Category 6™

Hurricane season is over--but not typhoon season!

By: JeffMasters, 2:53 PM GMT on November 30, 2006

The remarkably unremarkable Atlantic hurricane season of 2006 has now officially passed into the history books with the arrival of November 30. The nine named storms, five hurricanes, two intense hurricanes, 50 days with a named storm, and 20 days with a hurricane were all very close to the averages one expects for an Atlantic hurricane season. The only Atlantic hurricanes to affect land were Hurricane Gordon, which passed through the Azores Islands on September 19 as a Category 1 hurricane with 75 mph winds, and Hurricane Florence, whose eye passed about 50 miles west of Bermuda on September 11 and brought sustained 80 mph winds to the island. Neither hurricane did significant damage. The only significant damage done by a 2006 Atlantic storm was Hurricane Ernesto, which caused about $100 million in damage to North Carolina and Florida August 31-September 1. Ernesto was also responsible for the only fatalities of the season--five people in Haiti, and two victims in Florida. We were very fortunate, indeed, compared to the vicious hurricane seasons the previous two years!

A few interesting highlights from the 2006 Hurricane Season, taken in part from Dr. Bill Gray and Phil Klotzbach's forecast team at Colorado State University:

It was another early-starting season. Alberto formed on June 11. The climatological average date for the first named storm formation in the Atlantic, based on 1944-2005 data, is July 10.

The 9 named storms, 2 intense hurricanes, and 50 named storm days were the lowest observed since the El Nino year of 1997.

This is only the 11th year since 1945 that no hurricanes have made United States landfall.

No Category 4 or 5 hurricanes formed in the Atlantic basin this year. This is the first year with no Category 4-5 hurricanes in the Atlantic since 1997.

No named storms formed in October. This is the first time that no named storms have formed in October since 2002. Prior to 2006, only eleven years since 1950 witnessed no named storm formations in October.

Only two named storm days were observed in October (from Isaac which formed in late September). This is the fewest named storm days in October since 1994, when zero named storm days were observed.

Citizens Property Insurance Corp. increased their average homeowner rate by 56% in Florida this year, with another 27% increase scheduled for January 1. Imagine if another year like 2004 or 2005 had affected Florida what the insurance rates might have done!

27 percent: The Citizens rate increase approved to start Jan. 1.

Typhoon season is definitely not over!
Hurricane season may be over in the Atlantic and Eastern Pacific, but typhoon season continues in the Western Pacific. Tyhoons are common well into December most years, thanks to the large expanse of warm waters and the lower vertical wind shear experienced there compared to the Atlantic.

Typhoon Durian slammed ashore in the northern Philippine Islands this morning as a powerful and very dangerous Category 4 typhoon. Durian (named for a spiky tropical fruit) continues to track westward across the Philippines, pounding the the region with its 145 mph winds and rainfall amounts exceeding 12 inches per day (Figure 2). The winds and pressure at Calapan , the next major city Durian is expected hit, will be worth watching today. Durian remains in an environment of weak vertical wind shear, warm ocean waters, and favorable upper-level outflow, and should be able to maintain its Category 4 strength for another 12 hours, resulting in a very severe pounding for the Philippines. Beyond that time, interaction with land, dry air over the South China Sea, and increasing vertical wind shear will act to substantially weaken Durian. However, the damage and death toll in the Philippine is likely to be great, due to the slow movement of the storm, which will bring long-duration battering winds and extreme rainfall. Already, 9 inches of rain has fallen at Samar Island and 6 inches at Pili as of 3 GMT this morning, and rainfall amounts exceeding 12 inches in the mountainous areas are sure to cause life-threatening flash floods and mudslides all along the track of Durian. One major positive development is the storm's unexpected more westerly track, which is taking it well south of the capital city of Manila, with its 12 million residents. Still, damage and loss of life may rival what devastating Typhoon Xangsane did to the islands on September 27. Xangsane, a Category 4 typhoon that passed over Manilla, killed 218, did over $100 million in damage, and left tens of thousands homeless. Durian is the fourth major typhoon to hit the Philippines this year.

Figure 1. Latest satellite image of Durian from NOAA.

Figure 2. Latest precipitation forecast for a 24-hour period from NOAA's Satellite Analysis Branch.

I'll be back Friday with the latest on Typhoon Durian, plus an analysis of why the 2006 Atlantic hurricane season was so mild.

Jeff Masters

Super typhoon Durian aims for the Philippines; rare tornado hits Wales

By: JeffMasters, 2:48 PM GMT on November 29, 2006

Super Typhoon Durian put on a very impressive burst of rapid intensification today, and is now a large and very dangerous Category 4 storm headed towards the Philippines. Durian (named for a tropical fruit) is on track to make landfall on the main island of Luzon later today and pass over the island Thursday. Winds at Catanduanes and Daet, the first major cities that will be hit, had increased to 20 mph at 1am local time Thursday, and will steadily pick up. Durian is in an environment of weak vertical wind shear, warm ocean waters, and favorable upper-level outflow. In the past 24 hours, the storm has intensified from a Category 1 typhoon with winds of 85 mph to a Category 4 super typhoon with 155 mph winds and a central pressure of 916 mb. Durian has a good chance of intensifying into a Category 5 super typhoon later today, before interaction with land and passage over Luzon start to weaken the storm. Unfortunately, Durian is expected to slow down as it passes over the Philippines, and may pass near the heavily populated capital city of Manila, a city of 12 million. The slow motion will make Durian a prodigious rainmaker, and NOAA's Satellite Analysis Branch is predicting rain amounts of up to eight inches in 24 hours (Figure 2). Heavy rains that trigger flash floods and mudslides are the primary hazards of typhoons in the Philippines, and we can expect damage and loss of life similar to what devastating Typhoon Xangsane did to the islands on September 27. Xangsane, a Category 4 typhoon that passed over Manilla, killed 218, did over $100 million in damage, and left tens of thousands homeless. The Philippines have raised its highest alert level, and are moving coastal residents out where a storm surge of up to 15 feet is expected. Schools have been cancelled today and all sea travel suspended.

Figure 1. Latest satellite image of Durian from NOAA.

The Philippines have been hit particularly hard this typhoon season, and Durian will be the 4th major typhoon to wallop the island in the past three months. Typhoon Chebi hit Luzon as a Category 3 typhoon on November 11, but hit the less populated northern portion of the island and moved quickly enough that heavy rains and flooding caused relatively little damage. Super Typhoon Cimaron made landfall October 29 as a Category 5 storm with maximum sustained winds of 160-180 mph. Cimaron killed at least 27, destroyed 2600 homes, and damaged another 18,000.

Figure 2. Latest precipitation forecast for a 24-hour period from NOAA's Satellite Analysis Branch.

Tornado hits Wales
A rare tornado hit Wales in the British Islands yesterday, according to news reports from the BBC. The small tornado, which hit at 1:30 am local time, damaged 20 homes. Tornadoes are rare in the British Islands due to the lack of cold, dry continental air needed to generate severe thunderstorms. Here's the weather discussion put out by the UK Met office before the tornado:

CONVECTIVE DISCUSSION issued at 1045 GMT on Tuesday 28th November 2006 Valid from/until: 1045 - 2359 GMT on Tuesday 28th November for the following regions of the United Kingdom & Eire:

Coastal areas of Wales SW England Southern coastal counties of England Channel Islands

SYNOPSIS: Large upper trough/cold pool is approaching from the west. Cold advection aloft/synoptic lift will cause instability to increase with CAPE values of 2-300 J/Kg expected, with LIs down to -2C or so. Flow is rather unidirectional, and low-level/deep layer shear are not large. However, just ahead of the trough, some increase is 850 hPa winds are forecast by some mesoscale models, especially across northern parts of Wales early-mid afternoon.

THREATS: Heavy showers/a few thunderstorms are expected to affect the areas this afternoon and evening, with the risk shifting east over time. The main effects of these will be hail 15-20mm diameter, gusty winds, briefly torrential rain and a few cloud-ground lightning strikes. However, there is a small risk of tornadic development, especially across northern parts of Wales early-mid afternoon, as 850 hPa wind max moves through. Elsewhere, the risk is lower, but still there. Overall though, the risk is deemed too low for a WATCH to be issued.

Jeff Masters

A weather mystery solved!

By: JeffMasters, 2:28 PM GMT on November 27, 2006

I asked for some help earlier this month to solve the mystery of where the photos below of a hail-damaged aircraft came from. Thanks to email replies I received from Chris Trott, Patty Jones, Ennien Ashbrook, and the pilot, Richard Barrieau, the mystery has been solved! The airplane was a Boeing 727-200 jet flown by Capital Cargo International Airlines (aircraft registration N708A). It took off from Calgary, Canada, and was enroute to Minneapolis the night of August 10, 2006, when it encountered large hail as it climbed from 30,000 feet to 35,000 feet in a thunderstorm over Alberta. An upper-level disturbance, in concert with a warm, moist air mass, combined to produce a large area of severe thunderstorms, including the one that damaged the unfortunate airplane. The hail damaged the airplane's windshield, nose cone, cowling on the two engines, leading edge of the right wing, lenses, and right side lights. An in-flight emergency was declared, and the the aircraft returned safely to Calgary International Airport. The landing was routine, as the pilot's windshield was undamaged and the weather was clear in Calgary. In an email I received from the pilot, he ruefully informed me that August 10 was his birthday. I think next year he should ask for the day off!

According to some of the mechanics that worked on the aircraft, the damage was mostly cosmetic. Replacement of the nose cone, windshield, cowling on the two engines and the leading edge of the right wing, plus the damaged lenses and lights only took a few days, and the plane has been back in service since September. Some erroneous information on the Internet stated that the airplane was a total loss, and that two crew members quit after they walked off the airplane; that was not the case.

The size of the hailstones the airplane hit is impossible to judge, as none of the stones penetrated the windshield and gave themselves up for examination! As the First Officer commented in a blog entry, "there was no way to measure the size of the hail much less compare it to sporting equipment." So, we'll never know if the plane hit golf ball, tennis ball, softball, or beachball sized hail.

We do know that at the ground, the thunderstorm produced at least golf ball sized hail. According to an email I received from Ennien Ashbrook, "the storm caused record damage to several communities between Red Deer and Calgary. In a couple of heavily-hit rural communities, the entire west walls of houses were completely destroyed, not even the interior drywall left standing. Damage-causing hailstorms are common here, but this one was a real record-breaker."

Hail damage to commercial passenger aircraft is rare, as modern aircraft radar and air traffic control procedures are adept at helping aircraft avoid hail-producing thunderstorms. If anyone has photos or accounts of damaging hail that has affected a commercial jet aircraft, I'd be interested to try to discover the most severe hail damage ever suffered by a commercial aircraft. Send suggestions via email or in the comments section of the blog.
One such incident occurred when hail damaged a Brazilian Airbus jet in March of this year (see photos posted by the MetSul Meteorologia Weather Center). This website also mentions two other cases of hail damage to commercial aircraft--a hailstorm over Germany that left a hole the size of a football in an Airbus plane which had more than 200 passengers on board enroute to England, and an Easyjet 737 that had an emergency landing in Geneva in 2003 after hail did extensive damage to the nose and wings of the plane.

Tropical Storm Durian
In the Western Pacific, residents of the Philippine Islands are anxiously watching Tropical Storm Durian, which is on track to hit the main island of Luzon later this week. The storm is currently suffering from reduced outflow aloft thanks to the influence of a trough to the northwest. However, the influence of this trough is expected to wane over the next 24 hours, and Durian is expected to intensify into a major typhoon. If it hits the Philippines as a major typhoon, it would be the fourth such storm to hit the islands in the past two months.

Jeff Masters


Central American disturbance decays; Philippines brace for another typhoon

By: JeffMasters, 3:23 PM GMT on November 26, 2006

A tropical disturbance (95L) near 11N, 78W, just north of Panama, has continued to grow less organized. Wind shear has increased from 10 to 20 knots over the disturbance in the past 24 hours, which probably accounts for the storm's deterioration. There is now very little heavy thunderstorm activity, and this morning's QuikSCAT satellite pass showed no surface circulation, and winds of barely 20 mph. The system is expected to drift slowly westward towards Nicaragua, and could bring heavy rains there later this week. None of the computer models are developing the system, and NHC has stopped running its preliminary set of models on it.

In the Western Pacific, the Philippine Islands are anxiously watching Tropical Storm Durian, which is on track to hit the main island of Luzon later this week. Intensity forecasts have Durian developing into a Category 4 storm by landfall, which would make it the fourth major typhoon to hit Luzon in the past two monts.

I'll be back Monday morning with an update.
Jeff Masters

Central American disturbance less organized

By: JeffMasters, 4:29 PM GMT on November 25, 2006

A tropical disturbance (95L) near 11N, 79W, just north of Panama, has remained nearly stationary and become less organized over the past 24 hours. The amount of heavy thunderstorm activity has decreased, and the winds from the latest QuikSCAT satellite pass at 6:11pm EST last night revealed top winds of only 20-30 mph. An ill-defined and elongated surface circulation was apparent in the QuikSCAT data, and some evidence of rotation can be seen on the latest visible satellite loop of the region.

Figure 1. preliminary model tracks for the Panama disturbance, 95L.

Water temperatures are a warm 28C, and wind shear remains around 10 knots, which is low enough to allow some slow development over the next two days. It is possible a tropical depression could form on Monday, as wind shear is expected to remain low over the extreme southern Caribbean. None of the models are forecasting that 95L will develop into a depression--with the exception of the 00Z run of the GFDL model, which has a very unrealistic-looking forecast of a Cat 2 hurricane on Monday hitting Nicaragua. The Hurricane Hunters are on call to investigate the system on Monday afternoon, but given the current poor organization of the system, I doubt a flight will be needed. Steering currents are weak, but a slow westward motion is indicated by most of the models. The system appears to be a threat primarily to Nicaragua, Costa Rica, Honduras, and Panama. Any northward movement of the storm would bring it into a area of high wind shear that would quickly tear it apart.

I'll be back Sunday morning with an update.
Jeff Masters

New tropical disturbance 95L a threat to Central America

By: JeffMasters, 6:56 PM GMT on November 24, 2006

A tropical disturbance (95L) has formed near 11N, 79W, just north of Panama, in the extreme southern Caribbean. This disturbance has a large but disorganized area of heavy thunderstorm activity associated with it. The latest QuikSCAT satellite imagery from 5:45am EST today caught just the east side of the disturbance, and revealed top winds of 35-40 mph. An ill-defined and elongated surface circulation was apparent in the QuikSCAT data, and some evidence of rotation can be seen on the latest visible satellite loop of the region.

Figure 1. preliminary model tracks for the Panama disturbance, 95L.

Wind shear is around 10 knots over the disturbance, which is low enough to allow some slow development over the next two days. It is possible a tropical depression could form by Sunday, as wind shear is expected to remain low over the extreme southern Caribbean. Steering currents are weak, but a slow westward motion beginning on Saturday is indicated by most of the models. The system appears to be a threat primarily to Nicaragua, Costa Rica, Honduras, and Panama. Any northward movement of the storm would bring it into a area of high wind shear that would quickly tear it apart.

Figure 2. Visible satellite image from 2:15pm EST Nov 24, 2006.

I'll be back Saturday morning with an update.
Jeff Masters

Fourth warmest October on record

By: JeffMasters, 3:56 PM GMT on November 23, 2006

October 2006 was the 4th warmest October on record globally, according to the latest monthly report issued by the National Climatic Data Center. The period January through October was the fifth warmest on record. The El Ni�o episode that began in September significantly warmed ocean temperatures in the central and eastern equatorial Pacific, which helped make global ocean temperatures for October the 3rd warmest on record. Arctic sea ice extent remained near record low levels in October at 8.4 million square kilometers.

Figure 1. Departure of temperature from normal (anomaly) for October 2006. Siberia and parts of Indonesia joined North America with having below normal temperatures.

An average October for the U.S.
According to the National Climatic Data Center, October of 2006 was near average for temperature in the U.S., ranking as the 52nd coolest in the 110-year record. It was a very wet October, ranking as the 12th wettest October on record. The period January to October ranks as the 3rd warmest such period on record in the U.S., thanks to some unusually warm weather in January, April, and July.

Have a great Thanksgiving, everyone! I'll have some thoughts on Florida hurricanes in Friday's blog, inspired by my just-completed trip to Florida.

Jeff Masters

Climate Summaries

Interview with the Northwest Florida Daily News

By: JeffMasters, 10:11 PM GMT on November 21, 2006

Sorry for putting this out so late in the day. The fourth in the series of Dr. Masters' vacation blogs.

This is last part of an interview I did with the Northwest Florida Daily News of Fort Walton Beach, Florida, that was published on Sunday, May 28. The questions were posed to me by Del Stone Jr., Deputy Managing Editor and self-admitted weather nut. This portion of the interview was meant to run during my last vacation back in June, but Tropical Storm Alberto put an early end to that trip! I'll be back to live blogging Thanksgiving weekend.

Q. What about NHC's storm-naming convention? NHC uses anglicized and Latino names for storms, but clearly exhausted its list for 2005 and used letters of the Greek alphabet for storm names. But the Greek alphabet is limited. For instance, had NHC named the unnamed tropical storm that formed late in the 2005 season, then Hurricane Wilma would have been named Hurricane Alpha. Seeing as how Wilma has been retired, and the Greek alphabet cannot be expanded, the name Alpha came very close to being retired, which would mean busy seasons in the future would skip Alpha and go directly to Beta, possibly confusing the public. How would you fix this problem?

A. James Franklin, one of the NHC hurricane specialists, told me that he came up with an alternate list of names to replace Greek names and avoid this problem. He presented his list this year to the World Meteorological Organization (WMO) committee that decides such matters, but they unanimously rejected his proposal. He thought that when and if we ever do retire a Greek name, the WMO will then have no choice but to accept his alternate list.

Q. The Weather Underground has a space reserved for blogs. This is a lively venue, with amateur weather fans reporting and speculating about weather phenomena, including hurricanes. At times the blog entries seem to cross the line between amusing pastime and actual public service reporting, particularly during last year's Hurricane Wilma as the storm bore down on the Yucatan Peninsula and official reports were skimpy at best. How would you characterize the accuracy and utility of such blog dispatches? Does blogging have a role in weather reporting?

A. I think we're just starting to explore that. I tried to feature blogs from wunderbloggers who were in the path of last year's storms, but it was difficult to find the time to coordinate this, in addition to all of my other duties. We'll continue to explore how best to take advantage of this great new communication opportunity in the coming hurricane seasons. I think blogging offers a great alternative to the sensational journalism ones sees in the news media; you're more likely to get an honest picture of what's really happening.

Q: NHC seems to produce very accurate predictions of storm paths. Now, they will attempt to forecast storm intensity at landfall. What's your take on this? Does NHC have access to new technology that allows them to make such forecasts? And if they are wrong, do you foresee negative ramifications?

A. The NHC's best performing computer model the past three years, the GFDL, got an upgrade of the equations it uses for the coming hurricane season. The new model was retrospectively run on Ivan and Katrina, and made track forecasts that were 10-12% better, and 5-day intensity forecasts that were 30% better. However, the retrospective intensity forecasts for Rita and Emily were slightly worse, so our ability to make better intensity forecasts still has a long ways to go. There is also a new model being made available to the public next year, the Hurricane Weather Research Forecast (HWRF) model, which will replace the GFDL. So, the models are getting better, mostly thanks to the tremendous amount that has been learned through research over the past 20 years. However, intensity forecasting is still in the primitive stages, and we should continue to expect large errors in landfall intensity forecasts. I think that NHC has to put out intensity forecasts, because they do have some skill over chance.

Q: NHC debated eliminating the middle line in the cone of probability of landfalling hurricane predictions. Ultimately they decided to keep the middle line. What's your opinion about the middle line?

A. I like the middle line. As a scientist, I am used to seeing data presented as a line with error bounds.

Q. Lastly, here's a fun question. The Weather Underground is beginning to appear in news stories about hurricanes, and with the increase in tropical cyclone activity The Weather Underground has become one of the go-to places for storm information. How does it feel to be a "star"? Do you face any of the privations normally reserved for people like Brad Pitt or Madonna?

A. Well, living here in Michigan, I don't encounter too many people who've heard of me. When I travel, though, I've learned to be armed with Weather Underground pens to give away! I haven't signed any autographs yet, but have had to endure getting my picture taken with blog fans a few times. All in all, it's been a very modest amount of fame that hasn't been unpleasant at all, and I have been very much enjoying sharing my knowledge and stories with people.

Q. Many thanks, Dr. Masters!

A. You're welcome!

Jeff Masters

What's brewing in Greenland?

By: JeffMasters, 8:34 PM GMT on November 20, 2006

The third in the series of Dr. Masters' vacation blogs.

We've heard a lot about recent studies showing that glaciers in southern Greenland have accelerated sharply over the past ten years, and that Greenland's ice cap is melting at rates not seen since the 1930s. It may seem difficult to put a positive spin on these ominous developments, but that's just what some entrepreneurs in Greenland have done by establishing the world's only beer brewed with pure Greenland Ice Sheet meltwater. The Greenland Brewhouse microbrewery, located 390 miles south of the Arctic Circle, is the world's first Inuit brewery. Founders Salik Hard and Steen Outzen use ice from small icebergs that have broken off from the Greenland Ice Sheet. Local fishermen specially select the icebergs, and tow them to the brewery in Narsaq. The ice is between 2000 and 180,000 years old, so has no pollution. The brewmeisters, conscious of the dwindling resource that forms the basis for their unique beer, emphasize that they only use ice from icebergs that have already broken off from the ice sheet and would melt anyway. Their web site states, "We are very much aware of the global warming, and it is very important to us not to destroy or use the unique inland ice, but only use the ice that have broken off."

I'm not sure if Greenland Brewhouse beers are available outside of Greenland and Denmark, but if anyone has ever quaffed one, please give us a review!

Jeff Masters


Help solve a weather mystery

By: JeffMasters, 7:55 PM GMT on November 17, 2006

The second in the series of Dr. Masters' vacation blogs.

Help solve a weather mystery

I'm often asked why it is that the Hurricane Hunters are unafraid to fly in extreme Category 5 hurricanes with 200 mph winds, but refuse to fly in garden variety thunderstorms with winds of perhaps 30 mph. Well, airplanes don't care about wind, as long as it's all moving the same direction at the same speed (i.e., there is no wind shear). Granted, some hurricanes have outrageous wind shear that creates severe turbulence capable of damaging the airplane. However, threats of this nature pale in comparison to the chief hazard of flying into thunderstorms--hail. Even small hail poses a significant threat to airplanes. Hurricanes rarely have hail, except at high altitudes in some of the stronger storms. On a mission I flew into Category 3 Hurricane Emily of 1987, one of our airplanes encountered pea-sized hail in the eyewall at 18,000 feet, and the ice scoured off the airplane's paint job in some places. More seriously, hail damaged two of the engines, causing oil leaks that forced the airplane to abort the mission after a record 34 penetrations of the hurricane's eyewall.

Large hail can seriously damage an airplane, as seen in the incredible photos below. These origin of these photos is unknown, but they have been circulating on the Internet for a few months. Presumably, they were taken on August 10, 2006, but no one knows where. If you can shed some light on this mystery, drop and myself an email.

Armored T-28 hail research aircraft retires
Speaking of hail and airplanes, the world's only aircraft equipped to safely to fly into mature thunderstorms, the South Dakota School of Mines & Technology's armored T-28, is being retired this year after over 900 penetrations of thunderstorms and 37 years of service. The famed aircraft, which has survived updrafts as strong as 115 mph, 2-inch hail, and numerous lightning strikes, will go on display at the Strategic Air and Space Museum at Ashland, Nebraska. The National Science Foundation has requested to the Pentagon that a two-engine A-10 Thunderbolt aircraft be made available as a replacement. A two engine hail penetration aircraft is a good idea! I spoke with one of the pilots of the T-28 back in 1987, during a thunderstorm research program I was involved with. The pilot told me that he had done several "dead stick" landings on highways after lightning strikes had knocked out power to the single engine of the T-28.

Here's the specs on the special modifications the T-28 aircraft had, taken from the web site above:

The leading edges of the wings and tail surfaces are covered with 2.29 mm (0.090 inch) 2024T4 heat-treated aluminum sheets formed to fit and bonded to the existing wing and tail surfaces. The tops of the wings are covered with 0.81 mm (0.032 inch) sheets of the same material. The leading edges of the cowling are covered with an additional sheet of fitted 3.18 mm (0.125 inch) aluminum. This armor plating adds about 318 kg (700 lb) to the aircraft weight.

The carburetor is protected from ingestion of large hailstones by the addition of a metal grate to the air intake to break up the hailstones prior to entry. A similar device was installed over the oil cooler intake to prevent damage to the relatively fragile oil radiator.

The canopy also required substantial modification since the standard Plexiglas bubble canopy was much too weak to withstand encounters with large hail. The windshield was replaced with flat sheets of 1.91 cm (0.75 inch) stretched acrylic and the side panels were made of flat sections of 1.52 cm (0.60 inch) stretched acrylic. The windshield and the leading-edge armor were tested to withstand 7.6-cm diameter hail at penetration velocities by firing ice balls from a specially-built hail "cannon" at test sections of the aircraft.

Figure 1. The South Dakota School of Mines & Technology's armored T-28 weather research aircraft. Photo taken by Jeff Masters in June, 1987 in Huntsville, Alabama during T. Theodore Fujita's Microburst and Severe Thunderstorm (MIST) field program.

Jeff Masters


Winter forecast

By: JeffMasters, 4:47 PM GMT on November 15, 2006

Hello, Aaron here. Dr. Masters is on vacation and has taken an oath NOT to blog while out. He did leave some blogs for me to post periodically during that time. Here's the first one:

This Fall's ongoing El Ni�o event shows no signs of going away, and may grow stronger, according to the latest El Ni�o advisory issued last week by NOAA's Climate Prediction Center. The strength of an El Ni�o event is measured by how far above average the Sea Surface Temperatures (SSTs) in a region near the Equator off the Pacific coast of South America are. These SSTs are about 1 degree C above normal right now, qualifying this as a moderate El Ni�o event. A weak El Ni�o event has SSTs .5 degrees C above normal, and a strong one, 2 degrees C above normal. The strongest El Ni�o on record, in 1997, had SSTs 2.5 degrees C above normal.

The SSTs in the El Ni�o region are forecast to remain between .5 C and 2.0 C above normal through springtime by all of the El Ni�o models, so we can expect typical El Ni�o weather throughout this winter. This likely means warmer than average temperatures over western and central Canada, and over the western and northern United States. Wetter than average conditions can be expected over portions of the U.S. Gulf Coast and Florida, and drier than average conditions in the Ohio Valley and the Pacific Northwest. Global effects during November through March will likely include drier than average weather over Malaysia, Indonesia, the tropical North Pacific, northern South America, and southeastern Africa, and wetter than average conditions over equatorial East Africa, central South America (Uruguay, northeastern Argentina, and southern Brazil) and along the coasts of Ecuador and northern Peru.

It was a surprise to me to look at the global temperature forecast for the winter (Figure 1) and see NO areas with an above average chance to be cooler than normal. Usually, there is at least one region of the globe expected to be on the cool side of things. If this forecast verifies, 2006 should rank as one of the five warmest years on record, and may challenge 1997 and 2005 as the warmest year on record.

Figure 1. This winter's temperature forecast for the world from Columbia University's International Research Institute for Climate and Society.

Figure 2. This winter's precipitation forecast for the world from Columbia University's International Research Institute for Climate and Society.

Jeff Masters

Winter Weather

Hurricanes on other planets?

By: JeffMasters, 3:55 PM GMT on November 13, 2006

Saturn has joined Earth as the second planet known to harbor hurricane-like storms in its atmosphere. A huge, clockwise-rotating hurricane-like cyclone with a deep "eye" surrounded by towering "eyewall" clouds was discovered swirling directly over Saturn's south pole by the Cassini spacecraft, NASA announced Thursday. This "Saturnicane" is huge--about 2/3 the diameter of the Earth--and is composed of clouds of liquid ammonia. The 5000-mile diameter storm has an "eyewall" about 185 miles (300 km) across, which surrounds a 930 mile (1500 km) wide "eye". The "eyewall" clouds soar 20-45 miles above the "eye"--about 2-5 times higher than the eyewall clouds of Earthly hurricanes. Winds blow at 350 mph around the storm. I hope we never see a whopper of a storm like that on Earth!

Figure 1. October 11, 2006 "Saturnicane" observed by the Cassini spacecraft over the south pole of Saturn.

The Saturnicane's "eyewall" clouds appear to be formed by convection--the same process that helps form hurricane eyewall clouds on Earth. Heat from below warms the air, generating rising air currents. As this air rises, it expands and cools, condensing the gaseous ammonia into liquid ammonia clouds. NASA scientists speculate that the phenomena only occurs in summer, which is in full swing over Saturn's southern hemisphere at present. It is unclear whether the storm's "eye" and "eyewall" behave in a similar fashion to those features in Earthly hurricanes. The fact that the storm is anchored directly over the south pole and is not composed of water clouds must mean that there are significant differences from the hurricanes we are familiar with. In an interview with Yahoo, astrophysicist Michael Flasar said, "I'm hoping that as we puzzle over it, it will become even more exciting as we start to connect the dots in our brains. But right now, the wheels are a little creaky," Flasar said. "We're all arguing with each other about what it might or might not be."

Figure 1. The relative sizes of Earth (8000 miles in diameter), the October 11, 2006 "Saturnicane" (5000 miles in diameter), and Super Typhoon Tip of 1979 (1400 miles in diameter), the largest tropical cyclone ever observed on Earth.

What about other planets?
Mars also plays host to huge cyclones. These extratropical cyclones have clouds made of water ice, but do not resemble hurricanes. A Martian cyclone 1000 miles in diameter was observed in 1998 by the Hubble Space Telescope. The Great Red Spot on Jupiter is also a storm of huge dimensions with incredible wind speeds, but this storm is not hurricane-like--there is no "eyewall" surrounding a cloud-free "eye".

Figure 2. Martian cyclone 1000 miles in diameter spotted near Mars' north pole by the Hubble Space Telescope on April 27, 1999. Image credit: NASA and

Jeff Masters

Typhoon Chebi less destructive than feared

By: JeffMasters, 4:04 PM GMT on November 11, 2006

Typhoon Chebi slammed into the main island of Luzon in the Philippines last night at 6pm EST as a Category 3 storm with top winds of 120 mph. There are no reports of deaths yet, and damage appears to be much less than occurred for Super Typhoon Cimaron, which made landfall October 29 as a Category 5 storm with maximum sustained winds of 160-180 mph. Cimaron killed at least 15, left 2500 homeless, and destroyed about 8% of the island's rice and corn crop. However, Chebi was a much weaker typhoon, and dumped far less rain on the Philippines since it moved across the islands relatively quickly. Rainfall estimates by NOAA (Figure 1) show maximum rain amounts from Chebi were in the 4-7 inch range, which should not cause the kind of widespread flash flooding and landslides that are the primary hazard of typhoons in the Philippines. Cimaron dumped about 50% more rain on the Philippines than Chebi did.

Figure 1. Estimated rainfall for Typhoon Chebi. Image credit: NOAA

Figure 2. Typhoon Chebi shortly after landfall. Image credit: NRL Navy Reasearch Lab.

My next blog will be Monday, when I plan to discuss a new hurricane-like storm found on Saturn.

Jeff Masters

Another extreme typhoon for the Philippines

By: JeffMasters, 2:35 PM GMT on November 10, 2006

The Philippines are bracing for the onslaught of their third major typhoon of the past six weeks, as Category 4 Typhoon Chebi bears down on the main island of Luzon. The Philippines have been hit particularly hard this typhoon season. Super Typhoon Cimaron made landfall October 29 as a Category 5 storm with maximum sustained winds of 160-180 mph. Cimaron killed at least 15, left 2500 homeless, and destroyed about 8% of the island's rice and corn crop. However, disaster officials called the destruction wrought by Cimaron as "minimal" compared to the destruction of devastating Typhoon Xangsane, which hit Luzon on September 27 as a Category 4 storm. Xangsane killed 218 in the Philippines, did over $100 million in damage, and left tens of thousands homeless. Xangsane went on to deliver a serious blow to Vietnam as a Category 2 typhoon, killing 70.

Figure 1. Typhoon Chebi during its explosive deepening phase at 0600 GMT November 10, 2006. Image credit: Navy Research Lab.

The amazing thing about all three of these typhoons is that they performed remarkable feats of explosive intensification, deepening from a tropical storm to a Category 4 typhoon in less than 24 hours. It's unusual to see one storm do this in a season, let alone three--and all in the same place! Chebi, which means swallow in Korean, is expected to continue to intensify today into a Super Typhoon with 150 mph winds before making landfall early Saturday morning (Philippines time). The 7am satellite intensity estimate from the NRL Navy website put Chebi's winds at 145 mph, with a central pressure of 916 mb. Chebi is the 18th Category 4 or 5 tropical cyclone to form so far this year globally; the average number of these extreme cyclones is 17 per year.

I'll have an update on Chebi Saturday.

Jeff Masters

Thingamabobbercane revisited

By: JeffMasters, 3:21 PM GMT on November 08, 2006

In my blog last week, I discussed Thingamabobbercane, an oddball cyclone which had characteristics of both a tropical cyclone and extratropical cyclone. I referred to it as a subtropical storm, which the Glossary of Meteorology defines thusly: A cyclone in tropical or subtropical latitudes (from the equator to about 50°N) that has characteristics of both tropical cyclones and midlatitude (or extratropical) cyclones. I gave the storm the name Thingamabobbercane because although it fit the technical definition of a subtropical storm, it didn't look like a typical subtropical storm. In particular, it formed at 41 N latitude over very cold waters of 16-18C, which is unusually cold and far north for a subtropical storm. Well, there are some meteorologists who disagree with my classification of the storm as subtropical, and believe Thingamabobbercane had virtually no tropical characteristics. A detailed day-by-day analysis posted on argues that Thingamabobbercane was an extratropical cyclone that underwent a process known as warm seclusion. In the seclusion process, a strong extratropical cyclone draws in warm air from the south, and latent heat of condensation from the cyclone's intense precipitation makes this air even warmer. This extra-warm air spirals into the center of the low and wraps around to the west side, where it is pinched off. As result, one has an isolated "warm core" center where deep convection builds and spiral banding can occur. However, unlike a hurricane, there is no eyewall, and no cloud-free eye created by sinking air (subsidence) in the center. The eye-like feature in an extratropical cyclone undergoing warm seclusion has upward moving air, and is merely the center where the surface winds spiral into. Spiral bands of convection can develop in the warm air near the center, mimicking the spiral bands of a hurricane. If these convective bands become intense, subsiding air on the flanks of the bands may create subsidence that warms and dries out the surrounding air, creating cloud-free regions near the center that may give it a more eye-like appearance. I flew through a number of these type of systems in 1989 as a member of the ERICA field program, and noted in my blog on the Blizzard of 2006 that the storm had a warm seclusion.

Figure 1. Image of Thingamabobbercane from Nov. 1, 2006, taken by NASA's Terra satellite. Image credit: NASA's Earth Observatory web page.

Steve Gregory, who did an awesome job blogging for during last year's unbelievable hurricane season, and has moved on to form his own hurricane consulting firm for business and industry,, had this to say about Thingamabobbercane:

I think that just having a transitory very low level warm core doesn't warrant a system being called sub-tropical. We clearly do not want to name a Nor'easter simply because it may form a low level warm core and 'eye' for a day or two. These super storms, or 'Perfect Storms', usually get their very own 'names' anyway ("The Great Blizzard of 78', etc). I think most everyone agrees that sub-tropical storms evolve out of old occluded extra-tropical lows that typically drift southward, completely isolate themselves from any frontal systems, and start becoming warm core--and usually over water above 20°C or warmer. And, they have life spans of many days as they transition, and they either remain sub-tropical or go all tropical with absolutely no cold or warm fronts even remotely close to them.

Whereas these briefly lived specimens, especially when at such high latitudes (over 40N) and truly cold water (15 deg is cold), never really fully detach from frontal boundaries, do the classic counterclockwise track motion under the upper level 500mb low embedded, all of which is embedded within full latitude long wave TROFS--and then transition quickly into non-tropical systems that generate new frontal based surface lows--just shouldn't be called sub-tropical. And especially if the warm core remains below 5,000 ft.

We need a new classification for these types of half breeds that get some of their energy through the latent heat release process etc, but are 'clearly' not what we think of as sub-tropical storms that will either stay that way, or go all tropical, or after a few days, get picked up by an upper TROF and pulled north where they transition back to a fully non-tropical low.

And here is what Senior Hurricane Specialist James Franklin from the National Hurricane Center had to say about the system in an email I received:

The system was of frontal origin, that much is clear. But I believe the frontal structure was eventually lost (no way to know for sure). The convective structure resembled a tropical, rather than subtropical cyclone, and the radius of maximum winds (based on QuikSCAT) was very close to the center, also more typical of tropical cyclones. It was, for most of its existence, under an upper low, typical of subtropical cyclones. However, it was developing a modest mid to upper lever warm core, moving toward tropical structure. So structurally, on balance, it was more tropical than subtropical.

However - it was over sub 18C water, and part of the definition of a tropical cyclone is that it originates over tropical or subtropical waters. This one didn't, so it's not a tropical cyclone by our operational definition, even though it had some of the characteristics of one.

Our classification system is a convenience for man, but Nature is not the slightest bit interested in our classifications of cyclones. There is a complete spectrum of storms between extratropical and tropical. There are cyclones that have similarities to tropical cyclones in structure - even share some of their energetics, polar lows are an example of such a beast, and maybe it is unfair to exclude them based on their location of origin. I, however, don't sense a groundswell of opinion to strike the "originates over tropical or subtropical waters" from our definition. It has, on the whole, served us well.

So, take your pick of these ideas on what Thingamabobbercane was. We'll never know for sure, since there were no direct measurements of its structure by research aircraft. It will remain as a mysterious and beautiful example of the endless variety of weather on our planet.

There is nothing going on in the tropical Atlantic today, nor is there forecast to be any activity over the next six days. While this remains true, I will be posting blogs every Monday, Wednesday, and Friday.

Jeff Masters

Late season Atlantic tropical storms

By: JeffMasters, 7:50 PM GMT on November 06, 2006

There is currently no tropical activity of note in the Atlantic, nor do the models predict there will be any over the next six days. Wind shear over most of the tropical Atlantic is high and is expected to remain so for at least the next two weeks, which is typical for November in an El Nino year. However, we have to watch the Western Caribbean later this week, as the NOGAPS model predicts that wind shear may drop enough to support a tropical disturbance that could bring heavy rains to the region.

What are the odds of getting a tropical storm between now and April in the Atlantic? Well, if the past is any indication (Figure 1), we should expect no further activity in the Atlantic. Since 1950, when El Nino conditions have existed in the November-January period, as defined by NOAA's Climate Prediction Center, only 37% of those years have seen a late season tropical storm. There have been an average of 2.9 days per year when a named storm has been present in the Atlantic during those years. In La Nina years, late season tropical storm activity is 60% higher--about 5 named storm days per year. This year, we are experiencing a moderate El Nino (SSTs at least 1 degree above normal in the Equatorial region off the Pacific coast of South America). Late season Atlantic tropical storms have occurred in only 3 of 11 (27%) years with a moderate or strong El Nino.

Figure 1. Number of days per year that a named storm was present in the Atlantic during November-April. Years marked with a red "E" were El Nino years. Note that it is common to have zero late season tropical storms during El Nino years. It is interesting to note that there appears to be an increase in late season storms in the Atlantic in recent years. However, as I've discussed in a previous blog, this increase has not been seen in the Pacific Ocean.

My next update will be Wednesday, unless there's new tropical activity to talk about.

Jeff Masters

The tropics are quiet

By: JeffMasters, 2:29 PM GMT on November 05, 2006

There are no areas of interest to discuss in the tropical Atlantic or Eastern Pacific today, and the computer models are not predicting any significant development over the next six days.

Have a great Sunday, everyone!

Jeff Masters

The tropics are quiet

By: JeffMasters, 8:10 PM GMT on November 04, 2006

The area of disturbed weather that brought up to ten inches of rain to Belize over the past week has moved inland, and is no longer a threat. There are no other areas of disturbed weather worth mentioning in the Atlantic or Eastern Pacific, and the computer models are not forecasting any significant development over the next six days.

Jeff Masters

Heavy rains continue for the Western Caribbean

By: JeffMasters, 2:09 PM GMT on November 03, 2006

An area of disturbed weather in the Western Caribbean is associated with a tropical disturbance (93L). This disturbance has not gotten better organized since yesterday, and is not expected to become a tropical depression, due to 20 knots of wind shear and close proximity to land. A QuikSCAT satellite pass at 6:30am EST today showed some strong winds of 40-50 mph offshore of Belize, but there was no surface circulation evident, and not even a shift of wind direction. 93L will drift westward and continue to bring heavy rains to Belize, Guatemala, the Yucatan, and Honduras over the next two days. about seven inches of rain has fallen in Belize City in the past 72 hours, and rainfall rates of an inch per hour (yellow color, Figure 2) were apparent last night from this storm.

Figure 1. Preliminary model tracks for 93L in the Caribbean.

Figure 2. Rainfall rates from NASA's TRMM satellite taken at 8:39pm EST Thursday November 2. The yellow colors correspond to rainfall rates of about 1 inch/hour (25.4 mm/hr).

Thingamabobbercane is gone today, having been destroyed by high wind shear and cold waters. There is nothing else of note to discuss, and the models are not forecasting any significant developments in the tropical Atlantic for the coming week.

Jeff Masters

Thingamabobbercane forms off the coast of Oregon

By: JeffMasters, 2:54 PM GMT on November 02, 2006

An unusual storm with the satellite appearance of a hurricane formed 900 miles off the coast of Oregon yesterday. The storm is a hybrid between a warm-cored tropical cyclone, cold-cored extratropical cyclone, and an uncommon type of winter storm called a Polar Low. Since we're not really sure how to classify this odd beast, I'll call it "Thingamabobbercane". Thingamabobbercane is being called 91C at the Navy web site.

Figure 1. Thingamabobbercane forms 900 miles west of the Oregon coast, November 1, 2006.

Thingamabobbercane formed from a cold-cored extratropical storm that spent two days drifting over relatively warm waters of about 59-61F (15-16C). These temperatures were warm enough to warm the core of the storm and generate a cloud-free "eye" and an "eyewall" of intense thunderstorms surrounding the eye. The spiral bands of showers and eye/eyewall appearance look very similar to Hurricane Epsilon of 2005, which formed over waters of 75-77 F (22-23C). If Thingamabobbercane had been in the Atlantic, it would likely have been given a name and called a subtropical cyclone. The Central Pacific Hurricane Center in Honolulu isn't even mentioning it in their Tropical Weather Outlook, so Thingamabobbercane is not going to get a name. Hybrid storms of this nature are rare in the Central Pacific, and we really don't know what to do with them. It's worth noting that SSTs in the northeast Pacific are a substantial 2 C above normal; normally ocean temperatures are too cold to get hybrid subtropical storms off the coast of Oregon.

A QuikSCAT satellite pass from last night (Figure 2) shows wind speeds as high as 50 knots (57 mph) to the south of the circulation center of Thingamabobbercane. Cloud top temperatures in the "eyewall" were between -42 and -53 C, which correspond to heights of 35,000 to 40,000 feet. Satellite imagery from this morning shows that Thingamabobbercane has weakened, and resembles a donut with the bottom half missing. Wind shear, which was 15 knots yesterday, has increased to 25 knots over the storm, and is likely responsible for the weakening. Thingamabobbercane is expected to gradually weaken as it drifts northeastward over the next two days. The storm will make the transition to a regular extratropical cyclone by Saturday, and affect British Columbia with gale-force winds early next week.

Figure 2. QuikSCAT winds from 04 UTC November 2, 2006, show wind speeds as high as 50 knots (57 mph) to the south of the circulation center of Thingamabobbercane.

Thingamabobbercane is over much cooler waters than some of the late-season tropical storms of 2005--such as Vince and Epsilon--that looked similar. A drifting buoy 46637 100 miles to the north of the center is reporting SSTs of 58F (14.5C), and drifting buoy 46532 about 150 miles to the west is reporting SSTs of 62F (16.5C). Thingamabobbercane resembles the January 1995 weirdo storm that formed in the Mediterranean Sea. This unusual storm also looked like a hurricane, and formed over waters of similar temperature, 61F. Another odd hybrid storm like Thingamabobbercane formed over Lake Huron on September 14, 1996. Hurricane Huron started as a cold-cored low pressure system, then gradually acquired a warm core as it drifted over the relatively warm waters (64F, 18C) of Lake Huron. Hurricane Huron developed a cloud-free eye and spiral bands of showers and thunderstorms which brought up to four inches of rain and flooding problems to portions of Ontario and Michigan. It is the only recorded warm-core hybrid cyclone to affect the Great Lakes.

Figure 3. "Hurricane Huron" over Lake Huron closely resembles our Thingamabobbercane. Image credit: Dr. Todd Miner, Penn State University. Dr. Miner has authored an interesting techincal paper on Hurricane Huron.

For more on Thingamabobbercane
The University of Wisconsin CIMSS web site has an interesting blog with both visible and infrared Quicktime animations of the storm.

The Atlantic
An area of disturbed weather in the Western Caribbean is associated with a tropical disturbance (93L). This disturbance has gotten less organized since yesterday, and is not expected to become a tropical depression. It will continue to bring heavy rains to Belize, the Yucatan, and Honduras over the next two days. More than two inches of rain has fallen in Cancun, Cozumel, and Belize City in the past 24 hours.

Figure 1. Preliminary model tracks for 93L in the Caribbean.

Jeff Masters

Western Caribbean disturbance generating heavy rains

By: JeffMasters, 2:38 PM GMT on November 01, 2006

An area of disturbed weather in the Western Caribbean is associated with a tropical disturbance (93L). This disturbance has not gotten better organized over the past day, but has some potential for development over the next two days. The system does not have a well-defined surface circulation, but there is a sharp shift in wind direction along a line running from the western tip of Cuba down to the coast of Honduras, roughly along 85W longitude. QuikSCAT satellite-measured winds from 6:33pm EST last night were in the 20-30 mph range. This morning's QuikSCAT pass missed 93L, and we will have to wait until about 8:30pm EST tonight for the next pass to arrive. 93L will be near buoy 42056 at 20N 85W today. Winds at the buoy have been less than 15 mph the past two days. Wind shear increases from about 5 knots near the coast of Honduras to about 30 knots near Cuba. It is possible a well-defined surface circulation could develop along this wind shift line over the next day or two, but it is unlikely we'll see a tropical depression form. If a depression were to form, it would most likely affect Honduras, Belize, and Mexico's Yucatan, since wind shear is too high to the north. The disturbance should bring heavy rains to Belize, Honduras, and Mexico's Yucatan Peninsula Wednesday through Friday. At this time, it does not appear that 93L will affect South Florida, although moisture from the surface trough of low pressure 93L is embedded in will increase the chance of rain through Friday. Wind shear is expected to stay above 40 knots over the Gulf of Mexico, Florida, and the Bahamas over the next seven days, which will protect those regions from any tropical storms.

Figure 1. Preliminary models tracks for the Western Caribbean disturbance.

Typhoon Cimaron
Typhoon Cimaron has re-intensified to a major Category 3 storm, but its days of glory are numbered. The same trough of low pressure that is currently acting to steer the storm northwards towards Hong Kong is also expected to bring high wind shear over the storm beginning Thursday, and there is a good chance that Cimaron will get torn apart before it reaches China. Cimaron killed 19 people in the Philippines when it hit the mountainous northern portion of Luzon Island on Sunday. The storm injured 58 others, left 15 people missing, and damaged more than 5,000 homes.

Figure 2. Rainfall estimated by NASA's TRMM satellite for Typhoon Cimaron yesterday.

Jeff Masters

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