Category 6™

Severe weather moves into the Mississippi Valley

By: JeffMasters, 4:59 PM GMT on March 31, 2007

Severe weather continues today across the Plains, where flooding has been the main problem in the past 24 hours. Portions of Texas received up to seven inches of rain in the past day (Figure 1), causing closure of many roads. Seven tornadoes touched down in Texas yesterday, and one near Hallettsville injured three people. Four twisters touched down Thursday, and as many as 70 on Wednesday. The tornado outbreak killed four people on Wednesday. The strongest storm surveyed so far was an EF3 tornado that hit Holly, Colorado, killing one person and injuring eleven. The tornado was unusual in that it did not show up on radar until a few minutes after it touched down, and moved from east to west. Holly was not not under a watch, no warnings were issued, and the town sirens did not go off. Our tools and knowledge are still not good enough to always detect these storms before they touch down, unfortunately. The heavy rains these storms have brought--and the up to six feet of snow in the mountains of Wyoming--should help drought conditions relax in the Plains, though.

Expect the severe weather action to shift to the Mississippi Valley today and Alabama tomorrow. However, the storm system is gradually losing its punch, and we may not see any more tornadoes by Sunday out of the system.

Figure 1. Total storm precipitation estimated by radar for the Dallas/Fort Worth region for the period March 29 - March 31.

Jeff Masters


More tornadoes for the Plains

By: JeffMasters, 1:26 PM GMT on March 30, 2007

Severe weather and tornadoes continued to pound the Plains yesterday, and more severe weather is on the way today. On Thursday, four tornadoes ripped through Oklahoma, including a twister that hit the northwest suburbs of Oklahoma City. This tornado damaged 50 buildings and injured four people. All of the injuries were were people in mobile homes or vehicles, as is typical for tornado victims. Thursday's four twisters came a day after 65 tornadoes swept through Texas, Oklahoma, Kansas, Colorado, and Nebraska, killing four people. A tornado in Holly, Colorado did extensive damage, killing one person and injuring eleven. It was the first tornado fatality in Colorado since 1960. The two tornado fatalities in Oklahoma Wednesday were that state's first deaths in five years. One other person died in a tornado that struck the Texas Panhandle Wednesday. Several of Wednesday's tornadoes were strong EF2s with winds of 111 - 135 mph. Damage surveys have not yet been completed on the Holly, CO tornado, and most of the other 65 tornadoes from that day.

Expect another significant severe weather outbreak late this afternoon in the Plains, according to the latest severe weather outlook from the Storm Prediction Center. They have placed Central Texas, including Dallas/Fort Worth, in their "Moderate Risk" area for severe weather. Four tornadoes have already touched down in Texas this morning, but none caused significant damage. Flash flooding and large hail--including baseball sized hail--have also occurred in Southwest Texas this morning. Keep an eye on the Central Texas radar (Figure 1) all day, as these severe thunderstorms grow in intensity and start spawning tornadoes.

Figure 1. Current radar for Central Texas.

Jeff Masters


Tornadoes and huge hail pound the Plains

By: JeffMasters, 1:33 PM GMT on March 29, 2007

A barrage of 65 tornadoes ripped through Texas, Oklahoma, Kansas, Colorado, and Nebraska last night. Two people were killed in the Oklahoma Panhandle when a tornado destroyed their house. Tornadoes also killed one person in Colorado, and one person in Texas. Several of the tornadoes were large, long-lived, and possibly violent EF4 twisters. Since the Enhanced Fujita rating scale is a damage scale, we may never know how strong some of these tornadoes were, as they mostly missed populated areas where they could do damage.

One supercell thunderstorm in the Texas Panhandle spawned a tornado that hit a rest area along I-40, flipping 18-wheelers parked there. This storm may have done enough damage to get an EF-scale rating. The thunderstorm also produced 4.5 inch diameter hail (softball sized!), which one doesn't see very often anywhere in the world. Looking at the radar reflectivity from this storm (Figure 1), we see that the echoes from this storm were near the top of the scale--70 dBZ--thanks in part to these highly reflective large hailstones. Seeing 70 dDZ on the radar is another rarity!

Figure 1. Radar reflectivity image of the March 28, 2007 thunderstorm that produced a tornado and softball-sized hail as it crossed I-40 east of Amarillo, Texas.

We got lucky with last night's storms, which all missed populated areas. What would happen if we got unlucky? What would a violent EF5 tornado do to Chicago or some other densely populated urban area? That was the cover story of January's issue of the Bulletin of the American Meteorological Society, which I'll discuss tomorrow.

Jeff Masters


Major tornado outbreak in the Plains

By: JeffMasters, 1:00 AM GMT on March 29, 2007

A major severe weather outbreak is underway across the Plains this evening. Numerous tornadoes have been reported along a line stretching from the Texas Panhandle northwards through western Oklahoma, Kansas, and Nebraska. Softball-sized hail was reported at Pantex, Carson County, Texas, and numerous reports of high winds over 60 mph have also been relayed. You can keep track of all the storm damage reports from our Local Storm Report page. So far it appears that the tornadoes have all missed populated areas, although a tornado crossed over a rest area on I-40 in the Texas Panhandle and flipped 18-wheelers there. In addition, Sharon Springs, Kansas had an impressive looking tornado pass just two miles east of town. A large multi-vortex tornado was also reported three miles southeast of Elmwood, in the Oklahoma Panhandle. Goodland Kansas had a near miss by another impressive tornado that passed five miles to the east.

Figure 1. Radar reflectivity image of the March 28, 2007 tornado as it approached Sharon Springs, Kansas.

Figure 2. Radar velocity image of the March 28, 2007 tornado as it approached Sharon Springs, Kansas. Note the area of blue and red echoes just south of the circle with a "+" inside it that marks the location of Sharon Springs. The blues and reds show that strong winds going both towards and away from the radar exist in a small area, denoting the presence of a parent mesocyclone (rotating thunderstorm) and a tornado.

I'll be back Thursday morning with a summary of the severe weather outbreak.

Jeff Masters


Hurricane Katrina revisited: a book review of The Storm

By: JeffMasters, 4:56 PM GMT on March 26, 2007

Last week's stinging report lambasting the Army Corps of Engineers for its failure to build adequate levees to protect New Orleans was written by "Team Louisiana," headed by Dr. Ivor van Heerden of Louisiana State University. He published a book last year titled, The Storm: What went wrong and why during Hurricane Katrina--the inside story from one Louisiana scientist ($17 at Dr. van Heerden is cofounder and deputy directory of the Louisiana State University Hurricane Center and director of the Center for the Study of Public Health Impacts of Hurricanes. He holds a Ph.D. in marine sciences from LSU, and serves as associate professor of civil and
environmental engineering there. Van Heerden had a very unique perspective of Katrina. He worked tirelessly in the decade leading up to the storm to improve our scientific understanding of how Louisiana's wetlands protect New Orleans from hurricanes. He also worked extensively with FEMA, the Army Corps of Engineers, and political figures at the local, state, and U.S. Congressional levels to try to improve New Orleans' disaster readiness. In the aftermath of the storm, he provided support for the search and rescue efforts and plugging of the levee breaches, then headed one of the teams assigned to figure out what caused the levees to fail. PBS's NOVA did a nice story on him last year, featuring interviews with him from before and after Katrina.

Van Heerden is not afraid to speak his mind, and has made many enemies as a result. His criticisms in the book are far ranging, from university administrators to politicians to government administrators, particularly in FEMA and the Army Corps of Engineers. Some readers may not like the amount of criticism in the book, but I had no problem with it. Those responsible for the flooding of New Orleans, failed evacuation efforts, and tragically bungled recovery effort need to be held accountable, since it is crucial that we learn from our mistakes. Van Heerden also has considerable praise for the heros of the Katrina disaster--particularly scientists, the media, and recovery workers and volunteers who responded so magnificently.

Van Heerden is a big proponent of building a flood protection system that will protect Louisiana from a Category 5 hurricane. He proposes doing this by restoring wetlands, building armored levees, and installing huge flood gates on Lake Pontchartrain, similar to what the Dutch use to protect their country from the North Sea. I especially liked his continued emphasis on the importance of doing good science. He is not a fan of what politicians and business leaders do with good science: The science is the easy part. The hard part is overcoming the narrow-mindedness and selfishness of politics and business as usual. For decades the two have undermined plan after plan to restore wetlands, build new ones, and thereby protect people and property. They have played hell with improving the existing levee system. We must do better now, or we can kiss it all good-bye for good. I was not exaggerating in the introduction when I said that politics and business as usual in Louisiana will eventually put everything below Interstate 10 underwater. Science and engineering can save the day, but not if they're censored or manipulated. If that's to be the case, just shelve them and start packing. It's over.

The author is not a smooth and gifted writer--his writing is very blunt and somewhat clumsy, despite the help of his co-author, Mike Bryan, a professional writer brought in to make the book more readable. There are two nice graphics showing the Katrina flooding and the author's proposed flood control system, but most of the graphics are poor black-and-white hand-drawn diagrams. Still, I think the book is an important one to read, since van Heerden is an expert on both the science and the politics of the Katrina disaster. I found his descriptions of all the various political battles in the years leading up to Katrina particularly fascinating. His detailed treatment of how the levee system evolved, how it failed during Katrina, and how it should be rebuilt to prevent a future disaster are also interesting. I did skip over some of the more technical engineering details of the levees he presented, which were very detailed. Overall rating for The Storm: two and a half stars.

Van Heerden is pessimistic that the politicians and Army Corps of Engineers can be trusted to make the right decisions to bring about what Louisiana needs--protection from a Category 5 hurricane. Yet, he will continue to battle on for this goal, concluding the book with this cry to action:

As a nation, lets take up the "Rebuild!" battle cry. Now is the time to put politics, egos, turf wars, and profit agendas aside. We owe it to the thirteen hundred Americans who died in the Katrina tragedy. We owe it to their survivors and to all future generations. It's now or never. Let's show the world what we're all about, here in America in the twenty-first century.

I'll have a new blog Wednesday or Thursday.
Jeff Masters

Book and Movie Reviews

New Orleans levee report blames Army Corps

By: JeffMasters, 3:37 PM GMT on March 23, 2007

The Army Corps of Engineers is largely to blame for the disastrous flooding of New Orleans during Hurricane Katrina, according to a 475-page report commissioned by the state Department of Transportation and Development that was released Wednesday. The five major findings of the report by "Team Louisiana":

Figure 1. Team Louisiana researchers discuss forensic developments at a section of the 17th Street Canal breach. Image credit: Team Louisiana.

1) The Army Corps failed to follow the 1965 Congressional mandate to protect against the "most severe combination of meteorological conditions reasonably expected." This mandate specified a "1 in 100 year storm" that the New Orleans levee system must protect against, which was set as a Category 2 hurricane with winds of 107 mph. In 1972, the National Weather Service adjusted the expected "1 in 100 year storm" to be a Category 3 hurricane with 129 mph winds. This was adjusted again in 1979 to a Category 4 hurricane with 140 mph winds. The Army Corp never revised their protection plans based on these new estimates, despite their mandate to do so and their awareness of the requirement to do so.

2) The New Orleans levees were built 1-2 feet too low, because the Army Corps used elevation estimates taken in 1929 to design the levees. The city has sunk over the years, and was already 1.3-1.6 feet lower than the 1929 elevation estimates in 1965 when the levee system was designed. Continued subsidence of the land resulted in levees that were up to five feet too low when Katrina struck. The Corps was aware of the subsidence issue, but did not correct for it. The levees being too low caused many of the failures that flooded New Orleans, the report asserts: Crown elevation deficiencies ranging up to 5 feet at the time Katrina struck resulted in prolonged overtopping of floodwalls and levees along the Inner Harbor Navigation Canal (IHNC) and to the east in the Lake Borgne funnel that otherwise would have been overtopped only briefly. Prolonged overtopping led to catastrophic breaches into the Lower 9th Ward on the east and into Orleans Metro on the west, and contributed to the early failures of levees along the Gulf Intracoastal Waterway (GIWW)and MRGO. Early failure of the MRGO levee allowed the 32,000 acre wetland buffer between MRGO and 40 Arpent back levee to fill and overtop the 40 Arpent back levee while the surge was still rising, and resulted in catastrophic flooding in St.Bernard to an elevation of 11 ft.

3) The Army Corp did not follow existing engineering practice and guidance for construction of levees and floodwalls.

4) The free-flowing deep draft navigation channel on the east side (MRGO and GIWW channels) compromised system performance.

5) The levee system was "managed like a circa 1965 flood control museum", and was not maintained or upgraded properly.

The Army Corps yesterday issued a press release defending themselves, saying that all levels of government were involved in the poor decision making for New Orleans' levees, and the Corps should not be singled out for their failures. Regardless, the release of the Team Louisiana report will bolster the legal efforts to sue the Army Corps for damages from Katrina. These claims are currently at $400 billion and growing, including a claim of $77 billion from the city of New Orleans, and $200 billion from the state of Louisiana.

Next week, I plan to post a review of the Hurricane Katrina book by Team Louisiana's leader, Dr. Ivor van Heerden of Louisiana State University: The Storm: What went wrong and why during Hurricane Katrina--the inside story from one Louisiana scientist.

Jeff Masters

Lessons learned from the May 3, 1999 tornado

By: JeffMasters, 2:39 PM GMT on March 21, 2007

Storm Warning: The Story of a Killer Tornado, which I reviewed earlier this month, recounts the story of the May 3, 1999 monster F5 tornado that ripped through the southern suburbs of Oklahoma City. In addition to providing an exciting fast-paced narrative of the tornado's rampage, author Nancy Mathis also brings up a number of important lessons learned from this storm, which I detail below. With two strong spring storms capable of trigging tornado outbreaks expected to move through the Midwest U.S. Tuesday and Friday next week, everyone living in Tornado Alley would be wise to pay attention to these lessons learned!

A F-4 tornado rips through Kansas, May 8, 2003. Image credit: wunderphotographer Mike Theiss.

Reasons for the low death toll in the May 3, 1999 tornado
Considering that the May 3, 1999 tornado was the strongest ever measured (302 mph winds), hit a major metropolitan area, and destroyed or damaged over 11,000 buildings, the death toll of 38 was remarkably low. It's worth reviewing the major reasons for the low death toll:

1) National Weather Service Doppler radars. The NWS just completed installation of the new NEXRAD Doppler radars nation-wide in 1998. The NEXRAD radars increased tornado warning time from 5.3 to 9.5 minutes, and roughly doubled the percentage of tornadoes warned for from 30% to 60%. Warning times were as long as 39 minutes for the May 3, 1999 tornado. Mathis notes that the number of tornado deaths in the U.S. was cut in half, to roughly 80 per year, after the NEXRAD radars became operational. It took 20 years for the new radars to get procured, thanks to cost overruns and bureaucratic wrangling. Politicians, NOAA administrators, and private contractors involved during the procurement of the next generation of tornado detection equipment should seek to avoid a similar delay. The procurement process for the NEXRAD radars was a disaster that undoubtedly cost lives.

2) A great warning system. A coordinated warning effort by NOAA's Storm Prediction Center, the local NWS office, local media, and Oklahoma local government personel worked brilliantly. The big money and training pumped into tornado preparedness paid big dividends.

3) A tornado-savvy population. Oklahomans are the most tornado-savvy people in the world. They took warnings seriously, and acted on them. A survey of those injured found that the vast majority knew of the warnings and the tornado, but just did not have a proper place for shelter.

4) Luck. The tornado leveled schools that had already dismissed classes for the day, and a shopping mall that had closed earlier. Had the tornado hit several hours earlier, or late at night when its movement could not have been shown on live TV, the death toll could have been as high as 600, according to a NOAA study.

Highway overpasses are the worst place to shelter from a tornado!
Three people died at overpasses during the May 3, 1999 tornado. The presence of the bridge acts to focus the wind, making it stronger under the bridge. Some drivers abandoned their cars on the Interstate under overpasses, blocking traffic and creating a traffic jam where people were trapped when the tornado swept over. If you're caught in your car on the road and choose to abandon the vehicle, pull off the road and seek shelter in a ditch, not under a highway overpass!

Poor home construction contributed to the deaths and injuries
Tornado fatalities were primarily from those in mobile homes, cars, and homes without shelters. The tornado revealed many homes where builders had failed (illegally) to build up to code. Enforcing existing codes and mandating stronger building codes would have reduced the death toll. This, of course, is not popular with the powerful building industry, since better construction costs more.

Tornado forecasting is still in a primitive stage
A day before the May 3 tornado outbreak, the Storm Prediction Center was only forecasting their lowest alert level for severe weather, a "Slight Risk". The computer models were highly scattered in their predictions, and made significant changes with each new run. Nothing about the outbreak was textbook. Most supercell thunderstorms that spawn tornadoes form along a warm or cold front (or a "dryline" where a sharp gradient of moisture is present). However, none of the first few supercells in the May 3 outbreak were near a front or dryline. The classic clash of warm moist Gulf air with cold, dry Canadian air that usually provides the lift needed for supercells was not present. Researchers have a huge amount of work to do before they understand what causes tornadoes like the May 3, 1999 storm.

I'll be back Friday with a new blog.

Jeff Masters


NHC director Proenza calls for new satellite

By: JeffMasters, 12:52 PM GMT on March 19, 2007

At a news conference last week, incoming National Hurricane Center director Bill Proenza issued a plea for new funding to replace the aging QuikSCAT satellite. Ocean surface winds measured by the QuikSCAT satellite are one of the most important sources of data used by hurricane forecasters, and losing the satellite would be a major blow. The QuikSCAT satellite's "SeaWinds" instrument emits a pulse of microwave energy that bounces off the ocean surface and returns to the satellite. The amount of microwave energy bounced back to the instrument is inversely proportional to how rough the sea surface is, and one can compute the wind speed and direction at the ocean surface based on this information. These measurements, performed twice per day over most of the Earth's surface, are the only reliable source of wind information for much of the remote ocean areas. As a result, this data is critical for the computer models that forecast hurricanes, since hurricanes typically move over data-poor ocean areas. Proenza estimated that without winds from the QuikSCAT satellite, two day hurricane track forecasts would be 10% worse, and three day forecasts 16% worse. I imagine that these increased errors would primarily affect weaker systems far from land, where we don't have data from the Hurricane Hunters. Still, the average cost of putting a single mile of the U.S. coast under a hurricane warning is about $1 million. These are the costs due to evacuation, preparation, and lost business before the hurricane's winds start to blow. Given that the average error in a two-day forecast was about 100 miles last year, even a 5% increase in hurricane track errors could add up to more than $100 million in false alarm costs in just a few years. Consider the case of 1999's Hurricane Floyd--2000 miles of coast were warned, resulting in over $1 billion in false alarm costs.

Figure 1. The NASA QuikSCAT satellite. Image credit: NASA Earth Observatory.

The QuikSCAT satellite was launched in 1999, and was originally scheduled for a two-year mission. The satellite is now entering its 8th year of operation, and is down to its backup sensors. QuikSCAT could fail at any time. A replacement would cost about $400 million dollars and take at least four years to construct and launch, according to Proenza. No replacement is currently planned. Funding a replacement QuikSCAT satellite is one of the most urgent hurricane-related funding issues Congress needs to address, and I'm pleased the new NHC director is drawing attention to this need early in his tenure.

I'll have a new blog on Wednesday.
Jeff Masters

Warmest winter on record for the globe

By: JeffMasters, 4:25 PM GMT on March 15, 2007

Earth just experienced its warmest Northern Hemisphere winter on record, according to statistics released today by the National Climatic Data Center. The 3-month Northern Hemisphere winter period December 2006 through February 2007 had an average global temperature +0.72�C (+1.30�F) above normal, beating the previous record set in 2004 by a substantial +0.12�C. The Northern Hemisphere had its warmest winter ever measured, and the Southern Hemisphere (where it was summer) had its 4th warmest summer on record. Cooler than normal temperatures were observed over less than 15% of the globe, and nowhere did the cooling exceed 3� C (Figure 1). Record warmth was particularly noteworthy over land areas of the Northern Hemisphere poleward of 45� latitude, where temperatures a remarkable 5�C (9�F) above normal were common. Warming of almost the entire globe's land and ocean areas, with the greatest warming occurring in winter over the northern Northern Hemisphere's land areas, is a result that climate models have long been predicting would occur if human-emitted greenhouse gases were substantially affecting Earth's climate. This winter's pattern of record warmth closely matches the computer models projections, and adds additional support to the theory that human-emitted greenhouse gases are now causing a significant warming of the planet. We can expect further substantial warming in coming years as human-emitted greenhouse gases continue to increase at 2% per year.

Figure 1. Temperature departure from average for the winter of December 2006-February 2007. Image credit: National Climatic Data Center.

Influence of El Ni�o
The record warm winter was also partially due to the presence of a moderately strong El Ni�o event in the Eastern Pacific. December 2006 was the warmest December on record, January 2007 was the warmest January on record, and both of these record warmest months occurred when El Ni�o was at its peak strength. El Ni�o rapidly died out at the end of January, and global temperatures in February were not quite as warm, merely the 6th warmest on record. With El Ni�o gone and a possible La Ni�a event on the way later this year, we may not see any more record-breaking warmest months in 2007.

Sea ice extent and snow
The record winter warmth did not lead to record minimum sea ice coverage in the Arctic, which recorded its third lowest February coverage on record (Figure 2). Still, the sea ice coverage this month is very close to the minimum observed in 2005, and is 10% lower than it was 28 years ago. Winter 2006/2007 snow cover extent over the Northern Hemisphere was the 8th lowest extent in the historical record, and 3rd lowest on record over Eurasia. The low snow cover combined with the near record-low Arctic ice extent could lead to an early spring in the Arctic, and more record or near-record low sea ice coverage for the Arctic this year.

Figure 2. Arctic sea ice extent for February, for the years 1979-2007. The record lowest Arctic February sea ice extent occurred in 2005, and sea ice has increased slightly over that record low the past two years. Still, the February sea ice coverage has declined about 10% since 1979.

I'll be back with a new blog on Monday.
Jeff Masters

Climate Change Climate Summaries

A new rainfall world record

By: JeffMasters, 4:15 PM GMT on March 13, 2007

The world record for most precipitation in a 72-hour period was shattered this month when the French island of La Runion recorded 12.9 feet (3.929 meters) of rain. La Runion is a small island in the South Indian Ocean east of Madagascar. Despite the island's small size--about 30 miles across--it has two tall volcanoes that rise over 8,500 feet in altitude. These volcanoes can squeeze prodigious amounts of rain out of the moist tropical atmosphere when strong winds force this moist air up their flanks. La Runion already held the world record for a 3-day precipitation event, the 3.24 meters that fell during January 1980 in Tropical Cyclone Hyacinthe. Another tropical cyclone--Category 3 Tropical Cyclone Gamede--set the world record this time. Gamede never hit the island, but passed close enough (120 miles away) and moved slowly enough that its outer spiral bands stayed over the island for many days. The 3-day record was set at Commerson's Crater, a remote site at 7,500 feet altitude. The village of Hell Bourg at 3000 feet altitude also exceeded the former world record, measuring 3.264 meters of rain over the same 3-day period. Regions along the island's shore received much less rain--Gillot, 0.439 meters, St-Benot, 0.309 meters, and Pierrefonds, 0.247 meters.

Gamede's rains also brought world records for the most rain recorded for multi-day periods up to nine days:

3 days: 12.9 feet (3.93 meters)
4 days: 16.0 feet (4.87 meters)
5 days: 16.3 feet (4.98 meters)
6 days: 16.6 feet (5.07 meters)
7 days: 17.7 feet (5.40 meters)
8 days: 18.1 feet (5.51 meters)
9 days: 18.1 feet (5.51 meters)

The 10-day record was not broken, and is still held by Tropical Cyclone Hyacinthe's 18.4 feet of rain that fell from January 18-27, 1980.

Figure 1. Tropical Cyclone Gamede on February 27, 2007 at 10am local time, as it brought world-record rains to La Reunion Island in the Indian Ocean. At the time, Gamede was a Category 2 storm with top winds of 100 mph. Image credit: NASA Earth Observatory.

I'll be back Wednesday or Thursday with a new blog.

Jeff Masters

March madness forecast competition

By: JeffMasters, 1:30 PM GMT on March 12, 2007

March madness is upon us, and a just-for-fun weather forecasting contest--the annual Weatherdance competition--is now open for registration. The contest, sponsored by the Department of Atmospheric, Oceanic, and Space Science at the University of Michigan, challenges you to choose which of the competing campuses in the first round of the NCAA Men's and/or Women's Basketball Tournament will be warmer on game day. After the first round, the teams still in the Weatherdance will not be the same as those who continue on in basketball. Thus, the Final Four in the basketball tourney will be different than the "Fahrenheit Four" in the Weatherdance. Your picks for each round must be made by midnight on the night before the game.

If you'd like to play along this year for the prizes (and glory), please register by 11:59pm EDT Wednesday night at This year's prizes include our rainbow-colored Weather Underground umbrellas (not available to the public except through this contest) and copies of the book, Extreme Weather. If you're a K-12 teacher, you have the chance to win a the grand prize--a free storm-chasing trip in May with the University of Michigan/Texas Tech storm chasing team!

Southern California wild fires
Hot, dry Santa Ana winds have been blowing over Southern Califonia the past few days, bringing record high temperatures in the 90s and dangerous fire conditions. This weather pattern should continue to bring record warmth today, then subside by Tuesday.

There were 11 daily record highs set or tied in Southern California on Sunday March 11th:

Camarillo Airport (94 degrees)....old record 88/2004
Oxnard NWS (94 degrees)....old record 87/2004
Long Beach Airport (94 degrees)....old record 87/1959
Santa Maria Airport (91 degrees)....old record 85/1934
Santa Barbara (89 degrees)....old record 82/2004
Sandberg (72 degrees)....old record 67/2005
U.C.L.A. (87 degrees)....old record 86/1959
Pasadena (93 degrees)....old record 89/1997
Lancaster (82 degrees)....old record 80/1997
Paso Robles (83 degrees)....old record 82/2005
Cal Poly (86 degrees)....old record 86/1997 tied

I'll be back Tuesday with a look at the lessons learned from the great May 3, 1999 tornado.

Jeff Masters

Storm Warning--a book review

By: JeffMasters, 2:09 PM GMT on March 09, 2007

May 3, 1999 is a date forever etched in the memory of every Oklahoman. A series of 70 twisters tore through the state with unprecedented fury, leveling entire towns, killing 37 people, damaging or destroying 11,000 buildings, and racking up $1.2 billion in damage. The most powerful of these storms had the strongest winds ever measured at Earth's surface--302 mph. This F5 monster, 1.8 miles in diameter, ripped through the southern suburbs of Oklahoma City. Nancy Mathis, a veteran journalist and native Oklahoman, has just published a book chronicling this remarkable tornado--Storm Warning: The Story of a Killer Tornado. Mathis intersperses a fast-paced narrative of the armada of 50 storm chasers that tracked the May 3, 1999 tornado, with chapters exploring the history of tornado research, plus biographical information on the scientists who study these great storms. The result is a highly entertaining and informative book.

The book begins with a well-written and chilling account of the 1.8 mile wide F5 April 9, 1947 tornado that smashed Woodward, Oklahoma. Back in those days, the National Weather Service forbid their forecasters from using the word tornado in their forecasts, a practice that continued until 1950. The only weather alarms were sounded by rural telephone supervisors calling each other. Like most tornadoes of that era, the Woodward tornado stuck without warning. The twister killed 181 Oklahomans--the worst tornado disaster in Oklahoma history. Mathis writes:

"The tornado ate prickly sand sage to its roots, grabbed the barbed wire and telephone lines, and wrapped them into twisted strings strewn along the countryside.

One character Mathis follows is on a first date at a local movie theater when the tornado strikes: As he leaned in for a first kiss, the entire theater went black, and a tremendous roar from the winds outside drowned out the protests and rattled the building. The theater held together, but the couple emerged a few minutes later to find 100 blocks of the city destroyed, and much of it in flames. Now that's a memorable first date!

Half of the remainder of the book focuses on the May 3, 1999 tornado, with the other half tracing the history of tornado science. The two themes are interwoven, so that the fast-paced story of the chasers following the storm as it smashes through Oklahoma is interrupted by long, thoughtful chapters discussing such topics as the career of famed tornado scientist, Dr. T. Theodore Fujita (Dr. Tornado). Portions of these chapters had some really fascinating material. For example, Dr. Fujita's life was saved in 1945 when cloud cover over his city prevented the U.S. from dropping the second atom bomb on it. Nagasaki got the bomb instead. Dr. Fujita performed his first damage survey in Nagasaki, which helped him later in his career to develop theories of how thunderstorm downdrafts create similar damage patterns. However, I often found myself skipping over the tornado science chapters to resume the exciting story of the chase. I would then go back and read the portions I skipped over, which didn't detract from my reading experience. Here's an excerpt from the chase portion of the narrative, which uses the live broadcast of local KWTV weather forecaster Gary England for much of the story:

"It's approaching the river," Gary told viewers. "The sirens are going off in Moore. It's moving northeast to the Moore area. This is a long-tracked tornado, potentially deadly. The wind speeds are quite strong now, we fear. You have time, you still have a few minutes in Moore to move to a place of safety, but not much."

The tornado crossed I-44 and the South Canadian River. Dead ahead was Will Rogers World Airport, the region's main civilian airport, where hundreds of people were stranded as the airport waved away aircraft. Nothing could take off or land in this weather. The tornado took a right turn and entered a densely packed neighborhood just before officials evacuated the terminals.

Figure 1. Radar reflectivity image of the May 3, 1999 F5 tornado that devastated Moore, Oklahoma. note the classic "hook" shape of the echo, a common feature of strong (F2 or F3) and violent (F4 and F5) tornadoes. At the time of this image, the tornado was crossing Interstate 44 near the Canadian River, after producing F5 damage in Bridge Creek OK, and before causing more F5 damage in Moore. The bright red colors at the tornado location represent not rain or hail, but the aggregate signature of car parts, pieces of houses, shredded tree branches, dirt and other debris, hoisted thousands of feet skyward by the tornado vortex! Image credit: NOAA Storm Prediction Center.

A criticism I have of the book is that there is no map of Oklahoma City showing the landmarks described in the text, detailing where the storm struck. I had to pull out a road atlas and consult a storm survey map put together by the NWS in Norman to figure out what was going on. The addition of photos of the disaster would have been nice as well. However, the science presented in the book was well done, and was taken from interviews with many of the leading tornado researchers in the world. Overall, Storm Warning is book that everyone who lived through the disaster will certainly want to own a copy of, and one that will appeal to those who enjoy storm stories like The Perfect Storm.

I'll be back Monday with a look at the lessons learned from the great May 3, 1999 tornado.

Jeff Masters

Book and Movie Reviews

Atlantic hurricane season preview: what are SSTs doing?

By: JeffMasters, 4:18 PM GMT on March 07, 2007

Atlantic hurricane season is still a long way off, but we can start looking at Sea Surface Temperatures (SSTs) in the Atlantic to get some idea of the severity of the coming season. A plot of the current SST anomalies (that is, the departure of the temperature from average) shows that the Caribbean and Atlantic waters stretching to the coast of Africa remain much warmer than normal, as they have been since 2004 (Figure 1). How does this warmth compare to the record-breaking SSTs observed during the disastrous Hurricane Season of 2005? Figure 2 show the difference in SST between 2007 and 2005 for February, and we can see that SST were about 0.5 C warmer in February 2005 vs. February 2007 in the region we care about--the hurricane Main Development Region (MDR) between 10 N and 20 N extending from Africa to the Central American coast.

Figure 1. The departure of Sea Surface Temperature from average for March 7, 2007. Image credit: NOAA/NESDIS.

Figure 2. The difference in Sea Surface Temperature (SST) between February 2007 and February 2005. Cool colors (blues and purples) are shown where the SSTs were warmer during 2005. Warm colors (yellows and oranges) are shown where it was warmer in 2007. Note the presence of an El Nino event in 2007 but not 2005 caused warmer SSTs in the Equatorial Eastern Pacific. SSTs in the Hurricane Main Development Region (red box) were about 0.5 C warmer in February 2005 vs. February 2007. Image credit: NOAA Earth System Research Lab.

The SST forecast
What can we expect SSTs to do in the coming months? NOAA's SST forecast (Figure 3) for the peak months of hurricane season (August, September, and October) projects a continuation of the above-normal SSTs at about 0.5 C above normal. This is a lot of extra energy to fuel intense hurricanes, but not nearly as extreme as the 1-2 C above normal SSTs observed in 2005. Long range forecasts of SST are not very reliable, but this forecast appears to be a reasonable one. It would take a major reduction in the trade winds over the coming months to allow SSTs to climb to levels seen in 2005 (slower trade winds reduce the amount of evaporative cooling, resulting in increased SSTs). While it is impossible to predict what the trade winds might do over the next few months, a sustained weakening of the trade winds for many months is an event that is unlikely. The best guess right now is that SSTs will be above normal this hurricane season, but nothing like observed in 2005. Based on this expectation, plus the demise of El Nino, and the fact we are in an active hurricane period that began in 1995, I am expecting a hurricane season perhaps 50% above average in number of storms and intense storms--but not a repeat of 2005.

Figure 3. The departure of Sea Surface Temperature (SST) from a 1990-2003 average as forecast by NOAA's Climate Forecast System (CFS) model. Note that this model is forecasting a moderate La Nina event in the Eastern Pacific during the 2007 hurricane season, and SSTs about 0.5 C above normal in the Main Development Region (MDR) for Atlantic hurricanes. The MDR is the region between 10 N and 20 N extending from Africa to the Central American coast, and includes all of the Caribbean Sea.

The steering pattern forecast
The next key question is--what will the steering pattern be for 2007? Will there be a trough of low pressure over the Eastern U.S. that recurves storms out to sea, as happened in 2006? Or, will a ridge of high pressure set up, steering hurricanes into the Caribbean, Florida, and U.S. Gulf coast, as happened in 2004 and 2005? I won't have a speculation on that until late May.

My next blog will be Friday, when I plan to review a just-released book about the most intense tornado of all time--the May 3, 1999 Oklahoma City twister. It's a great read.

Jeff Masters

An early and vicious tornado season

By: JeffMasters, 2:22 PM GMT on March 05, 2007

It's been a vicious and early tornado season in the U.S. this year. Already, two major tornado outbreaks have killed 20 people each--the Central Florida tornado event of February 2, and last week's swarm of at least 35 tornadoes in the Southeast. In addition, an outbreak of 10 tornadoes hit the deep south February 12, killing one person in New Orleans. Only one year in recorded history has had more tornado deaths so early in the year--1949, when a tornado in Warren, Arkansas killed 55 people on January 3. The 45 fatalities in 2007 is close to the 3-year average of 46 fatalities observed for the entire year, and the 151 tornadoes observed so far in 2007 is about double what is usually observed.

Damage surveys are still being done of the devastation from last week's tornado outbreak, but it appears that five strong EF-3 tornadoes with winds of 136-165 mph touched down. Three of these twisters were killers, including the tornado that hit Enterprise, Alabama, killing eight students at the high school. The two EF-3 tornadoes observed during the Central Florida tornado event bring this year's total of EF-3 twisters to seven, a very high number of these strong tornadoes for so early in the year. What's causing such an early and severe tornado season? Well, the Central Florida outbreak can be blamed on El Nio. The other two outbreaks occurred when El Nio was suffering a rapid demise, so we'll have to blame them on unusually early spring-like weather in the U.S. With the peak months of tornado season still to come, let's hope for an unusally early end to tornado season as well!

Jeff Masters

Deadly tornadoes rip Alabama, Georgia, and Missouri

By: JeffMasters, 1:59 PM GMT on March 02, 2007

A powerful storm system that brought heavy snow, flooding, high winds, ice storms, and deadly tornadoes yesterday continues to sweep across the Eastern U.S today. Tornado warnings have already been issued for coastal North Carolina this morning, and tornado watches are up for much of eastern Virginia, North Carolina, and Maryland. However, the front that brought dozens of tornadoes to the Southeast yesterday has lost much of its punch, and only weak tornadoes are likely today.

Hardest hit yesterday was Enterprise, Alabama, where a strong tornado 200 yards wide hit the high school, killing at least eight teenagers, according to preliminary reports. According to the Tornado Project, this is one of the ten most deadly tornadoes to hit a U.S. school. The last tornado to kill so many school children occurred in 1967 when an F-4 tornado hit Belvidere High School in Illinois. The storm hit while high school students were boarding sixteen buses already containing elementary school students. Twelve of the buses were overturned or thrown. One bus driver and 12 students were killed after being "tossed like leaves" into adjacent fields. Students and teachers used school doors and plywood from nearby houses as stretchers for the injured students, of which there were 300. In nearby Harvard, a school bus was ripped in half and thrown into power lines as the driver and 20 students hid in a ditch.

The Enterprise tornado was an EF-3--Enhanced Fujita Scale 3--with winds of 136-165 mph. Radar imagery of the Enterprise storm (Figure 1) shows a classic hook echo characteristic of a strong or violent tornado. The Doppler radar winds (Figure 2) shows the classic signature of a strong tornado--blue colors right next to red colors, indicating winds moving towards and away from the radar in a tightly rotating storm. I've also saved a radar animation of the tornado as it passed over Enterprise.

Figure 1. Radar reflectivity image of the Enterprise, AL tornado ten minutes before it hit.

Figure 2. Doppler winds image of the Enterprise, AL tornado ten minutes before it hit.

A confirmed EF-3 tornado hit Howell County, Missouri, killing 7-year old girl and injuring four people at 6:33am Thursday. This tornado had a 15 mile long path up to 1/4 mile wide.

Preliminary reports indicate that at least 15 tornadoes hit Georgia last night, killing eight and injuring many more. Americus, Georgia, where two people died, was particularly hard hit. The twister struck a hospital, destroying its fleet of ambulances and forcing closure of the hospital. I've also saved a radar animation of this storm.

Here is a sampling of all the NWS damage reports from suspected tornadoes for Georgia as of 8am EST today (Friday):

03/01/2007 0922 PM
Americus, Sumter County.
*** 2 fatal *** possible tornado. Significant damage to
homes and the hospital. Numerous trees and power lines
down. Gema confirmed two fatalities.

03/01/2007 0810 PM
4 miles ENE of Warrenton, Warren County.
*** 3 inj *** possible tornado. Numerous homes damaged
with a few injuries. Significant damage to Briarwood
Academy on Highway 278.

03/01/2007 0820 PM
Thomson, McDuffie County.
Possible tornado. Houses damaged...along with trees and
power lines down near the intersection of GA 150 and
Dallas drive. Structural damage near the intersection of
GA 150 and Old Washington Road. Numerous trees down near
the National Guard Armory.

6 miles S of Gray, Jones County.
Possible tornado. Numberous trees and power lines down
along Highway 49.

03/01/2007 0535 PM
Potterville, Taylor County.
*** 1 fatal *** possible tornado damaged unkn number of
homes and buildings and downed numerous trees and power
lines on bear Road. Rolled a Mobile home. One fatality.

03/01/2007 0550 PM
4 miles NW of Macon, Bibb County.
Possible tornado has knocked over traffic lights...power
poles and business signs. A gas station was damaged near
Zebulon Road near Interstate 475.

03/01/2007 1045 PM
12 miles SE of Irwinton, Wilkinson County.
Tornado reported by the public. Law enforcement has
confirmed at least one home damaged near Nickelsville.

03/01/2007 0630 PM
2 miles N of Columbus, Muscogee County.
Several commercial buildings with structural damage in
2400 block of Brookstone Parkway. Windows blown out...
large AC units tossed aside...porch poles missing...
power poles twisted and down...and trees down across
parked cars.

03/01/2007 0855 PM
Weston, Webster County.
Possible tornado. Tractor trailer was overturned on
Highway 520.

03/01/2007 0230 PM
5 miles N of Fort Gaines, Clay County.
Apparent tornado approximately 5 miles north of Fort
Gaines, GA. Numerous trees down and homes damaged.

03/02/2007 1218 am
3 miles S of Isabella, Worth County.
Numerous trees down. Just north of Bridgeboro 2 houses
were destroyed. Significant damage has been reported off
Sumner Lakes Road. Only minor injuries reported but
information remains in the preliminary stages. One 18
wheeler jackknifed in the median of U.S. Hwy 19.

03/02/2007 0100 am
3 miles NNE of Tempy, Worth County.
*** 1 inj *** home leveled.

03/01/2007 1150 PM
11 miles N of Mitchell Co A, Baker County.
Mobile homes damaged just north of Newton in Baker
County. Estimated time of tornado touchdown is 1150 PM
EST. Report of 6 fatalities at the Mobile Home Park is
now confirmed from GEMA as of 730 am EST...March 2.

03/02/2007 1204 am
2 miles NE of Baconton, Mitchell County.
Tornado on the ground in Baker County moved into Mitchell
County at 1204 am EST. This tornado stayed on the ground
across the northern portion of the county for 7 miles
until crossing into Worth County. 13 structures were
damaged in the Baconton and Pleasant Grove communities.
No injuries or fatalities reported.

Thursday's wild weather made it the second busiest day ever for the web site. The 17 million web pages we served from our public site was second only to the 18 million served during Hurricane Rita on September 23, 2005.

Jeff Masters

Tornadoes rip the U.S.

By: JeffMasters, 11:19 PM GMT on March 01, 2007

March roared in like a lion today across much of the U.S., as a powerful storm system brought heavy snow, flooding, high winds, ice storms, and deadly tornadoes. The Storm Prediction Center placed a large, multi-state area under their highest level of tornado risk today, and we may see the largest tornado outbreak of the year. Dozens of tornadoes have touched down across the Midwest and Southeast in the past 24 hours, and many more will touch down by morning as a powerful cold front sweeps across the Eastern U.S. At least one strong tornado has been confirmed--an EF-3 (Enhanced Fujita Scale 3--winds of 136-165 mph) tornado that hit Howell County, Missouri, killing one person and injuring three at 6:33am Thursday. This tornado had a 15 mile long path up to 1/4 mile wide.

Figure 1. Radar reflectivity image of the Enterprise, AL tornado ten minutes before it hit.

Figure 2. Doppler winds image of the Enterprise, AL tornado ten minutes before it hit.

Another strong or violent tornado hit Enterprise, Alabama at 1:10pm CST today, killing 18 and injuring at least 50. The tornado completely destroyed the football stadium and injured children at the Enterprise High School, which lost a portion of its roof. Radar imagery of the Enterprise storm (Figures 1) shows a classic hook echo characteristic of a strong or violent tornado. The Doppler winds (Figure 2) showed the classic signature of a strong tornado--blue colors right next to red colors, indicating winds moving towards and away from the radar in a tightly rotating storm. I've also saved a radar animation of the tornado as it passed over Enterprise.

Today is an appropriate day to welcome our new featured blogger, Mike Theiss. Mike is a professional weather photographer and storm chaser, and will be sharing his awesome storm photos with us for the coming tornado season. He wasn't able to make it to today's storms, unfortunately, but will be in Tornado Alley for much of the next three months documenting this year's tornado season. He also intercepts all landfalling U.S. hurricanes (check out his amazing Katrina videos), so be sure to tune in this hurricane season to his blog.

My condolences and prayers go out to all those affected by today's storms, particularly those in Enterprise. The March 1, 2007 tornado will scar the memories of those who lived through it for a long time to come.

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