Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 3:59 PM GMT on May 26, 2007
Flash flooding triggered by heavy thunderstorm rains of up to seven inches in 24 hours claimed at least five lives in Texas Friday, and large portions of the state remain under flood warnings or flood watches today, as thunderstorms continue across the state. All of those killed were swept away in their vehicles, and police were still looking for a missing man who drove around a barricade blocking a swollen creek.
Figure 1. Precipitation for the 24 hours ending at 8am EDT Saturday May 26, 2007.
Drought last year, floods this year
As I discussed in a March blog last year, grass fires in drought-parched Texas killed seven people on March 12 in the Panhandle, four of them in a car crash on I-40 caused by thick smoke obscuring visibility. More than 1,000 square miles of Texas burned that day--an area about two-thirds the size of Rhode Island. It's amazing what a turnaround has occurred in the past year. Most of Texas and Oklahoma were under drought conditions that reached the extreme level last spring (Figure 2), but this year, the Texas/Oklahoma drought is gone (Figure 3), and instead has moved into the Southeastern U.S. We don't understand very well what causes these shifts in drought patterns, but they do seem to be linked to changes in large-scale sea surface temperature patterns in the Atlantic and Eastern Pacific, plus shifts in the jet stream pattern. Are the floods in Texas this year and drought last year partially due to global warming? Yes, they might be. Global warming theory predicts that both droughts and floods will grow more severe as the climate warms. Floods will increase, since a warmer atmosphere holds more water vapor that can then rain out into heavier floods. Scientists have already documented about a 5% increase in global atmospheric water vapor due to global warming, and this extra moisture is undoubtedly causing heavier rains and more flooding in some regions. Drought will increase in intensity due to global warming, thanks to the hotter temperatures drought-striken areas will receive when jet stream and sea surface temperature patterns conspire to keep rainfall from the drought area.
Figure 2. Drought map for March 7, 2006.
Figure 3. Drought map for May 22, 2007.
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