Category 6™

The global hurricane season of 2007: was it unusual?

By: JeffMasters, 10:22 PM GMT on January 31, 2008

The year 2007 was a fairly normal year for world-wide tropical cyclone activity. The total number of storms world-wide was 84, two less than the average of 86 (Figure 1). The total number of hurricanes was 43, which is six less than the average of 49. Major hurricanes (Category 3 and higher) and extreme hurricanes (Category 4 and higher) were both slightly below average. No records were broken in any ocean basin for number of storms of any particular category, although the South Indian Ocean did tie its record for number of major hurricanes (seven) and the North Indian Ocean tied its record for number of Category 4 and higher storms (two). One of the North Indian storms (Category 5 Cyclone Gonu) was tied for the strongest tropical cyclone ever observed in the North Indian Ocean. Reliable tropical cyclone records for the globe extend back to 1970, the beginning of the satellite era.

Figure 1. Statistics for the global tropical cyclone season of 2007. The three numbers in each box represent the actual number observed in 2007, followed by the averages from the period 1970-2005 (in parentheses), followed by the record (in red).

Only four Category 5 hurricanes were reported globally in 2007: Tropical Cyclone Gonu (160 mph winds), which hit Oman on June 6 as a Category 1 storm; Super Typhoon Sepat (160 mph winds), which hit Taiwan as a Category 4 storm on August 18; Hurricane Felix (165 mph winds), which hit Nicaragua as a Category 5 hurricane on September 4; and Hurricane Dean (175 mph winds, pressure 905 mb), which hit Mexico's Yucatan Peninsula on August 21 at peak intensity. It is remarkable that half of the globe's Category 5 storms in 2007 occurred in the Atlantic basin, which normally has only about 11% of the globe's tropical cyclones. The globe's strongest tropical cyclone was an Atlantic storm (Dean, 175 mph winds), which is also unusual. I'll have a detailed blog summarizing 2007's notable tropical cyclones next week.

Figure 2. Satellite image of 2007's strongest tropical cyclone at maximum intensity: Hurricane Dean. Post analysis of Dean determined that the storm hit the Yucatan with top sustained winds of 150 knots (175 mph), and a central pressure of 905 mb, the third lowest pressure ever recorded in the Atlantic basin for a landfalling storm. Only the 1935 Labor Day Florida Keys storm (892 mb) and Hurricane Gilbert (900 mb) had lower pressures at landfall.

Jeff Masters

The Rough Guide to Climate Change: A book review

By: JeffMasters, 1:47 PM GMT on January 29, 2008

If you're bewildered by the complexity of the climate change/global warming issue, and want a comprehensive, easy-to-understand guide that presents an unbiased view of the important issues, look no further than Robert Henson's Rough Guide to Climate Change. In fact, we've found the Rough Guide to Climate Change so helpful and well written, that wunderground has licensed a copy of the introductory chapter and featured it on our Climate Change web page. This chapter is a "sneak preview" of the Second Edition, which is scheduled to be released February 4. If I were teaching a course on climate change at the high school or introductory college level, this would be the text.

However, the Rough Guide does not read like a textbook. It presents the key issues in a straightforward, clear, and conversational manner. The author, Robert Henson, is a meteorologist and journalist who works as a writer/editor at the University Corporation for Atmospheric Research in Boulder, Colorado. He organizes his book into four sections: "The basics"--global warming in a nutshell; "The symptoms"--what's happening now, and what might happen in the future; "The science"--how we know what we know about climate change; and "Debates & solutions"--from spats and spin to saving the planet. The book has information current up to September 2007, and discusses the major climate change event so far this century--the record melting of the Arctic's sea ice that peaked in September 2007, opening the Northwest Passage for the first time in recorded history.

Helpful graphics and interesting sidebars are interspersed throughout the text. Some of the more interesting sidebars include an interview with James Lovelock, originator of the Gaia Hypothesis that treats Earth as a living being; "The Nights Chicago Fried", an account of the deadly 1999 heat wave in Chicago; and "The Fast-Disappearing Snows of Kilimanjaro", discussing the controversy over why Mt. Kilimanjaro's ice is disappearing. My favorite sidebar is "Climate Change and the Cinema", where we learn that the first movie to discuss artificial climate change was probably Zombies of the Stratosphere (1952), which featured a young Leonard Nimoy as part of a gang of Martians bent on exploding Earth from its orbit so Mars can move sunward and benefit from a warmer climate. The sidebar also discusses the impact of movies like The Day After Tomorrow and Al Gore's An Inconvenient Truth.

The 2006 first edition of the Rough Guide is my favorite climate change reference book, and I highly recommend purchasing the second edition when it comes out February 4. You can preorder a copy of the second edition from ($16.99, softcover). Overall rating: four stars out of four.

Jeff Masters

Book and Movie Reviews

The new NHC director is Bill Read

By: JeffMasters, 5:08 PM GMT on January 25, 2008

NOAA announced today that the new director of the National Hurricane Center will be Bill Read, 58, who has served as the center's acting deputy director since August 2007. Previously, he served as director of Houston's National Weather Service office, a post he took in 1992. Bill was called in to work at NHC three times between 1992 and 2005 to help out with hurricane emergencies. Prior to his job in Houston, Bill served in the U.S. Navy, where his duties included an assignment as an on-board meteorologist with the Hurricane Hunters. He began his career in 1977 with the National Weather Service test and evaluation division in Sterling, VA; developed his forecasting skills in Fort Worth and San Antonio, Texas; and, served as severe thunderstorm and flash flood program leader at the National Weather Service headquarters in Silver Spring, MD.

I got a chance to speak with Bill this week at the annual meeting of the American Meteorological Society in New Orleans. I asked him what his focus would be as director of NHC, and he promised to continue the main themes of Max Mayfield, emphasizing hurricane preparedness and education. I asked him what we should do with the Saffir-Simpson scale, which rates hurricanes as Category 1 through 5, based on their wind speeds. This scale has obvious limitations, as proved when a weakening Category 3 Hurricane Katrina brought a storm surge characteristic of a Category 5 storm to the shore. Bill responded that we absolutely had to keep the Saffir-Simpson scale, since it has proved its usefulness in many situations. Discarding it would cause confusion. He promised, however, to explore ways to improve public outreach efforts and educate people on the limitations of the Saffir-Simpson scale. I agree with both of these points. Finally, I asked him how he was progressing with the technical aspect of issuing hurricane forecasts. His predecessor, Bill Proenza, was criticized by his staff for not taking an interest in forecasting. Bill Read responded that he was involved in forecasting for all of the tropical storms and hurricanes that occurred in 2007, after his August arrival at the center. In particular, he emphasized how he happened to be on duty the night Hurricane Humberto blew into a hurricane just 18 hours after it formed as a tropical depression. He's definitely experienced some time on the hot seat with that storm! All in all, my impression is that the new director will fit in much better at NHC than Bill Proenza did, since Read is less of an outsider. He is a good listener, easy to talk to, and a good communicator, traits essential for a successful NHC director. In the coming months, we'll have a chance to see how the new director fits. I'm optimistic that Bill can become a top-notch NHC director, and wish him well in his mission.

Jeff Masters


Robot aircraft get major funding for hurricane work

By: JeffMasters, 12:36 AM GMT on January 25, 2008

The 88th annual meeting of the American Meteorological Society, the world's largest gathering of meteorologists, has drawn to a close here in New Orleans. The biggest news, from my biased view as a former Hurricane Hunter, was the announcement Tuesday of funding for a major project to fly remotely piloted aircraft into hurricanes. NOAA has approved a $3 million research program that will use these aircraft (also called Uncrewed Aerial Vehicles, or UAVs) for three purposes: to take measurements in the core of hurricanes, track how fast Arctic summer ice melts, and take observations of Pacific storms that represent a flood risk to the U.S. West Coast. One of the aircraft planned for the study, the aerosonde, successfully flew into what was the core of Hurricane Noel on November 2, 2007. The hurricane had just completed the transition to a powerful extratropical storm as it moved northward along the U.S. East Coast. The aerosonde spent 7.5 hours in the storm, recording winds as high as 80 mph at altitudes as low as 300 feet.

"A big chunk of the atmosphere remains relatively unobserved. I think unmanned aircraft are a key to that solution and they will become ubiquitous in the coming decade," said Marty Ralph, a research meteorologist at NOAA's Earth System Research Laboratory, Colorado, in press release published by BBC News. In particular, the "atmospheric boundary layer"--the region close to the surface--is a very dangerous place to fly a crewed aircraft in, but is an essential part of the atmosphere to sample in order to learn more about how hurricanes intensify. Collecting data with UAVs offers real hope that we can finally make headway making better hurricane intensity forecasts.

Image: the aerosonde getting launched from a pickup truck. Image credit: NASA.

Jeff Masters

Hurricane Katrina--Looking Back to Look Ahead

By: JeffMasters, 2:40 PM GMT on January 23, 2008

I'm in New Orleans this week for the 88th annual meeting of the American Meteorological Society, the world's largest gathering of meteorologists. This year's meeting has a special focus on Hurricane Katrina. Yesterday's session: "Hurricane Katrina--Looking Back to Look Ahead" sought to review what happened during Katrina with an aim to improve our ability to prepare for the inevitable next "Big One". The keynote speaker was former National Hurricane Center director Max Mayfield. He took the audience back through those painful days in late August 2005 as Katrina exploded into one of the most intense hurricanes ever recorded in the Gulf of Mexico, forever altering the lives of those caught in its path.

Katrina could have been much worse
Max reviewed the forecasts issued by the NHC for Katrina, showing how these predictions gave a full 2 1/2 days for New Orleans and Mississippi to prepare for the onslaught of a major hurricane. "I don't want people to think we're going to be able to do that well all the time," he said. "One of these days, people will go to bed with a Category 1 hurricane expected to hit the next day, and wake up to a Katrina or an Andrew. That will be a catastrophe." Max stressed the importance of not focusing on the skinny black line showing the forecast track of a storm--pay attention instead to the cone of possible landfall locations. Better communication and education to the public on hurricane dangers are needed, and he encouraged all coastal residents to participate in National Hurricane Preparedness Week, May 25-31 of this year.

Figure 1. The exhibit hall from the 2008 meeting of the American Meteorological Society in New Orleans.

How do we change the outcome?
Max showed that while errors in hurricane track forecasts have improved a factor of two in the past 15 years, and are now down to 55 miles for a 24-hour forecast, forecasts of intensity have not improved at all. In fact, the intensity forecasts for 2007 were worse than those of 2005 and 2006. Part of the credit for the improvement in track forecasts goes to a $1 million/year research project called the Joint Hurricane Test-bed--a project former NHC director Bill Proenza called attention to when it received budget cuts. An increase in funding for this program, as well as other hurricane research efforts, are needed to help improve hurricane intensity forecasts, Max urged.

Another way to change the outcome would be through the adoption of improved building codes. Adoption of the tough South Florida building codes all along the coast would save lives and cut down on insurance pay-outs. Max brought up the analogy of a airplane crashing due to a defect in manufacture. When investigators find the cause of the defect, immediate steps are taken to ensure that no airplane is ever built again with that defect. Why, then, do we continue to build houses with known defects? He advocated the formation of a National Disaster Review Board to analyze and adopt new building codes for the coast. This board would consist of meteorologists, emergency managers, and representatives from the insurance and building industries.

Final thoughts on being in New Orleans
Max recounted his own sobering tour of the damaged neighborhoods still devastated more than two years after Katrina. My own experience here was also sobering, as this is my first visit since the hurricane. It felt eerie to stalk the halls of the Convention Center, the site of so much pain and suffering in the aftermath of the storm. I was very conscious of being in the bottom of a bowl everywhere I went within the city, and the damaged, shuttered buildings were a constant reminder that the Gulf of Mexico lay at our doorstep--and would someday send another "Big One" to challenge the city's defenses. Yet many of the people I met have adapted to the post-Katrina life with an admirable stoicism. "They don't call New Orleans the Big Easy for nothing", one cab driver told me. "Life is still good and laid-back here".

Jeff Masters

Green Bay vs. Siberia: comparing Poles of Cold

By: JeffMasters, 5:02 PM GMT on January 20, 2008

Sure, it's cold in football's Pole of Cold--Green Bay, Wisconsin--where game time temperatures for today's NFC Championship Game will be lucky to crack zero degrees Fahrenheit, making it the third coldest NFL playoff game ever. Yeah, those crazy bare-chested Green Bay fans sure look pretty tough in that extreme cold, but they are total wimps compared to the people living in Siberia's Pole of Cold--Ojmjakon, Russia. The temperatures in Ojmjakon this weekend fell to -76°F, making the game being played in Green Bay seem like a summer tea party.

This weekend's -76°F reading was not very unusual for Ojmjakon (also spelled Oymyakon), which is considered to be the coldest inhabited town on earth. Ojmjakon also reached -76°F in both 2007 and 2005. The city lies in a river valley in eastern Siberia, and the cold air pools at night in the bottom of the valley, creating ridiculously low temperatures. On February 6, 1933, an absolute minimum of -67.7°C (-89.9°F) was registered in Oymyakon, putting the city in a virtual tie with the -67.8°C (-90.0°F) measured at Verkhoyank, Siberia on January 15, 1885. These are the two coldest temperatures ever measured on earth, outside of Antarctica. On January 26, 1926, a astonishing -71.2°C (-96.2°F) was measured at Ojmjakon. However, this temperature is unofficial, since the temperature was not directly measured, but obtained by extrapolation.

Figure 1.The world's coldest inhabited city, Ojmjakon, Russia, lies in a river valley in eastern Siberia. Image credit: Google.

According to Chris Burt's Extreme Weather: A Guide and Record Book, supply trucks servicing the area must never turn off their engines in winter. If the engine block freezes, truckers light a fire underneath it to warm it up. When the temperature falls below -58°F (-50°C), ice crystals in the atmosphere make a swishing sound called the "whispering of the stars". What's it like at -80°? Again, Chris Burt's book provides some insight. Two weather observers at the Snag airport in the Yukon of Canada experienced -81.4°F on February 3, 1947, and reported:

"We threw a dish of water high into the air, just to see what would happen. Before it hit the ground, it made a hissing noise, froze, and feel as tiny round pellets the size of wheat kernels. Spit also froze before hitting the ground. Ice became so hard the axe rebounded from it. At such temperatures, metal snapped like ice; wood became petrified; and rubber was just like cement. The dogs' leather harness couldn't bend or it would break...It was unique to see a vapor trail several yards long pursuing one as he moved about outside. Becoming lost was of no concern. As an observer walked along the runway each breath remained as a tiny motionless mist behind him at head level. These patches of human breath fog remained in the still air for three or four minutes before fading away. One observer even found such a trail still marking his path when he returned along the same path 15 minutes later".

Jeff Masters

Winter Weather

2007: Fifth warmest year on record

By: JeffMasters, 7:47 PM GMT on January 17, 2008

The data is in, and 2007 finished as the 5th warmest year on record for the globe, according to figures released by the National Climatic Data Center. For land areas only, 2007 ranked as the warmest year on record. For the oceans, 2007 was the ninth warmest year on record. La Niña continued to strengthen at the end of the year, creating ocean surface temperatures in large areas of the central and eastern equatorial Pacific more than -3°F (-1.7°C) below average. The rapid decay of the El Niño event that rang in 2007 and subsequent development of a moderate La Niña event caused the failure of the forecast issued by the United Kingdom Meteorological Office on January 4 of 2007, predicting a a 60% chance that 2007 would be the warmest year on record. The forecasters cited the combined influence of the continuing global warming trend, and the presence of a moderate El Niño event.

Figure 1. Global temperatures (land plus ocean) for 1880-2007. Image credit: National Climatic Data Center.

The warmest years on record globally were 2005 and 1998, when the global average temperatures were 1.08°F and 1.04°F higher than the long-term average of 57°F. The 2007 temperature was .99°F above average. Seven of the eight warmest years on record have occurred since 2001, part of a rise in temperatures of more than 1°F (0.6°C) since 1900. Within the past three decades, the rate of warming in global temperatures has been approximately three times greater than the century scale trend. All ten of the top ten warmest years for the globe have occurred since 1995. The global temperature record goes back to 1880.

Tenth warmest year on record for the U.S.
For the contiguous U.S., 2007 was the tenth warmest year on record. U.S. weather records go back to 1895. Six of the 10 warmest years on record for the contiguous U.S. have occurred since 1998, part of a three decade period in which mean temperatures for the contiguous U.S. have risen at a rate near 0.6°F per decade.

Figure 2. U.S. temperatures for 1895-2007. Image credit: National Climatic Data Center.

Arctic sea ice remains near record low levels
December 2007 Northern Hemisphere sea ice extent was the second lowest on record for the month of December, 13% below its extent in 1979 when satellite measurements began, according to the National Snow and Ice Data Center. December was the second straight month that a new monthly minimum Arctic sea ice record was not set, following a string of five months in a row where monthly records were set. However, the December 2007 sea ice extent was very close to the record low extent set in 2006, and the ice is much thinner than it was in 2006. This will likely cause a very early melting season and a probable return to record lows by April.

Jeff Masters

Climate Change Climate Summaries

Extreme Weather: a book review

By: JeffMasters, 2:39 PM GMT on January 15, 2008

If you're looking for a U.S. and world weather record book, there is none finer than Chris Burt's Extreme Weather: A Guide and Record Book (Climate Change Edition). His fantastic new second edition comes complete with full weather records for over 300 U.S. cities, plus over 100 photos of some of the most beautiful and amazing weather events of all time. Also included are historical examples of bizarre weather events such as heat bursts, electrified dust storms, snow rollers, pink snowstorms, luminous tornadoes, falls of fish and toads, ball lightning, and super lightning bolts. My two favorite extreme weather stories are also included--the tale of the farmer in Kansas who watched as a tornado lifted off the ground and passed directly over him, and the story of the Marine Corps pilot who bailed out in the midst of a severe thunderstorm and lived to tell about it.

While the book focuses mostly on the U.S., there is a good amount of detail about weather extremes world-wide. Many of the book's 47 maps and 65 tables and graphs show where weather extremes occur world-wide. The graphics are clear, colorful, and easy to understand (with only one minor exception, a plot of storm surge heights from the 1970 Bangladesh cyclone that was very difficult to interpret). There were a few minor errors I caught, such as the use of the term "El Nina" instead of "La Nina", giving 1" hail as the criteria for a severe thunderstorm (it is 3/4" hail), and the table for the Saffir-Simpson Scale having a number 1 mph off for the definition of Category 5 storms. However, the author maintains a web site,, where one can report errors and new records that need to be added to the book for the next edition.

A few remarkable facts I learned from Extreme Weather:

Perhaps the most extraordinary rain event in world history occurred in the unlikely location of Smethport, Pennsylvania. An incredible 28.50" fell in just three hours during a July 18, 1942 thunderstorm. All told, 34.30" fell in a 12-hour period. No such rain intensity has been recorded anywhere in the world. The resulting floods stripped hillsides in the Smethport area to bare rock and killed 15 people.

An F5 tornado completely destroyed the Texas Panhandle town of Glazier on April 9, 1947, leaving only one damaged structure standing. The town was never rebuilt.

Twenty inches of snow fell on Houston, Texas February 14-15, 1895. Brownsville got six inches, and snow was reported all the way down to Tampico, Mexico--the southernmost fall of snow at sea level ever observed in the Western Hemisphere.

Climate change
The book bills itself as the "climate change edition", but there is very little information on climate change in the book. The discussion on heat waves brings up the role of climate change, and two pages in the introduction discuss if weather is becoming more extreme. Burt presents a nice analysis of the temperature and precipitation records for the U.S. to show that there has been a an increase in extreme heat and intense precipitation events since 1990. However, the decade of the 1930s had more temperature extremes than any other decade. The book's strength is its focus on extreme weather, and I'm pleased that Burt limits his discussion of climate change to just a few pages.

Extreme Weather: A Guide and Record Book is $15.57 from Four stars out of four.

Jeff Masters

Book and Movie Reviews

Rare January tornado hits Vancouver, Washington

By: JeffMasters, 1:33 PM GMT on January 11, 2008

A rare tornado hit Vancouver, Washington (just north of Portland, Oregon) on Thursday at noon local time. The unusual twister demolished a rowing club, downed power lines, uprooted trees, and tossed shopping carts into cars along its four mile path. No injuries were reported, though. The state of Washington averages about two tornadoes per year. Yesterday's tornado was only the third January tornado observed in Washington since 1950, according to the National Climatic Data Center (2000 and 2006 were the other years). Tornadoes were also reported yesterday in Louisiana, Mississippi, and Alabama. About 100 houses were damaged and destroyed and 11 people were injured in Lowndes County, Mississippi from one of the tornadoes. A total of 34 tornadoes have been confirmed for the severe weather outbreak that began on January 7th, and total number of tornadoes could reach 60 or more by the time all the damage surveys are complete. More tornadoes are expected today from the Florida Panhandle northeastward to coastal North Carolina. Watch the Weather Underground's Severe Weather Page and Tornado Page to keep up with the storms.

Figure 1. Storm reports for Thursday, January 10, 2008. Image credit: NOAA's Storm Prediction Center.

Katrina damage claims exceed $3 quadrillion
According to the Associated Press, $3,014,170,389,176,410 in claims have been filed against the federal government over damage from the failure of levees and flood walls following Hurricane Katrina. Of the 489,000 total claims, the U.S. Army Corps of Engineers said 247 were for at least $1 billion, including one for $3 quadrillion.

"That's the mother of all high numbers," said Loren Scott, a Baton Rouge-based economist.

Jeff Masters


More tornadoes and flooding for the Midwest

By: JeffMasters, 4:21 PM GMT on January 09, 2008

Wild spring-like severe weather continued Tuesday, with eight tornadoes reported in Arkansas, Missouri, and Tennessee. One Arkansas man died in Appleton when a tornado rolled his mobile home. The same tornado gave a cow a wild ride of 3/4 mile before setting it down unharmed. A total of 48 tornadoes have been reported for the two day severe weather outbreak that has affected much of the Midwest. Two people were killed and three critically injured in southern Missouri on Monday near the town of Marshfield, northeast of Springfield, when a tornado rated EF3 with winds of 136-165 mph smashed through a mobile home park. In Wheatland, Wisconsin, just north of the Illinois border, another EF3 tornado damaged or destroyed 55 buildings and injured 13 people. Twelve homes were demolished down to their foundations. The Wheatland tornado was only the second January tornado on record in Wisconsin. The only other one was a long-track F3 in Green and Rock counties on 24 January 1967. Detailed imagery and analysis of this tornado are available from the National Weather Service in Milwaukee and the CIMSS Satellite Blog.

Figure 1. Storm reports for Tuesday compiled by the Storm Prediction Center.

In north central Indiana, heavy rains of up to eight inches triggered floods along the Wabash and Tippicanoe rivers that killed three people and forced the evacuation of hundreds. No further rain or severe weather is expected in the Midwest today. A new storm system on Thursday may bring the risk of severe weather to Alabama and surrounding states on Thursday.

Figure 2. Heavy rains of up to eight inches hit portions of Indiana and Illinois this week. Image credit: NOAA.

Jeff Masters


Rare January tornadoes rip the Midwest

By: JeffMasters, 4:39 PM GMT on January 08, 2008

Wild spring-like severe weather swept through the Midwestern U.S. last night, unleashing tornadoes, baseball-sized hail, flooding, and extreme wind gusts. Up to 37 tornadoes ripped through Missouri, Oklahoma, Illinois, Arkansas, and Wisconsin. Two people were killed and three critically injured in southern Missouri near the town of Marshfield, northeast of Springfield, when a tornado smashed through a mobile home park. In Wheatland, Wisconsin, in Kenosha County, just north of the Illinois border, a strong or possibly violent tornado damaged or destroyed 55 buildings and injured 13 people. Twelve homes were demolished down to their foundations. The Wheatland tornado was only the second January tornado on record in Wisconsin. The only other one was a long-track F3 in Green and Rock counties on 24 January 1967. A radar animation of the Wheatland tornado is at right, and more detailed imagery and analysis of this tornado are available from the CIMSS Satellite Blog.

Record warm temperatures helped fuel yesterday's severe weather outbreak. The 63° F reading in Milwaukee was the warmest temperature ever recorded there in the month of January. Many locations in Michigan, Wisconsin, and Illinois posted record highs within three degrees of their warmest-ever January readings. The record warmth will continue to fuel more severe thunderstorms today from northern Louisiana to Ohio, and the Storm Prediction Center has already issued a Tornado Watch for portions of Arkansas, Missouri, Tennessee, Mississippi, and Kentucky. Severe thunderstorms have already been reported in Arkansas this morning.

Last night's severe thunderstorm I observed from my house was the first I've ever experienced in my 40 years living in Michigan. One thunderstorm, 100 miles north of where I live, covered the ground up to two inches deep with hail (Midland, Michigan). Michigan has had three consecutive Januarys with record warmth and spring-like thunderstorms. Northern Illinois recorded its first January tornado since 1950 last night, and Wisconsin its second January tornado on record. Is it global warming? Well, one can't blame a single weather event on climate change. Also, it was eight below zero here just five days ago, so there has been some very normal winter weather this year. Furthermore, the 37 tornadoes reported yesterday don't come close to the 102 twisters recorded during the huge January 17-22, 1999 tornado outbreak across Arkansas and Tennessee. But the string of unusual January warmth in three straight years, accompanied by severe thunderstorms far to the north, is broadly consistent with what one would expect to see in a warming climate. Expect to see a lot more spring-like weather in January in coming years.

Jeff Masters


Blizzard of '08 leaves 11 feet of snow in the Sierras

By: JeffMasters, 2:12 PM GMT on January 07, 2008

The blizzard of '08 is over in hard-hit California, Oregon, and Washington, but the storm has left in its wake flooding, downed power lines, and prodigious amounts of snow. In the Sierra Mountains, 4-8 feet of snow were common. At the Kirkwood ski resort near Lake Tahoe, an astounding 11 feet of snow fell in just 72 hours--10 feet of that in only 48 hours.

Figure 1. Cleared tracks on the Southern Pacific Railway at Blue Canyon during the winter of 1917. Some of the heaviest snow in North America occurs in the Sierra Nevada Mountains; 60 to 65 feet of snow is not uncommon in a winter season. In: "Monthly Weather Review," October 1919, p. 698. Image credit: NOAA Photo Library.

The massive Tahoe snows from this storm are not a record, however, however. According to Chris Burt's book Extreme Weather, in April 1880, an incredible storm dropped 16 feet of snow (194 inches) in just four days on Norden, near Donner Summit in the Sierras. This stands as the greatest amount of snow ever recorded from a single storm anywhere in the world. The total snowfall that winter at the Summit station (7,017 feet) was a whopping 783" (over 65 feet). An even greater amount was recorded during the winter of 1951-1952 at Donner Summit--815" (over 67 feet). The Southern Pacific Railroad's flagship, the City of San Francisco, was trapped by an avalanche near Yuba Pass on January 13 during that winter. The train lost power, and food for the 226 passengers nearly ran out by the time rescuers arrived. Another bad storm occurred on January 9-10, 1890, when ten feet of snow fell, blocking the rail line and stranding train passengers for days. One of those trapped was New York newspaper woman Nellie Bly, who was attempting to travel 'round the world in 80 days, besting the heroes of Jules Verne's Around the World in Eighty Days. She was forced to detour to the south via the Southern Pacific Railway, and made it back to New York in under 73 days.

Jeff Masters

Winter Weather

Heavy snow and rain continue to pound California

By: JeffMasters, 8:30 PM GMT on January 05, 2008

Heavy snow, flash floods, and damaging winds continue to pound California today as a weakening Pacific storm moves inland over British Columbia. The winds have died down considerably in the Sierra Mountains, where hurricane force winds were common on Friday. The storm's highest winds occurred at Ward Mountain near Lake Tahoe--sustained at 110 mph, gusting to 163 mph, on Friday. Prodigious snow amounts of up to six feet have fallen in the Sierras, with Blackcap Basin in Fresno County (elevation 10300 feet) reporting 71.3 inches (5.9 feet) of new snow as of 4 am PST Saturday. Continued heavy snows are expected in the Sierras through Sunday, with total amounts up to ten feet possible.

At lower elevations, heavy rain has triggered flash floods. In Chino Hills, just east of Los Angeles, a flash flood swept away a vehicle that had gone around a barricade. One occupant was found hypothermic and clinging to a tree, but the vehicle and its other occupant are missing. A mudslide forced the temporary closure of Interstate 15 nearby. Rain amounts exceeding ten inches (Figure 1) have fallen in the mountains of Central and Northern California, and in Nevada, heavy rains caused a levee to burst along the Truckee Canal in Fernley, flooding hundreds of homes.

Figure 1. Estimated rainfall from the blizzard of '08 in Central California as of 3 pm PST Saturday.

The storm pounded the San Francisco Bay area Friday with remarkable ferocity, bringing winds of tropical storm force to the entire region, accompanied by extremely heavy rain. Sustained winds of 53 mph gusting to 67 mph were measured at the San Francisco airport, forcing cancellation of 35 flights. High winds on the Richmond-San Rafael Bridge forced closure of the bridge during the morning commute, when trucks toppled over on both upper and lower spans. Winds gusting to 70 mph were recorded on the Golden Gate bridge. At Mt. Diablo State Park just east of Oakland, sustained winds of 62 mph were reported at 9 am PST. A wind gust of 105 mph was reported at Los Gatos south of San Jose at 12pm PST.

The CIMSS satellite blog has a nice description of the unique meteorology of this storm.

Jeff Masters

Winter Weather

Blizzards, hurricane force winds pound California

By: JeffMasters, 8:37 PM GMT on January 04, 2008

A mighty hurricane-force Pacific storm continues to clobber California with blizzards, damaging winds, and flooding rains. Hardest hit are the Sierra Mountains, where winds at Ward Mountain near Lake Tahoe were 86 mph, gusting to 163 mph, at 11 am PST. The storm responsible is visible just off the coast of Washington (Figure 1), and has a central pressure near 960 mb--similar to that of a Category 2 hurricane. Blizzard conditions will continue over much of the Sierras, with 2-5 feet likely to fall by Saturday. Travel will be difficult of impossible in the northern mountains of California Friday and Saturday. Snow amounts may reach 10 feet by Monday in some mountain regions of California.

Figure 1. Visible satellite image of the California blizzard of 2008.

The storm pounded the San Francisco Bay area this morning with remarkable ferocity, bringing winds of tropical storm force to the entire region, accompanied by extremely heavy rain. Sustained winds of 53 mph gusting to 67 mph were measured at the San Francisco airport, forcing cancellation of 35 flights. High winds on the Richmond-San Rafael Bridge forced closure of the bridge during the morning commute, when trucks toppled over on both upper and lower spans. Winds gusting to 70 mph were recorded on the Golden Gate bridge. At Mt. Diablo State Park just east of Oakland, sustained winds of 62 mph were reported at 9 am PST. A wind gust of 105 mph was reported at Los Gatos south of San Jose at 12pm PST. Ten inches of rain in 24 hours fell 13 miles southeast of Los Gatos.

In Southern California, the concern is heavy rain and flooding. Rainfall rates of up to an inch per hour are expected in the mountains, with total rain amounts of up to 10 inches expected in the south facing mountains. Landslides and debris flows are likely on the hillsides burned by the recent fires. Strong, damaging winds are expected over much of Southern California, as well. High winds over the the ocean will bring swells of 6-10 feet to the coast and 20 foot seas offshore, and isolated thunderstorms could spawn waterspouts. The storm responsible for the wild weather will weaken and move ashore on Saturday over British Columbia, but will still be strong enough to bring additional heavy rains, high winds, and mountain snows to California through Sunday.

Jeff Masters

Winter Weather

Huge storm poised to pound California; snow falls in Florida

By: JeffMasters, 7:59 PM GMT on January 03, 2008

A large and very powerful Pacific storm is poised to hammer California this weekend, bringing blizzard conditions and sustained winds over hurricane force to the Sierra Mountains. The mighty storm, currently about 1000 miles west of the state of Washington, is intensifying rapidly today. As the system approaches the coast of Washington State on Friday afternoon, its pressure is expected to bottom out at 960 mb--a pressure similar to that of a Category 2 hurricane. High winds will buffet all of California Friday and Saturday, with sustained winds of hurricane force and gusts of 145 mph expected along the high ridge tops of the Sierra Mountains. Blizzard conditions will envelop much of the Sierras, with 2-5 feet of snow likely to fall by Saturday. Snowfall rates up to six inches per hour are expected. Travel will be difficult or impossible in the northern mountains of California Friday and Saturday.

Figure 1. A massive winter storm (left side of image) prepares to hammer the U.S. West Coast on Friday and Saturday. A second, weaker storm is affecting the coast today.
In Southern California, the concern is heavy rain and flooding. Rainfall rates of up to an inch per hour are expected in the mountains, with total rain amounts of up to 10 inches expected in the south facing mountains. Landslides and debris flows are likely on the hillsides burned by the recent fires. Strong, damaging winds are expected over much of Southern California, as well. High winds over the the ocean will bring swells of 6-10 feet to the coast and 20 foot seas offshore, and isolated thunderstorms could spawn waterspouts. The storm responsible for the wild weather will weaken and move ashore on Saturday over British Columbia, but will still be strong enough to bring additional heavy rains, high winds, and mountain snows to California through Sunday.

Florida snow
It's cold in Florida! Snow flurries were reported along the east central coast of the state this morning, near Daytona Beach and Cocoa. It was the first snow seen in the region since 2003.The cold air behind the cold front responsible for the freeze was pushed by an unusually strong high pressure system. Tallahassee, Florida reported a new atmospheric pressure record at 11 am today: 30.77 inches (1042 mb). The previous record was 30.74 inches (1041 mb) which occurred on January 4th 1979 and again on February 5th 1996. Record low temperature records were set in Fort Myers (32° F), Miami Beach (40° F) and Key West (45° F) this morning, and citrus growers worked hard to keep their orange crops from freezing.

Jeff Masters

Winter Weather

Top U.S. weather story of 2007: the Southeast U.S. drought

By: JeffMasters, 3:29 PM GMT on January 01, 2008

The year 2007 is in the record books as the driest or second driest year on record for much of the Southeastern U.S. A mere 31.85 inches of rain fell in Atlanta, Georgia, during the year, 62% of the average of 48 inches. This year's rainfall total just missed breaking the record of 31.80 inches set in 1954. Rainfall records in Atlanta go back to 1930. The drought was worse in Alabama, where Birmingham had its driest year on record--just 28.86", a full 25 inches below average, smashing the record low of 36.14" set in 1931. Huntsville was even drier--a mere 28.65"--29 inches below average. Surrounding areas of Tennessee, North Carolina, South Carolina, Kentucky and Virginia also experienced extraordinarily dry years (Figure 1).

Figure 1. Drought conditions in the Southeastern U.S. were at the highest level possible--exceptional drought--at the end of 2007. Image credit: NOAA.

Although the current drought is exceptional, Atlanta has had much drier 2-year periods. During the drought of 1954-1955, Atlanta received 68.23 inches of precipitation--a 28 inch deficit from the normal 2-year rainfall. The deficit for the past two years is only 16 inches, since an average amount of rain fell in 2006 (48.46 inches). Based on the climatological record, Georgia can expect a two-year drought about once in 25 years, and a drought lasting three or more years about once every 40 years. Drought is part of the natural cycle in Georgia, and it would not be a surprise to see the drought of 2007 continue until the winter of 2008. Although December 2007 saw Atlanta's first above average month of rainfall since November 2006, the coming two weeks look very dry, and the current La Nina atmospheric pattern usually brings below average rainfall.

What is causing the Georgia drought?
Two main factors are responsible for the Southeast U.S. drought. Most importantly, a persistent jet stream pattern has set up that steers storms away from the region, and into Texas instead. Texas, which suffered extreme drought in 2006, found itself awash in floods in 2007, as the jet stream pattern brought storm after storm to the state. Another contributing factor to the current Southeast drought is the absence of tropical storms and hurricanes during 2006 and 2007. These storms are an important part of the annual rainfall budget for the Southeast. For example, in 2005, 29% of Atlanta's yearly rainfall came from five tropical storms:

1.36" Arlene June 11-12, 2005
1.40" Katrina, August 29-30, 2005
5.48" Cindy, July 6-8, 2005
5.41" Dennis, July 9-12, 2005
2.94" Tammy, October 6-8, 2005

Figure 2. Over ten inches of rain fell on Atlanta in 2005 from two tropical cyclones, Dennis and Cindy. Tropical cyclones accounted for 29% of Atlanta's rainfall that year. Image credit: NOAA/HPC.

There is little evidence that global warming contributed to this drought. The Southeastern U.S. has cooled by about 0.1° F over the past 100 years, even as the rest of the globe has warmed 1° F. The reasons for this lack of warming in the Southeast are not fully understood. One theory is that the cooling is due to air pollution blocking sunlight. Another theory, proposed by Georgia State Climatologist David Stooksbury, attributes the cooling to the shift from 80 percent row crops (like corn and cotton) to 60 percent forest. Land use changes like this can have a significant impact on how solar energy heats the air once it is absorbed by the soil.

Why Atlanta is vulnerable to drought
Atlanta, unlike most major cities, grew up around rail lines rather than a major body of water. Although the Chattahoochee River runs through Atlanta, the city lies on top of a watershed, with no large bodies of water upstream. The rivers and streams in the region are small, and the bedrock limits how much ground water is available. The Lake Lanier reservoir that supplies Atlanta with most of its water was constructed in the 1950s. Since that time, the population of Atlanta has quadrupled, increasing the pressure on the reservoir's limited water. Lake Lanier is at its record lowest level--more than 19 feet below average. If the drought continues into the summer of 2008, and no tropical storms arrive to break the drought, Atlanta may run out of water.

By 2030, the population of the Atlanta metropolitan area is expected to increase from 5 million to 9 million. Current water resources in the regions will be unable to support this population increase, unless planners make a concerted and expensive effort to plan ahead. The expected increase in temperatures over the coming decades due to global warming will make future droughts in the region even more severe, so Atlanta has a very tough road ahead of it.

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