Category 6™

Winter rains ease Southeast U.S. drought; Brazilian storm could go subtropical

By: JeffMasters, 5:59 PM GMT on February 29, 2008

The winter of 2007-2008 is in the books, as today marks the last day of meteorological winter (December, January, and February). Winter rains have eased the drought gripping the Southeast U.S., where the area covered by extreme to exceptional drought has shrunk by about 50% since the beginning of the year (Figure 1). Some regions of southern Georgia and southern Alabama, where winter rains have been more than six inches above average (Figure 2), are no longer suffering drought conditions at all.

Figure 1. Drought categories for the Southeast U.S. from December 25, 2007, and February 28, 2007. Image credit: U.S. Drought Monitor.

However, A large swath of the Southeast U.S., including Atlanta, Charlotte, and Huntsville, have received 1-4 inches of precipitation below usual for this time of year. The shortfall is particularly acute in northern Alabama, where Huntsville has received only 6.77" this year, compared to the normal 10.47". The below average rains during this winter rainy season bode ill for the summer, when drought conditions could easily return to last year's extreme levels. The Southeast badly needs one or two landfalling tropical storms or hurricanes in 2008 to help break the drought.

Central Florida surrounding Lake Okeechobee is also suffering from below average rains this winter. The lake, which reached its all-time low water mark of 8.82 feet on July 2, 2007, has risen to 10.02 feet, but this is still a record low for this time of year. The surface area of the lake has shrunk to about 2/3 of normal, and the water level is more than four feet below normal. Part of the reason for the record low lake levels is the fact that the lake was deliberately drawn down before the 2006 hurricane season, in anticipation of another very active hurricane season.

Figure 2. Departure of precipitation from average for January and February 2008. Image credit: NOAA Advanced Hydrologic Prediction Service.

The forecast
The short-range rainfall forecast is good for the Southeast, with significant rainstorms possible both Tuesday and Thursday. The longer range three-month forecast calls for a continuation of below average precipitation for the spring season, thanks to the continued presence of a strong La Niña event in the Equatorial East Pacific. La Niña events usually deflect the jet stream into a pattern that takes the Southeast U.S. out of the the usual storm track needed to bring typical spring rains. However, for the summer months of June, July, and August, NOAA's CFS Climate Forecast System Model is predicting a return to normal levels of rainfall over the Southeast U.S.

Severe weather outbreak coming on Monday
A strong low pressure system is forecast to develop over Texas on Sunday, bringing a slight chance of severe weather to eastern Texas Sunday afternoon. By Monday afternoon, the storm is expected to track northeastwards over the Ohio Valley, dragging a strong cold front across the south. A significant severe weather outbreak is possible Monday afternoon in advance of this cold front.

Interesting South Atlantic storm could become subtropical
An extratropical storm centered near 31S 30W, a few hundred miles east of the Brazil-Uruguay border, has begun to acquire subtropical characteristics and could become a subtropical storm this weekend. The storm is not expected to hit land. NASA/MSFC has a clickable satellite image of Southern Hemisphere one can use to zoom in on the storm. An ASCAT pass at 5:29am EST this morning showed winds of 50 mph near the center of the storm. Water temperatures are about 26°C, which is right at the boundary where tropical storm formation can occur. Subtropical and tropical storms are quite rare in the South Atlantic. I'll update this section of the blog through the weekend if the storm develops. There is no naming system in place to name any tropical or subtropical storm that may form in the South Atlantic. It would be up to the World Meteorological Organization (WMO) to institute such a scheme. The last time I checked into this, they had no plans to consider a naming system. Here's nice MODIS image of the storm from 15:30 GMT today.

Figure 3. Visible satellite image of extratropical low off the coast of Brazil that is beginning to acquire some subtropical characteristics. Image credit: NASA/MSFC.

Jeff Masters


Are tornadoes getting stronger and more frequent?

By: JeffMasters, 4:24 PM GMT on February 26, 2008

Are tornadoes and severe thunderstorms getting more numerous and more extreme due to climate change? To help answer this question, let's restrict our attention to the U.S., which has the highest incidence of tornadoes and severe thunderstorms of any place in the world. At a first glance, it appears that tornado frequency has increased in recent decades (Figure 1).

Figure 1. The number of EF-0 (blue line) and EF-1 and stronger tornadoes (maroon diamonds) reported in the U.S. since 1950. There is not a decades-long increasing trend in the numbers of tornadoes stronger than EF-0, implying that climate change, as yet, is not having a noticeable impact on U.S. tornadoes. However, statistics of tornado frequency and intensity are highly uncertain. Major changes in the rating process occurred in the mid-1970s (when all tornadoes occurring prior to about 1975 were retrospectively rated), and again in 2001, when scientists began rating tornadoes lower because of engineering concerns and unintended consequences of National Weather Service policy changes. According to Brooks (2013), "Tornadoes in the early part of the official National Weather Service record (1950-approximately 1975) are rated with higher ratings than the 1975 - 2000 period, which, in turn, had higher ratings than 2001 - 2007." Also, beginning in 2007, NOAA switched from the F-scale to the EF-scale for rating tornado damage, causing additional problems with attempting to assess if tornadoes are changing over time. Image credit: Kunkel, Kenneth E., et al., 2013, "Monitoring and Understanding Trends in Extreme Storms: State of Knowledge," Bull. Amer. Meteor. Soc., 94, 499–514, doi:

However, this increase may be entirely caused by factors unrelated to climate change:

1) Population growth has resulted in more tornadoes being reported.

2) Advances in weather radar, particularly the deployment of about 100 Doppler radars across the U.S. in the mid-1990s, has resulted in a much higher tornado detection rate.

3) Tornado damage surveys have grown more sophisticated over the years. For example, we now commonly classify multiple tornadoes along a damage path that might have been attributed to just one twister in the past.

Given these uncertainties in the tornado data base, it is unknown how the frequency of tornadoes might be changing over time. The "official word" on climate science, the 2007 United Nations IPCC report, stated it thusly: "There is insufficient evidence to determine whether trends exist in small scale phenomena such as tornadoes, hail, lighting, and dust storms." Furthermore, we're not likely to be able to develop methods to improve the situation in the near future.The current Doppler radar system can only detect the presence of a parent rotating thunderstorm that often, but not always, produces a tornado. Until a technology is developed that can reliably detect all tornadoes, there is no hope of determining how tornadoes might be changing in response to a changing climate. According to Doswell (2007): I see no near-term solution to the problem of detecting detailed spatial and temporal trends in the occurrence of tornadoes by using the observed data in its current form or in any form likely to evolve in the near future.

Are strong tornadoes increasing?
Stronger tornadoes (greater than EF-0 on the Enhanced Fujita Scale, or F0 on the pre-2007 Fujita Scale) are more likely to get counted, since they tend to cause significant damage along a long track. Thus, the climatology of these tornadoes may offer a clue as to how climate change may be affecting severe weather. Unfortunately, we cannot measure the wind speeds of a tornado directly, except in very rare cases when researchers happen to be present with sophisticated research equipment. Tornadoes are categorized using the Enhanced Fujita (EF) scale, which is based on damage (note that the EF scale to rate tornadoes was adopted in 2007, but the transition to this new scale still allows valid comparisons of tornadoes rated, for example, EF-5 on the new scale and F-5 on the old scale.) So, if a strong tornado happens to sweep through empty fields and never destroy any structures, it will never be rated as a strong tornado. Thus, if the number of strong tornadoes has actually remained constant over the years, we should expect to see some increase in these twisters over the decades, since more buildings have been erected in the paths of tornadoes. However, if we look at the statistics of U.S. tornadoes stronger than EF-0 or F-0 since 1950, there does not appear to be any increase in their number. Not surprisingly, a study accepted for publication in Environmental Hazards (Simmons et al., 2012) found no increase in tornado damages from 1950 - 2011, after normalizing the data for increases in wealth and property (note, though, that I am suspicious of studies that normalize disaster data, since they are prone to error, as revealed by a 2012 study looking at storm surge heights and damages.)

The future of tornadoes
An alternate technique to study how climate change may be affecting tornadoes is look at how the large-scale environmental conditions favorable for tornado formation have changed through time. Moisture, instability, lift, and wind shear are needed for tornadic thunderstorms to form. The exact mix required varies considerably depending upon the situation, and is not well understood. However, Brooks (2003) attempted to develop a climatology of weather conditions conducive for tornado formation by looking at atmospheric instability (as measured by the Convective Available Potential Energy, or CAPE), and the amount of wind shear between the surface and 6 km altitude. High values of CAPE and surface to 6 km wind shear are conducive to formation of tornadic thunderstorms. The regions they analyzed with high CAPE and high shear for the period 1997-1999 did correspond pretty well with regions where significant (F2 and stronger) tornadoes occurred. The authors plan to extend the climatology back in time to see how climate change may have changed the large-scale conditions conducive for tornado formation. Riemann-Campe et al. (2009) found that globally, CAPE increased significantly between 1958 - 2001. However, little change in CAPE was found over the Central and Eastern U.S. during spring and summer during the most recent period they studied, 1979 - 2001. A preliminary report issued by NOAA’s Climate Attribution Rapid Response Team in July 2011 found no trends in CAPE or wind shear over the lower Mississippi Valley over the past 30 years. However, preliminary work by J. Sander of Munich Re insurance company, presented at the December 2011 American Geophysical Union meeting in San Francisco, found that the number of days with very high CAPE values over the eastern two-thirds of the United States between 1970 and 2009 did increase significantly.

Del Genio et al.(2007) used a climate model with doubled CO2 to show that a warming climate would make the atmosphere more unstable (higher CAPE) and thus prone to more severe weather. However, decreases in wind shear offset this effect, resulting in little change in the amount of severe weather in the Central and Eastern U.S. late this century. The speed of updrafts in thunderstorms over land increased by about 1 m/s in their simulation, though, since upward moving air needed to travel 50-70 mb higher to reach the freezing level. As a result, the most severe thunderstorms got stronger. In the Western U.S., the simulation showed that drying led lead to fewer thunderstorms, but the strongest thunderstorms increased in number by 26%, leading to a 6% increase in the total amount of lighting hitting the ground each year. If these results are correct, we might expect more lightning-caused fires in the Western U.S. late this century, due to enhanced drying and more lightning.

Using a high-resolution regional climate model (25 km grid size) zoomed in on the U.S., Trapp et al. (2007) and Trapp et al. (2009) found that the decrease in 0-6 km wind shear in the late 21st century would more than be made up for by an increase in instability (CAPE). Their model predicted an increase in the number of days with high severe storm potential for almost the entire U.S., by the end of the 21st century. These increases were particularly high for many locations in the Eastern and Southern U.S., including Atlanta, New York City, and Dallas (Figure 3). Cities further north and west such as Chicago saw a smaller increase in the number of severe weather days.

Figure 3. Number of days per year with high severe storm potential historically (blue bars) and as predicted by the climate model (A2 scenario) of Trapp et al. 2007 (red bars).

We currently do not know how tornadoes and severe thunderstorms may be changing due to changes in the climate, nor is there hope that we will be able to do so in the foreseeable future. At this time, it does not appear that there has been an increase in U.S. tornadoes stronger than EF-0 in recent decades. Preliminary research using climate models suggests that we may see an increase in the number of severe storms capable of producing tornadoes over the U.S. late this century. However, this research is just beginning, and much more study is needed to confirm these findings.

Brooks, H.E., 2013, "Severe thunderstorms and climate change," Atmospheric Research, Volume 123, 1 April 2013, Pages 129–138,

Brooks, H.E., J.W. Lee, and J.P. Craven, 2003, "The spatial distribution of severe thunderstorm and tornado environments from global reanalysis data", Atmospheric Research Volumes 67-68, July-September 2003, Pages 73-94.

Doswell, C.A., 2007, "Small Sample Size and Data Quality Issues Illustrated Using Tornado Occurrence Data", E-Journal of Severe Storms Meteorology Vol 2, No. 5 (2007).

Del Genio, A.D., M-S Yao, and J. Jonas, 2007,
Will moist convection be stronger in a warmer climate?, Geophysical Research Letters, 34, L16703, doi: 10.1029/2007GL030525.

Kunkel, Kenneth E., et al., 2013, "Monitoring and Understanding Trends in Extreme Storms: State of Knowledge," Bull. Amer. Meteor. Soc., 94, 499–514, doi:

Marsh, P.T., H.E. Brooks, and D.J. Karoly, 2007, Assessment of the severe weather environment in North America simulated by a global climate model, Atmospheric Science Letters, 8, 100-106, doi: 10.1002/asl.159.

Riemann-Campe, K., Fraedrich, K., and F. Lunkeit, 2009, Global climatology of Convective Available Potential Energy (CAPE) and Convective Inhibition (CIN) in ERA-40 reanalysis, Atmospheric Research Volume 93, Issues 1-3, July 2009, Pages 534-545, 4th European Conference on Severe Storms.

Simmons, K.M., Dutter, D., and Pielke, R., 2012, "Normalized Tornado Damage in the United States: 1950-2011," DOI: 10.1080/17477891.2012.738642

Trapp, R.J., N.S. Diffenbaugh, H.E. Brooks, M.E. Baldwin, E.D. Robinson, and J.S. Pal, 2007, Severe thunderstorm environment frequency during the 21st century caused by anthropogenically enhanced global radiative forcing, PNAS 104 no. 50, 19719-19723, Dec. 11, 2007.

Trapp, R. J., Diffenbaugh, N. S., & Gluhovsky, A., 2009, "Transient response of severe thunderstorm forcing to elevated greenhouse gas concentrations," Geophysical Research Letters, 36(1).

Jeff Masters

Climate Change Tornado

The future of flooding

By: JeffMasters, 10:06 PM GMT on February 19, 2008

Are storms getting more extreme due to climate change? That is a difficult question to answer, since reliable records are not available at all in many parts of the world, and extend back only a few decades elsewhere. However, we do have a fairly good set of precipitation records for many parts of the globe, and those records show that the heaviest types of rains--those likely to cause flooding--have increased in recent years. According to the United Nations' Intergovernmental Panel on Climate Change (IPCC) 2007 report, "The frequency of heavy precipitation events has increased over most land areas". Indeed, global warming theory has long predicted an increase in heavy precipitation events. As the climate warms, evaporation of moisture from the oceans increases, resulting in more water vapor in the air. According to the 2007 IPCC report, water vapor in the global atmosphere has increased by about 5% over the 20th century, and 4% since 1970. Satellite measurements (Trenberth et al., 2005) have shown a 1.3% per decade increase in water vapor over the global oceans since 1988. Santer et al. (2007) used a climate model to study the relative contribution of natural and human-caused effects on increasing water vapor, and concluded that this increase was "primarily due to human-caused increases in greenhouse gases". This was also the conclusion of Willet et al. (2007).

More water vapor equals more precipitation
This increase in water vapor has very likely led to an increase in global precipitation. For instance, over the U.S., where we have very good precipitation records, annual average precipitation has increased 7% over the past century (Groisman et al., 2004). The same study also found a 14% increase in heavy (top 5%) and 20% increase in very heavy (top 1%) precipitation events over the U.S. in the past century. Kunkel et al. (2003) also found an increase in heavy precipitation events over the U.S. in recent decades, but noted that heavy precipitation events were nearly as frequent at the end of the 19th century and beginning of the 20th century, though the data is not as reliable back then. Thus, there is a large natural variation in extreme precipitation events.

Pollution may contribute to higher precipitation
It is possible that increased pollution is partly responsible for the increase in precipitation and in heavy precipitation events in some parts of the world. According to Bell et al. (2008), summertime rainfall over the Southeast U.S. is more intense on weekdays than on weekends, with Tuesdays having 1.8 times as much rain as Saturdays during the 1998-2005 period analyzed. Air pollution particulate matter also peaks on weekdays and has a weekend minimum, making it likely that pollution is contributing to the observed mid-week rainfall increase. Pollution particles act as "nuclei" around which raindrops condense, increasing precipitation in some storms.

The future of flooding
It is difficult to say if the increase in heavy precipitation events in recent years has led to more flooding, since flooding is critically dependent on how much the landscape has been altered by development, upstream deforestation, and what kind of flood control devices are present. One of the few studies that did attempt to quantify flooding (Milly et al., 2002) found that the incidence of great floods has increased in recent decades. In the past century, the world's 29 largest river basins experienced a total of 21 "100-year floods"--the type of flood one would expect only once per 100 years in a given river basin. Of these 21 floods, 16 occurred in the last half of the century (after 1953). With the IPCC predicting that heavy precipitation events are very likely to continue to increase, it would be no surprise to see flooding worsen globally in the coming decades.

Jeff Masters

Bell, T. L., D. Rosenfeld, K.-M. Kim, J.-M. Yoo, M.-I. Lee, and M. Hahnenberger (2008), "Midweek increase in U.S. summer rain and storm heights suggests air pollution invigorates rainstorms," J. Geophys. Res., 113, D02209, doi:10.1029/2007JD008623.

Kunkel, K. E., D. R. Easterling, K. Redmond, and K. Hubbard, 2003, "Temporal variations of extreme precipitation events in the United States: 1895.2000", Geophys. Res. Lett., 30(17), 1900, doi:10.1029/2003GL018052.

Groisman, P.Y., R.W. Knight, T.R. Karl, D.R. Easterling, B. Sun, and J.H. Lawrimore, 2004, "Contemporary Changes of the Hydrological Cycle over the Contiguous United States: Trends Derived from In Situ Observations," J. Hydrometeor., 5, 64.85.

Milly, P.C.D., R.T. Wetherald, K.A. Dunne, and T.L.Delworth, Increasing risk of great floods in a changing climate", Nature 415, 514-517 (31 January 2002) | doi:10.1038/415514a.

Santer, B.D., C. Mears, F. J. Wentz, K. E. Taylor, P. J. Gleckler, T. M. L. Wigley, T. P. Barnett, J. S. Boyle, W. Brüggemann, N. P. Gillett, S. A. Klein, G. A. Meehl, T. Nozawa, D. W. Pierce, P. A. Stott, W. M. Washington, and M. F. Wehner, 2007, "Identification of human-induced changes in atmospheric moisture content", PNAS 2007 104: 15248-15253.

Trapp, R.J., N.S. Diffenbaugh, H.E. Brooks, M.E. Baldwin, E.D. Robinson, and J.S. Pal, 2007, Severe thunderstorm environment frequency during the 21st century caused by anthropogenically enhanced global radiative forcing, PNAS 104 no. 50, 19719-19723, Dec. 11, 2007.

Trenberth, K.E., J. Fasullo, and L. Smith, 2005: "Trends and variability in column-integrated atmospheric water vapor", Climate Dynamics 24, 741-758.

Willett, K.M., N.P. Gillett, P.D. Jones, and P.W. Thorne, 2007, "Attribution of observed surface humidity changes to human influence", Nature 449, 710-712 (11 October 2007) | doi:10.1038/nature06207.

Climate Change Flood

A cool, snowy January for the globe in 2008

By: JeffMasters, 4:25 PM GMT on February 15, 2008

It's been a cool and snowy winter across much of the Northern Hemisphere so far this year, making it pretty unlikely that 2008 will end up ranking as one of the top five warmest years on record. January 2008 was just the 31st warmest January for the the globe on record, according to statistics released by the National Climatic Data Center. For land areas only, January 2008 ranked near average--63rd warmest in the 130 years since global record keeping began in 1880. It was the coldest January since 1982, and marked a noticeable departure from the string of much warmer than average months the globe has experienced over the past eight years. A good portion of the global cool down in January can be credited to the current strong La Niña episode. Ocean surface temperatures in large areas of the central and eastern equatorial Pacific were more than 3°F (1.7°C) below average in January. The continuation of cooler-than-average temperatures dampened the global ocean average, which was the 17th warmest on record for January. The last time the globe was this cold was in November of 2000. Not coincidentally, that month marked the peak of the last major La Niña episode, as defined by NOAA's Climate Prediction Center.

Figure 1. Northern Hemisphere snow cover set a new record for January, narrowly besting the record set in 1985. Image credit: National Climatic Data Center.

The extent of January snow cover in 2008 was the greatest on record for the Northern Hemisphere, narrowly besting the record set in 1985. Snow cover records extend back to 1967. Much of the record snow cover can be attributed to the cold and snowy weather experienced in China and southern Asia. However, Australia experienced its warmest January on record, and much of northern Russia had temperatures more than 5°C (9°F) above average in January.

U.S. temperatures: below average in January
For the contiguous U.S., January 2008 was 0.3°F (0.2°C) below average, and was the 49th coolest January since U.S. weather records began in 1895. It was the coldest January in the U.S. since 2003. January 2008 temperatures across much of the western U.S. were below normal, with near-normal temperatures across the Midwest, South, and Southeast regions. In contrast to the rest of the country, temperatures were above normal in the Northeast, which had its 20th warmest January on record.

Sea ice extent
January 2008 Northern Hemisphere sea ice extent was the fifth lowest on record for the month of January, 8% below its extent in 1979 when satellite measurements began, according to the National Snow and Ice Data Center. January was the third 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, while the ice extent is not at a record low this month, the volume of the arctic ice is probably at a record low for January. The ice is exceptionally thin across the Arctic this winter, and the edge of this thin first-year ice extends all the way to the North Pole. The latest sea ice extent map and temperature anomaly map for the globe are available at our Climate Change web page, which we update each month.

Severe weather in Texas Saturday
If you live in Texas, keep a wary weather eye on Saturday. NOAA's Storm Prediction Center has placed a portion of Eastern Texas, including Houston, Austin, and San Antonio, under its Moderate Risk region for tornadoes and severe thunderstorms.

Jeff Masters

Geoengineering: should we pump sulfur into the stratosphere?

By: JeffMasters, 3:43 PM GMT on February 13, 2008

Professor Paul Crutzen, winner of the 1995 Nobel Prize for his work on the Antarctic ozone hole, has proposed an emergency geoengineering solution to cool off the planet: dump huge quantities of sulfur particles into the stratosphere to reflect sunlight. His paper, "Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma?" was published in the August 2006 issue of the journal Climatic Change. A recent editorial in the New York Times by Ken Caldeira called for more research into geoengineering schemes like this to cool the planet, proposing that 1% of the $3 billion federal Climate Change Technology Program should be spent thusly.

Dr. Crutzen proposes that balloons or artillery guns could propel burning sulfur into the stratosphere, where chemical reactions would convert the sulfur to highly reflective sulfate aerosol particles. This is the same process that occurs when a major volcanic eruption throws sulfur high into the atmosphere, cooling the planet. The 1992 eruption of Mt. Pinatubo in the Philippines cooled the Earth by about 0.5° C the following year. Crutzen estimates that a lesser amount of sulfur would be required to compensate for a doubling of carbon dioxide, and that the cost of lofting the required sulfur into the stratosphere would be about $132 billion. These costs would be per year, since the sulfur only stays in the stratosphere about a year.

Could it work? Sure it could. Volcanos periodically pump huge quantities of sulfur into the stratosphere, cooling the planet. Wunderblogger Dr. Ricky Rood shows a nice plot in his blog this week showing how three major volcanic eruptions in the past 50 years have cooled off the planet. Are there problems with the scheme? Yes, many:

1) The climate might undergo substantial and disruptive changes. Evaporation from the oceans would lessen, changing precipitation patterns. The sulfate aerosols would warm the upper troposphere and lower stratosphere, changing the stability of the atmosphere. This would affect thunderstorm activity and large-scale weather patterns. Increased warming of Europe and Asia in winter has been noted after volcanic eruptions, for example. A 2005 study tied an increase in greenhouse gases and sulfur particles to drought in the Sahel region of Africa. Increasing greenhouse gases and sulfur particles even further might intensify drought conditions there.

2) The small sulfur particles might settle into the upper troposphere, where they might act as condensation nuclei for the formation of cirrus clouds. An increase in these high cirrus clouds may warm the planet, since they keep heat from escaping to space.

3)Stratospheric sulfur causes destruction of the protective ozone layer. The 1982 eruption of the El Chichon volcano reduced ozone by 16% at 20 km altitude at mid-latitudes. Decreased ozone would result in an increase in ultraviolet light at the surface, potentially increasing skin cancer rates.

4) Acid rain would increase.

5) The scheme would do nothing to reduce CO2, and the oceans would continue to acidify. The rate of acidification of the Earth's oceans is causing concern that regional collapses of the food chain may occur later this century.

6) A sudden collapse of the effort to keep firing sulfur into the stratosphere, due to the lack of political will to continue to fund this expensive effort, would result in a sudden transition of the climate to a radically warmer state. The resulting shock to the world's weather might cause dramatic changes that would be difficult to adapt to.

7) What do you do if the scheme causes serious climate problems in a country that then threatens war unless the effort is stopped?

As climate scientist Ray Pierrehumbert wrote in a 2007 blog on, "It's not really insurance. It's more like building a lifeboat, but a lifeboat based on a design that has never been used before which has to work more or less perfectly the first time the panicked passengers are loaded into it." Pierrehumbert thought that the proposal to spend $30 million of the annual $3 billion climate change research budget was far too much money.

I'm not a big fan of geoengineering schemes. It makes far more sense to spend this kind of money of reducing carbon emissions, since the cure may be worse than the disease. Still, research into geoengineering should continue. We need to keep all of options open for the very uncertain future of our climate. When you're team's down two touchdowns late in the game, sometime you have to take risks you ordinarily would not take. But how much money should be spent on geoengineering research? If you're a wunderground member, take the wunderpoll at the right.

Jeff Masters

Climate Change

Science Debate 2008

By: JeffMasters, 7:06 PM GMT on February 11, 2008

The issues of global warming and climate change are important to many voters, yet the media has done a poor job asking the U.S. presidential candidates about these topics. In a study quoted by The Boston Globe, in 2007 the major TV networks asked presidential candidates 2,679 questions. Of those questions, only three were about global warming--the same number of questions that were asked about UFOs. With the presidential race narrowed down to four main candidates--Hillary Clinton, Mike Huckabee, John McCain, and Barack Obama--it's time that the candidates' views on climate change be given more attention. To address this need, the four major candidates have been invited to participate in Science Debate 2008, a verbal debate to be held on April 18, 2008, at Philadelphia's Franklin Institute. The debate is cosponsored by the American Association for the Advancement of Science (AAAS), the Council on Competitiveness, the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. Nearly 100 leading American universities and other organizations have signed on to promote the effort, along with many prominent scientists, writers, and members of Congress. The debate is designed to discover the candidates' views on many science-related topics, such as climate change, clean energy, health care, science education and technology in schools, scientific integrity, GM agriculture, transportation infrastructure, the genome, data privacy, intellectual property, pandemic diseases, the health of the oceans, water resources, stem cells, conservation and species loss, population, and the space program.

We need your help to make this debate happen! Contact the campaigns of the candidates to ask them to participate in the debate, sign a petition to approve of the debate, or write a letter to the editor of your local paper. Chris Mooney, who authored the excellent 2007 book, Storm World: Hurricanes, Politics, and the Battle Over Global Warming, is one of the leaders of the initiative, and has posted links one can use to help with these tasks, in his blog, The Intersection. Thanks for helping out!

Jeff Masters


Super Tuesday Outbreak damage surveys find five EF-4 tornadoes

By: JeffMasters, 10:21 PM GMT on February 07, 2008

Residents of the South continue to mourn the dead and clean up the tremendous destruction wrought by the Super Tuesday tornado outbreak. Tennessee suffered the most, with 33 dead, 189 injured, and at least 525 homes destroyed. Damage surveys indicate that at least five of this week's tornadoes were violent EF-4's on the Enhanced Fujita Scale, with winds of 166-200 mph. The tornado that hit Jackson, Tennessee, causing $40 million in damage to Union University, was rated an EF-4. Another Tennessee tornado that hit the Morris Chapel area, killing three mobile home residents, was also rated EF-4. Northern Alabama suffered two EF-4's--one that hit Rosalie on Wednesday, killing one person, and a second tornado that hit Moulton, killing four and injuring 25. In Arkansas, an EF-4 tornado cut a 120-mile damage swath through the northern part of the state. Thirteen people died in this tornado, including four people in Atkins, and seven in Clinton. The NWS office in Little Rock has an excellent web page summarizing the Arkansas storms, complete with radar animations and jet stream graphics.

At least seven other tornadoes from the outbreak have been rated EF-3, according to the excellent Wikipedia page on the event. The Memphis metropolitan area was affected by an EF-2 and an EF-3 twister, and an EF-2 tornado hit the northeastern end of the Nashville metropolitan area.

Figure 1. Preliminary tornado tracks and death toll from the Super Tuesday tornado outbreak. Image credit: NOAA Storm Prediction Center.

Figure 2. Damage near Mountain View, Arkansas, along the 120-mile long track of the EF-4 tornado that swept through Clinton and Atkins. Image credit: wunderphotographer dennisearle.

The total death toll currently stands at 59, across five states and 19 counties, with hundreds of others injured. The outbreak is the deadliest in the U.S. since the May 31, 1985 outbreak that killed 76 across Ohio and Pennsylvania (and also 12 in Ontario, Canada). This week's outbreak was also the deadliest tornado outbreak in Kentucky since the April 3, 1974 Super Outbreak. In Arkansas, the 14 fatalities is the most since 25 were killed during the Benton, Arkansas Tornado Outbreak on March 1, 1997. Only one other February tornado outbreak in the past century compares to the Super Tuesday outbreak--the great February 21, 1971 Mississippi Valley outbreak, which left 119 dead across the South.

Record heat helped fuel the tornadoes
Record high temperature readings were recorded at 94 airports in 18 states across southeastern portion of the U.S. on Tuesday, according the the National Climatic Data Center. The spring-like warmth, when contrasted with the very wintry conditions on the other side of the strong cold front that pushed through the region on Super Tuesday, helped to fuel the formidable tornadoes observed.

As new damage surveys come in, I'll update this blog.

Six Degrees: Our Future on a Hotter Planet
Sunday at 8pm EST (9pm PST), there promises to be an interesting show on the National Geographic Channel called Six Degrees, which explores what might happen to the Earth for each degree of warming up to six degrees centigrade. The program is based on the book by Mark Lynas, Six Degrees: Our Future on a Hotter Planet (London: Fourth Estate, 2007). According to a review of this book posted by climate scientist Eric Steig at, "Mark Lynas will no doubt be pleased that I very much like the book. To be sure, it is alarming, but the question of whether it is alarmist is a more difficult one..."

Jeff Masters

Super Tuesday tornado outbreak: deadliest in 23 years

By: JeffMasters, 4:00 PM GMT on February 06, 2008

Violent tornadoes rampaged across the South last night, killing at least 52 people, injuring hundreds, and destroying thousands of buildings. The death toll from the 2008 Super Tuesday Tornado Outbreak makes it the deadliest tornado outbreak in the past 23 years. The last time tornadoes killed so many people in the U.S. was on May 31, 1985, when 88 people died in a tornado outbreak that hit Ohio, New York, and Pennsylvania. What is really unusual about yesterday's Super Tuesday Outbreak is that it occurred in early February. Only one other tornado outbreak in the past century killed so many people so early in the year--the great Warren, Arkansas tornado outbreak of January 3, 1949, which killed 60 people.

Figure 1. Storm reports for the Super Tuesday tornado outbreak of 2008. Image credit: NOAA's Storm Prediction Center.

Tornado outbreak fueled by record warm temperatures
Yesterday's outbreak was fueled by record warmth over the South. Record high temperatures were recorded in Little Rock, Arkansas (75), Shreveport, LA (78), El Dorado, AR (77), Memphis, TN (75), Jackson, MS (81), and Charleston, SC (79), to name a few locations. A strong cold front associated with a powerful winter storm over the north central U.S. pushed into this warm, unstable air mass, triggering Tuesday's bout of violent weather. From what I've seen of the damage photos so far, some of these tornadoes were undoubtedly strong EF-3 and possibly violent EF-4 twisters. I did not see any damage characteristic of the highest EF-5 level. Among the areas hard-hit were Memphis, TN (Figure 2), where a tornado smashed through the Hickory Ridge shopping mall on the southeast side of town, killing one person. In Jackson, Tennessee, a tornado devastated Union University, destroying 40% of the all the student dormitories and damaging another 40%. At least 1100 cars were damaged at the university, but no one was killed.

Figure 2. Radar reflectivity image of the February 5, 2008 Memphis, Tennessee tornado.

How bizarre is this?
The Super Tuesday tornadoes disrupted polling in many locations in Tennessee and Arkansas, where voters were forced to take cover when tornadoes swept through in the late afternoon and early evening. In a bizarre twist, the town of Clinton, Arkansas was hit by a tornado on a day when Arkansas voters journeyed to the polls to vote for Hillary Clinton in the state's democratic primary. The Clinton tornado also ripped through the town of Atkins, Arkansas, about 30 miles southwest of Clinton. Three people died and damage was very heavy in Atkins, a small town of about 3,000 people.

Figure 3. Radar reflectivity image of the February 5, 2008 Atkins/Clinton tornado as it approached Clinton, Arkansas. Note the classic hook-shaped echo characteristic of a tornado.

Figure 4. Radar velocity image of the February 5, 2008 Atkins/Clinton tornado as it approached Clinton, Arkansas. Note the area of blue and red echoes just south of Clinton. 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.

Continued threat of severe weather today
Severe weather continues today, with tornado watches posted in Florida, Alabama, and Georgia. Stay turned to our Severe Weather Pages and Interactive Tornado Page to keep up with what's happening. Today's weather should not be nearly as violent as yesterday's, however.

Jeff Masters


The biggest storms of the 2007 global hurricane season

By: JeffMasters, 9:36 PM GMT on February 04, 2008

Last week, I took a look at the statistics for the global 2007 hurricane season. Today, let's look at the significant storms from each ocean basin.

The Atlantic's (and the world's) most intense tropical cyclone of 2007 was Hurricane Dean. Dean peaked at an intensity of 905 mb, with 175 mph winds, as it made landfall on Mexico's Yucatan Peninsula on August 21, 2007. Dean killed a total of 32 people, 12 of them in Mexico. Remarkably, no deaths occurred in the Yucatan. Dean's Mexican deaths all occurred due to Dean's second Mexican landfall in the Gulf of Mexico, after it had crossed the Yucatan Peninsula.

Figure 1.The world's strongest tropical cyclone of 2007, Hurricane Dean, as seen from the Space Shuttle Endeavour, Saturday August 18, 2007 at 1pm EDT. Image credit: NASA.

The Atlantic's deadliest storm was Hurricane Noel, which killed up to 222 people. Noel dumped up to 15 inches on Haiti and 35 inches of rain on the Dominican Republic between October 28-31. The resulting floods killed 219 people in those countries. Flooding killed three other people in Cuba, the Bahamas, and Jamaica.

Also notable: Hurricane Felix killed 200 people in Nicaragua and Honduras after striking the northwest coast of Nicaragua as a Category 5 hurricane with 175 mph winds on September 4, 2007.

Figure 2. Moonrise over the eyewall of Hurricane Felix as it intensified into a Category 5 hurricane. Wunderblogger Randy Bynon has more great photos in his blog where he recounts his mission into Hurricane Felix.

North Indian Ocean
The world's two deadliest tropical cyclones of 2007--and its costliest--all occurred in the North Indian Ocean.

Deadliest storm: Cyclone Sidr was the worst weather disaster in the world in 2007. The Category 4 cyclone crashed ashore on the heavily populated coast of Bangladesh in the Bay of Bengal on November 15, bringing winds of 150 mph and a storm surge of up to 5 m (16 ft) to the coast. At least 3447 people were killed. Damage was estimated at $450 million. Despite the high death toll, the evacuation and preparedness efforts were considered a success. Similar storms have exacted much higher death tolls in Bangladesh in the past.

Strongest storm: Tropical Cyclone Gonu, a Category 5 storm with 160 mph winds, was the strongest tropical cyclone on record in the Arabian Sea, and tied for the strongest tropical cyclone on record in the northern Indian Ocean (Wikipedia). Gonu caused about $4 billion in damage and over 50 deaths in Oman, where the cyclone was considered the nation's worst natural disaster of all time. Gonu dropped heavy rainfall near the eastern coastline, reaching up to 610 mm (24 inches) which caused flooding and heavy damage. In Iran, the cyclone caused 23 deaths and $215 million in damage.

Also notable: Cyclonic Storm Yemyin was 2007's second deadliest tropical cyclone. Yemyin hit the coast of Pakistan on June 22, killing as many as 933 people in Pakistan and 140 people in India. An additional 80 people died in Afghanistan due to flooding from Yemyin's remnants. Incredibly, the Indian Meteorological Service (IMD), who is responsible for tropical cyclone warnings in the North Indian Ocean, never classified Yemyin as anything stronger than a tropical depression. As I noted in a blog on the disaster, there was ample evidence that Yemyin was at least a strong tropical storm and perhaps a weak Category 1 hurricane. The Joint Typhoon Warning Center on Guam classified Yemyin as a strong tropical storm with 50 knot (60 mph) winds.

Figure 2. The North Indian Ocean's fearsome threesome of 2007. Left, Cyclone Gonu at Cat 5 intensify (160 mph winds), 0900Z Jun. 4, 2007. Middle, Cyclone Sidr at 0445Z Nov. 14, 2007 (Cat 4, 140 mph winds). Right, Cyclone Yemyin at 0610Z Jun. 25, 2007 (tropical storm, 40 mph winds). Image credit: NASA.

Eastern Pacific
Deadliest storm: Hurricane Henriette, a Category 1 hurricane that hit tip of the Baja California peninsula near San Jose del Cabo on September 4, killed seven people near Acapulco due to landslides; two fishermen also died off the Sonora coast. Henriette caused $275 million in damage to Mexico.

Strongest storm: Cat 4 Flossie (140 mph, 949 mb). Flossie did not hit land.

South Indian
Deadliest storm: Tropical Cyclone Indlala killed 80 people on Madagascar March 15 when it hit the island as a Category 3 storm with 120 mph winds. Indlala had 145 mph winds at its peak intensity, shortly before landfall on Madagascar.

Strongest storm: Cat 4 Favio (145 mph). Favio hit Mozambique on February 22 as a Category 3 storm, killing 4 and injuring 70.

Also notable: Tropical Cyclone George killed three people when it made landfall March 8 in the Port Hedland region of Western Australia. George was a Category 3 storm with winds of 125 mph at peak intensity.

South Pacific
Deadliest storm: Tropical Cyclone Guba killed 150 people on Papau New Guinea when it brushed the island on November 20. Guba was a Category 1 storm with 85 mph winds at peak intensity.

Strongest storm: Cat 3 Daman (120 mph), Dec. 5-9.

Western Pacific
Deadliest storm: Tropical Storm 06W had top winds of only 40 mph, but the storm was a prodigious rain maker, dumping up to two feet of rain on Vietnam August 3-4. At least 60 people died in the resulting flooding.

Strongest storm: Category 5 Super Typhoon Sepat (160 mph). Sepat hit Taiwan as a Category 4 storm on August 18, then mainland China as a strong tropical storm on August 19. Sepat killed 39 people in China and did $658 million in damage.

Also notable: Typhoon Man-Yi, a Category 4 typhoon, killed nine people when it sank a ship near Guam on July 9. Man-yi made landfall on Okinawa with 150 mph winds, and later hit Japan as a Category 1 typhoon.

Jeff Masters

Groundhog sees his shadow--six more weeks of winter?

By: JeffMasters, 3:24 PM GMT on February 02, 2008

Punxsutawney Pennsylvania's famous prognosticating rodent, Punxsutawney Phil, saw his shadow this morning. According to tradition, this means that a solid six more weeks of winter can be expected across the U.S. From the official web site of the Punxsutawney Groundhog Club,

Here Ye! Here Ye! Here Ye!

On Gobbler's Knob on this fabulous Groundhog Day, February 2nd, 2008
Punxsutawney Phil, the Seer of Seers, Prognosticator of all Prognosticators,
Rose to the call of President Bill Cooper and greeted his handlers, Ben Hughes and John Griffiths.

After casting a weathered eye toward thousands of his faithful followers,
Phil consulted with President Cooper and directed him to the appropriate scroll, which proclaimed:

"As I look around me, a bright sky I see, and a shadow beside me.
Six more weeks of winter it will be!"

I'm hesitant to disagree with a forecaster of Phil's stature, but I see only about of week of hard-core winter left over the U.S. The 16-day run of the GFS model shows the jet stream retreating to a position in southern Canada in about a week, which will usher in mild temperatures for this time of year across most of the U.S. The latest 1-month outlook from NOAA's Climate Prediction Center shows an above normal chance of warmer than average temperatures across a large portion of the U.S. for February.

How did this this crazy tradition start?
It all started in Europe, centuries ago, when February 2 was a holiday called Candlemas. On Candlemas, people prayed for mild weather for the remainder of winter. The superstition arose that if a hibernating badger woke up and saw its shadow on Candlemas, there would be six more weeks of severe winter weather. When Europeans settled the New World, they didn't find any badgers. So, instead of building wooden badgers, they decided to use native groundhogs (aka the woodchuck, land beaver, or whistlepig) as their prognosticating rodent.

The Groundhog Oscillation: convincing evidence of climate change
According to a 2001 article published in the prestigious Annals of Improbable Research titled, "The Groundhog Oscillation: Evidence of Global Change", Punxsutawney Phil's forecasts have shown a high variability since 1980. This pattern, part of the larger "Groundhog Oscillation" or GO cycle, is convincing evidence of human-caused climate change.

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