earth's lower atmosphere temperature hit record levels late this year and/or early next year.


Figure 2. Departure of temperature from average for June 2015, the warmest June for the globe since record keeping began in 1880. Record warmth occurred across the western United States, parts of northern South America, several regions in central to western Africa, central Asia around and to the east of the Caspian Sea, and parts of southeastern Asia. Western Greenland and some areas in India and China were cooler than average, and northern Pakistan was much cooler than average. Over the oceans, record warmth was observed across much of the northeastern and equatorial Pacific as well as parts of the equatorial and southern Indian Ocean, various regions of both the North and South Atlantic Ocean, and the Barents Sea to the northeast of Scandinavia. Only part of the North Atlantic between Greenland and the United Kingdom was much cooler than average. Image credit: National Centers for Environmental Information (NCEI) .

Deadliest weather disaster of June 2015: Pakistan's brutal heat wave
The deadliest weather-related disaster of June 2015 was an intense heat wave in Pakistan that killed approximately 1,242 people. If these numbers are correct, this year's heat wave would beat the 1991 heat wave (523 deaths) as Pakistan's deadliest in recorded history, and would rank as Earth's eighth deadliest heat wave, according to statistics from EM-DAT, the International Disaster Database. The terrible heat wave that hit India in May 2015 ranks as Earth's fifth deadliest heat wave:

The 10 Deadliest Heat Waves in World History
1) Europe, 2003: 71,310
2) Russia, 2010: 55,736
3) Europe, 2006: 3,418
4) India, 1998: 2,541
5) India, 2015: 2,500
6) U.S. and Canada, 1936: 1,693
7) U.S., 1980: 1,260
8) Pakistan, 2015: 1,242
9) India, 2003: 1,210
10) India, 2002: 1,030
10) Greece and Turkey, 1987: 1,030


Figure 3. Pakistanis receive ice outside a hospital during heatwave in Karachi on June 24, 2015. A state of emergency was declared in hospitals. Image credit : RIZWAN TABASSUM/AFP/Getty Images.

By the time summer is over, it is possible that a third heat wave may be added to this list: the on-going European heat wave. Excess mortality in France, the U.K., and Italy during the late June to early July portion of Europe's 2015's heat wave was over 1,200 people: 700 in France, at least 447 in the U.K., and 140 in Italy. Hundreds more probably died in surrounding countries, during some of the hottest temperatures ever recorded in Western Europe. Direct deaths, not excess mortality, are tabulated in the EM-DAT database for heat waves, though, and direct deaths can be a factor of eight less than deaths tabulated by considering excess mortality, as I discussed in more detail in my May 29 post on the heat wave in India. For example, the U.S. National Climatic Data Center (NCDC) and EM-DAT list the total direct deaths from the U.S. heat wave of 1980 at 1,260, but NCDC estimated that the combined direct and indirect deaths (i.e., excess mortality) due to heat stress was 10,000. Extreme heat capable of causing high excess mortality will affect portions of Southeast Europe late this week, when some of the highest temperatures on record will likely occur.



One billion-dollar weather disaster in June 2015: flooding in China
Thankfully, only one billion-dollar weather-related disaster hit the Earth last month, according to the June 2015 Catastrophe Report from insurance broker Aon Benfield: flooding in China that caused $2 billion in damage and killed sixteen people. With eight billion-dollar weather disasters occurring during the first half of 2015, Earth is on pace for its lowest number of such disasters since 2004, when sixteen occurred.


Disaster 1. Severe thunderstorms and torrential seasonal Mei-Yu rains rains inundated northern and southern sections of China on June 7 - 11, killing 16 people and doing at least $2 billion in damage. The provincial regions of Hunan, Guizhou, Hubei, and Gansu were the most severely impacted, with more than 20,000 homes damaged. In this picture, we see houses along a river submerged in floodwaters in Kaili in Qiandongnan, southwest China's Guizhou province on June 8, 2015. Image credit: STR/AFP/Getty Images.

Arctic sea ice falls to 3rd lowest June extent on record
Arctic sea ice extent during June 2015 was the 3rd lowest in the 36-year satellite record, and June snow cover was the 2nd lowest, according to the National Snow and Ice Data Center (NSIDC). A large area of high pressure that has set up shop north of Alaska is expected to persist for the remainder of July, and is likely to bring sunny skies and a warm flow of air into the Arctic that will lead to rapid ice loss in the coming weeks. Later this month, low pressure is expected to develop over Northeastern Eurasia, which could lead to the establishment of the Arctic Dipole pattern. This pattern of airflow develops in response to high pressure north of Alaska and low pressure over Northeastern Eurasia, and brings large amounts of warm air into the Arctic. The Arctic Dipole pattern occurred in all the summer months of 2007, and helped support the record 2007 summer reduction in sea ice extent (that record was beaten in 2012, a year that did not feature an Arctic Dipole pattern.)

Notable global heat and cold marks set for June 2015
Hottest temperature in the Northern Hemisphere: 51.7°C (125.1°F) at Death Valley, California, U.S., June 30
Coldest temperature in the Northern Hemisphere: -30.0°C (-22.0°F) at Summit, Greenland, June 1
Hottest temperature in the Southern Hemisphere: 38.1°C (100.6°F) at Bacabal, Brazil, June 15
Coldest temperature in the Southern Hemisphere: -81.3°C (-114.3°F) at Concordia, Antarctica, June 21

Major stations that set (not tied) new all-time heat or cold records in June 2015
Mercedes, Uruguay, min, -8.2°C, June 19
Durazno, Uruguay, min, -6.8°C, June 19
Pukaki Aerodrome, New Zealand, min, -19.8°C, June 23
Omarama, New Zealand, min, -21.0°C,  June 24
Cartagena, Colombia, max. 40.4°C,  June 24
Santa Marta, Colombia, max, 38.6°C, June 24
Arjona, Colombia, max, 40°C, June 24
Urumitia, Colombia, max, 42.0°C, June 27
Riohacha, Colombia, max, 40.0°C, June 29
Ashgabat, Turkmenistan, max., 47.2°C, June 29



New all-time national and territorial heat records set or tied in 2015
As of July 20, 2015, nine nations or territories have tied or set all-time records for their hottest temperature in recorded history thus far in 2015, and one (Israel) has set an all-time cold temperature record. For comparison, only two nations or territories set all-time heat records in 2014, and nine did in 2013. The most all-time national heat records held by any year is nineteen in 2010. Most nations do not maintain official databases of extreme temperature records, so the national temperature records reported here are in many cases not official. I use as my source for international weather records researcher Maximiliano Herrera, one of the world's top climatologists, who maintains a comprehensive list of extreme temperature records for every nation in the world on his website. If you reproduce this list of extremes, please cite Maximiliano Herrera as the primary source of the weather records. Wunderground's weather historian Christopher C. Burt maintains a database of these national heat and cold records for 235 nations and territories on wunderground.com's extremes page. Here are the all-time national or territorial heat and cold records set so far in 2015:

Germany set its national heat record on July 5, when the mercury soared to 40.3°C (104.5°F) at the Kitzingen station in Bavaria.
Vietnam tied its national heat record of 42.7°C (108.9°F) at Con Cuong on May 30.
Palau tied its national heat record of 34.4°C (94.0°F) at Koror Airport on May 14.
Venezuela set a new national heat record of 43.6°C (110.5°F) at Coro on April 29. Previous record: 42.0°C (107.6°F) at Machiques, Zulia State in February 1983.
Laos tied its national heat record of 42.0°C (107.6°F) at Thakhek on April 20.
Ghana set a new national heat record of 43.3°C (109.9°F) at Navrongo on April 10. This is the third time this year Ghana has tied or set a new all-time heat record. Previous records: 43.1°C (109.6°F), set the previous day, on April 9, and 43.0°C (109.4°F) on February 12.
Cocos Islands (Australian territory) tied their all-time heat record with 32.8°C (91.0°F) on April 8.
Equatorial Guinea set a new national heat record of 35.5°C (95.9°F) at Bata on March 17. Previous record: 35.3°C (95.5°F) at Malabo in February 1957.
Wallis and Futuna Territory (France) set a new territorial heat record with 35.5°C (95.9°F) on January 19 at Futuna Airport.

Israel set a new national cold record of -14.2°C (6.4°F) at Merom Golan on January 10.

Special Mentions:
Antarctica set a new heat record for its mainland of 17.5°C (63.5°F) at Esperanza Base on March 24. Previous record: 17.4°C (63.3°F) at Marambio Base, set the previous day. The World Meteorological Organization (WMO) has appointed a committee to study this event and determine if this represents an official record for the continent. Note that this is a record for mainland Antarctica, not a territorial or continental record. The all-time maximum record for the continent and territory of Antarctica is 19.8°C (67.6°F) on January 30, 1982, in Signy Island, South Orkney, an island group located about 450 miles northeast of the tip of the Antarctic Peninsula, the northernmost portion of mainland Antarctica. Geologically, the South Orkney are on the Antarctic plate, and politically, they are part of Antarctica. This record was improperly listed as a territorial record for Antarctica in last month's global summary.

Switzerland had its highest reliably measured temperature on record in Geneva on July 7, when the mercury hit 103.5°F (39.7°C). The only higher temperature ever measured in the country was a 106.7°F (41.5°C) reading on August 11, 2003 at Grono. As reported at the Swiss news site swissinfo.ch, this old record was achieved "using an old measurement technique of weather huts, which generally recorded temperatures a few degrees higher than modern instruments." Weather records researcher Maximiliano Herrera agrees that this year's 39.7°C reading in Geneva is the highest reliably measured temperature ever in Switzerland, though the August 11, 2003 temperature at Grono was probably warmer (near 40°C), after correcting for the known problems with the site.

Mr. Herrera originally listed Samoa as tying its national heat record with 36.5°C (97.7°F) on January 20 at Asau, but a subsequent review of the record revealed possible issues with the measurement equipment, so this record is dubious.

Kudos also to Mr. Herrera for supplying the data for the "Notable global heat and cold marks set for June 2015" and "Major stations that set (not tied) new all-time heat or cold records in June 2015" sections.

Jeff Masters

Climate Summaries

An Avalanche of New Models for Severe Weather Prediction

By: Bob Henson , 6:33 PM GMT on July 18, 2015

Not so long ago, forecasters at NOAA had just one high-resolution computer model to tell them where thunderstorms might erupt later in the day. Now there’s a whole cornucopia of models that project how storms will evolve, hour by hour, at fine scale. It’s a bit like having a large network of friends and family to consult when you’re making a big personal decision, instead of asking just one person for a single opinion that might steer you right or wrong. Processing all those viewpoints does take some time, though. Forecasters practiced using the array of new guidance during May and early June as part of the 2015 Spring Forecasting Experiment at the NOAA Hazardous Weather Testbed (HWT) in Norman (see my posts of May 5 and May 21).

Here’s one reason why predicting specific thunderstorms has remained such a challenge: traditional computer models simply aren’t fine-grained enough to explicitly portray individual showers and storms. Instead, they use convective parameterization, where a model takes favorable large-scale conditions as a cue to place showers and thunderstorms (convection) inside model grid cells that may be 10 or 20 miles wide. In contrast, “convection-allowing” models have grid cells that are 6 miles wide or less, which means a single large thunderstorm can emerge naturally across multiple grid cells instead of being artificially implanted by the model within each cell. This allows for a much more realistic portrayal of thunderstorms, with chunky blobs replaced by finely detailed filaments and bands (see Figure 1).


Figure 1. A little over a decade ago, operational forecasters might have used a model-generated forecast of 3-hour precipitation (left image, at 40-km resolution) to gain insight into thunderstorm development. Advances in computing power and modeling have allowed for higher resolution, explicit modeling of showers and thunderstorms, and more frequent time steps within the model. At right: simulated radar reflectivity from a numerical model with 4-km grid resolution and hourly forecast output. Image credit: Greg Carbin, NOAA/SPC.


This year's forecasting experiment called on 18 different model configurations, issued as often as once per hour, with resolutions mostly between 1 and 4 km. Most of these models were run multiple times in ensemble mode, with small variations in the starting-point data designed to mimic the uncertainty in initial observations. All this added up to a bounty of model-generated guidance.

The main job in the forecasting experiment was to issue short-term probabilities for the likelihood of tornadoes, severe hail, severe wind, and "significant" severe hail and wind (2" diameter hailstones or 65-knot winds). SPC already estimates such odds for the current day and the following two days, but this experiment tested more frequent probabilities, issued several times a day for periods spanning 1 to 4 hours. The new convection-allowing models provided ample raw material for this task. A variety of forecasters from the public, private, and academic sectors, including participants from across the United States as well as from Australia, Canada, England, and Hong Kong, convened at the testbed to evaluate the new guidance. “Part of what makes this experiment special is the diversity of the participants,” said Adam Clark (NOAA’s National Severe Storms Laboratory), one of the experiment’s lead planners. “It’s designed to mix folks together who typically don’t interact much as part of their regular jobs. The different perspectives make things fun, engaging, and interesting, and most importantly help foster new ideas and directions for future research.”


Figure 2. Ariel Cohen (left), from NOAA’s Storm Prediction Center, was among the participants in the 2015 Spring Forecast Experiment. Image credit: NOAA.

The task facing all this talent was to see how much value they could add to an automated short-term outlook derived from the ensembles. Of course, there’s not nearly enough time to scrutinize every model run. “We could look at individual ensemble members, but that gets a little cumbersome,” said Greg Carbin, warning coordination meteorologist at the NOAA Storm Prediction Center (SPC). “The more important questions are: What’s the model spread? Where do the models agree and disagree? What’s the character of storms within the ensembles? We issued forecasts based on all this information, then determined how well the forecasts verified.”


Figure 2. An experimental forecast, issued seven hours in advance, for the likelihood of any type of severe weather in a one-hour period (6:00 - 7:00 pm on May 19, 2015), based on probabilities generated by model ensembles. Colored circles show the percentage likelihood of at least one severe report within a 25-mile radius of any point. Colored icons show the actual severe weather that occurred: red = tornado, blue = severe wind, green = severe hail, and green triangle = “significant” severe hail, or at least 2” in diameter. Image credit: Greg Carbin, NOAA/SPC.


Carbin saw encouraging signs this spring in the ensembles’ ability to provide insight into storm mode, such as whether a day will feature potentially tornadic supercells. On May 19, forecasters used the model output to place parts of north Texas in a 2-to-5 percent tornado risk (the odds that a tornado would occur in the next hour within 25 miles of a given point). “This was a day with some uncertainty in tornado potential, especially south of the Red River,” said Carbin. “There was a robust signal in the ensemble data that short-track, but intense, rotating storms were likely. Our experimental forecast for total severe threat, based almost entirely on the ensemble information, verified very well.” (See Figure 2, above, for an example.)

James Correia (NOAA), SPC’s liaison to the testbed, also came away from this spring’s test with some cautious optimism. “As in years past with multiple ensembles, we always get multiple answers. I fully expected to get 60+ answers from 60+ members. I think we learned, again, that we need to go beyond probability to really hear what the ensembles are telling us.” For example, the high-resolution models often produce high values of updraft helicity, an indicator of storm rotation. But there aren’t enough fine-scale observations to confirm that storms are in fact producing that much helicity. In this sense, said Correia, “the ensembles are showing us what’s possible but not necessarily probable.”

Along with providing more confidence and lead time on the biggest, most dangerous outbreaks, ensembles may help get a handle on what some meteorologists call “mesoscale accidents”. This informal term refers to localized severe events that develop against the grain of mesoscale conditions that seem to be unfavorable for a significant event. “Mesoscale accidents are common in at least one or two members of an ensemble and can give forecasters a heads-up that something 'unexpected' has a small, but non-negligible, chance of occurring,” Correia said. “Knowing when and how to trust such a signal or classify it as noise is a challenge.” Getting familiar with the quirks of each model is a crucial step, but many models are so fresh on the scene that their idiosyncrasies aren't yet fully known.

MPAS: The future of multiday storm modeling?
Along with drawing on a new wealth of same-day model guidance, forecasters at the 2015 Spring Forecasting Experiment also test-drove output from a newly configured model that provides what was once thought to be either pointless or impossible: explicit modeling of showers and thunderstorms up to five days in advance.

The Model for Prediction across Scales (MPAS) is being developed by the National Center for Atmospheric Research (atmospheric component) and Los Alamos National Laboratory (ocean component). As its name implies, MPAS can operate on a variety of scales in both space and time. It uses an innovative grid: unlike the standard array of grid cells carved out by latitude and longitude, MPAS uses a hexagon-based grid called an unstructured Voronoi mesh (think of the pattern on a soccer ball). This eliminates problems like the narrowing of grid cells closer to the poles. The MPAS grid also allows for a near-seamless tightening of resolution where it’s most desired, such as over the deep tropics to depict hurricane development.


Figure 3. The honeycomb-like structure of MPAS (left) eliminates many of the challenges of model grids based on latitude and longitude. Each day in May 2015, MPAS was run with a grid-cell spacing of 3 km across most of North America (right; 3-km cells lie within the 4-km contour), with the resolution tapering off at greater distances from the continent. Forecasts were continued with a slightly different configuration for the PECAN field experiment in June and early July. Image credits: MPAS/Bill Skamarock, NCAR.


For the 2015 experiment, the atmospheric component of MPAS was run daily with a top resolution across a circle centered on North America of 3 kilometers (about 2 miles) between grid cells, surrounded by a concentric mesh with progressively lower resolution (see Figure 3). The result was a total of nearly 7 million grid cells covering the Northern Hemisphere. In the real world, each day’s convection shapes how the next day's will evolve, so the point of this MPAS test wasn’t to determine exactly where a particular thunderstorm would be in 120 hours. Instead, the idea was to employ MPAS’s skill at modeling larger-scale features in order to gauge what types of convection to expect over the next five days--squall lines, supercells, etc.--and where the heaviest activity might be focused.

Like any fine-scale model, MPAS includes much more realistic topography and land use than that found in a traditional, coarser model. Also, MPAS appears to capture the diurnal cycle of convection especially well, which is vital for multiday prediction. In a couple of cases, MPAS gave several days’ notice of where a large tornadic supercell was likely to emerge and track. (See Figure 4.)


Figure 4. Five days in advance, MPAS predicted that a band of strong updraft helicity (an index of potential storm rotation and severe weather) would emerge around Wichita Falls, TX, to near Tulsa, OK, on May 16, 2015 (left). A supercell ended up producing multiple tornadoes and very large hail close to that track (right). A second area of severe weather predicted for south-central Kansas ended up smaller and further to the northeast. Image credits: NCAR (left), NOAA/SPC (right).


According to Bill Skamarock, who leads the MPAS project at NCAR, this appears to be the first time that any model on Earth has carried out such high-resolution forecasting of showers and thunderstorms out to five days on a daily basis. “We have been pleasantly surprised as to how consistent, plausible, and even correct the longer-term forecasts from MPAS have been,” said Louis Wicker (NOAA National Severe Storms Laboratory). Wicker and Skamarock are collaborating with Joseph Klemp (NCAR), Steven Cavallo (University of Oklahoma), and Adam Clark (NOAA) on post-experiment analysis. One test is to see how the MPAS results compare to the predictions from a traditional large-scale model (GFS) with an embedded finer-scale model (WRF).

“What an opportunity to see what a global model can do at convection-allowing scales!” said NOAA’s James Correia. "We learned that convection is at the beck and call of the larger-scale features…no surprise there. But to see a model predict mesoscale convective systems a few days out and be 'close' is always very encouraging.”

According to Skamarock, much work remains to be done on how best to assimilate radar, satellite, and other data into the starting-point analyses of each MPAS run. Depending on the forecast goal, it’s an open question whether it makes more sense to put resources into an MPAS-like system versus a full set of shorter-range, convection-allowing models. But MPAS may be just the first of its kind. Skamarock pointed to the European Center for Medium-Range Weather Forecasts, where global model resolution has been steadily rising in line with Moore’s Law. The current high-resolution version of the flagship ECMWF model has a 16-km resolution covering the globe. If you extend the ECMWF progress from the 1980s to the year 2030, you end up with a global model that boasts 2.5-km resolution. According to Skamarock, "We are not that far from the point where we can run global models at convection-resolving scales."

Bob Henson


Mesoscale Forecasting

State of the Climate Report: Warm and Warmer (except for eastern North America)

By: Bob Henson , 8:51 PM GMT on July 17, 2015

Although the tropical Atlantic is heating up slightly with the appearance of a Cape Verde wave (see this morning’s tropical roundup post), we also have some toasty news on the national and global front. With our planet showing more and more symptoms of running a fever, the annual State of the Climate reports make for compelling lab results that confirm the diagnosis. This year’s State of the Climate report was released on Thursday as part of the July issue of the Bulletin of the American Meteorological Society. Like a mini-IPCC assessment, this year’s annual report--compiled by NOAA’s National Centers for Environmental Information--involved 413 authors and 17 editors from 58 countries who reviewed and synthesized a vast body of data on what’s happened to our Earth system in the past year, from greenhouse gas increases to sea level rise.

The 2014 State of the Climate report makes it plain that last year was a landmark in global warming. The record high in globally averaged temperature (a mark almost certain to be topped in 2015) got plenty of press, but other records were set as well:

• Carbon dioxide, methane, and nitrous oxide—three of the most important human-produced greenhouse gases—all reached their highest global concentrations since records have been kept.

• More than 20 nations reported their warmest year on record, as did the continent of Europe. The only large land area with below-average temperatures for the year (apart from western Siberia) was eastern North America.

• Sea surface temperatures and global sea level both reached record highs, continuing the trends of recent years.

• The extent of summertime Arctic sea ice remained well below its 1980s – 1990s average, though the ice loss in 2014 was less dramatic than in several years of the past decade. Meanwhile, Antarctic sea ice set new monthly extent records in each month from April to November, and the single largest extent on record was observed on September 20. It’s important to note that this wintertime ice growth around Antarctica has much less effect on climate than the summertime loss in the Arctic, largely because the Arctic loss occurs when more sunshine has a chance to be absorbed by open water.

More highlights from the report can be found in a NOAA news release and in the report itself.

Warmest June nights on record for contiguous U.S.
NOAA’s summary of June climate, also released on Thursday, revealed that last month was the second warmest June across the 48 contiguous states, beaten only by June 1933. And nighttime didn’t offer much relief.


Figure 2. Daily minimum temperatures averaged across the contiguous U.S. for June soared well above the previous record, set in 2010, and more than 1°F above any other year in records extending back to 1895. Image credit: NOAA/NCEI.


Figure 3. State-by-state rankings of temperature (top) and precipitation (bottom) for June 2015. Image credit: NOAA/NCEI.


Averaged across the nation, last month saw the warmest minimum temperatures of any June on record (see Figure 2). In Cheyenne, Wyoming, each night during the entire month saw a low temperature above the norm. June’s balmy nights were largely a result of the cloudiness and rich low-level moisture that prevailed over much of the country, keeping lows from dipping to their usual values. In the western U.S., scorching days accompanied the warm nights: more than 150 western cities broke all-time record highs for June. The states of California, Oregon, Washington, Idaho, and Utah all notched their warmest Junes on record (Figure 3). This Climate Central analysis will show you how much your own state’s summer nights have warmed in the last few decades.

June was also very damp across much of the country (see Figure 2). The Midwestern triad of Illinois, Indiana, and Ohio all experienced their wettest Junes on record; Illinois had its all-time second-wettest month (9.30”, behind only the 9.62” of September 1926). The downpours put a damper on agriculture, with many plantings delayed or compromised. Up to 5 percent of Indiana’s corn and soybean production was lost in June. “We went from a well above-normal crop to a very discouraging, below-normal crop," said Purdue Extension economist Chris Hurt at a briefing on June 26. As of July 13, about a quarter of Indiana corn and soybean crops were rated as poor or very poor.


Figure 4. Cornfields across Jay County in eastern Indiana were doused with heavy rain during the week of June 22. Image credit: Purdue University Agricultural Communication photo/Darrin Pack.

Northeast stays relatively cool
Missing out on the heat in June were Michigan and northern New England, where temperatures ran well below average for the month. As one might expect with plenty of clouds and rain, some states had an unusually compressed temperature range. In Pennsylvania, June’s average daily highs were the 37th coolest on the record, but the daily lows were the 7th warmest. Areas northeast of Pennsylvania are finding it especially tough to warm up this year, even with all the winter snow long gone. The first half of 2015 was among the top 20 coldest January-to-June periods on record for New York and all the New England states. This month, temperatures are running cooler than average across most of the country east of the Rockies, in keeping with the warm-west/cool-east pattern that’s been so persistent for the past year-plus. Meanwhile, the Pacific states continue to roast, including California, with this year to date warmer than all previous Jan-Jun periods in California, Oregon, Washington, and Nevada (see Figure 5).


Figure 5. Average temperatures across California for the period January through June 2015 topped the previous record for the first half of the calendar year, which had been set in 2014. Image credit: NOAA/NCEI.


Heat and drought across the Caribbean into South Florida
Along with the Pacific states, Florida is also cooking: the year to date is the fourth warmest on record for the Sunshine State. In particular, South Florida and the Caribbean have been extremely hot and dry. It was the driest June in 81 years of recordkeeping in Stuart, Florida, and in 110 years of records at Coloso, Puerto Rico. Strict water rationing is now in effect across eastern Puerto Rico: in one location, water is turned off for 48 hours and then on for 24 hours. According to the NWS office in San Juan, El Niño tends to bring the north Caribbean ample moisture during the normally dry months of winter and spring, but below-average rainfall from May through November.

I’ll have a special report this weekend on progress in severe weather modeling and prediction. Jeff Masters and I will both be back on board next week. Have a great start to your weekend!

Bob Henson


Climate Summaries Climate Change

A Cape Verde Wave in the Central Atlantic

By: Bob Henson , 3:41 PM GMT on July 17, 2015

The ferocious wind shear associated with El Niño has remained far enough west to give a tropical wave in the central Atlantic at least a slender chance of development. Invest 93L was located near 10.7°N and 38.4°W at 8:00 am EDT Friday, moving west at about 18 mph. Peak winds are close to 30 mph, with disorganized showers and thunderstorms evident on satellite imagery within a fairly large envelope of moisture. 93L has formed a bit early for systems in the Cape Verde region, which typically peaks in production during August and September. An upper-level anticyclone over 93L has resulted in low wind shear of 5 - 10 knots immediately over the circulation. Water temperatures are slightly below average across the deep tropical North Atlantic, but at around 26 - 27°C (79° - 81°F), they are just warm enough to support development along the track of 93L. Track models generally take 93L toward the northern Leeward Islands over the weekend before projecting a gradual recurvature. Statistical models bring AL93 up to minimal tropical storm strength, but the dynamical models most reliable for predicting tropical genesis are failing to develop AL93 substantially. Any embryonic system will soon ingest drier air toward the west, not to mention struggling against powerful wind shear that now tops 50 knots around the Leeward Islands. NHC gives the system 10 percent chance of tropical cyclone development in the next 48 hours and a 20 percent chance in the next five days. Given the currently favorable upper-level conditions and marginally warm water, I would give 93L a modest chance of becoming a minimal-strength named storm for a day or two.


Figure 1. An infrared satellite image from GOES-East of Invest 93L, taken at 1515 GMT (11:15 am EST) on Friday, July 17. Image credit: NOAA/NESDIS.


Pacific tropics calming down after a hectic few days
Tropical action in the hyperactive 2015 Pacific season looks set to take something of a breather over the next several days. Former Typhoon Nangka is now a weak tropical storm in the Sea of Japan after having swept over the Japanese islands of Shikoku and western Honshu. At least two deaths and 32 injuries have been reported. The nation’s rail lines and air traffic were seriously disrupted by Nangka, which came ashore as a minimal Category 1 typhoon around 11:00 am local time on Thursday. The remnants of Nangka are projected to arc eastward close to the north end of Japan’s Honshu island this weekend. To the southeast, Tropical Storm Halola is still fighting moderate to strong wind shear, but it should enter a more favorable environment over the next couple of days and gradually intensify to typhoon status. Halola could take a swipe at Japan next week before recurving.


Figure 2. Waves crash against the coast of Katsurahama on the island of Shikoku, western Japan, during the approach of Typhoon Nangka on July 16, 2015. Image credit: Kyodo News via AP.


Figure 3. A channel of upper-level moisture extended from Tropical Storm Dolores into Arizona and New Mexico on Friday morning. Image credit: Stu Ostro, The Weather Channel.

In the Northeast Pacific, Tropical Storm Dolores weakened below hurricane strength overnight, with colder waters and greater wind shear lying in wait on its northwestward path. The National Hurricane Center expects Dolores to weaken further over the next several days. Moisture associated with Dolores will continue to mix with monsoonal moisture moving toward the southwest U.S., bringing a threat of heavy showers and thunderstorms to Arizona on Friday and Saturday and a rare chance of July sprinkles over the Los Angeles area. Flash flood watches are in effect for much of Arizona and far southeast California. The remnant circulation of Dolores itself is predicted to stall early next week several hundred miles southwest of Los Angeles, but slugs of moisture from Dolores and the larger monsoonal pattern may get drawn as far north as central California, perhaps bringing an enhanced chance of thunderstorms there. Farther out to sea, weak Tropical Storm Enrique continue to spin harmlessly, while NHC is giving a tropical wave south of Mexico a 30 percent chance of development between Sunday and Wednesday.

I’ll have a post later today on the 2015 State of the Climate release, and a special report this weekend on progress in severe weather modeling and prediction. Jeff Masters and I will both be back on board next week.

Bob Henson

Hurricane

Typhoon Nangka Brings Torrential Rains to Japan

By: Bob Henson , 7:11 PM GMT on July 16, 2015

Extreme rainfall is dousing much of Japan in the wake of Typhoon Nangka, which made landfall at 11:07 pm Thursday local time (10:07 am EDT Thursday) near Muroto City, on the south coast of the island of Shikoku. Nangka came ashore as a minimal typhoon, with sustained winds of just 75 mph. However, its shield of rich moisture is colliding with Japan’s mountains and a preexisting stationary front, making floods and mudslides the main hazard to contend with. At least two deaths have been reported from Nangka thus far. Radar-estimated rainfall rates are topping 3”/hour in some locations, and a total of 521 millimeters (20.51”) had fallen by late Thursday at the village of Kamikitayama, south of Osaka. Up to three feet of rain could fall in some locations, according to the Japan Meteorological Agency. Nangka’s trek over the Japanese mountains will leave it in a weakened state as it arcs northeastward as a tropical storm. A second landfall—perhaps as a weak tropical storm or depression--is possible in northern Japan on Sunday morning local time, as Nangka recurves sharply toward the east. This path will keep much of Japan in the southeastern quadrant of the storm, with rains pushing into the northern islands of Honshu and Hokkaido, although the amounts should decrease as Nangka weakens. “Sediment disaster alerts” for potential mudslides are in effect along the south coast of Japan, including the Tokyo region. For more on Nangka, including precipitation outlooks by region, see the detailed weather.com post by Nick Wiltgen and Jon Erdman. At the bottom of this post is an animated loop of Nangka’s approach to Japan as captured by Japan’s Himiwari-8 satellite.

On the heels of Nangka is Tropical Storm Halola, now located about 170 miles west-southwest of Wake Island. Halola has weakened over the last 12 – 24 hours, thanks to moderate westerly shear (15 – 20 mph), but conditions will support restrengthening as Halola begins bending around a strong ridge to its north and wind shear decreases. There is model disagreement over Halola’s eventual track next week: the 0000 GMT Thursday run of the ECWMF model keeps Halola moving westward to Japan’s latitude, while the last several GFS runs have consistently recurved Halola before it has a chance to threaten Japan. There is plenty of time for track forecasts to evolve over the next few days.


Figure 1. Tropical Storm Enrique (left) and Hurricane Dolores (right), as of 1830 GMT (2:30 pm EDT) on Thursday, July 16. Image credit: NOAA.

Dolores to send moisture into southwest U.S.
Hurricane Dolores continues churning through the Northeast Pacific as a Category 3 storm. At 11:00 am EDT, the center of Dolores was located about 240 miles south-southwest of Cabo San Lucas, Mexico. Peak sustained winds were just above the Cat. 3 threshold, at 115 mph. Dolores is moving steadily northwest at about 7 mph. As it encounters colder waters and greater wind shear, Dolores should begin to weaken by Friday, if not sooner.

Dolores’s southern (weaker) eyewall passed over tiny Socorro Island, about 370 miles west of Mexico’s west coast, on Wednesday. According to weather.com, an automated weather station reported winds of 80 mph, with gusts to 114 mph. There were no immediate reports of damage from the island, which hosts a small naval station. Officers there could be excused for some nervousness during a major El Niño event. In September 1997, during the onset of the last El Niño that was comparable in strength to the current one, Category 5 Hurricane Linda became the Northeast Pacific’s strongest tropical cyclone on record. Linda passed just south of Socorro Island (the only land area affected by the storm), putting the island in its northern eyewall while packing winds of 150 knots (more than 170 mph) and a central pressure of 905 mph. Some damage to meteorological equipment was reported.

Models are now in general agreement that Dolores will continue moving west-northwest and weaken before it has a chance to recurve toward the Pacific coast (although I would not be surprised if the cyclone holds together longer than usual for such a system). A moisture plume now extending from Dolores across southern Baja California is expected to push into the southwest U.S. by this weekend. Precipitable water—the amount of moisture above a given spot—is projected to climb as high as 2” over the lower Colorado Valley by Friday night. NOAA’s Weather Prediction Center is calling for a slight chance of rainfall exceeding the local flash flood guidance values across central Arizona on Friday and Saturday.

Further west, Tropical Storm Enrique is doggedly clinging to life. Although little convection is evident, RapidScat data from the International Space Station continues to indicate tropical storm force winds, according to the National Hurricane Center. NHC projects Enrique to become a depression by Thursday night and a remnant low by Friday night.

Bob Henson



Video 1. Infrared imagery from Japan’s Himiwari-8 satellite shows the evolution of Typhoon Nangka as it makes landfall on Japan’s south coast. Image credit: NWS Ocean Prediction Center, via #GRPG.





Hurricane Dolores Hits Category 4 Strength

By: Bob Henson , 7:37 PM GMT on July 15, 2015

A pulse of rapid intensification late Tuesday and early Wednesday pushed Hurricane Dolores to borderline Category 4 intensity in the Northeast Pacific. Dolores’s peak winds surged from 85 mph at 3:00 pm EDT Tuesday to 130 mph at 3:00 am Wednesday, which translates to a leap from Category 1 to Category 4 status in just 12 hours. The rapid intensification leveled off this morning, with Dolores’s peak winds at 9:00 am EDT Wednesday holding at 130 mph. Dolores is now heading west-northwest at 6 mph on a track somewhat south of earlier predictions, which will keep the hurricane over warmer water for a longer period. Dolores has a well-defined eye surrounded by strong thunderstorms, although the coldest cloud tops around the eye have warmed somewhat over the last few hours. Dolores is currently over 29°C (84°F) water, and vertical wind shear is quite low (5 – 10 knots). Some additional strengthening is thus possible later today into Thursday, although Dolores may not reach Category 5 strength unless another rapid intensification cycle gets under way; such cycles remain difficult to predict. By Friday morning, the center of Dolores should be moving over SSTs cooler than 26°C, with a gradual weakening expected thereafter.


Figure 1. An image of Hurricane Dolores collected by the GOES-East satellite at 1445 GMT (10:45 am EDT) on Wednesday, July 15. Image credit: NOAA Environmental Visualization Laboratory.


Figure 2. Infrared image of Hurricane Dolores from GOES-East, collected at 1800 GMT (2:00 pm EDT) on Wednesday, July 15. Image credit: NOAA Environmental Visualization Laboratory.


Earliest trio of Category 4s on record for Northeast Pacific
Of the season’s first four named storms in the Northeast Pacific, only Carlos has fallen short of Category 4 strength. Dolores is the earliest occurrence of the season’s third Cat 4 system in this basin, beating out Hurricane Frank, which became a Cat 4 on July 17, 1992. Northeast Pacific records go back to 1949. (Thanks to Brian McNoldy, University of Miami/RSMAS, for this factoid). It’s also the first time that three of the first four named systems in the Northeast Pacific have all reached Category 4 intensity. Dolores’s record comes no major surprise, given the persistently favorable wind shear and very high sea-surface temperatures induced by a strong and still-intensifying El Niño event. As noted by Michael Ventrice (WSI), a very strong pulse of the Madden-Julian Oscillation has influenced the eastern tropical Pacific for the last few weeks, enhancing the upward motion that fuels hurricane development. This MJO event is now subsiding, but the presence of a strong El Niño continues to favor above-average activity in the Northeast Pacific.

Especially noteworthy with this El Niño is the northward extent of the unusually warm water off Baja California and the U.S. Pacific states, meeting up with the “blob” of warm water off the Canadian west coast that’s persisted for months (Figure 3). Even with these impressive anomalies, SSTs are still far too cool to support tropical development immediately off the California coast. However, the zone of SSTs greater than 26°C, which is considered the threshold for maintaining a tropical cyclone, now extends several hundred miles further north than usual. This lays the groundwork for any hurricane recurving toward the southwest U.S. to maintain its strength longer than usual, all else being equal. Of course, the particulars of any given storm (its strength, structure, upper-level support, etc.) will determine how much of an impact might result. Over the next few weeks, residents of southern California, Arizona, and New Mexico will need to keep tabs on any hurricanes whose track would take remnants in their direction, as the risk for heavy rain, flash flooding, and even tropical-storm force winds could be elevated by the presence of such warm SSTs upstream.



Figure 3. Sea-surface temperatures (top) and anomalies (bottom) over the northeast Pacific Ocean, averaged for the week ending on Monday, July 13. Image credit: National Hurricane Center.


A weakening Typhoon Nangka approaches Japan
Dry air has taken its toll on Typhoon Nangka as it continues moving north-northwest at about 15 mph toward Japan. As of 1500 GMT (11:00 am EDT) on Wednesday, Nangka was located about 430 miles south-southwest of Iwakuni, Japan, with sustained winds now down to around 90 mph. Although wind shear remains low along Nangka’s immediate path (10 knots or less) and SSTs are above 26°C (79°F), the typhoon has been ingesting dry air from the west, eroding the convection on the left side of the eye over the last few hours. A strong ridge to the northeast of Nangka should keep the hurricane on a north-northwest bearing until landfall on Saturday local time near the islands of Shikoku and western Honshu. This track would put some of Japan’s biggest cities on the more dangerous eastern side of Nangka, so the weakening trend is good news indeed. The Joint Typhoon Warning Center projects Nangka to be a Category 1 storm at landfall. As noted by The Weather Channel’s Jon Erdman, heavy rains, high winds, and some power outages can be expected in the cities of Kyoto, Kobe, and Osaka, as Nangka comes ashore and encounters Japan’s mountainous islands. Further to the north, Tokyo may experience tropical-storm-level impacts. The north-northwestward path of the storm is nearly perpendicular to the coastline, which would maximize any coastal flooding from Nangka (a major storm surge is not expected, though).

Halola still on course for Japan
With top sustained winds of 85 mph, Typhoon Halola continues its steady trek west-northwest trek through the Northwest Pacific at about 17 mph. As of 11:00 am EDT Wednesday, Halola was located about 175 miles southeast of Wake Island. It now appears Halola will remain weak enough and far enough south of Wake Island to avoid major impacts there. Wind shear has kept Halola from strengthening as much as expected, but the shear should relax in a couple of days, which will give Halola a chance to intensify atop very warm SSTs. Halola could approach Japan next week, although the long-range GFS and ECMWF models suggest the typhoon will recurve before that point.

Elsewhere in the Pacific and Atlantic
The leisurely demise of Tropical Storm Enrique continues in the remote Northeast Pacific, about 1500 miles west of Cabo San Lucas, Mexico. Enrique’s top winds are 45 mph, and slow weakening is expected, with dissipation in the next couple of days.

There are no systems of interest in the Atlantic basin, and prospects are minimal for any tropical development there for at least the next several days.

Bob Henson

Hurricane

Moisture-Packed Atmosphere Fueling a Week of Severe Weather

By: Bob Henson , 7:29 PM GMT on July 14, 2015

While the North Atlantic has yet to produce a hurricane this year (see our post from Tuesday morning for a full tropical update), extremely muggy air across a broad swath of the Midwest has millions of people wiping their brows, downing untold gallons of iced beverages, and keeping an eye out for severe storms. The upper-level flow is often too weak by midsummer to support supercells, but a band of stronger jet-stream winds now extends from the Midwest toward the Northeast, lending support to evening thunderstorms congealing overnight into mesoscale convective systems (MCSs). One such MCS maintained itself across a jaw-dropping distance: it developed over Minnesota on Sunday night and was still recognizable as a weak line of storms pushing offshore from the Carolinas early Tuesday morning. Four tornadoes were reported late Sunday as the system organized over western Minnesota, and NOAA’s Storm Prediction Center (SPC) logged several hundred reports of high wind over the MCS track on Sunday night and Monday. Was this event a derecho (a long-lived, thuderstorm-related wind storm)? Although its winds were widespread, most reports were in the 60 – 70 mph range, which resulted in mainly minor damage. Derechoes typically have at least a few reports of winds gusting to at least 75 mph, as implied in SPC’s website on derechoes. However, the Sunday-Monday event as a whole is consistent with the characteristics of derechoes put forth in a widely cited 2005 BAMS paper. (Thanks to Stu Ostro, The Weather Channel, for background on derecho definitions.)


Figure 1. The progress of the mesoscale convective complex from Minnesota across the Midwest from late Sunday into Monday afternoon. Image credit: Greg Carbin/NOAA Storm Prediction Center.


Severe storms regenerated behind the initial MCS on Monday evening, bringing more heavy rain and high wind to parts of Illinois, Indiana, Kentucky, Ohio, and West Virginia that were struck the night before. Tennis-ball sized hail (2.5” diameter) was reported by a CoCoRaHS observer at Burnham-Wegewisch, IL (in Cook County, just southeast of Chicago), and hail close to 4” in diameter was observed near Marseilles, IL. Far west of the main action on Monday evening, a lone supercell in central Kansas produced a photogenic tornado northwest of Hutchinson (see Figure 2). By Monday evening, close to 200,000 customers had lost power as a result of the day’s storms, and flash flooding led to at least one fatality and some 150 homes damaged or destroyed in Johnson County, KY. All told, Monday produced a total of at least 477 “filtered” severe reports in the SPC database. That's the largest number on a single date since November 17, 2013, according to The Weather Channel’s Nick Wiltgen.

Yet another large MCS was making its way across southeastern Ohio on Tuesday afternoon. SPC has placed a region from eastern Kentucky and Tennessee through the Carolinas in an enhanced risk of severe weather for Tuesday afternoon and evening, with a large slight risk area covering much of the east-central U.S. and a smaller slight-risk area in western Kansas. Several dispersed areas of slight risk are in the SPC’s Day 2 outlook for Wednesday.


Figure 2. The only tornado reported with Monday’s severe weather occurred in central Kansas. Image credit: wunderphotographer rrose1. A YouTube video features a brief but spectacular clip of this tornado obtained via drone.


What’s making this summer so humid?
From the Midwest to the Southeast, the summer thus far has been marked by frequently sultry conditions. Dew point readings in the vicinity of 75°F have been commonplace; for a temperature of 95°F, this would correspond to a relative humidity of 53% and a heat index of 108°F. Nashville recorded a dew point of 81°F on Tuesday afternoon, its highest reading since August 1995. The moist conditions have been fostered by consistent southerly flow of near-surface air from the Gulf of Mexico, and at times by upper-level moisture streaming into the U.S. from the tropical Pacific, where El Niño continues to intensify. Some of the moisture has arrived from below, as summer heat allows water vapor to escape from wet soils left behind by record-setting rains. Both Texas and Oklahoma saw their wettest month on record in May, and Indiana, Illinois, and Ohio all saw their wettest June on record.


Figure 3. Temperature and dewpoint trace for Monday, July 13, from WU personal weather station KIAWATER4, located in Waterloo, IA. Dewpoints touched 80°F around midday.


The extremely unstable air across the Midwest this week is also a partial byproduct of agriculture. The highest U.S. dewpoints in July are often found not along the Gulf Coast but in the heart of the Corn Belt, as the enormous leaves of fast-growing corn plants send vast amounts of moisture into the air through evapotranspiration. As covered in depth by WU weather historian Chris Burt, the highest reliably measured dew point in the United States—an excruciating 90°F—was reported at Appleton, Wisconsin, on July 13, 1999 (with an air temperature of 101°F!). As farmers learn how to pack plants ever more tightly into limited space, there’s more leaf area per acre, which means more moisture pulled into the plant from deep roots can be sent back into the atmosphere. A team led by David Changnon (Northern Illinois University) published an analysis in 2003 of dewpoint increases observed at Chicago’s Midway Airport from 1928 through 2002. The authors attribute the rise to two factors: “(1) the existence of average to above-average regional precipitation anomalies occurring in May and during the [20-day] period prior to the heat event, and (2) changes in agricultural practices that have led to enhanced evapotranspiration rates in the Midwest.” A 2010 analysis by the Iowa Environmental Mesonet found that the average moisture content in the summertime atmosphere [Jun-Aug) at Des Moines increased by about 13% from 1974 to 2008, as cited in a report by Eugene Takle (Iowa State University).

We’ll have a new post by Wednesday afternoon at the latest.

Bob Henson


Figure 10. An eerie set of mammatus clouds developed over Otter Tail County, Minnesota, as a long-lived storm complex began taking shape on Sunday. Image credit: wunderphotographer spacey84.


Figure 10.. Monday’s fast-moving storm complex pushes through Indianapolis, IN, near Kuntz Stadium. Image credit: wunderphotographer mkennindy.



Severe Weather

A Busy Northern Hemisphere: Five Named Systems in the Atlantic and Pacific

By: Bob Henson , 3:40 PM GMT on July 14, 2015

The “string of pearls” effect continued on Tuesday morning over the Northern Hemisphere, with an arc of tropical cyclones extending from south of Japan to east of the United States. According to Eric Blake (National Hurricane Center) and Phil Klotzbach (Colorado State University), this is the first year on record with so many named systems to date for the Atlantic, Central Pacific and Eastern Pacific combined: a total of 11 as of Monday, July 13, with the previous record of 10 occuring in 2012.


Figure 1. A multispectral (RGB) image of Tropical Storm Claudette, from 9:45 am EDT Tuesday, reveals the highly offset nature of the system. Image credit: NOAA/NESDIS.

A weakening Claudette spins into the northwest Atlantic
Tropical Storm Claudette, which formed quickly on Monday, is losing its tropical characteristics just about as quickly today. As of 8:00 am EDT Tuesday, Claudette was located about 250 miles south-southeast of Halifax, Nova Scotia, with peak sustained winds down to 40 mph, the minimal strength for tropical-storm status. High wind shear (more than 35 mph) is taking its toll on Claudette, with the storm’s paltry convection shoved well northeast of the circulation. Claudette has been riding the north edge of the Gulf Stream, where sea-surface temperatures (SSTs) have been 1 – 2°C above average. However, the system is quickly moving toward much cooler waters, and NHC is predicting that Claudette will become post-tropical by Tuesday night.

Across the deep Atlantic tropics and the Caribbean, conditions remain very unfavorable for tropical cyclone formation. SSTs are close to 1°C below average, and El Niño is contributing to high values of deep-layer wind shear (generally above 30 knots, with widespread pockets of greater than 50 knots). At least for the time being, whatever systems manage to claw their way into existence in the Atlantic are most likely to form in the subtropics, north of at least 20°N.


Figure 2. Wind shear is producing hostile conditions for tropical storm development over much of the Atlantic south of 30°N. Image credit: CIMSS/University of Wisconsin.

Nangka churns its way toward Japan
A potent Typhoon Nangka continues to organize as it moves north-northwest at about 8 mph across the Northwest Pacific toward Japan. As of 1200 GMT (8:00 am EDT) on Tuesday, Nangka was located about 800 miles south-southwest of Tokyo, with sustained winds of 105 mph. Wind shear is low along Nangka’s immediate path (5 -10 knots) and SSTs above 26°C (79°F) support strengthening. An unusual double-eyewall structure developed on Tuesday local time as part of an eyewall intensification process, which delayed further strengthening in spite of the otherwise favorable conditions. In addition, the ridge north of Nangka that’s keeping it from moving northeast is also feeding dry air into the system, tamping down on its intensification rate. This strengthening ridge should cause Nangka to bend toward the northwest as it approaches Japan. Though the ECMWF model keeps Nangka stronger than the GFS, both models consistently point toward a likely landfall in or near Japan’s large western islands of Kyushu and Shikoku, with impacts possibly extending east toward Honshu and the large cities of Kyoto, Kobe, and Osaka. As with the U.S. mid-Atlantic coast, most typhoons approaching Japan are moving toward the northeast. The currently projected motion toward the north-northwest, more perpendicular to Japan’s southern coastlines, would bolster Nangka’s destructive power, much as Hurricane Sandy’s unusual approach from the southeast in 2012 increased the damage it wreaked on New York and New Jersey.


Figure 3. Infrared imagery from the Himawari-8 satellite revealed an unusually well-defined double eyewall structure in Typhoon Nangka on Tuesday local time, with strong subsidence on either side of the inner and outer eyewalls and a resulting “moat” (grey semicircle) evident between the two. This image was collected at 1300 GMT on July 13. Image credit: SSEC/University of Wisconsin.

Elsewhere in the Pacific
In the Northwest Pacific, Typhoon Halola continues a gradual strengthening, with peak winds of close to 100 mph as of 1200 GMT Tuesday. Halola was located about 475 nautical miles east-southeast of Wake Island, and the Joint Typhoon Warning Center predicts that Halola will pass just south of Wake Island on Thursday local time as a strong Category 2 typhoon. Such a trajectory would place the island in the dangerous right eyewall of the typhoon. The last major hurricane to strike Wake Island was Ioke, which brought sustained winds estimated at 155 mph and a minimum central pressure measured at 934 mb on August 31, 2006.

In the Eastern Pacific, we have two active named storms, neither of which is expected to hit land: Tropical Storm Enrique and Hurricane Dolores. Now packing sustained winds of 85 mph, Dolores is predicted to hit a peak intensity of at least Category 3 strength by Thursday as it gradually moves away from the Mexican coastline. Meanwhile, Enrique will struggle to maintain itself as a minimal tropical storm over the next couple of days, with current sustained winds at 45 mph and gradual weakening predicted.

I’ll have an update later today on this week's multiday severe weather episode across the Midwest and mid-Atlantic.

Bob Henson

Hurricane

Chan-hom Makes Final Landfall in North Korea

By: Bob Henson and Jeff Masters , 3:33 PM GMT on July 13, 2015

After nicking the coast of China as a Category 2 typhoon on Saturday afternoon local time, Tropical Depression Chan-hom made landfall on Monday morning just south of Pyongyang, North Korea, according to the final advisory from the Joint Typhoon Warning Center (JTWC). The mountains of North Korea brought a rapid end to Chan-hom’s life as a tropical cyclone. Damage in China’s coastal province of Zhejiang has been estimated at more than $400 million US, with total losses nationwide estimated at close to $1 billion. One fatality and several injuries were reported in the city of Ningbo, near Chan-hom’s path, where the ceiling of a hotel room reportedly collapsed. Ningbo reported 217 mm (8.54”) of rain from the typhoon. Chan-hom also caused dozens of injuries in Japan, as it passed between the southern islands of Okinawa and Miyako-jima while at Category 4 intensity. On the plus side, the huge urban area of Shanghai and its 23 million residents dodged a bullet with Chan-hom, as a track just slightly further west could have brought a record storm surge into the city. More than 1 million people in China evacuated during the approach of Chan-hom, which was the strongest typhoon to pass within 100 miles of Shanghai in at least the past 35 years.


Figure 1. MODIS image of Typhoon Nangka, taken at 0140 GMT on Monday, June 13, from NASA’s Terra satellite. Image credit: NASA/GSFC.

Nangka intensifies in northwest Pacific
Japan may face a serious threat late this week from a revitalized Typhoon Nangka, which reached super typhoon status with 155 mph winds late last week before weakening to Category 1 strength over the weekend. Nangka is again looking impressive on satellite, with a very symmetric circulation and a double-eyewall structure now evident on water vapor imagery from the MTSAT satellite. This structure indicates an eyewall replacement cycle, after which Nangka will have ample time to strengthen further. Peak winds are estimated at 120 mph. Wind shear is low (5 – 10 knots) and there is plenty of oceanic heat content ahead of Nangka. Nangka is expected to follow a somewhat unorthodox path toward Japan: the typhoon has already recurved, now moving almost due northward at around 10 mph, but a ridge to its north is expected to strengthen and bend Nangka back toward the northwest. The latest JTWC forecast brings Nangka close to the threshold of super typhoon status by Wednesday night local time, with top sustained winds predicted to reach 125 knots (145 mph). The GFS and ECMWF models are both bullish on Nangka, keeping the cyclone close to its peak strength until just before landfall. This appears most likely to occur in or near Japan’s large western islands of Kyushu and Shikoku, with impacts possibly extending east toward Honshu and the large cities of Kyoto, Kobe, and Osaka, as noted by The Weather Channel’s Jon Erdman. As with the U.S. mid-Atlantic coast, most typhoons approaching Japan are moving toward the northeast. An approach from the southeast, more perpendicular to the coastline, would bolster Nangka’s destructive power, much as Hurricane Sandy’s unusual approach from the southeast in 2012 increased the damage it wreaked on New York and New Jersey.

Halola nears hurricane strength in Central Pacific
A record-smashing burst of activity continues over the Central Pacific as Tropical Storm Halola continues to gradually strengthen. Halola should reach hurricane strength by Monday night, making it one of the earliest central Pacific hurricanes on record in the NOAA database. The JWTC projects Halola to be a Category 3 storm by the end of the week, moving just south of Wake Island as a strong Category 2 hurricane. The last major hurricane to strike Wake Island was Ioke, which brought sustained winds estimated at 155 mph and a minimum central pressure measured at 934 mb on August 31, 2006. Elsewhere in the Central Pacific, Tropical Depression Iune is now dissipating over open water several hundred miles southwest of Hawaii. In the Eastern Pacific, we have two active named storms, neither of which is expected to hit land: Tropical Storm Enrique and Tropical Storm Dolores.


Figure 2. A conga line of tropical cyclones straddles the Pacific this morning on Weather Underground’s tropical cyclone home page.

Eric Blake (National Hurricane Center) and Phil Klotzbach (Colorado State University) called attention this weekend to some remarkable statistics. Since Thursday, we’ve seen three tropical storms develop in the central Pacific, all of which broke early-bird records in the period of reliable data that extends back to 1949:



Earliest tropical storm during hurricane season: Ela (July 9).
Previous record: Wali, July 17, 2014
2nd earliest tropical storm during hurricane season: Halola (July 11).
Previous record: Maka, Aug. 11, 2009
3rd earliest tropical storm during hurricane season: Iune (July 11).
Previous record: Moke, Sep. 4, 1984

Sea-surface temperatures over the central Pacific are substantially warmer than average, a result of the potent El Niño event that continues to intensify. This is allowing far more activity than usual over the basin, which does not usually host many hurricanes. The closest analog to this year’s record burst of central pacific activity is in 1982, just prior to the intense 1982-83 El Niño event. That year, the central Pacific saw a record total of four named storms for the season and a record three named storms in an 18-day period (that mark has been just broken with the three-day streak noted above). A powerful Madden-Julian Oscillation is moving across the central Pacific, likely adding to the very favorable conditions for tropical cyclone formation. According to NOAA’s weekly update (see PDF), the MJO is expected to remain in place or perhaps even retrogress over the next few days, which should help keep the central Pacific uncharacteristically active.

Update: Tropical Storm Claudette forms in northwest Atlantic
Disturbance 92L was upgraded to Tropical Storm Claudette by the National Hurricane Center at 1:00 pm EDT Monday, after ASCAT scatterometer data showed winds of tropical storm force within a well-defined circulation. Claudette's top sustained winds are now estimated at 45 knots (50 mph), with a center of circulation about 330 miles south-southeast of Nantucket, Massachusetts. Claudette is heading northeast at 15 mph, and its forward motion should increase over time. By Tuesday afternoon, wind shear will rise to a very high 25 - 30 knots and ocean temperatures will fall below 24°C, likely bringing Claudette below tropical storm strength no later than Wednesday morning.

Bob Henson and Jeff Masters

Hurricane

Category 2 Typhoon Chan-hom Makes Landfall 80 Miles From Shanghai, China

By: Jeff Masters , 4:21 PM GMT on July 11, 2015

Typhoon Chan-hom made landfall in the Chinese island city of Zhoushan, Zhejiang Province, about 80 miles south-southeast of Shanghai, at 4:40 p.m local time Saturday, reported the official Chinese news agency. At landfall, Chan-hom was a Category 2 storm with winds of 100 mph, making it the strongest typhoon to pass within 100 miles of Shanghai in at least the past 35 years. Since Shanghai was on the weak (left) side of the typhoon, the city did not see strong winds. The strongest winds at Shanghai Pudong Airport on Saturday were sustained at 40 mph, gusting to 56 mph. The city of Shipyu, located about 150 miles south of Shanghai, reported sustained winds of 74 mph at 2 am Saturday local time. Over a million people were evacuated in advance of Chan-hom, and I expect that considerable storm surge damage will be reported. Chan-hom has made its closest approach to Shanghai, and late on Saturday morning was headed north-northeast at 10 mph towards Korea. With cool waters of 21 - 22°C in front of it and high wind shear of 20 - 25 knots expected, Chan-hom should rapidly weaken, and make landfall on Monday morning local time in North Korea as a tropical storm with 50 - 60 mph winds.


Figure 1. People gather to see huge waves as Typhoon Chan-hom comes near Wenling, in east China's Zhejiang province on July 10, 2015. Image credit: STR/AFP/Getty Images.


Figure 2. Typhoon Chan-hom as seen by the MODIS instrument on NASA's Aqua satellite at approximately midnight EDT Friday, July 10, 2015 (04 UTC Saturday.) At the time, Chan-hom was a Category 2 storm with winds of 100 mph. Image credit: NASA Worldview.

Links
The new Japanese Himawari satellite has some spectacular imagery of Chan-hom (Sector 4 in Band 3=visible, and Sector 6 in Band 13=IR.)
Chan-hom satellite imagery from NOAA/NESDIS.
Weather radar from China.
Chan-hom weather radar loop from Brian McNoldy, Univ. of Miami, Rosenstiel School.


Figure 3. Surface winds in the tropical Pacific at 11 am EDT Saturday July 11, 2015, revealed the presence of five tropical cyclones, one ex-tropical storm (Ela near Hawaii), and one tropical depression about to form (97E.) Image credit: earth.nullschool.net.

Hyperactive Pacific; Quiet Atlantic
The exceptionally warm surface waters in the tropical Pacific, in combination with the activity of a strong phase of the Madden Julian Oscillation (MJO), has led to the formation of a remarkable simultaneous five tropical cyclones (tropical cyclones is a catch-all phrase to describe all tropical depressions, tropical storms, and hurricanes/typhoons.) On Saturday morning, the most dangerous of these appeared to be Category 2 Typhoon Nangka, which is expected to move northwards and affect Japan by Friday. The other storms besides Chan-hom (none of which are likely to affect any land areas through Wednesday): Tropical Depression 5-E, which formed 265 miles south of Acapulco, Mexico on Saturday morning, and is expected to move the west-northwest, parallel to the coast; Tropical Storm Halola, located in a remote portion of the Pacific about 555 mi Southwest of Johnston Island; and Tropical Depression Two-C, located about 515 miles south of Honolulu, Hawaii, and headed northwest, away from Hawaii. Another tropical disturbance (Invest 97E), located about 1200 miles southwest of the southern tip of Baja California, was close to tropical depression status, and will likely be a tropical depression on Sunday. 97E will head westwards towards Hawaii, but is not likely to survive the long trek there.

The Atlantic remains quiet, and is dominated by high wind shear and stable dry air. None of our reliable genesis models are showing tropical storm formation in the Atlantic over the next five days, though an area of low pressure expected to form off the coast of North Carolina on Sunday will bear watching for development as it heads northeastwards out to sea early in the week.

There will be a new post by Monday morning at the latest.

Jeff Masters

Hurricane

Weakening Typhoon Chan-hom Still a Major Storm Surge Threat for Shanghai

By: Jeff Masters , 4:08 PM GMT on July 10, 2015

Category 3 Typhoon Chan-hom is steadily weakening as it heads northwest at 10 mph towards China. The storm has slowed down and turned more to the north as it "feels" the steering influence of a trough of low pressure to its north, and the latest round of computer model forecasts have nudged the track of Chan-hom to the east, and it is possible that the center of Chan-hom will not make landfall in China. The 10 am EDT Friday forecast from the Joint Typhoon Warning Center (JTWC) and 8:50 am EDT Friday forecast from the Japan Meteorological Agency (JMA) predicted that Chan-hom would graze the coast of China and pass close to or just offshore from Shanghai on Saturday evening local time (Saturday morning in the U.S.) On this path, Shanghai, China's most populous city with 23 million people in the metro area, would be on the weak side of the storm, and receive only modest wind damage and heavy rain. However, Chan-hom would still drive a large storm surge into Shanghai, and this storm surge could be one of the highest ever observed, equivalent to a 1-in-200 year flood. Even though Chan-hom is weakening due to cooler waters and interaction with land, part of the weakening is due to an eyewall replacement cycle, where the inner eyewall collapses and is replaced by a larger-diameter outer eyewall. While this process weakens the peak winds near the center, it spreads the typhoon-strength winds over a larger area, increasing the size of the storm surge.


Figure 1. Typhoon Chan-hom as seen by the MODIS instrument on NASA's Aqua satellite at approximately 10 pm EDT Thursday, July 9, 2015 (02 UTC.) At the time, Chan-hom was a weakening Category 4 storm with winds of about 130 mph. Image credit: NASA Worldview.

Chan-hom's storm surge
Chan-hom is a very large typhoon with tropical-storm force winds that extended outwards up to 310 miles from the center, which will pile up a large storm surge throughout the Yellow Sea, from China to the Korean Peninsula. Since the Yellow Sea is shallow and enclosed on three sides, this water will be forced up onto land over Shanghai as Chan-hom makes its closest approach. In their 10 am EDT Friday forecast, JTWC predicted that Chan-hom would be a Category 1 storm with 80 mph winds (1-minute average) at 12 UTC Saturday, which would make it just 5 mph weaker than the strongest landfalling storm to hit within 200 miles of Shanghai in the past 35 years, Typhoon Winnie of August 1997. As I discussed in detail in my previous post, the storm surge from Winnie was only 5.5" (14 cm) below the top of the 19.2-foot (5.86 meter) Suzhou Creek floodgate that protects downtown Shanghai.

Low tide in Shanghai is at 07:07 UTC Saturday, and high tide is at 12:48 UTC Saturday, at a time when the center of Chan-hom is predicted to be 20 - 80 miles south of the city. Thus, the counter-clockwise circulation around the center will be pushing water into the city at high tide. Fortunately, this high tide is not a very high one--high tides late next week will be more than two feet higher than this. Though Chan-hom will be weakening as it approaches Shanghai during Saturday's high tide, the typhoon will be capable of pushing a record-size storm surge into the city during this 12:48 UTC Saturday high tide. I've read several studies explaining how storm surge propagation in the Yellow Sea is extremely complicated, so I am unsure just how the great the risk is from this storm without seeing data from a sophisticated real-time storm surge model.



Figure 2. Predicted swath of winds (top) and precipitation (bottom) for Typhoon Chan-hom, made by the 06 UTC (2 am EDT) Friday, July 10 run of the HWRF model. The model predicted that Chan-hom would graze the coast near Shanghai as a strong tropical storm, bringing rainfall amounts of 4 - 8" near the coast (dark yellow colors), and 2 - 4" farther inland. The typhoon was also forecast to bring large areas of 4 - 8" of rain to North Korea, which is suffering one of its worst droughts on record. Image credit: NOAA.

Chan-hom's rains and winds
With the latest round of model runs showing the Chan-hom will not penetrate far inland, wind damage is looking to be less of a concern, since most of the land areas affected will be on the weaker (left) side of the eye. The prospect for heavy damage due to flooding from torrential rains is also looking lower, as Chan-hom may only dump heavy rains of 4 - 8" along the immediate coast (Figure 2.) As Chan-hom turns to the north, it is expected to track over North Korea, which could use the rain--they have reportedly been suffering through their worst drought in 100 years, though rains in June have likely eased the drought.


Figure 3. Tracks of all typhoons with at least 75 mph winds (10-minute average winds as rated by the Japan Meteorological Agency) to pass within a 230-mile diameter circle (light shaded region) near Shanghai, China. Typhoon Winnie is labeled in white. Ten-minute average winds of 75 mph are roughly equivalent to 85 mph winds for the one-minute averaging time winds used for the U.S. Saffir-Simpson scale. All of the storms in this plot had sustained 10-minute average winds of 75 mph or less when they made landfall. Image credit: NOAA.

Strong typhoons hitting near Shanghai: a rare occurrence
China gets hit by about nine tropical cyclones (tropical depression, tropical storms, or typhoons) each year (Chen, 2000), but these strikes occur primarily in the southern portion of the country. The Jiangsu Province where Shanghai lies received only seven landfalls in the 50-year period 1947 - 1999, so the region does not have a lot of typhoon experience. Since 1979, no typhoon with winds in excess of about 85 mph (75 mph winds using a 10-minute averaging time) has made landfall within about 200 miles of Shanghai (Figure 2.) Historically, the strongest typhoon to affect the city in the past century may be Typhoon Gloria of July 24 - 25, 1949, whose storm surge overwhelmed the city's flood walls and left much of Shanghai a flooded ruin, with over 250,000 people homeless (See David Longshore's Encyclopedia of Hurricanes, Typhoons, and Cyclones). Note that Typhoon Wanda of 1956 was at Category 3 strength when it hit the coast of China about 100 miles south of Shanghai. Wanda killed 2000 people in China. China has had four typhoons that have killed at least 37,000 people each--most recently in 1975, when torrential rains from what had been Super Typhoon Nina caused the Banqiao Dam to fail, killing 90,000 - 230,000 people.

Links
The new Japanese Himawari satellite has some spectacular imagery of Chan-hom (Sector 4 in Band 3=visible, and Sector 6 in Band 13=IR.)

Chan-hom satellite imagery from NOAA/NESDIS.

Weather radar from China.

Shanghai webcams (thanks to wunderground member fuzed for posting this link.)

Wunderblogger Steve Gregory has the latest on the status of El Niño in his latest post.

Jeff Masters

Hurricane

Category 3 Chan-hom: One of Shanghai's Strongest Typhoons on Record?

By: Jeff Masters , 12:29 AM GMT on July 10, 2015

Category 3 Typhoon Chan-hom is headed northwest at 14 mph towards China, and appears poised to make landfall as one of the strongest typhoons on record for a portion of the country unused to strong typhoons. Of particular concern is Chan-hom's storm surge, which has the potential to bring the highest water levels ever observed into Shanghai, China's most populous city, with 23 million people in the metro area. In their 5:45 am EDT Friday advisory, the Japan Meteorological Agency (JMA) put Chan-hom's central pressure at 935 mb; in their 5 am EDT Friday advisory, the Joint Typhoon Warning Center (JTWC) rated Chan-hom's top winds at 125 mph. A storm of this magnitude is sure to pile up a large storm surge, particularly since Chan-hom is a very large typhoon with tropical-storm force winds that extended outwards up to 310 miles from the center. This storm surge will pile up throughout the Yellow Sea, from China to the Korean Peninsula. Since the Yellow Sea is shallow and enclosed on three sides, the potential exists for some of the highest water levels ever recorded along portions of the coast south of Shanghai, to the right of where the center makes landfall. Chan-hom is likely to weaken significantly as the storm approaches landfall, due to cooler waters, higher wind shear, and interaction with land. JTWC and JMA were forecasting on Friday morning (U.S. EDT) that Chan-hom would make landfall between 06 - 09 UTC Saturday (2 am - 4 am EDT, or 3 - 5 pm JST.) In their 5:45 am EDT Friday forecast, JMA predicted that Chan-hom would have a 950 mb pressure and sustained 10-minute average winds of 90 mph at landfall. In their 5 am EDT Friday forecast, JTWC predicted that Chan-hom would be a Category 1 storm with 90 mph winds (1-minute average) at landfall. Even at this lowered intensity, Chan-hom would still be the strongest landfalling storm to hit within 200 miles of Shanghai in at least 35 years. On Friday morning, the typhoon was undergoing an eyewall replacement cycle, where the inner eyewall collapses and is replaced by a larger-diameter outer eyewall. While this process weakens the peak winds near the center, it spreads the typhoon-strength winds over a larger area, increasing the size of the storm surge.


Figure 1. Typhoon Chan-hom as seen by radar on Okinawa at 7:45 pm EDT Thursday (08:45 JST Friday, July 10), 2015. At the time, Chan-hom was a Category 4 storm with 130 mph winds. Image credit: JMA.

Strong typhoons hitting near Shanghai: a rare occurrence
China gets hit by about nine tropical cyclones (tropical depression, tropical storms, or typhoons) each year (Chen, 2000), but these strikes occur primarily in the southern portion of the country. The Jiangsu Province where Shanghai lies received only seven landfalls in the 50-year period 1947 - 1999, so the region does not have a lot of typhoon experience. Since 1979, no typhoon with winds in excess of about 85 mph (75 mph winds using a 10-minute averaging time) has made landfall within about 200 miles of Shanghai (Figure 2.) Historically, the strongest typhoon to affect the city in the past century may be Typhoon Gloria of July 24 - 25, 1949, whose storm surge overwhelmed the city's flood walls and left much of Shanghai a flooded ruin, with over 250,000 people homeless (See David Longshore's Encyclopedia of Hurricanes, Typhoons, and Cyclones). Note that Typhoon Wanda of 1956 was at Category 3 strength when it hit the coast of China near where Chan-hom is predicted to strike. Wanda killed 2000 people in China. China has had four typhoons that have killed at least 37,000 people each--most recently in 1975, when torrential rains from what had been Super Typhoon Nina caused the Banqiao Dam to fail, killing 90,000 - 230,000 people.


Figure 2. Tracks of all typhoons with at least 75 mph winds (10-minute average winds as rated by the Japan Meteorological Agency) to pass within a 230-mile diameter circle (light shaded region) near Shanghai, China. Typhoon Winnie is labeled in white. Ten-minute average winds of 75 mph are roughly equivalent to 85 mph winds for the one-minute averaging time winds used for the U.S. Saffir-Simpson scale. All of the storms in this plot had sustained 10-minute average winds of 75 mph or less when they made landfall. Image credit: NOAA.

A historical analogue: Typhoon Winnie of 1997
The largest storm surge observed at the coast in Shanghai since 1921 was 5.9 feet (1.81 meters) during Typhoon Emma of 1956. However, Emma's maximum surge did not occur at high tide (the difference between low tide and high tide in Shanghai is about 7.2 feet or 2.2 meters, so it makes a big difference when the maximum storm surge arrives, relative to high tide.) The highest storm tide (water level) in Shanghai came during Typhoon Winnie of August 1997. Although Winnie was only a Category 1 storm with 85 mph winds when it made landfall, and the storm struck relatively far from Shanghai, about 180 miles to the south, the storm surge from Winnie was only 5.5" (14 cm) below the top of the 19.2-foot (5.86 meter) Suzhou Creek floodgate that protects downtown Shanghai on the Huangpu River, which flows through the center of town. This floodwall was rated to protect against a 1-in-200 year flood, and was overtopped by about one foot (30 cm) along a 8.5 mile (13.7 km) section inland from the downtown area, flooding over 400 homes (source: Flood probability analysis of the Huangpu barrier in Shanghai, M.S. thesis by Qian Ke.) According to EM-DAT, Winnie killed 240 people and did $2.7 billion (1997 dollars) in damage to China. The floodwall protecting downtown Shanghai has been raised by 3.4 feet (1.05 meters) since then, giving the city protection against a 1-in-1000 year flood. Thus, it will take a much stronger storm than Winnie to flood the city. Chan-hom is predicted to be a much stronger storm at landfall than Winnie was, and is forecast to hit closer to Shanghai. The newly raised floodwalls of Shanghai may see their highest water levels in history when Chan-hom makes landfall, depending upon whether or not the peak storm surge occurs near high tide.

Low tide in Shanghai is at 07:07 UTC Saturday, about the time that Chan-hom is forecast to make landfall. That is potentially good news for the coastal region near the landfall point. However, high tide is at 12:48 UTC Saturday, at a time when the center of Chan-hom is predicted to be over land but just south of the city, so the counter-clockwise circulation around the center will be pushing water into the city. Fortunately, this high tide is not a very high one--high tides late next week will be more than two feet higher than this. Though Chan-hom will be weakening as it approaches Shanghai during Saturday's high tide, JTWC is predicting the storm will still be at Category 1 strength. If Chan-hom follows the JTWC track and intensity forecast, it will be capable of pushing a record-size storm surge into the city during this 12:48 UTC Saturday high tide, potentially challenging the 1-in-200 year water levels observed during Typhoon Winnie of 1997. I've read several studies explaining how storm surge propagation in the Yellow Sea is extremely complicated, so I am unsure just how the great the risk is from this storm without seeing data from a sophisticated real-time storm surge model, though.


Figure 3. Typhoon Winnie as it passed just south of Okinawa on August 17, 1997, at 11:36 UTC. Note that the small inner eyewall of the typhoon had become completely surrounded by a concentric 230-mile diameter eyewall. Image credit: Navy Research Lab, Monterey.

Why was Typhoon Winnie's storm surge so high?
If Typhoon Winnie was only a Category 1 storm, and its center crossed the coast relatively far away from Shanghai (180 miles), why did it bring such a large storm surge to the city? Well, Winnie was a freak. According to the Joint Typhoon Warning Center (JTWC) 1997 Annual Tropical Cyclone Report, as Winnie moved toward Okinawa on August 16, 1997, a large outer rain band began to encircle the inner eyewall. By the time the typhoon passed over Okinawa, the rain band had become a complete, 230 mile (370 km) diameter concentric outer eyewall, possibly the largest ever observed (tied with 1960's Typhoon Carmen, which also had a 230-mile diameter outer eyewall.) Whenever an intense tropical cyclone forms concentric eyewalls, the peak winds of the inner eyewall fall significantly, but the hurricane-force winds of the storm spread out over a wider area that encompasses the outer eyewall, increasing the size of the storm surge. Winnie's strong winds were able to pile up a massive mound of water into the relatively shallow waters of the Yellow Sea off the coast of Shanghai. Since the Yellow Sea is enclosed on three sides, with the Korean Peninsula blocking the flow of water to the northeast, this extra water had nowhere to go except up onto land when the center of Winnie pushed inland.


Figure 4. The 22.6-foot (6.9 meter) Suzhou Creek floodgate that protects downtown Shanghai from storm surges coming up the Huangpu River, which flows through the center of town. This floodwall is rated to protect against a 1-in-1000 year flood. Image credit: Dorothy Tang.

Sea level rise and Shanghai
Sea levels have been rising globally by about 3.3 mm per year over the past few decades. According to a 2015 study, Sea level change and city safety—The Shanghai as an example, sea levels have been rising a bit slower in Shanghai--about 2 mm/year, but the land has been sinking at more than double that rate, due to compaction of soil and groundwater pumping to support intensive urban development. As a result, the relative rise of sea level in the city has been about 7 mm/year, which is a huge concern for a city whose average ground level is already below the average high tide level. The authors predicted that over the next twenty years, Shanghai will see the relative sea level rise by 10 - 16 cm (3.9 - 6.3 inches), which will make storm surges from typhoons like Chan-hom more dangerous. With sea level rise likely to accelerate due to increased melting of the Greenland and Antarctic ice sheets, Shanghai will be increasingly hard-pressed to keep the ocean at bay this century using ever-higher flood walls. A new approach, called the Yangtze River Delta Project (YDRP), offers a more innovative way to manage Shanghai's increasing flood risk due to the steadily rising seas. The YRDP research group develops "soft" infrastructural strategies (as opposed to "hard" floodwalls) to respond to sea level rise and storm surge. For example, the team is studying the flood control techniques devised by Yu the Great (2200-2100 BCE, founder of China's Xia Dynasty), who created a system of irrigation canals that channeled river floodwaters into agricultural fields, building low earthen dikes to guide the water’s flow. Other studies undertaken by the research group include projects for the transformation of New York and New Jersey’s Upper Harbor and a land-building sediment diversion proposal for the Mississippi River Delta.

The new Japanese Himawari satellite has some spectacular imagery of Chan-hom (Sector 4 in Band 3=visible, and Sector 6 in Band 13=IR.)

Jeff Masters

Hurricane Sea level rise

Tropical Storm Ela Little Threat to Hawaii; Category 3 Chan-hom Heads for China

By: JeffMasters, 4:22 PM GMT on July 09, 2015

Tropical Storm Ela, the first named storm of the 2015 Central Pacific hurricane season, got its name Wednesday night when an Air Force hurricane hunter aircraft found a small area of 40 mph winds to the northeast of the center. Named storms are rare in the Central Pacific (west of 140°W longitude) this early in the season; the last time the Central Pacific saw a named storm this early in the year was on June 21, 2001 (Tropical Storm Barbara). Ela's formation so early in the year was aided by ocean temperatures about 2°F above average. Ela is headed northwest at 15 mph on a path that should keep the center of the storm at least 200 miles to the northeast of the islands at the time of closest approach on Saturday. Satellite loops continue to show an unimpressive storm, with just one spot of heavy thunderstorms located to the northeast of the center of circulation. High wind shear of about 20 - 25 knots, due to strong upper-level winds out of the south, was keeping any heavy thunderstorms from developing on the southwest side of the storm, closest to the Hawaiian Islands. Ocean temperatures are marginal, near 25.5°C (78°F). The 8 am EDT Thursday run of the SHIPS model predicted that wind shear would slowly rise over the next few days, and ocean temperatures would stay cool, near 25.5 - 26°C. These conditions should cause weakening of Ela. Our two most reliable track models, the GFS and European models, show Ela dissipating by Saturday. I doubt Ela will bring much rain to the islands, and high surf will the main impact on Hawaii.


Figure 1. Typhoon Chan-hom as seen by the MODIS instrument on NASA'a Aqua satellite at 10:05 pm EDT Wednesday, July 8, 2015. At time time, Chan-hom was a Category 2 storm with 105 mph winds. Image credit: NASA.

Dangerous Category 3 Typhoon Chan-hom headed for China
Intensifying Category 3 Typhoon Chan-hom is headed northwestwards at 15 mph towards China, and promises to be a dangerous and very expensive typhoon for a portion of the country unused to strong typhoons. Thursday morning satellite images showed that Chan-hom was a huge storm with a prominent 15-mile diameter eye that was contracting as the storm continued its slow intensification process. Some dry air to the northwest of the storm was keeping the intensification rate relatively slow, as was the lack of a strong upper-level outflow channel. The typhoon is on a track to pass between Japan's Miyakojima and Okinawa islands today. Since Chan-hom's wind field is exceptionally large, with tropical storm-force winds that go out 230 miles from the center, these islands will receive an extended pummeling. As of noon EDT Thursday (midnight local time), Kadena Air Base on Okinawa had already seen sustained tropical storm-force winds of at least 39 mph for eight hours, with sustained peak winds of 58 mph, gusting to 78 mph, at 11:57 pm Thursday local time. With the center of Chan-hom expected to make its closest approach to the island near 2 pm EDT (3 am Friday local time), Okinawa can expect to see at least an 18-hour period of sustained tropical storm-force winds.

Wind shear will be light to moderate and ocean heat content will be high until just after the storm passes these islands, so intensification into a Category 4 storm by Thursday night (U.S. EDT) is likely. On Friday, as Chan-hom approaches China, ocean heat content will fall and wind shear is expected to rise, which should cause weakening. Even so, Chan-hom's very large wind field will be capable of bringing an usually high storm surge to the coast; I expect the storm surge will be one of the five highest in the past century for the coastal region just to the north of where the center makes landfall on Friday evening (U.S. EDT.) However, the exact landfall location in China is quite uncertain, as a strong trough of low pressure is expected to turn the typhoon northwards as the center nears the coast on Friday. As Chan-hom curves to the north a weakens due to interaction with land, the storm is expected to pass very close to Shanghai as a very large and very wet tropical storm. Significant wind damage, coastal flooding, and flooding due to heavy rain is possible in Shanghai, which is China's most populous city (14 million people.)

Dan Lindsey of NOAA/CIRA has put together two impressive loops of Chan-hom at sunset on July 9, 2015, as seen using the high-resolution 0.5 km imagery from the Himawari Satellite: zoomed out and zoomed in.


Figure 2. Triple trouble in the Pacific. From left to right: Tropical Storm Linfa (70 mph winds) just after landfall in South China; Category 2 Typhoon Chan-Hom (105 mph winds) approaching Okinawa; and Category 4 Typhoon Nangka (145 mph winds) passing through the Northern Mariana Islands. Six hours before this image was taken, Linfa was also a typhoon, making it the first time in twenty years the Northwest Pacific had seen three simultaneous typhoons (thanks go to TWC's Michael Lowry for this stat.) Image was taken by the JMA MTSAT at 0530Z on July 9, 2015. Image credit: NOAA Viz Lab.

Elsewhere in the tropics
Typhoon Linfa hit South China's Guangdong province on Thursday at 12:15 local time Thursday as a Category 1 typhoon with 75 mph winds. Linfa has since weakened to a tropical storm, and is expected to track west-southwest towards Hong Kong. Category 4 Super Typhoon Nangka (155 mph winds) is just below Category 5 strength, but is fortunately affecting only a sparsely populated portion of the Northern Mariana Islands. Nagka is on a track that could bring it near Japan on Friday, July 17, but it is too early to assess the risk this storm might pose to Japan. The Atlantic remains quiet, and is dominated by high wind shear and stable dry air. None of our reliable genesis models are showing tropical storm formation in the Atlantic over the next five days.


Video 1. Storm chaser James Reynolds is on Japan's ‪Miyakojima Island, and shot this impressive video (used here with permission) of the massive waves of Typhoon Chan-hom hitting the island. He is posting updates on his Twitter feed.

Jeff Masters

Hurricane

TD 4-E Little Threat to Hawaii; Switzerland has its 2nd Warmest Temperature on Record

By: Jeff Masters , 4:05 PM GMT on July 08, 2015

Tropical Depression Four-E spun into life Tuesday night in the waters about 1000 miles east-southeast of Hawaii, and is headed northwest at 16 mph on a path that should keep the center of the storm about 200 miles to the northeast of the islands at the time of closest approach on Saturday. Satellite loops show an unimpressive storm, with heavy thunderstorm activity not is not particularly intense or well-organized. Wind shear is moderately high, near 20 knots, and ocean temperatures are marginal, near 26°C. The 8 am EDT Wednesday run of the SHIPS model predicted that wind shear would steadily rise over the next few days, and ocean temperatures would stay cool, near 26°C. These conditions should prevent much intensification of TD 4-E. Given its current state of organization, it is questionable whether or not this system can become a tropical storm. One of our two most reliable track models, the GFS model, shows TD 4-E dissipating by Friday before the storm reaches Hawaii, and I give a 70% chance that TD 4-E will be dead by Saturday.


Figure 1. Typhoon Chan-hom as seen by the MODIS instrument on NASA'a Aqua satellite at 8:25 pm EDT Tuesday, July 7, 2015. At time time, Chan-hom was a Category 1 storm with 90 mph winds. Image credit: NASA.

Typhoon Chan-hom a dangerous storm for China
Category 2 Typhoon Chan-hom is headed west-northwest at 12 mph towards China, and promises to be a dangerous and very expensive typhoon for a portion of the country unused to strong typhoons. Chan-hom will be steered by a strong ridge of high pressure towards the west-northwest through Thursday night (U.S. EDT), when the typhoon will pass between Japan's Miyakojima and Okinawa islands. Wind shear will be moderate and ocean heat content will be high until just after the storm passes these islands, so intensification into a Category 4 storm by Thursday night is expected. On Friday, as Chan-hom approaches China, ocean heat content will fall and wind shear is expected to rise, which should cause weakening. Chan-hom is likely to make landfall in Mainland China north of Taiwan on Saturday morning (U.S. EDT.) However, the landfall location in China is quite uncertain, as a strong trough of low pressure is expected to turn the typhoon northwards as the center nears the coast on Friday. As Chan-hom curves to the north and weakens, due to interaction with land, the storm is expected to pass very close to Shanghai as a very large and very wet tropical storm. Significant coastal flooding and flooding due to heavy rain is possible in Shanghai, which is China's most populous city (14 million people.)

Elsewhere in the tropics
Category 4 Typhoon Nangka is expected to pass through a sparsely populated portion of the Northern Mariana Islands on Thursday. Nangka could threaten Japan 8 - 10 days from now as a weaker storm. Tropical Storm Linfa hit the Philippines' northern island of Luzon over the weekend, and is expected to make landfall in China on Thursday as a tropical storm. The Atlantic remains quiet, and is dominated by high wind shear and stable dry air. None of our reliable genesis models are showing tropical storm formation in the Atlantic over the next five days.


Figure 2. People re-fill bottles of water at a fountain in front of Rome's Pantheon, Wednesday, July 8, 2015, during Europe's record heat wave. (AP Photo/Andrew Medichini)

Switzerland has its highest reliably measured temperature on record
It was another day for the record books on Tuesday as Europe's intense heat wave broke scores of all-time heat records at cities in Spain, Switzerland, France, and Italy. Geneva, Switzerland hit 103.5°F (39.7°C), smashing its old historical record of 102.0°F (38.9°C) set almost a century ago, in July 1921. The only higher temperature ever measured in the country was a 106.7°F (41.5°C) reading on August 11, 2003 at Grono. As reported at the Swiss news site swissinfo.ch, this was recorded "using an old measurement technique of weather huts, which generally recorded temperatures a few degrees higher than modern instruments." Weather records researcher Maximiliano Herrera agrees that yesterday's 39.7°C reading in Geneva is the highest reliably measured temperature ever in Switzerland, though the August 11, 2003 temperature at Grono was probably warmer (near 40°C), after correcting for the known problems with the site. Although Tuesday does not hold the official record for hottest day in Swiss history, it was their hottest July day, and they have joined five other nations that have set all-time July national heat records this month: Germany, the Netherlands, the U.K., Thailand, and Colombia. The European heat wave continues, with more all-time heat records at risk across Southeast Europe on Wednesday, and possibly on Thursday. The heat wave will finally die down by Friday, ending a remarkable 9-day span.

Jeff Masters

Hurricane Heat

Typhoon Chan-hom Heads for China; Invest 96E a Threat to Hawaii

By: Jeff Masters , 4:22 PM GMT on July 07, 2015

Category 1 Typhoon Chan-hom is headed westwards towards China, where it is expected to make landfall on Friday or Saturday. Chan-hom passed just north of Guam on Sunday, bringing sustained winds of 46 mph, gusting to 62 mph, to Andersen Air Base; a 3-day rainfall total of 13.83" was recorded. Satellite images show that Chan-hom is a large storm with a prominent eye, and it is expected to take advantage of moderate wind shear and very warm ocean waters and intensify into a Category 4 storm by Thursday.


Figure 1. Triple trouble in the Pacific. From left to right: Tropical Storm Linfa in the South China Sea, Category 1 Typhoon Chan-Hom, and Category 3 Typhoon Nangka. Image was taken by the JMA MTSAT-2 satellite at 0230Z on July 7, 2015. Typhoon Nangka is expected to intensify to Category 5 strength and pass near the uninhabited island of Agrihan in the Northern Mariana Islands on Thursday. Nangka could threaten Japan 8 - 10 days from now as a weaker storm. Tropical Storm Linfa hit the Philippines' northern island of Luzon over the weekend, and is expected to make landfall in China on Thursday as a tropical storm. Image credit: NOAA Viz Lab.

Forecast for Chan-hom
Chan-hom will be steered by a strong ridge of high pressure towards the west-northwest through Thursday, when the typhoon will pass near Miyakojima in the Miyako Islands of Okinawa Prefecture, Japan. Chan-hom is then likely to make landfall in Mainland China north of Taiwan on Friday afternoon or Saturday morning. However, landfall in China is not a sure thing, as a strong trough of low pressure is expected to turn the typhoon northwards as the center nears the coast on Friday. A potential worst-case scenario would be if Chan-hom turns northwards just before hitting the coast, and passes just offshore and very close to Shanghai as a Category 1 or stronger typhoon. The counter-clockwise flow of air around the storm could then potentially bring a significant storm surge to China's most populous city (14 million people.) The majority of Shanghai lies less than 2 meters (6.6 feet) above sea level, and the city is very vulnerable to flooding from storm surge and the heavy rains of typhoons. Shanghai is very important economically--about 14% of China's freight goes through the city. The models are divided in how they handle the trough of low pressure that Chan-hom will encounter late this week, and it is too early to say how much concern we should have for this worst-case scenario. According to 2011 New York Times article, engineers have stretched hundreds of miles of levees along the Yangtze River where it meets the sea in the city. The lowest of those levees were built to withstand a one-in-1,000-year storm surge, and defended Shanghai against the highest tidal surge in modern times, which came during Typhoon Winnie of 1997.


Figure 2. Latest satellite image of Invest 96E.

Invest 96E a threat to Hawaii
Hawaii needs to watch Invest 96E, located about 1300 miles east-southeast of the Big Island. Satellite loops show that 96E is close to tropical depression status, with a pronounced low-level spin and plenty of heavy thunderstorm activity. Wind shear is light, 5 - 10 knots, and ocean temperatures are warm, near 27.5°C. The 8 am EDT Tuesday run of the SHIPS model predicted that wind shear would rise to the moderate level, 10 - 20 knots, by Friday, and ocean temperatures would cool to a marginal 26°C. These conditions should prevent rapid intensification of 96E. Our two most reliable track models, the GFS and European models, show 96E coming within 200 miles of the Hawaiian Islands on Friday. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave 96E 2-day and 5-day odds of development of 90%. An Air Force hurricane hunter aircraft is scheduled to investigate 96E on Wednesday afternoon.

Hawaii has seen an unusual amount of hurricane activity over the past three years. Tropical Storm Flossie passed with 100 miles of the islands in 2013, and an unprecedented three hurricanes in one year passed within 200 miles of Hawaii in 2014. This included Hurricane Iselle, which made landfall on the Big Island on August 8, 2014 as a tropical storm with 60 mph winds--only the second recorded landfall of a tropical storm on the Big Island. Warmer than average ocean temperatures have made this action possible--ocean temperatures along the track of Invest 96E are about 2°F above average, similar to what was seen in 2014.

Jeff Masters

Hurricane

Germany Breaks its All-Time Heat Record

By: Jeff Masters , 4:24 AM GMT on July 06, 2015

Germany broke its all-time heat record on Sunday July 5, when the mercury soared to 104.5°F (40.3°C) at the official Kitzingen station in Bavaria. According to the German weather service's Facebook page, the record is now confirmed as official. The previous official national heat record recognized by the German meteorological agency (DWD) was 104.4°F (40.2°C), set in July 1983 and matched in August 2003. Numerous cities in Germany set all-time heat records over the weekend, including Saturday's 100.2°F (37.9°C ) reading at Berlin's Dahlem station, which has a very long period of record going back to 1876. Frankfurt beat its all-time heat record on Sunday--both at the airport (38.8°C) and downtown (39.0°C). Thanks go to weather records researcher Maximiliano Herrera and Klimahaus' Michael Theusner for these stats. According to an analysis of DWD observing station data done by Dr. Theusner, 131 of 492 stations in Germany set an all-time heat record during the July 2 - 5 heat wave, and another 7 tied their previous record.


Figure 1. A young boy jumps from a 7.5 meter platform at a crowded outdoor pool during a record heat wave in Frankfurt, Germany, Friday, July 3, 2015. (AP Photo/Michael Probst)

More near-record heat on the way
Germany has joined four other nations that have set all-time July national heat records this month: the Netherlands, the U.K., Thailand, and Colombia. Intense heat will continue over portions of Europe the next three days, with more national July heat records at risk. The fiercest heat will be over Poland on Monday, over Germany, Switzerland, and Austria on Tuesday, then shift to Southeast Europe on Wednesday. High temperatures close to the highest values ever measured can be expected in all these locations. For reference:

Poland's all-time hottest temperature is 104.4°F (40.2°C), measured on July 29, 1921 at Proszkow.

Switzerland's all-time hottest temperature is 106.7°F (41.5°C), measured on August 11, 2003 at Grono.

Austria's all-time hottest temperature is 104.9°F (40.5°C), measured on August 8, 2013 at Bad Deutsch-Altenburg.

Liechtenstein's all-time hottest temperature is 99.3°F (37.4°C), measured on August 13, 2003 at Ruggel.

Andorra's all-time hottest temperature is 101.3°F (38.5°C), measured on July 16, 2005 at Andorra La Vella.

Climate Change Playing a Significant Role in 2015 European Heat Wave
According to a press release by Climate Central, an international team of scientists from Oxford University, KNMI, Red Cross Red Crescent Climate Centre, along with regional partners from CNRS and MeteoSwiss says it is virtually certain that climate change increased the likelihood of the ongoing heat wave stretching across much of Europe. The risk increased by a factor of two or more over a large part of Europe, and up to more than a factor of four in some of the hottest cities. For example, the 3-day heat wave over the past three days in Mannheim, Germany would have been a 1-in-100 year event around the year 1900. It is now likely to happen roughly 1 in 15 years, thanks to climate change. The results are a part of the developing field of “weather attribution” that uses observational weather and climate data, weather forecasts and climate models.

Jeff Masters

Heat Climate Change

All-time July National Heat Records Fall on Three Continents

By: Jeff Masters , 4:56 PM GMT on July 03, 2015

Brutally hot conditions fried portions of three continents during the first three days of July, and four nations have already set all-time July national heat records this month: the Netherlands, the U.K., Thailand, and Colombia. Below is a break-down of the July national heat records set so far this month, courtesy of weather records researcher Maximiliano Herrera.


Figure 1. People cool off in the water fountains at Haarlemmerplein square in Amsterdam, the Netherlands, on Thursday, July 2, 2015. It was the warmest July day since records began in the Netherlands. (AP Photo/Margriet Faber).

Europe
The temperature in Maastricht, the Netherlands, hit 100.8°F (38.2°C) on July 2, setting an all-time July heat record for the nation. According to data from the Royal Netherlands Meteorological Institute, only two other hotter temperatures have been recorded in the nation: 101.5°F (38.6°C), on August 23, 1944 at Warnsveld, and 101.1°F (38.4°C), on June 27, 1947 at Maastricht. Thanks go to wunderground member cRRKampen for this info. According to to weather records researcher Maximiliano Herrera, three stations in the Netherlands set all-time (any-day) highs Thursday:

Volkel (Netherlands), 36.9°C
Twenthe (Netherlands), 36.1°C
Leeuwarden (Netherlands), 34.0°C

Mr. Herrera notes that the Netherlands' all-time hottest temperature in 1944 was surely beaten on July 2, 2015, but all stations in the warmest area were closed many years ago. For example, the city of Maastricht itself, where Thursday's near-record 100.8°F (38.2°C) was recorded at the airport, is slightly warmer in its downtown (perhaps by 1°C) than at the airport station (which is more elevated), but the town station doesn't exist any longer. He also pointed out that Belgium's official all-time hottest temperature is 101.8°F (38.8°C), measured on June 27, 1947. However, according to the Belgian Meteorological Agency, RMI, this value was likely 2.2°C too high, due to improper measurement techniques. If we make this correction, Belgium's all-time hottest temperature was beaten on Thursday, as well as during the 2003 and 2006 heat waves. And in Paris, which measured its 2nd hottest temperature in its history on July 1 (39.7°C), the Paris Observatory had its grass watered (as it should be), but the grass was never watered for the record value of 40.4°C of 1947. This could have been the difference between the two measurements.

London's Heathrow Airport hit 98.1°F (36.7°C) on July 1, setting an all-time July heat record for the UK. Previous record: 97.7°F (36.5°C) in Wisley on July 19, 2006.

Asia
On July 2, the mercury hit 105.8°F (41.0°C) at Kamalasai, Thailand, setting a mark for the hottest July temperature ever recorded in that nation. Previous record: 104.4°F (40.2°C) at Uttaradit on July 12, 1977. Approximately half of all the reporting stations in Thailand set their all-time July monthly heat records on July 1 or July 2 this year. UPDATE: Today (Friday, July 3), Kamalasai, Thailand bested yesterday's July record with a reading of 106°F (41.1°C).

South America
On July 1, Urumitia, Colombia beat that nation's all-time July national heat record, with a 108°F (42.2°C) reading. Urumitia also set Colombia's all-time June heat record last week on June 27, with a 107.6°F (42.0°C) mark.

The heat continued in all these places on Friday. In Europe, the hottest temperatures were over Central France, where Clermont Ferrand hit 104°F (40°C). Meteo France has a color-coded map of current temperatures that show the heat wave in excellent detail. The most intense heat will shift eastwards over Germany and Luxembourg on Saturday and Sunday, into Poland and Southeast Europe on Monday, then over Germany, Switzerland, Austria, and Liechtenstein on Tuesday. High temperatures close to the highest values ever measured can be expected in all these locations. From wunderground's extremes page, we can see that these all-time national heat records may be challenged:

France's all-time hottest temperature is 111.4°F (44.1°C), measured on August 12, 2003 at Conqueyrac and Saint-Christol-Les-Ales Gard Department.

Germany's all-time hottest temperature is 104.5°F (40.3°C), measured on August 8, 2003 at Perl-Nennig, Saarland State.

Switzerland's all-time hottest temperature is 106.7°F (41.5°C), measured on August 11, 2003 at Grono.

Luxembourg's all-time hottest temperature is 104.9°F (40.5°C), measured on August 8, 2003 at Remich.

Poland's all-time hottest temperature is 104.4°F (40.2°C), measured on July 29, 1921 at Proszkow.

Austria's all-time hottest temperature is 104.9°F (40.5°C), measured on August 8, 2013 at Bad Deutsch-Altenburg.

Liechtenstein's all-time hottest temperature is 99.3°F (37.4°C), measured on August 13, 2003 at Ruggel.

Four tropical cyclones in the Pacific
Typhoon Watches continue in the Northern Mariana Islands on Guam and nearby Rota, Saipan, and Tinian islands for Tropical Storm Chan-hom, which is expected to pass through the islands Saturday evening (U.S. EDT time) as an intensifying Category 1 storm. Chan-hom had unexpected troubles on Friday, when it interacted with tropical disturbance 94W to its west. The upper-level outflow from 94W created high wind shear over Chan-hom, which tore away most of the typhoon's heavy thunderstorms and exposed the low-level circulation to view. Dan Lindsey of NOAA/CIRA put together an impressive closeup view of Chan-Hom's evolution on Friday from the Himawari-8 satellite's 0.5 km visible 2.5-min imagery. Here is a link to all the Himawari-8 satellite imagery.

The Philippines are watching Tropical Storm Linfa, which is expected to hit the northern island of Luzon over the weekend at tropical storm strength.

Newly-formed Tropical Depression Eleven is in the Marshall Islands, where it has already caused considerable trouble. According to hurricane scientist Mark Lander of the University of Guam, tropical cyclones in the Marshall Islands occur almost exclusively during El Niño years. So far this year, three tropical cyclones have caused damaging sea inundation in the islands. According to a source of his on Majuro Island:

"We [Majuro] got the weaker side.  Even so, this was the strongest West Wind I have seen here in about 18 years.  And believe it or not, it was not that strong [~25 G40 mph], just steady.  I see 2 fishing boats aground; another one partially sunk already, with a small and large yacht on the beach, and many power boats a mess. The Uliga dock area was a circus all day.  Also add lots of erosion, you can see the Mobil Oil fuel lines exposed. All the mooring failures for boats on the beach so far was due to chafing as we have had happy weather for years and I think few were ready.  If a storm of this nature had hit at King Tides, we would have had a national emergency."

Two areas of disturbed weather in the Central Pacific east-southeast of the Hawaiian Islands, Invest 95E and Invest 96E, are moving west-northwest towards Hawaii. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave 95E and 96E 5-day odds of development of 50% and 70%, respectively. 96E, the disturbance farther from Hawaii, may pose a long-range threat to Hawaii, as the Friday morning runs of the GFS and European models showed the storm coming close to the islands on Friday, July 10.

In the South Pacific, a rare winter tropical cyclone, Raquel, is drenching the Solomon Islands.

Mercifully, the Atlantic remains quiet, with none of the reliable tropical cyclone genesis models showing anything developing over the next five days.

Have a great holiday weekend, everyone! I'll be back by Monday morning at the latest with a new post.

Jeff Masters

Heat

Kids, Cars, and Heatstroke: A Lethal Summer Mix

By: Bob Henson , 3:21 PM GMT on July 02, 2015

Any child’s death is heartbreaking, but there is something uniquely poignant about the way in which dozens of U.S. youngsters die each year: trapped in an oven-like vehicle on a quiet summer day. “That pain is every day. It’s always there,” one grief-stricken mother told CNN seven years after she inadvertently left her 9-month-old baby in her car. Close to 400 children have died across the nation over the last decade in this tragic way.

You don’t have to live in Phoenix or Houston for your car to become a death trap in summer heat. Jan Null (Department of Meteorology & Climate Science,San Jose State University) discovered how easy it is for a vehicle to heat up when it’s getting the intense solar radiation of summertime. Formerly a lead forecaster for the National Weather Service in the San Francisco Bay area, Null was interviewed by media in 2001 after a baby’s death in San Jose on an 86°F day. “Out of scientific curiosity, I started casually tracking temperatures in my own vehicles and was startled at not only how hot the readings were but also how rapidly they rose,” he recalled. He soon joined forces with two Stanford University Hospital doctors, Catherine McLaren and James Quinn, to carry out a more thorough analysis that was published in Pediatrics in 2005. The take-home finding was that full sunlight hitting a dark sedan boosted interior temperatures by more than 6°F every 10 minutes, even when outdoor temperatures were in the 70s. The paper concluded: “Even at relatively cool ambient temperatures, the temperature rise in vehicles is significant on clear, sunny days and puts infants at risk for hyperthermia. Vehicles heat up rapidly, with the majority of the temperature rise occurring within the first 15 to 30 minutes. Leaving the windows opened slightly does not significantly slow the heating process or decrease the maximum temperature attained.”


Figure 1. Even when temperatures outside are only 80°F, sunshine entering a closed vehicle can push the temperature to 109°F in just twenty minutes. After an hour, the car’s interior air can reach a blistering 123°F. Cracking windows does not reduce the ability of the air to reach such high temperatures. The sunshine entering the car rapidly heats up surfaces (the dashboard or steering wheel can reach 180 – 200°F on an 80°F day). These surfaces, in turn, heat up the interior through convection and conduction as well as by longwave radiation, in much the same way that an asphalt parking lot sends heat upward. An hour’s worth of warming is depicted in this QuickTime animation. Image credit: GM and Jan Null.

Null is passionate about providing good scientific information to advocates, policymakers, and emergency responders about how hot cars can get and the circumstances that lead to children dying in vehicles from heatstroke. His website noheatstroke.org includes a set of frequently updated statistics that bring home the problem vividly. Of the 637 such deaths recorded from 1998 to 2014, just over half involved children who were “forgotten,” many of them left in a vehicle by a parent or caregiver rushing to work in the morning. Maps that show the location of each incident from year to year make it abundantly clear that latitude is no protection: 2014 saw deaths in Michigan New York, and Connecticut, and 2015 has already seen a confirmed death in northern Idaho. Perhaps surprisingly, Null reports that only 20 states have laws regarding leaving children unattended in vehicles.


Figure 3. Geographic distribution of heatstroke deaths involving children and vehicles, 1998 – 2014. Image credit: Jan Null.

Here are Null’s safety recommendations:

Never leave a child unattended in a vehicle—not even for a minute!
—If you see a child unattended in a hot vehicle, call 911.
—Be sure that all occupants leave the vehicle when unloading. Don't overlook sleeping babies.
—Always lock your car and ensure children do not have access to keys or remote entry devices. Teach children that vehicles are never to be used as a play area.
—If a child is missing, always check the pool first, and then the car, including the trunk.
—Keep a stuffed animal in the carseat, and when the child is put in the seat, place the animal in the front with the driver. Or place your purse, briefcase, or cell phone in the back seat as a reminder that you have your child in the car.
—Make "look before you leave" a routine whenever you get out of the car.
—Have a plan that your childcare provider will call you if your child does not show up for school.

For a look at how heat affects the human body, check out our latest WU infographic (excerpted at the bottom of this post).


And don’t forget about Fido!

Smokey the Wonder Dog (right) joins Bob in reminding you that a vehicle roasting in the summer sun can be dangerous to pets, too. Hundreds are believed to die around the country each year after being left in hot cars. At least 16 states have laws of various types that prohibit endangering a pet’s life by leaving it unattended in a parked car. As of July 1, police officers across the state of Washington can break into parked cars as needed to rescue pets, with limits on their liability for vehicle damage. The pet’s guardian can face a $125 fine.

The Humane Society offers these tips on how you can help if you see a pet in a parked car on a sunny summer day:

—Take down the car's make, model and license-plate number.

—If there are businesses nearby, notify their managers or security guards and ask them to make an announcement to find the car's owner.

—If the owner can't be found, call the non-emergency number of the local police or animal control and wait by the car for them to arrive.

The American Veterinary Medicine Association suggests: “Before you put your pet in the vehicle, ask yourself if you really need to take your pet with you--and if the answer is no, leave your pet safely at home.”

Have a happy and safe Fourth of July weekend, everybody!

Bob Henson

Figure 3 (below). An excerpt from “Heat and the Human Body,” the latest infographic from Weather Underground. The full version, created by WU’s Jerimiah Brown, can be found online.





European heat wave continues
Brutally hot conditions continued over Europe on Thursday, with the hottest temperatures shifted eastwards over Eastern France, the Netherlands, and Western Germany. The temperature in Maastrict, the Netherlands, hit 100.8°F (38.2°C), just missing the Netherlands' all-time hottest temperature record of 101.5°F (38.6°C), set on August 23, 1944 at Warnsveld.

According to Meteo France, on Wednesday, the high temperature at the official Montsouris station in Paris, France hit 103.5°F (39.7°C), the second warmest temperature ever measured there, and not far from Paris' all-time record of 104.7°F (40.4°C) set in July 1947. At least three stations in France set all-time heat records on Wednesday:

Boulogne-sur-Mer (station opened in 1947): 35.4°C (Previous record 34.8°C on 08/11/2003)
Dieppe (station opened in 1949): 38.3°C (Previous record 37°C on 07/09/2006)
Melun (station opened in 1947): 39.4°C (Previous record 38.9°C on 08/12/2003)

Three tropical cyclones in the Pacific
A Typhoon Watch is up for Guam for Typhoon Chan-hom, which is expected to pass very close to the island late morning U.S. EDT time on Saturday as an intensifying Category 2 storm. The NWS in Guam is putting out special advisories and local statements on the typhoon.

Chan-hom will be the second typhoon to affect the island this year; in May, the eye of Category 2 Typhoon Dolphin passed through the channel between the islands of Guam and Rota, bringing sustained winds of 84 mph, gusting to 106 mph, to Andersen Air Force Base on Guam. Dolphin knocked out power and damaged some homes, but the islands escaped serious destruction.

The Philippines are watching Tropical Depression Ten, which is expected to skirt the northern island of Luzon over the weekend as a Category 1 typhoon. In the South Pacific, a rare winter tropical cyclone, Raquel, is drenching the Solomon Islands.

Jeff Masters

Heat

Unprecedented June Heat on Four Continents; Wimbledon Roasts in Record Heat

By: JeffMasters, 3:52 PM GMT on July 01, 2015

Unprecedented June heat scorched portions of four continents during the past week, and many all-time heat records are likely to fall across multiple continents this July as the peak heat of summer arrives for what has been the hottest year in recorded human history. Already on July 1, in Wimbledon, England--site of the classic Wimbledon tennis tournament--players are enduring the city's hottest day in tournament history. The mercury hit 96.3°F (35.7°C) at Kew Gardens, the nearest recording site, topping the previous record of 94.3°F (34.6°C) on June 26, 1976. London's Heathrow Airport has risen to 98.1°F (36.7°C) so far on July 1. This is not only a new all-time July record at that location, but also a July heat record for the UK, topping the previous record of 97.7°F (36.5°C) in Wisley on July 19, 2006.

We've already seen two of the planet's top ten deadliest heat waves in history over the past two months; the Pakistani government announced on Wednesday that the death toll from the brutal June heat wave in Pakistan's largest city, Karachi, had hit 1,250. According to statistics from EM-DAT, the International Disaster Database, this makes the 2015 heat wave in Pakistan the 8th deadliest in world history. The heat wave that hit India in May, claiming approximately 2,500 lives, ranks as the 5th deadliest:

Death Tolls From the 10 Deadliest Heat Waves in World History
1) Europe, 2003: 71,310
2) Russia, 2010: 55,736
3) Europe, 2006: 3,418
4) India, 1998: 2,541
5) India, 2015: 2,500
6) U.S. and Canada, 1936: 1,693
7) U.S., 1980: 1,260
8) Pakistan, 2015: 1,250
9) India, 2003: 1,210
10) India, 2002: 1,030
10) Greece and Turkey, 1987: 1,030


Figure 1. Novak Djokovic of Serbia wipes his face during the hottest day in Wimbledon history, in a match against Jarkko Nieminen of Finland, at the All England Lawn Tennis Championships in Wimbledon, London, Wednesday July 1, 2015. (AP Photo/Alastair Grant).

Extreme June heat hits four continents
Portions of four continents--Asia, Europe, North America, and South America--broke all-time June heat records during the past week, with some locations surpassing their all-time heat records for any date:

Asia In addition to the record deadly heat wave that hit Pakistan over the past few weeks, other portions of Asia also saw extreme June heat. According to weather records researcher Maximiliano Herrera, Ashkabad, the capital of Turkmenistan, set a new all-time record (for any month) with 117°F (47.2°C) on June 30, 2015, smashing the old record of 46.7°C from June 30, 1995. The national all-time heat record of June for Kazakhstan of 45.0°C came within 0.5°C of being matched, as well.

Europe
An extreme jet stream configuration is in place over Western Europe, where a strong ridge of high pressure has brought the warmest June temperatures ever recorded to the Spanish cities of Madrid (39.1° on June 28) and Toledo (40.8° on June 30).

The heat will continue over much of Western Europe the remainder of the week, when the hottest temperatures since 2006 are expected. According to Meteo France, on Wednesday, the high temperature at the official Montsouris station in Paris, France hit 103.5°F (39.7°C), the second warmest temperature ever measured there, and not far from Paris' all-time record of 104.7°F (40.4°C) set in July 1947. At least three station in France set all-time heat records:

Boulogne-sur-Mer (station opened in 1947): 35.4°C (Previous record 34.8°C on 08/112003)
Dieppe (station opened in 1949): 38.3°C (Previous record 37°C on 07/09/2006)
Melun (station opened in 1947): 39.4°C (Previous record 38.9°C on 08/122003)

North America A searing heat wave unprecedented for June scorched the Northwest U.S. and Western Canada last weekend, sending temperatures soaring to their highest June levels in recorded history for portions of Washington, Idaho, Montana, and British Columbia. Both Idaho and Washington set all-time high temperature records for the month of June on Sunday. According to wunderground's weather historian, Christopher C. Burt, the 113°F measured in Walla Walla, Washington beat that state's previous June record of 112°F, set at John Day Dam on June 18, 1961. In addition, the 111°F reading at Lewiston, Idaho was that state's hottest June temperature on record. An automated station at Pittsburg Landing, Idaho hit 116°F, but that reading will have to be verified before being considered official. A few stations had their hottest temperature for any day in recorded history on Sunday, June 28:

• Chief Joseph Dam, Washington, hit 113 degrees, topping the previous all-time record of 110 degrees most recently set on July 23, 2006. This is located near the town of Bridgeport, in north-central Washington. Records date to 1949.
• LaCrosse, Washington, tied their all-time record high of 113 degrees, set previously on Aug. 4, 1961. LaCrosse is in eastern Washington, about 40 miles west-northwest of Pullman. Records, there, date to 1931.
• Chelan, Washington, reached 110 degrees, topping their previous all-time record set just one day earlier (109 degrees). Prior to this heat wave, their all-time record was 106 degrees set most recently on July 22, 1985. Records date to 1958.
• Omak, Washington, also reached 110 degrees, topping their previous all-time record of 109 degrees set on July 8, 2001. Records date to 1931 (Maximiliano Herrera points out, though, that the station has moved 3 times, so this record may be unrepresentative of the conditions at all 3 locations.)
• Bonners Ferry, Idaho, soared to 105 degrees, eclipsing their previous all-time record of 104 degrees on July 16, 1941. Records date to 1907. 

Thanks go to TWC's Jon Erdman for compiling this list.

South America
Prior to 2015, the hottest Colombia had ever been in June was 40.8°C in June 1973 at Guaymaral. That mark was tied on June 20, 2015, at Agustin Codazzi. That mark was smashed on June 25, when both Valledupar and Urumitia hit 41.6°C. On June 27, Urumitia, Colombia beat the new June national record, with a 42.0°C reading. Three major cities, Cartagena, Santa Marta and Riohacha all set their all-time heat records in June. Argentina and Venezuela also recorded their highest June temperatures ever recorded. Thanks go to weather records researcher Maximiliano Herrera for these stats.

Jeff Masters

Heat


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Category 6™

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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather