Category 6™

Last Day of Winter Brings Record Cold to Midwest; More Heavy Rain in California

By: JeffMasters, 4:20 PM GMT on February 28, 2014

Friday, February 28 marked a fitting final day of meteorological winter over Michigan, which has seen one of its most severe winters in memory during 2013 - 2014. An Arctic blast of cold air poured out of Canada over the Great Lakes, bringing the coldest temperatures ever measured so late in the year to Flint (-16°F), Gaylord (-29°F), and Houghton Lake (-29°F). The coldest spot in the country was in Michigan's Upper Peninsula city of Newberry, where the mercury plunged to a remarkable -41°F. In the Lower Peninsula, the cold spot was Pellston with -33°F--the city's 7th coldest morning on record. In Michigan's Upper Peninsula, the -29°F reading in Marquette was that city's coldest temperature since March 3, 2003, and only the 8th time since record keeping began in 1872 that a temperature of -29° or colder had been observed. Farther to the north, Peawanuck, Ontario hit -47°F. What's remarkable about these records is that they were set without fresh snow on the ground--though there is plenty of horrible-looking old snow around! I still have about 20" on the ground at my place, 30 miles south of Flint. My backyard Davis weather station recorded -18°F Friday morning, which was the 2nd coldest temperature of the winter.

It's been another month of remarkably persistent cold over the Upper Midwest in February, and as of February 27, these cities were on track to have a top-ten coldest February on record:

Chicago (9th coldest)
Green Bay, WI (4th)
Minneapolis, MN (9th)
Kansas City, MO (9th)
Fort Wayne, IN (6th)
Dubuque, IA (3rd)
Peoria, IL (6th)
Rochester, MN (4th)
Madison, WI (10th)
Moline, IL (5th)

Figure 1. Winter Storm Titan coils up off the coast of California in this MODIS image taken on Thursday, February 27, 2014. Image credit: NASA.

A second day of heavy rains for California
A very moist “Pineapple Express” atmospheric river of moisture from the Hawaiian Islands will bring much-needed rains to nearly all of drought-ravaged California Friday and Saturday. As of 8 am PST Friday, Downtown Los Angeles had received 1.17" of rain since midnight. It was the second consecutive day Los Angeles had received over 1" of rain, as 1.05" fell on Thursday. The last time Los Angeles had received more than 2" of rainfall in a 48-hour period was nearly 3 years ago--March 20 - 21, 2011, when 2.58” fell. Today's rains have forced the closure of a 10-mile stretch of the Pacific Coast Highway in Ventura County because of a high likelihood of rock slides in an area made bare by last year's Springs Fire in Camarillo, according to the Associated Press. Mandatory evacuation orders were also issued for about 1,000 homes in the eastern foothill suburbs of Glendora and Azusa, which lie beneath nearly 2,000 acres of steep mountain slopes denuded by the Colby fire in January. NOAA's Storm Prediction Center has placed coastal Southern California in their "Slight Risk" area for severe weather, with a few waterspouts and severe thunderstorms possible. Storm total rain amounts of 2 - 4 inches are expected through Saturday night at lower elevations in Southern California, with 4 -7" in the foothills and 8 - 10" in the mountains.

Two Pacific tropical storms form, boosting the odds of an El Niño
The atmospheric and oceanic conditions in the Equatorial Pacific are ripe for an El Niño event to develop this spring or summer. As detailed in a guest blog post by WSI's Dr. Michael Ventrice on February 21, all that is needed to trigger an El Niño this spring or summer are strong and persistent bursts of westerly winds in the Equatorial Pacific to help push warm water from the Western Pacific Warm Pool eastwards towards South America. Two tropical storms capable of doing just that formed in the Pacific on Friday, boosting the odds that we will see an El Niño event this spring or summer. In the Western Pacific, Tropical Storm Faxai formed Friday morning about 400 miles southeast of Guam. The minimal 40 mph tropical storm is located close to the Equator, at 9°N latitude, which means the the counterclockwise wind circulation around the storm will drive west-to-east winds along the Equator, giving a substantial push to warm waters attempting to slosh eastwards towards South America and start an El Niño event. Faxai is expected to intensify to a Category 1 typhoon by Monday, but is not a threat to any islands. In the South Pacific, Tropical Cyclone Sixteen formed Friday morning near the island of Fiji. This minimal 40 mph tropical storm is moving south-southeast at 10 mph, and is expected to slowly intensify to a strong tropical storm with 70 mph winds by Monday. The clockwise circulation of winds around the storm will also help drive westerly winds near the Equator that will boost the odds of an El Niño event. However, since this storm is farther from the Equator (16°S), it will not have a strong an impact on boosting El Niño odds as Tropical Storm Faxai will.

Figure 2. Visualization of the GPM Core Observatory satellite orbiting the planet Earth. Image credit: Britt Griswold, NASA Goddard.

Important new precipitation measurement satellite launched
A key new NASA satellite called the Global Precipitation Measurement (GPM) Core Observatory was launched into low-Earth orbit, 253 miles above the ground, on Thursday from the Tanegashima Space Center in Japan. NASA confirmed that the satellite successfully deployed its solar arrays and is stable and pointed at the sun. The satellite is a joint venture between NASA and the Japan Aerospace Exploration Agency. The new satellite has the most sophisticated instruments ever launched into space for the study of precipitation, and allows the first-ever space-borne measurements of snow. The satellite carries two instruments to measure rain and snowfall:  the Dual-frequency Precipitation Radar (DPR), and the GPM Microwave Imager (GMI). Together, these two instruments will collect improved observations that will allow scientists to better "see" inside clouds. In particular, they both provide new capabilities for observing smaller particles of rain, ice and snow. The satellite is scheduled to begin providing useful data in May 2014, and will allow worldwide precipitation measurements every three hours. Data from the satellite will be fed into global computer forecast models, and should help improve weather and climate forecasts.

Have a great weekend, everyone, and I'll be back Monday with a new post.

Jeff Masters

Winter Weather

Heavy Rains Make Modest Dent in California Drought

By: JeffMasters, 4:05 PM GMT on February 27, 2014

A very moist “Pineapple Express” atmospheric river of moisture from the Hawaiian Islands is bringing much-needed rains to nearly all of California today. As of 7 am PST Thursday, Downtown Los Angeles had received 0.97" of rain since midnight. The last calendar day when Los Angeles received more than 1" of rainfall was over two years ago--Oct. 5, 2011, when 1.15” fell. Substantial rains also fell in Central California, and heavy rains triggered a rock slide that shut down Highway 1 in Big Sur Wednesday night.

Figure 1. Total precipitable water (TPW) for Thursday, February 27, 2014. TPW is how much rain (in inches) would fall at a given location if one condensed out all of the water vapor in a column above the location into rain. For reference, 1 inch = 25.4 mm. A narrow “Atmospheric River” of moisture is seen extending from the subtropics near Hawaii into Southern California. A larger pulse of moisture is curled up a few hundred miles offshore, and will arrive on Friday. Image credit: University of Wisconsin SSEC.

Figure 2. Rains that fell over California on February 8 - 9 raised water levels on the critical Central California reservoir Folsom Lake by twelve feet in one day, and boosted water levels above the record low levels set during 1977. Rainfall in the Folsom Lake drainage basin on February 26 - 27 has been about 0.5 - 1.5", which will raise the lake level even more. Image credit: California Department of Water Resources.

An even wetter storm coming Friday and Saturday to California
A second, stronger storm system will hit California on Friday and Saturday, generating 1 - 3" rainfall
totals for most coast and valley locations in Southern California, with 3 - 6" in the foothills and coastal mountain slopes. The powerful storm will be capable of spawning severe thunderstorms with wind gusts in excess of 58 mph, and a few waterspouts and weak tornadoes. The NWS office in Los Angeles is warning that Friday and Saturday's storm has the potential to bring rainfall rates of up to 1 - 2" per hour in the foothills and coastal mountain slopes, which will be capable of causing debris flows in areas recently burned by fires. About a foot of snow will likely fall from 6000 feet to 7000 feet, and 1 - 3' of snow is likely above 7000 feet. In the Sierras of Central California, 1 - 2' of snow is expected.

This storm, which has been named "Titan", will move eastwards over the weekend,and an Arctic front will combine with moisture associated with Titan to produce near-blizzard conditions across the northern Rockies Friday into Friday night. As it moves through the Central Plains, the storm will strengthen and begin to pull Gulf moisture northward into the cold air, triggering moderate to heavy snows across portions of Kansas, Nebraska and Missouri Saturday night into Sunday. The snow will spread across Illinois, Kentucky, Indiana, Ohio, West Virginia, and portions of the Mid-Atlantic and Northeast U.S. on Monday, and along the southern side of the snow band, a significant ice storm is likely. The ice storm will affect Oklahoma through Southern Missouri, northern Arkansas and northern Kentucky Saturday night and Sunday, and by Sunday night, parts of the Mid-Atlantic across Virginia and Maryland may also see significant icing. Small changes in the track of the storm will move the areas of freezing rain tens of miles north or south of the current forecast, so stay tuned to the latest forecasts.

Figure 3. The February 25, 2014 U.S. Drought Monitor showed 95% of California in drought, with 26% of the state in the highest level of drought, "Exceptional." Image credit: U.S. Drought Monitor.

Drought situation in California still extreme despite today's rains
While this week's rains and snows in California are a welcome respite, they will put only a modest dent in what is one of the worst droughts in California history. Today's U.S. Drought Monitor showed that the portion of the state in "Exceptional Drought"--the worst category of drought--was 26%, nearly double the previous week's value. This year is the first year since the Drought Monitor product began in 2000 that portions of California have been in "Exceptional Drought". California's area experiencing the two highest categories of drought, extreme to exceptional, increased to 74% this week, and only 5% of the state was not in drought (the Mojave Desert region of Southeast California, where almost no agriculture happens anyway, since it is desert.) To break the drought, much of the state needs more than 12" of precipitation.

Wunderground's weather historian Christopher C. Burt discusses how this week's storm will affect California rainfall totals in his latest post.

Video 1. The new ‪Radius ‬hyper-local weather information app‪, powered by Weather Underground‬

Wunderground Releases New Hyper-Local Weather Information App
Weather Underground released today a new app for iPhone and iPod touch called Radius™. Using Radius™, users can set a designated radius from a desired location to receive free push notifications of NWS severe alerts, lightning, and precipitation heading into that area. Our new predictive radar tool can then be used to determine precisely when to take cover.

With thousands of weather apps available to smartphone users, we set out to build a completely new way for people to receive hyper-local weather information. Radius ensures that its users are the first to know about severe weather in their area, while also delivering an interactive experience that only Weather Underground’s community-sourced data can provide. We have an unrivaled network of personal weather stations--more than 21,000 across the U.S.--and images from over 12,000 webcams. Even when there isn’t active weather, Radius™ provides an engaging experience for users to browse community wunderphotos and webcam images.

The app can be downloaded at: ‪‬

Jeff Masters


New Blast of Cold Air Invades Midwest U.S.

By: JeffMasters, 3:31 PM GMT on February 26, 2014

A frigid blast of Arctic air will bring some of the coldest late February temperatures seen in decades to the eastern 2/3 of the U.S. this week, with temperatures 15 - 30° below normal commonplace. The cold air isn't going anywhere fast, and will stick around through early next week. The cold blast is due to an extreme jet stream pattern we have seen before this winter--a sharp ridge of high pressure over California, and a large trough of low pressure over Eastern North America. This upper air pattern was described by the National Weather Service in Buffalo, New York on Tuesday as one that occurs less than once every 30 years in late February. The intense cold is already affecting the Upper Midwest this Wednesday morning. My vote for worst winter weather of the day goes to Central Minnesota at Alexandria, where a temperature of -8°F this morning combined with winds of 14 mph to make a wind chill of -28°. The winds are expected to increase to 25 - 30 mph Wednesday afternoon with higher gusts, creating blizzard conditions. In Chicago, the intense cold is expected to put the December - February average temperature for this winter below 19°, making the winter of 2013 - 2014 the 3rd coldest winter in the Windy City's history. Only the winters of 1978 - 1979 and 1903 - 1904 were colder.

Figure 1. Great Lake ice cover as seen on February 19, 2014, by the MODIS instrument on NASA's Aqua satellite. Ice cover on North America’s Great Lakes reached 88 percent in mid-February 2014—levels not observed since 1994. The average maximum ice extent since 1973 is just over 50 percent. It has surpassed 80 percent just five times in four decades. The lowest average ice extent occurred in 2002, when only 9.5 percent of the lakes froze. Image credit: NASA Earth Observatory.

Rain coming to California
Unlike previous versions of this extreme jet stream pattern, though, the ridge over the Western U.S. will not be very persistent. The ridge of high pressure over California, which brought numerous record high temperatures for the date on Tuesday, will get broken down by a weak low pressure system on Wednesday and Thursday. On Friday and Saturday, a more intense storm system will smash through the ridge, bringing moderate to heavy rain to much of drought-parched California. This storm will then track eastwards, potentially bringing a major snowstorm and destructive ice storm on Monday to Illinois, Kentucky, Indiana, Ohio, West Virginia, and portions of the Mid-Atlantic and Northeast U.S.

Figure 2. Departure of temperature from average at 2 meters (6.6') as diagnosed by the GFS model at 00 UTC February 26, 2014. A negative phase of the Arctic Oscillation (AO) created a sharp kink in the jet stream (Figure 3), which allowed cold air to spill southwards out of the Arctic over the Eastern U.S. Compensating warm air flowed northwards into the Arctic underneath ridges of high pressure over Alaska and Europe. Data/image obtained using Climate Reanalyzer™ (, Climate Change Institute, University of Maine, Orono, Maine.

Figure 3. Winds at a height where the pressure is 250 mb show the axis of the jet stream, seen here at 00 UTC February 26, 2014. A sharp trough of low pressure was present over the Eastern U.S., and unusually strong ridges of high pressure were over the Western U.S. and the North Atlantic. Data/image obtained using Climate Reanalyzer™ (, Climate Change Institute, University of Maine, Orono, Maine.

Wanted: professionals willing to speak about climate change to local groups
If you are a professional or graduate student with a strong background in climate science, the world needs you to reach out to local audiences at schools, retirement homes, the Chamber of Commerce, etc., and share your expertise. A new initiative by the University Corporation for Atmospheric Research (UCAR) and the United Nations Foundation called is launching a Science Speakers Network this spring, with the goal of bringing scientists and their local communities together for real dialogue on climate science that speaks to citizens’ current and future well-being and responsibility as members of a community and democracy. Materials for context-setting presentations will be offered as will coaching regarding how to begin conversations about climate change with fellow citizens. If you are interested in volunteering for this network, please go to and create a profile.  Profiles will “go public” when the full web site is launched in April. Once you create a profile, you will be kept up to date on Climate Voices progress including construction of the full web site, availability of presentation materials, webinar coaching, and plans for project launch. For any questions, please contact: Cindy Schmidt (UCAR), I have my own set of slides I use for such talks that anyone is welcome to borrow from, available at

Jeff Masters

Winter Weather

January 2014: Earth's 4th Warmest January on Record

By: JeffMasters, 1:34 PM GMT on February 24, 2014

January 2014 was the globe's 4th warmest January since records began in 1880, according to NOAA's National Climatic Data Center (NCDC) and NASA. January 2013 global land temperatures were the 4th warmest on record, and global ocean temperatures were the 7th warmest on record. In the Southern Hemisphere, land temperatures were the warmest on record. Global satellite-measured temperatures in January 2013 for the lowest 8 km of the atmosphere were 9th or 6th warmest in the 36-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH), respectively. Northern Hemisphere January snow cover was the 10th lowest in the 48-year record.

Figure 1. Departure of temperature from average for January 2014, the 4th warmest January for the globe since record keeping began in 1880. All-time record warmth was observed over portions of Greenland, Brazil, and Central and Southern Africa. Much cooler than average temperatures were observed over portions of the eastern half of the U.S. and Northern Siberia. Image credit: National Climatic Data Center (NCDC) .

One billion-dollar weather disaster in January 2014
One billion-dollar weather-related disaster hit the Earth during January 2014, according to the January 2014 Catastrophe Report from insurance broker Aon Benfield: the cold wave and winter weather associated with the Midwest and Eastern U.S. "Polar Vortex" episode of January 5 - 8, 2014, which cost an estimated $3 billion. Damage estimates from the ongoing extreme drought in California are not yet available, though the California Farm Water Coalition, an industry group, estimates that lost revenue in 2014 from farming and related businesses such as trucking and processing could reach $5 billion.

Figure 2. The cold wave and winter weather associated with the Midwest and Eastern U.S. "Polar Vortex" episode of January 5 - 8, 2014, cost an estimated $3 billion. In this picture, we see snow shovelers take a break in South Haven, Michigan after an epic lake effect snowstorm buried the city on January 8, 2014. Image credit: Wunderphotographer nanamac.

An extremely wet January in the UK; extreme dryness in Norway
An unusually wavy jet stream over Europe in January 2014 brought remarkable wet and dry extremes. Radcliffe Meteorological Station at Oxford University in the U.K. measured 146.9 mm (5.78”) of precipitation in January 2014, the wettest winter month ever observed there since records began in 1767. As wunderground's weather historian Christopher C. Burt writes, this is one of the longest periods of record for precipitation in the world. In Ireland, Valentia Observatory has seen rain every day but one since December 22--an astounding 64 of the past 65 days. Parts of Norway had their driest January ever, with no precipitation at all at several locations, e.g.: Bodø, Narvik, Harstad, Tysfjord, Fauske. The record dry conditions sparked January wildfires that destroyed over 200 buildings, a highly unusual occurrence for January in Norway.

Figure 3. One piece of good news: preliminary measurements from the CryoSat satellite show that the volume of Arctic sea ice in autumn 2013 was about 50% higher than in the autumn of 2012: 9,000 cubic kilometers vs. 6,000 cubic kilometers. About 90% of the increase in volume between the two years was due to the retention of thick, multiyear ice around Northern Greenland and the Canadian Archipelago. However, this apparent recovery in ice volume should be considered in a long-term context. It is estimated that in the early 1980s, October ice volume was around 20,000 cubic kilometers, meaning that more than half of the polar ice has been lost in the past 30 years. Image credit: National Snow and Ice Data Center.

Arctic sea ice falls to 4th lowest January extent on record
Arctic sea ice extent during January was 4th lowest in the 36-year satellite record, and was very similar to the January extents measured in 2013 and 2012, according to the National Snow and Ice Data Center (NSIDC). Sea ice extent so far during February has been tracking near or below the all-time record low levels for this time of year set in 2012, according to data from the University of Illinois Cryosphere Today. This is due, in part, to a large surge of warm air that pushed into the Arctic in late January and early February, which has kept the Arctic 5 - 15°C (9 - 27°F) warmer than average since January 25, according to data from Danish Meteorological Institute. Greenland temperatures were more than 5°C above average for a month beginning in the second week of January 2014, and "the snowpack heating the abnormal warmth increase the likelihood of an earlier melt onset and above average Greenland melting this coming summer," says Greenland expert Dr. Jason Box in his blog.

Thanks go to Maximiliano Herrera and Michael Thuesner for the Europe weather information. Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the notable weather events of January 2014 in his January 2014 Global Weather Extremes Summary.

Wundermap now available on iPhone and iPod Touch
Our interactive WunderMap® application that allows one to overlay multiple weather fields has now been released for both iPhone and iPod Touch. Initially released in 2010, the WunderMap® app is a favorite among weather enthusiasts, who can choose from a variety of weather layers, including current conditions from one of the 33,000+ weather stations, severe weather warnings, animated radar and satellite imagery, live webcam images, hurricane tracks, wildfires, and more. The latest features of the app include:

All new design for iOS 7
Faster load times of radar and satellite imagery
Enhanced webcam experience with full-screen capability, traffic-cam access
Customizable location presets and favorites
map interface options
Free to download in iTunes Store
Ad-free membership upgrade available for $1.99

I'll have a new post by Wednesday at the latest.

Jeff Masters

An El Niño Coming in 2014?

By: Michael Ventrice , 2:58 PM GMT on February 21, 2014

Today's guest blog post is by Dr. Michael Ventrice, an operational scientist for the Energy team at Weather Services International (WSI) - Jeff Masters

We are seeing increasing evidence of an upcoming change in the Pacific Ocean base state that favors the development of a moderate-to-strong El Niño event this Spring/Summer. To begin, here is a snap shot of global sea-surface temperature (SST) anomalies (the departure of temperature from average) 30 days ago:

Note the relatively weak look to the SST anomaly pattern in the equatorial Pacific, with warm anomalies in the western half of the basin and mixed warm and cold anomalies in the eastern half of the basin. The mixed warm/cold signals in the equatorial eastern Pacific are the result of instability “easterly” waves in the ocean, which are associated with short distances between “warm” and “cold” phases. Now let’s compare to what the SST anomaly map looks this week:

We’ve observed strong cooling in the eastern half of the Pacific Basin, giving a spatial map that strongly resembles “La Niña”--the opposite of El Niño. So why I am pushing the idea that El Niño might be right around the corner if the map looks like La Niña!?

It comes down to ocean dynamics. There are other types of waves that are deep in the Pacific Ocean. One such wave is called an “Oceanic Kelvin Wave”. Oceanic Kelvin waves travel only from West to East at extremely slow speeds (2-3 m/s). These waves have been alluded to as the facilitators of El Niño. There two phases of an Oceanic Kelvin wave, the “Upwelling” phase and the “Downwelling” phase. The Upwelling phase of an Oceanic Kelvin wave pushes colder water from the sub-surface towards the surface, resulting in cooling at the surface. The Downwelling phase of an Oceanic Kelvin wave is the opposite, where warmer waters at the surface of the West Pacific warm pool are forced to sink, resulting a deepening of the thermocline and net warming in the sub-surface. To try to illustrate this, imagine someone holding a blanket. They rapidly lift the blanket up (Step 2) and then push it back down (Step 3).

You will get a wave in the blanket, where it travels from the source region (you) towards the opposite direction. This same exact thing happens during Oceanic Kelvin wave events, where the general wave pattern will propagate from west to east. Since Oceanic Kelvin waves travel only from west to the east, you can expect when one phase is located over a region (i.e., today an “Upwelling” phase is in the East Pacific), the opposite phase will soon to follow (i.e., the “Downwelling” phase will be in the East Pacific in 1-2 months). It may be appropriate to illustrate the evolution of the 1997 Super El Niño event to shed some more light on the similarities of the pattern then when compared to now.

Three fields are shown above in the panel of time-longitude plots. The left most figure is of the departure of the west-to-east winds (the "zonal wind anomalies') in the lower troposphere, averaged about the Equator. The figure in the middle is essentially a field to monitor the fluctuations of the thermocline in the Pacific Ocean, or can be thought of as a crude way to isolate the depth of the SST gradient. The right most figure is SST anomalies. In February and March of 1997, we observed strong westerly winds on the surface of the western Pacific (known as “westerly wind bursts”). Strong westerly wind bursts in the lower atmosphere can initiate an oceanic Kelvin wave. We observed a number of oceanic Kelvin waves that Spring, both having upwelling and downwelling phases. With each oceanic Kelvin wave event, the warm pool kept “sloshing” around until the final Kelvin wave event, which reconstructed the base state of the thermocline, and the Super El Niño was born beginning in May 1997, and lasting through April 1998. It was the strongest El Niño event ever recorded.

Let’s take a look at what happens in the sub-surface during one of these “Oceanic Kelvin waves”. Here’s an example from 2003. During the onset of an oceanic Kelvin wave, you will see strong sub-surface warming in the western Pacific, and strong cooling near the surface in the Pacific. With time, the warming pushes eastward in the sub-surface, eventually eroding the cold anomalies in the East Pacific surface, which switch to warm anomalies thereafter.

Some Oceanic Kelvin waves are not strong enough to reconstruct the Pacific Ocean base state, and will only result in minor adjustments. One way to see this is by using the current 20°C isotherm depth and anomaly Hovmoeller plots from February 2014 below. The black solid line represents the center of the “Downwelling” phase (or warming in sub-surface phase); the black-dashed line represents the center of the “Upwelling” phase (or cooling at surface phase).

There have been a series of 3 strong Kelvin waves over the past 7 months. Each Kelvin wave pushed some water from the West Pacific Warm Pool towards the East Pacific, but the subsequent upwelling phase resulted in cooling. This week, a very strong “Upwelling” phase of a Kelvin wave is pushing across the Eastern Pacific, forcing colder waters from the subsurface towards the surface, cooling the Eastern Pacific surface waters. This cooling has put the index we use to track El Niño--the so-called "ENSO 3.4 index"--at -0.5°C, right at the border of La Niña conditions. This is happening while warm surface water is being pushed down into the sub-surface, resulting in massive warming below the surface. Here is the evolution of the sub-surface SST structure beginning in January and ending this week:

Note that there has been strong cooling in the East Pacific, associated with the strong “Upwelling” phase of the Kelvin wave and strong sub-surface warming in the western-central Pacific associated with its “Downwelling” phase. This strong Oceanic Kelvin wave is the reason why today’s SST anomaly snap-shot map has the appearance of a strong La Niña, but is just the result of processes occurring in the Pacific Ocean at sub-seasonal time scales.

The current Kelvin wave in the Pacific Ocean has achieved the same strength as the one that preceded the 1997 Super El Niño event. This is an extremely rare feat but there still has to be a number of things to happen before we can say we are headed towards a strong El Niño. We need to see the continuation of strong westerly winds near the Equator over the Central Pacific to keep the momentum forward.

What caused the development of the strong Oceanic Kelvin wave? A strong westerly wind burst (WWB1) was observed during January 19 - 30 over the equatorial West Pacific:

Note from the time-longitude plot of Madden Julian Oscillation (MJO) filtered velocity potential anomalies at 200 mb (VP200), the convectively active phase of the MJO passed across the Western Pacific in late December through early January. Therefore, WWB1 on January 19 - 30 was likely driven by other features in the atmosphere other than the MJO:

Looking more into the finer details, there was a pair of strong gyres (or “low pressure systems”) mirroring each other about the Equator. One gyre set up shop over the Philippines, and caused major flooding. The gyre south of the Equator set up over northern Australia, and also produced a great deal of precipitation and thunderstorm activity.

Since the flow in the Northern Hemisphere around a low pressure system (or gyre) is counterclockwise, it produces low-level westerly flow to the south of the gyre. Vice versa, flow around a low pressure system in the Southern Hemisphere is clockwise. Thus, to the north of the low, there is also accelerated westerly flow. The net combination of these gyres over the equatorial West Pacific aided in a significant westerly wind burst in late January, as these gyres persisted for nearly 1-2 weeks.

Note that the GFS forecast calls for another amplification of mean westerly flow about the Equator west of the Date Line February 18 - 28 (WWB2). Looking at the 1000mb standardized geopotential height anomaly map, the forecast calls for *two* sets of twin cyclones mirroring each other about the Equator, with one of the Southern Hemisphere gyres forming into a tropical cyclone near the Date Line!

The pair of twin cyclones will likely amplify westerly flow in the medium range, and would likely keep the forward momentum of the Oceanic Kelvin wave, providing more evidence in a possible change of the base state in the Pacific. The kicker for a full blown 1997-like Super El Niño to develop would likely be some additional assistance from the development of early-season Pacific tropical cyclones near the Equator, as the GFS model is starting to hint at south of the Equator. Note that the 1997 Super El Niño event had the help from Category 5 Super Typhoon Isa during early April, which developed close enough to the Equator over the Central Pacific to produce another significant westerly wind burst there, and continue to push the West Pacific Warm Pool eastward.

So as it stands now, the ocean has geared in towards another big eastward push of the West Pacific Warm pool towards the East Pacific. We do need to see more westerly winds develop across the Central Pacific to completely swap the base state this Spring. This piece of the puzzle is difficult to predict at such long time-scales, but there are some indications for this to occur at least in the medium-range. Both the CFSv2 and European seasonal model forecasts are extremely aggressive with this transition to El Niño idea, as shown in the time series plots below:

What does this mean for the U.S. this summer? Well, why it’s still a bit early to be certain, typical conditions over the U.S. during strong El Niño’s favor a ridge over the West and a trough over the East. Therefore, you typically see warmer than average summers over the West Coast, and colder than average temperatures over eastern two thirds of the nation, as shown by a simple surface temperature correlation map with the ENSO 3.4 index:

BOTTOM LINE: The Pacific Ocean is now in a state that could reconstruct the base state of the Pacific, favoring an El Niño to develop later this Spring. That being said, it’s not a locked in solution yet as we need to monitor the atmosphere for future westerly wind bursts to help push the Western Pacific Warm Pool along. Thanks go to NOAA for providing the majority of the images used in this post.

Michael Ventrice

Dr. Michael Ventrice is an operational scientist for the Energy team at Weather Services International (WSI), who provide market-moving weather forecasts and cutting-edge meteorological analysis to hundreds of energy-trading clients worldwide.  Follow the WSI Energy Team on Twitter at @WSI_Energy and @WSI_EuroEnergy.

Climate Summaries

Midwest's February Thaw to be Followed by a Return of the Polar Vortex

By: JeffMasters, 3:27 PM GMT on February 19, 2014

A major February thaw is underway across the Midwest U.S., where high temperatures are above freezing for a second consecutive day in cities like Chicago, Minneapolis, and Detroit. The welcome thaw is bringing significant melting of the heavy snowpack over the Midwest, raising flooding concerns. Much of Illinois, Iowa, Wisconsin, Michigan, Minnesota, and Indiana are covered by snows of 10 - 30" that if melted, would be equivalent to 2 - 6" of rain. With temperatures in the 40s and low 50s coming on Thursday, accompanied by up to 1" of rain, flash flooding is expected in many regions of the Midwest. Soils are still frozen, which will limit the infiltration of the rain into the ground, providing faster run-off and greater flooding potential. Also of concern are ice jams on rivers, caused when the ice on top of rising rivers breaks up and jams together, creating blockages that back up river waters. NOAA's Storm Prediction Center has placed much of the Midwest under their "Slight Risk" area for severe weather on Thursday, with portions of Kentucky and Tennessee in their first "Moderate Risk" area of the year. Severe thunderstorms with strong winds, hail, and few tornadoes will make it seem like spring. However, it will be winter on Thursday over Northern Iowa and Southern Minnesota, where blizzard warnings are posted.

Figure 1. The equivalent amount of rain stored in the Midwest snowpack as of February 19, 2014, ranges from 2 - 6" over much of Iowa, Illiinois, Indiana, Wisconsin, Michigan, and Ohio. Image credit: NOAA/NOHRSC.

Return of the Polar Vortex Next Week
Fortunately (?) for the Midwest, this week's thaw will be short-lived, preventing the kind of major flooding that would result if all of the snowpack were to melt in a week. This morning's runs of the GFS and European models were better able to handle the evolving upper-air pattern over the Pacific Ocean, and it appears that their earlier runs seriously underestimated the strength of a ridge of high pressure forecast to build over the Western U.S. 6 - 10 days from now. This ridge will be accompanied by a return of the cold "Polar Vortex" over the Midwest and Northeast U.S., bringing bitter cold temperatures and strong winds. Temperatures 20°F below normal will likely invade the Upper Midwest on Sunday, and gradually spread southeastwards during the week. The peak cold is predicted to occur late next week, with temperatures 20 - 35° below normal covering much of the eastern 2/3 of the country. As a result of these new model runs, the natural gas market has been soaring ever since early this morning, and is now approaching a five-year high of $6. 

Figure 2. The 6 - 10 day forecast for February 24 - 28, made on February 19, 2014, calls for a high probability of below-average temperatures over the eastern 2/3 of the contiguous U.S., as the dreaded "Polar Vortex" drops southwards over the U.S. again. Image credit: NOAA/CPC.

Thanks go to WSI's Mike Ventrice for the info on the natural gas market. He posts to @WSI_Energy on Twitter.

Jeff Masters

Winter Weather Flood

NHC Adds Unnamed Subtropical Storm to 2013's Atlantic Tally

By: JeffMasters, 3:19 PM GMT on February 17, 2014

The National Hurricane Center (NHC) announced last week that the hurricane season of 2013 had one more storm that should have been named--a short-lived low that developed south of the Azores during early December, which became a subtropical storm on December 5. "Should-Have-Been-Named-Subtropical-Storm-Nestor" reached top sustained winds of 45 mph. The storm formed over unusually cool waters of 22°C (72°F), and brought sustained 10-minute winds of 37 mph with a gust to 54 mph near 00 UTC December 7 to Santa Maria in the southeastern Azores. With this addition, the 2013 Atlantic season ended with 14 tropical and subtropical storms. Two, Ingrid and Humberto, became hurricanes, but neither became a major hurricane.

Figure 1. True-color MODIS satellite image of Unnamed Subtropical Storm Fourteen at 15:30 UTC December 6, 2013, as it approached the Azores Islands. At the time, "Should-Have-Been-Named-Subtropical-Storm-Nestor" had 45 mph sustained winds. Image credit: NASA.

December named storms are rare
The unnamed 2013 subtropical storm is the Atlantic's first December tropical or subtropical storm since Tropical Storm Olga of 2007. There have been eighteen Atlantic tropical or subtropical storms that have formed in the month of December since record keeping began in 1851. Only four have hit land. Eight of the eighteen storms have occurred since 1995. Eight have been hurricanes, with a Category 2 hurricane in 1925 being the only December storm to hit the mainland U.S.

December named storms have higher than usual odds of being subtropical in nature, since the ocean temperatures required to create a fully tropical system are typically lacking. The NHC began naming subtropical storms in 2002. Between 1968 and 2001, subtropical storms were simply given numbers ("One", "Two", etc). Before 1968, subtropical storms were never classified as such, but were sometimes called "Unnamed storm". A landmark study performed by Herbert and Poteat (1975) led to a substantial increase in the identification and naming of subtropical storms in the late 1970s and early 1980s. However, when Bob Sheets became director of the National Hurricane Center between 1987 and 1995, he declared that subtropical storms should not be recognized, and very few subtropical storms were classified during this period. Prior to 1968, there are many systems that were subtropical in the Atlantic that should have been included in the official HURDAT database. I've seen estimates that 5-10 storms were missed in the 1950s, and ten between 1969 and 1999. A reanalysis effort is underway to include these "missed" storms into the database. However, it will be several years before this process is complete. Here are all of the tropical and subtropical storms that have formed in December in the Atlantic since 1995:

2013: Unnamed Subtropical Storm Fourteen, December 5
2007: Tropical Storm Olga, December 11
2005: Tropical Storm Zeta, December 30
2003: Tropical Storm Odette, December 4
2003: Tropical Storm Peter, December 7

Dr. Jim Kossin of the University of Wisconsin published a 2008 paper in Geophysical Research Letters titled, "Is the North Atlantic hurricane season getting longer?" He concluded that yes, there is an "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high".

Mexican National Hurricane Agency formed
The president of Mexico announced in mid-January the creation of a new National Hurricane Agency. The new institution may begin operations as soon as this summer, and will study how to generate and communicate hurricane and severe weather forecasts.

Jeff Masters


Snowstorm Kills 21, Drops 2' of Snow; January U.S. Temperatures Near Average

By: JeffMasters, 3:47 PM GMT on February 14, 2014

The latest blow from the Eastern United States' endless winter of 2013 - 2014 is winding down, as Winter Storm Pax scoots northeastward into Canada. Pax was the biggest Nor'easter of the winter so far, and dumped more than two feet of snow in the higher elevations of Virginia, West Virginia, Maryland, and New York. Snowfall rates as high as 6" per hour were observed in an intense band that accompanied the storm over portions of New Jersey and New York. As of 9 am EST Friday, over a foot of snow (12.5") had fallen in New York City's Central Park, 12.3" in Baltimore, 11.9" at Newark, 9.8" at Philadelphia, and 6" in Washington D.C. at Reagan Airport. The storm dumped 5.8" on Knoxville, Tennessee--the city's first 5"+ snowfall since Jan. 17, 1996. Columbia SC recorded snow for the third day in a row on Thursday, marking the first time since January 1940 that had occurred.

From the 10 am EST Friday NWS storm report, here are the top snowfall totals by state from Pax:

Virginia: 28.5", Pilot
West Virginia: 27.5", Mount Storm
Maryland: 26", Glyndon
New York: 25.8", Jewett
Pennsylvania: 22.5", Glencoe
North Carolina: 21", Boones Hill
Vermont: 20", Mt. Holly
New Jersey: 19.2", Highland Lakes
Massachusetts: 16", Ludlow
Delaware: 14.4", Greenville
Maine: 14", Farmington
Connecticut: 14", Fairfield
Kentucky: 14", Jenkins
New Hamshire: 11.6", Washington
Tennessee: 11.3", Jonesborough
Alabama: 10", Cullman, Hunstville
Georgia: 10", Batesville
South Carolina: 10", Clover
Rhode Island: 9.6", West Glocester

Figure 1. Can you find the car? Image taken on Thursday, February 13, 2014 from Frostburg, Maryland, where 21.5" of snow fell. Image credit: wunderphotographer ftaccino1.

Twenty-one Deaths, 400,000 Without Power
At least 21 deaths are being blamed on the storm, including three people who died of heart attacks while shoveling heavy snow in Maryland on Thursday. As of 9 am EST on Friday, approximately 400,000 customers were without power, almost entirely in the states that received the worst freezing rain: Georgia, North Carolina, and South Carolina. At the ice storm's peak on Thursday, about 700,000 customers were without power.

Figure 2. Historical temperature ranking for the U.S. for January 2014. A persistent trough of low pressure over the East brought a top-ten coldest January on record to eight states, but an equally strong ridge of high pressure over the West Coast brought a top-ten warmest January on record to California, Arizona, and Nevada. Image credit: National Climatic Data Center (NCDC).

A slightly cooler than average January for the U.S.
January of 2014 saw the most severe cold in twenty years over much of the Eastern half of the U.S., but no states had their coldest January on record, said NOAA's National Climatic Data Center (NCDC) in their latest State of the Climate report. A persistent trough of low pressure over the East brought a top-ten coldest January on record to eight states, but an equally strong ridge of high pressure over the West Coast brought a top-ten warmest January on record to California, Arizona, and Nevada. As a result, the January temperature over the entire contiguous U.S. was only slightly cooler than average, ranking as the 53rd coolest January in the past 120 years. According to the Rutgers Global Snow Lab, January snow cover extent across the contiguous U.S. was the 16th smallest in the 48-year period of record. Above-average snow cover was observed across the Northern Plains, Midwest, and Northeast where numerous winter storms brought heavy snowfall during the month, but below-average snow cover was observed for most of the West and Southern Rockies.

According to NOAA's U.S. Climate Extremes Index (CEI), which tracks the percentage area of the contiguous U.S. experiencing top-10% and bottom-10% extremes in temperature, precipitation, and drought, January extremes were below average, with 12% of the nation experiencing top-10% extreme conditions, compared to an average of 18%.

Figure 3. Drought conditions in California in January 2014 were the most severe ever observed in January, dating back to 1895. Image credit: NOAA/NCDC.

Dry in the west
January was a very dry month, ranking as the fifth driest January on record for the contiguous U.S., with eight states having a top-ten driest January. New Mexico had its driest January on record, with just 0.03" of precipitation, averaged over the entire state. The 0.02" of precipitation for Arizona ranked as their 2nd driest January on record. Drought conditions in California in January 2014 were the most severe ever observed in January, dating back to 1895. California had its driest 3rd driest January. It was the state's driest December-January on record, with 0.94 inch of precipitation, 7.35 inches below average. The previous record dry December-January occurred in 1975/76, when the two-month precipitation total was 1.32 inches. The December-February period is typically the wettest three months for California, and is an important time for the state's water resources. Winter precipitation is vital to replenish reservoirs and builds mountain snowpack that melts during the spring and summer. Last week's "Pineapple Express" storm over Northern California helped reduce the area of California in extreme drought from 67% to 61%, but the drought situation remains dire.

Warm again in Sochi
Friday was the warmest day yet of the Winter Olympics in sunny Sochi, Russia, where the temperature rose to 64° at 12:30 pm local time. We can expect continued issues with excessive warmth as high temperatures rise into the low 60s again on Saturday, before cooling off to more seasonable highs in the low 50s on Sunday. Temperatures at the mountain venues are typically 10 - 20° cooler than in Sochi, but have still been well above freezing during the daytime hours. According to an article in the USA Today, more than 100 winter Olympians have signed a petition urging world leaders to fight climate change. "The once-consistent winters that I saw as a young kid are no more, especially near my home in Vermont," U.S. cross country skier Andrew Newell, 30, says in a statement seeking support. At least 105 Olympians from 10 countries have signed on, including 85 Americans. They're asking countries to reduce heat-trapping carbon dioxide emissions, embrace "clean energy" and prepare for a global agreement at the United Nations' climate convention in Paris next year.

Have a great weekend, everyone!

Jeff Masters

Winter Weather Climate Summaries

Heavy Snow Belts East Coast; Southeast Ice Storm Leaves 700,000 Without Power

By: JeffMasters, 4:01 PM GMT on February 13, 2014

The memorable winter of 2014 continues over the Eastern U.S., where an intensifying Winter Storm Pax has dumped up to a foot and a half of snow. Snowfall rates of 3" per hour have been observed in North Carolina, Pennsylvania, and New York this morning. A band of super-heavy snow set up over northern New Jersey, with some reports of 3 - 4" of snow falling in just 30 minutes. As of 9 am EST, over a foot of snow (12.3") was observed at the Baltimore Airport, 7" at New York City's Central Park, and 11" in Washington D.C. at American University. The 8.8" of snow so far today in Philadelphia makes the winter of 2013 - 2014 the 5th snowiest on record there, and the first time since record keeping began in 1884 that Philadelphia has had four separate six inch or greater snowstorms in a winter. From the 10 am EST Thursday NWS storm report, here are the top snowfall totals from Pax:

West Virginia, 19", Cherry Grove
Virginia: 18", Winchester
Maryland: 18", Frewerick, Damascus, Glyndon
North Carolina: 15", Saluda
Delaware: 13.4", Newark
New Jersey, 11.8", Pittsgrove Twp
Alabama: 10", Cullman, Hunstville
Georgia: 9.8", Summerville
New York, 9.8", Commack
South Carolina: 8", Heath Springs
Kentucky: 7", Harlan, Lunch
Tennessee: 6", Erwin

Figure 1. Satellite image of Winter Storm Pax at 9:45 am EST Thursday, February 13, 2014. Image credit: NASA GSFC.

Thirteen Deaths, 700,000 Without Power
At least thirteen deaths are being blamed on the storm, including car crashes on icy roads that killed seven people in Texas on Monday and Tuesday. As of 10 am EST on Thursday, approximately 700,000 customers were without power, with 470,000 of these in Georgia and South Carolina. Freezing rain amounts up to 1/2" were common there, and the ice storm was the worst to affect Georgia since 2000, when a January ice storm knocked out power to approximately 500,000 customers. However, only a few locations in the Southeast recorded 0.75 - 1.0" of ice, and the catastrophic ice storm that was feared did not materialize. The worst ice conditions from the storm generally rated a "3" on a scale of 1 to 5 of the Sperry-Piltz Ice Accumulation Index. The impacts expected from a level 3 ice storm: "Numerous utility interruptions with some damage to main feeder lines and equipment expected. Tree limb damage is excessive. Outages lasting 1 - 5 days."

Figure 2. The Sperry-Piltz Ice Accumulation Index. Image credit: Sidney K. Sperry,

Too Warm in Sochi
Thursday was another warm, sunny day in Sochi, Russia, home of this year's Winter Olympics. The temperature rose to 62°--an unseasonably warm day for February. The unusual warmth caused numerous problems for skiers and snowboarders, and we can expect continued issues with excessive warmth as high temperatures rise into the low 60s again on Friday and Saturday. Beginning on Sunday, temperatures will cool down to more seasonable levels, with highs in the low 50s. Temperatures in the mountains above Sochi are typically 10 - 20 degrees colder than what are observed in the city. The New York Times has an interesting editorial, The End of Snow?, describing how a warming climate will make it increasingly difficult to hold Winter Olympics games.

Video 1. I appeared on Democracy Now this morning to put this winter's extreme weather into context.

Figure 3. Screen shot of the new hazard reporting feature of the wunderground iPhone and Android app.

New Wunderground Hazard Reporting Feature launched today
Wunderground users, we have a request: if you spot hazardous weather or road conditions in your locale, share them with other members of the wunderground community, using the wunderground iPhone or Android app. Users will have the option to submit hazards that include: flooding, power outages, road debris and high surf, as well as, winter weather conditions such as slippery roads, white outs, and street plowing. In addition to submitting hazard reports within the app, users can also share current severe weather alerts or screenshots of selected hazards with friends and family via SMS text, email, Facebook or Twitter. Previously submitted sky and hazard reports can be easily accessed as a layer within the app’s interactive weather map, known as WunderMap®. As hazardous conditions can only be reported for one’s current location, app users can be sure they are viewing weather information within their immediate proximity. The new hazard-reporting feature comes in response to the success of our initial crowd-reporting feature launched in December of 2013, which allows users to verify observed sky conditions. Over one million sky conditions reports were submitted in two months.

Jeff Masters

Winter Weather

Dangerous Winter Storm Pounds Georgia and South Carolina

By: JeffMasters, 3:03 PM GMT on February 12, 2014

A historic Southeast U.S. winter storm is pounding Georgia and South Carolina with heavy snow and thick coatings of freezing rain. Car crashes on icy roads from the storm have already killed six people--four in Texas, and two in Mississippi--and travel will be extremely dangerous over much of the South on Wednesday. As of 9 am EST on Wednesday, freezing rain amounts as high as 1/2" had already been observed in Central South Carolina near Columbia. Freezing rain rates as high as 0.1" per hour are expected along a swath from Atlanta, Georgia to the northeast coast of South Carolina. Over 1" of ice may accumulate from freezing rain in areas near Augusta, Georgia. Strong winds will combine with the freezing rain to blow down trees and power lines, and the Sperry-Piltz Ice Accumulation Index rates the potential impacts from areas which receive at least 3/4" of ice accompanied by winds in excess of 15 mph at a 4 on a scale of 1 to 5. At this level, expect "prolonged and widespread utility interruptions with extensive damage to main distribution feeder lines and some high voltage transmission lines/structures. Outages lasting 5 - 10 days." As of 9:45 am EST, 78,000 customers in Georgia had lost power, and power outages were increasing at a rate of 30,000 customers per hour. About 30,000 customers had lost power in South Carolina.

Figure 1. Predicted snow amounts and freezing rain amounts for the period ending at 7 pm EST Thursday, February 13, 2014. Image credit: National Weather Service Southern Region.

Atlanta shuts down for snow and ice
Atlanta, Georgia, which was shut down by the 2.6" of snow Winter Storm Leon brought to the city on January 28, has been shut down again on Wednesday by Winter Storm Pax. Downtown Atlanta had already received 1/2" of sleet and 1/4" of freezing rain as of 7:30 am EST, making travel dangerous or impossible. Up to 1/2" of ice and 3 - 5" of snow are predicted for the city; Atlanta has only had seven snowstorms in its history greater than 4". The 7 am EST weather balloon launched from Atlanta iced up too much and was lost at about 630mb (12,500'). They decided not to launch another one, since it would probably suffer the same fate. The sounding showed a classic freezing rain profile: temperatures near freezing at the surface, cooling to 24° at 2600', with a a 3000-foot thick layer of warm air above that, peaking at a temperature of 38°. That thick layer of cold air above the surface is supercooling the rain as it falls though, allowing the rain to freeze at impact even if the surface temperatures are 33°. One positive aspect: the ice from this storm will melt out rather quickly compared to previous historic Southeast U.S. ice storms. High temperatures are expected to warm into the lower 40s by Thursday and lower 50s by Friday across South Carolina and Northern Georgia.

Figure 2. Atlanta shut down: At 9 am EST on Wednesday, February 12, 2014, the normally busy lanes of I-75 in Atlanta near the I-285 interchange were deserted. Image credit: Greg Diamond, TWC.

Heavy snow for the Mid-Atlantic and Northeast coast Wednesday night and Thursday
The storm will move up the Eastern Seaboard Wednesday night into Thursday, likely bringing six or more inches of snow to major East Coast cities, including Washington D.C., Baltimore, New York City, and Philadelphia. However, depending upon the exact track of the storm, rain may mix with the snow near the coast on Thursday afternoon, potentially keeping snowfall amounts under six inches in New York City and Philadelphia. The winds from the storm are not going to be strong by Nor'easter standards, and only minor coastal flooding is expected. In Philadelphia, where 6 - 10" of snow are predicted, the storm could set a bit of history. If Philadelphia International Airport receives 6 inches or more of snow from this system, it would be the first time since record keeping began during the winter of 1884 -1885 that Philadelphia has had four separate six inch or greater snowstorms in a winter.

Historic U.S. ice storms
Today's ice storm is likely to be more damaging than the January 2000 ice storm, which caused $48 million in losses in north Georgia. However, it will not compare to the damage from the most expensive ice storm in U.S. history, the great February 1994 Southeast U.S. ice storm. That storm killed nine people and caused $4.7 billion (2013 dollars) of damage in portions of TX, OK, AR, LA, MS, AL, TN, GA, SC, NC, and VA. At least 2 million customers were without electricity at some point, and 1/2 million were still without power three days after the storm. Hardest hit was Northern Mississippi, which was deluged with 4 - 5" of freezing rain that created flooding problems. Ice thicknesses of 3.5 - 5.5 inches were common in the state, causing catastrophic damage estimated at $3 billion. Some residents were without power one month after the storm.

TWC has put together a Top Ten Worst U.S. Ice Storms list, and the 1994 storm ranks as the South's worst ice storm. The record for greatest accumulation of ice in the U.S. occurred during the New Year's ice storm of January 1 - 3, 1961, in Northern Idaho, with up to 8" of ice.

Jeff Masters

Winter Weather

Dangerous Ice Storm Hitting Southern U.S.

By: JeffMasters, 2:10 PM GMT on February 11, 2014

A state of emergency has been declared for all of Alabama, Northern Georgia, Northern Mississippi, and Northern Louisiana as the South's second serious winter storm of 2014 spreads snow, sleet, and freezing rain across the region on Tuesday and Wednesday. Freezing rain at a temperature of 29° was falling at 9 am EST Tuesday morning in northern Mississippi in Columbus, and in Birmingham, Alabama, where it was 32°. The storm, called Winter Storm Pax, begins its most dangerous phase Tuesday night into Wednesday, when rain changes to freezing rain from Eastern Georgia through Central South Carolina. As much as 1" of freezing rain is expected in Augusta, Georgia and Columbia, South Carolina, and widespread power outages would result if these ice amounts materialize. Atlanta, Georgia, which was shut down by the 2.6" of snow Winter Storm Leon brought to the city on January 28, is expected to receive a nasty mix of freezing rain, snow, and sleet Tuesday night and Wednesday from the new storm, making travel dangerous or impossible. Just a slight shift in the track of the storm or atmospheric conditions could greatly alter the amount of snow and freezing rain this storm brings, and residents impacted by this storm should follow the latest forecast updates. One positive aspect: the cold air behind this storm will be short-lived, and high temperatures are expected to warm into the upper 40s by Thursday across South Carolina and Northern Georgia.

Figure 1. Predicted freezing rain amounts for the period ending at 6 pm CST Wednesday, February 12, 2014. Image credit: National Weather Service Southern Region.

Heavy snow for the Mid-Atlantic and Northeast coast Wednesday night and Thursday
The storm will move up the Eastern Seaboard Wednesday night into Thursday, potentially bringing six or more inches of snow to major East Coast cities, including Washington D.C., Baltimore, New York City, and Philadelphia. However, depending upon the exact track of the storm, rain may mix with the snow near the coast, resulting in snowfall amounts under six inches in New York City. The winds from the storm are not going to be strong by Nor'easter standards, and only minor coastal flooding is expected from the storm. In Philadelphia, where 6 - 10" of snow are predicted, the storm could set a bit of history. If Philadelphia International Airport receives 6 inches or more of snow from this system, it would be the first time since record keeping began during the winter of 1884-5 that Philadelphia has had four separate six inch or greater snowstorms in a winter.

Figure 2. Remote-controlled robot snowplow, available for $7,900 from

Robot snow shoveling help?
For those of you with a little extra disposable income who are sick of shoveling this winter's epic snows, check out this 393-pound remote-controlled robot snowplow, available for $7,900 from I like my robot vacuum cleaner, but I have my doubts that I'll be buying a robot snowplow!

Video 1. An avalanche sweeps down a mountainside in the South Tyrol region of the Alps on February 6, 2014. Thomas Ennemoser, a farmer from Orsteil Pill, filmed from a safe distance on a hill. The avalanche damaged several buildings, and 15 people were forced to evacuate.

Jeff Masters

Winter Weather

California's Sierras Get Over 10 Inches of Precipitation; Snow, Ice Coming to South

By: JeffMasters, 4:46 PM GMT on February 10, 2014

California's biggest rainstorm since December 2012 brought much-needed moisture to the state over the weekend, thanks to a very moist “Pineapple Express” atmospheric river of moisture from the Hawaiian Islands. The storm brought more than 2" of precipitation to most of Northern California, and more than 10" to the Northern Sierra Mountains, where as much as six feet of snow fell above 9,000'. Some locations saw more rain in a four-day period than they had during the previous eight months. San Francisco got 2.58" of rain Thursday through Sunday, which isn't far below the 4.24” of rain it received during the previous thirteen months. The city averages about 20" of rain per year. Water levels on the critical Central California reservoir Folsom Lake rose by twelve feet in one day between February 8 and 9, 2014. However, the lake remains at just 41% of its average capacity for this time of year, and is well below the record low levels set during 1977. California probably needs at least five more storms like this to pull them out of drought. Wunderground's weather historian Christopher C. Burt discusses the amazing January 2014 California heat wave in his Saturday post, and has a detailed update on precipitation totals from the past weekend's Pineapple Express storm in his latest post.

Figure 1. Observed precipitation for the 7-day period ending at 12 UTC on Monday, February 10, 2014. Portions of the northern Sierra Mountains received more than ten inches of precipitation. Image credit: NOAA/HPC.

Figure 2. Water levels on the critical Central California reservoir Folsom Lake rose by twelve feet in one day between February 8 and 9, 2014. However, the lake remains at just 41% of its average capacity for this time of year, and is well below the record low levels set during 1977. Image credit: California Department of Water Resources.

The forecast: a return to mostly dry conditions this week
The persistent and intense ridge of high pressure that has dominated the West Coast since December 2012, bringing California's record dry spell, has broken down over the past week. While the models show generally dry conditions for the state during the coming ten days, the ridge is not forecast to build back at anywhere near its former intensity, giving me some hope that the state will experience more rainy weather during the last half of February.

Figure 3. Predicted precipitation for the 7-day period ending on Monday, February 17, 2014. California will mostly be dry, with heavy rains confined to the far Northern Coast. Image credit: NOAA.

Significant winter storm takes aim at Southern U.S.
The Southern U.S. gets its second serious winter storm of 2014 this week, as Winter Storm Pax brings a dangerous mix of snow, sleet, and freezing rain. The snow and freezing rain action begins Monday night over Northeast Texas, Southeast Oklahoma, Southern Arkansas, and Northern Louisiana, then spreads eastwards on Tuesday into northern portions of Mississippi, Alabama, Georgia, and South Carolina, and over much of North Carolina. Atlanta, Georgia, which was shut down by the 2.6" of snow Winter Storm Leon brought to the city on January 28, is under a Winter Storm Watch. Snow and sleet are expected to begin on Tuesday morning. After warming afternoon temperatures bring a period of plain rain on Tuesday afternoon, the rain may change to freezing rain on Tuesday night and Wednesday, making travel dangerous or impossible. The greatest accumulations of freezing rain may fall in Central South Carolina, where up to 3/4" of ice is predicted. However, this is a complex forecast, and just a slight shift in the track of the storm or atmospheric conditions could greatly alter the amount of snow and freezing rain this storm brings. The storm will move up the Eastern Seaboard Wednesday night into Thursday, potentially bringing snow to major East Coast cities.

Jeff Masters

Drought Winter Weather

Pineapple Express Bringing Significant Rains to Drought-Stricken California

By: JeffMasters, 10:10 PM GMT on February 06, 2014

A very moist “Pineapple Express” flow of air from the Hawaiian Islands will impact California through Sunday, likely bringing enough precipitation to make a noticeable dent in the state’s dire drought conditions (though the exceptionally dry and hard soils caused by California’s driest year in its history are forcing the heavy rains to run off faster than usual, reducing the amount of moisture that can soak into the soil.) Some locations may see more rain in a four-day period than they have had during the previous eight months. NOAA’s Weather Prediction Center is calling for most of Northern California to receive more than 2” of precipitation through Sunday, with many higher elevation areas expected to get 4 - 6”. Up to three feet of snow is predicted to fall in the Sierra Mountains, though it appears much of the precipitation will fall as rain, reducing the benefit of the moisture during the coming summer months (when Sierra snow melt provides an important source of water.) As of Thursday at 1 pm PST, Big Sur had received 2.14” of rain, which triggered a rock slide onto Highway 1.

Figure 1. Total precipitable water (TPW) for Thursday, February 6, 2014. TPW is how much rain (in inches) would fall at a given location if one condensed out all of the water vapor in a column above the location into rain. For reference, 1 inch = 25.4 mm. A narrow “Atmospheric River” of moisture is seen extending from the subtropics near Hawaii into California. Image credit: University of Wisconsin SSEC.

Drought far from busted
This weekend’s Pineapple Express is a marvelous break from the extraordinary dry conditions that have gripped California for the past thirteen months. If one could put a monetary value on the moisture from this storm, I speculate that it would easily be worth a billion dollars. But the state is in such a deep precipitation hole that it needs at least six more events like this over the next two months to pull them out of drought. Between January 1, 2013 and February 5, 2014, the San Francisco Airport received just 4.24” of rain, which is 21.19” below normal for the period—by far the driest such period in their history. The last time San Francisco had more than 1” of rain was Christmas Day, 2012. Thursday’s new Drought Monitor product showed that drought conditions in the state had remained almost the same as the previous week, with 94% of the state in drought, and a slight expansion of the area in the worst category of drought—exceptional—from 9% to 10%.

Figure 2. Comparison of how much rain is needed to relieve drought conditions in Central California, via Twitter from NWS Sacramento.

Figure 3. Amount of precipitation needed in one month to end drought conditions. In San Francisco, more than 18” of rain is needed in one month, and the average annual rainfall in the city is about 20”. Image credit: NOAA.

Atmospheric rivers: California’s big drought busters
Narrow bands of copious moisture originating in the subtropics like this weekend’s “Pineapple Express” are called “atmospheric rivers”, and are responsible for about 30 - 50% of California’s yearly precipitation. A strong “atmospheric river” transports an amount of water vapor roughly equivalent to 7.5 - 15 times the average flow of liquid water at the mouth of the Mississippi River. As discussed in a blog post today by Climate Central’s Andrew Freedman, research by Michael Dettinger of the U.S. Geological Survey and the Scripps Institution of Oceanography, published in December 2013 in the Journal of Hydrometeorology, found that atmospheric river events can effectively end major droughts in California within just one month, pulling the state from a significant precipitation deficit to a surplus. Wunderground weather historian Christopher C. Burt has a post on the last drought-busting atmospheric river event, in March 2012. I don’t see that happening this month, though. The latest 2-week run of the GFS model shows the state returning to relatively dry conditions beginning on Monday, with a ridge of high pressure dominating the weather for the remainder of the week. The most recent 1-month and 3-month forecasts from NOAA’s Climate Prediction Center call for higher than average possibilities of dry conditions into the spring of 2014. California’s best hope of busting the drought lies in the formation of an El Niño event next winter. The warm waters that El Niño events bring to the Eastern Pacific typically shift the jet stream to a position over California, bringing numerous low pressure systems and the occasional atmospheric river during the winter rainy season. The latest February 6, 2014 El Niño outlook from NOAA gives some hope that this will happen:

”An increasing number of models suggest the possible onset of El Niño. Strong surface westerly winds in the western Pacific and the slight eastward shift of above-average temperatures in the subsurface western Pacific potentially portend warming in the coming months.”

Have a great weekend, everyone, and I’ll be back Monday with a new post.

Jeff Masters


Top Ten Extraordinary Weather Videos of 2013

By: JeffMasters, 3:51 PM GMT on February 04, 2014

The year 2013 was another extraordinary one for weather extremes, with a world-record 41 billion-dollar weather disasters. With the rise of smart phones and YouTube, we now have an amazing capability to document and make available videos of disasters like these, and I present here my pick for the top ten most remarkable weather videos of 2013.

#1. As the EF-4 tornado that hit Washington, Illinois on November 17, 2013 leveled his home, this videographer kept the camera rolling. Warning: Chilling, much foul language, and extremely intense. Definitely R-rated. No one in the video was injured, but the tornado killed two people in a nearby home.

#2. Probably the most remarkable video of storm surge ever taken: footage from Super Typhoon Haiyan in Hernani, Eastern Samar, Philippines. The video was taken by Nickson Gensis, Plan Philippines Community Development Worker, from the top floor of a boarding house on November 8, 2013.

#3. The May 31, 2013 El Reno, Oklahoma EF-3 tornado as filmed from a commercial tornado tour led by Tempest Tours. This is one of the most impressive videos I've ever seen, from a meteorological standpoint, of a developing tornado. The chasers got closer to the tornado than they liked, as evidenced by the honking horns you hear, telling people to leave, a few minutes into the video.

#4. When the hunters became the hunted: Weather Channel storm chasers Mike Bettes and two photographers were in their Tornado Hunt vehicle when they were hit by a tornado in El Reno, Oklahoma on May 31, 2013. The tornado picked their car up off the ground and rolled it 6 - 8 times before depositing it in a field 200 yards away. All the occupants were wearing seat belts and the air bags deployed, likely saving their lives. Bettes sustained minor injuries, including stitches in his hand. Producer Austin Anderson suffered broken bones and required hospitalization. The El Reno tornado killed four storm chasers,including veteran chasers Tim Samaras, 55; Paul Samaras, 24; and Carl Young, 45.

#5. The Weather Channel storm chasers weren't the only ones who got themselves in an extremely dangerous situation on May 31. storm chaser Brandon Sullivan and his chase partner Brett Wright got caught in the tornado northwest of Union City, OK and slammed with debris as the tornado hit a barn that exploded in front of them.

#6. Storm chasers James Reynolds, Josh Morgerman and Mark Thomas of were in the capital of Leyte Province, Tacloban, which received a direct hit from Super Typhoon Haiyan. Video includes the remarkable winds and storm surge of Haiyan, and the rescue of injured people from flood waters.

#7. You can see why landslides triggered by heavy rains from a tropical cyclone are among the most dangerous hazards of these storms, thanks to a dashboard cam that caught this extraordinary rock slide in Northeast Taiwan on August 31, 2013, after heavy rains from a cold front drenched the island with up to 200 mm (7.87") of rain in 24 hours. The rains fell upon soils already saturated by torrential rains from Tropical Storm Kong-Rey, which dumped up to 482 mm (19") of rain on Taiwan, killing three people. The driver of the car caught in the rock slide survived with minor injuries. Thanks go to wunderground member Robert Speta for bringing this video to my attention. A separate video showing the damage to the car and the course of the rock slide is here.

#8. Flooding in China from July 7 - 17, 2013 cost at least $4.5 billion. Rainfall amounts as high as 1,150 millimeters (45.3 inches) of rain fell in the Dujiangyan region, triggering Sichuan Province's worst floods in at least 50 years. In this remarkable video, we see a violent landslide engulf a car in on 13th July in Shaanxi Province, China. Amazingly, all four occupants survived. Dang Earthbenders!

#9. A tornado in Milan, Italy on July 29 hurls huge amounts of debris against the office building the video was taken from. The photographer is lucky the building's windows didn't shatter and seriously injure him. Jason Samenow at the Capital Weather Gang has more videos and details on the event.

#10. The view from veteran storm chaser Chris Novy's D-TEG dashcam as he accidentally drove his storm chasing vehicle into a swollen creek, nearly killing him. He posted this image on Facebook of the bridge that he drove off of. Note the guard rail that stops short of the plunge he took. I hope the road commission extends this guard rail to prevent a future accident!

Special mention for most artistic video of 2013: Adrift from Simon Christen on Vimeo. It's a spectacular 4-minute time-lapse video of fog rushing in past the Golden Gate Bridge into San Francisco. He writes: ""Adrift" is a love letter to the fog of the San Francisco Bay Area. I chased it for over two years to capture the magical interaction between the soft mist, the ridges of the California coast and the iconic Golden Gate Bridge. This is where “Adrift” was born. The weather conditions have to be just right for the fog to glide over the hills and under the bridge. I developed a system for trying to guess when to make the drive out to shoot, which involved checking the weather forecast, satellite images and webcams multiple times a day. For about 2 years, if the weather looked promising, I would set my alarm to 5am, recheck the webcams, and then set off on the 45-minute drive to the Marin Headlands. I spent many mornings hiking in the dark to only find that the fog was too high, too low, or already gone by the time I got there. Luckily, once in a while the conditions would be perfect and I was able to capture something really special. Adrift is a collection of my favorite shots from these excursions into the ridges of the Marin Headlands."

I'm in Atlanta this week for the 94th annual meeting of the American Meteorological Society, and will probably be too busy to put up another post until Thursday at the earliest.

Jeff Masters

Climate Summaries Extreme Weather

Groundhog Says: 6 More Weeks of Winter

By: JeffMasters, 1:34 PM GMT on February 03, 2014

Sunday had a Super mix of winter prognostications from North America’s bevy of rodent winter prognosticators, who emerged from their burrows on Groundhog Day to offer their predictions of an early or late end to winter. America’s most famous groundhog, Punxsutawney Phil, in Punxsutawney, PA had this to say:

“A Super Bowl winner I will not predict,
But my weather forecast, you cannot contradict,
That’s not a football lying beside me
It’s my shadow you see
So, six more weeks of winter it shall be!”

Figure 1. Canada's famous albino groundhog named Wiarton Willy from the town of Wiarton, Ontario. Image credit: wunderphotographer pincollector1.

Results of other groundhog forecasters
Wiarton Willie in Ontario, Canada saw his shadow, so 6 more weeks of winter.

General Beauregard Lee in Lilburn, GA, did not see his shadow, predicting an early end to winter.

Staten Island Chuck, AKA Charles G. Hogg, of the Staten Island Zoo, New York City saw his shadow, so six more weeks of winter. Chuck was dropped by New York City mayor Bill de Blasio, but was unharmed.

Buckeye Chuck in Ohio did not see his shadow, predicting an early end to winter.   

Shubenacadie Sam in Nova Scotia did not see his shadow, predicting an early end to winter.

Winnepeg Willow in Manitoba, Canada, did not see his shadow, predicting an early end to winter.

Dunkirk Dave in Dunkirk, NY, the world's second longest prognosticating groundhog, did not see his shadow, predicting an early end to winter. 

A quick look back at NOAA’s winter forecast issued in November
NOAA’s National Climatic Data Center (NCDC) analyzed Punxsutawney Phil’s forecasts over the past 26 years (thanks to Doyle Rice of USA Today for pointing this out.) If we evaluate just the eleven years both when the departure of February and March temperatures from average over the contiguous U.S. were both of the same sign, Phil had only three correct forecasts, and eight blown forecasts. NOAA concludes that “It really isn't a 'bright' idea to take a measure such as a groundhog's shadow and use it as a predictive meteorological tool for the entire United States.” But how well does NOAA forecast the winter weather? NOAA’s annual Winter Outlook, released on November 21, called for increased chances of a warmer than average winter across much of the Southern U.S. and New England, and a cooler than average winter across portions of the Northern Plains near the Canadian border. NOAA relied heavily on climate trends over the past fifteen years and long-range computer models such as their CFS forecast model to predict this year's winter weather. While winter is not yet over so we cannot yet fully verify this forecast, we can get a good idea of how well it is doing by taking a look at the actual departure of temperature from average for December and January (Figure 3.) The region NOAA gave the highest chance for a cold winter, the Upper Midwest, was indeed the area that experienced the coldest temperatures, relative to average. However, the two areas they predicted would have the best chances of above average temperatures—the South and New England—did not, so NOAA gets no points there so far. The latest NOAA 8 - 14 day outlook calls for a winter pattern very similar to what was observed in December and January: the east half of the national colder than average, and the west half warmer than average. We’ll call the verification of NOAA’s winter temperature forecast inconclusive at this point. Their forecast for precipitation, though, is right on so far over the Southwest U.S., where they called for drought to persist and intensify.

Figure 2. Forecast temperature and precipitation for the U.S. for the winter of 2013 - 2014 as predicted in the NOAA Winter Outlook, released on November 21, 2013.

Figure 3. Departure of temperature from a 1981 - 2010 average over the Contiguous U.S. during December 2013 and January 2014. An unusually kinked jet stream pattern brought colder than average temperatures to the eastern half of the country, and warmer than average conditions to the western half. Image credit: NOAA/ESRL.

I'm in Atlanta this week for the 94th annual meeting of the American Meteorological Society. I plan on being at Stu Ostro's poster on crazy jet stream shenanigans, being presented at 2:30pm Wednesday in Hall C3, if any of you reading this want to stop by and meet.

Jeff Masters

Winter Weather

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™


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