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 , 01:49 PM GMT on mai 12, 2009
Tornado season is in full swing, and researchers are now poised in America's Great Plains with the largest armada of storm chasing vehicles and equipment ever assembled, in order to learn more about these enigmatic and violent storms. The massive Vortex2 field study began Sunday, and for the next seven weeks over 100 scientists in up to 40 science and support vehicles will be roaming through Tornado Alley, seeking to catch tornadoes on the rampage. The three basic questions the $10 million study will attempt to answer are:
- How, when, and why do tornadoes form? Why some are violent and long lasting while others are weak and short lived?
- What is the structure of tornadoes? How strong are the winds near the ground? How exactly do they do damage?
- How can we learn to forecast tornadoes better? Current warnings have an only 13 minute average lead time and a 70% false alarm rate. Can we make warnings more accurate? Can we warn 30, 45, 60 minutes ahead?'
Figure 1. Tornado over Matador, Texas on April 29, 2009. Photo taken by Texas Tech meteorology graduate student Danielle Turner.
Major tornado outbreak possible Wednesday
The Vortex2 project will have its first good chance to help answer these questions on Wednesday, when a strong cold front is expected to pass through an unstable air mass over Missouri and Illinois, triggering severe thunderstorms with tornadoes. The Storm Prediction Center has given these states a "Moderate" chance of severe weather, the second highest alert level. Today, the Vortex2 armada is stationed in western Oklahoma. The cold front that is expected to trigger Wednesday's severe weather outbreak will be moving through Oklahoma today, bringing a slight chance of severe weather to that state. You can follow the progress of the Vortex2 field project this Spring through our new featured Vortex2 blog. This blog is being written by a team of six University of Michigan students that will help deploy the Texas Tech "Sticknet" sensors during a tornado.
Figure 2. Severe weather outlook from NOAA's Storm Prediction Center for Wednesday, May 13.
An average tornado season so far over the U.S.
Through April, U.S. tornado activity was very close to the mean observed during the past five years, according to NOAA's Storm Prediction Center. However, there were just 15 tornado deaths through April, compared to 70 deaths through April of 2008, and the 3-year average of 60 deaths. According to the unofficial seasonal stats at Wikipedia, we've had 57 strong EF2 and EF3 tornadoes so far this year, and two violent EF4 tornadoes. These are fairly typical numbers of strong and violent tornadoes for this point in the season. The season's first EF4 hit Lone Grove, Oklahoma on February 10, killing eight, injuring 46, and destroying 114 homes, and was the strongest February tornado to hit Oklahoma since 1950. The season's second EF4 hit Murfreesboro, Tennessee on April 10, killing two.
Wunderground launches high-definition radar product
In case you missed my post on this in December, wunderground is now providing imagery from a network of 45 Terminal Doppler Weather Radar (TDWR) units located at airports across the U.S. The radars were developed and deployed by the Federal Aviation Administration (FAA) beginning in 1994, as a response to several disastrous jetliner crashes in the 1970s and 1980s caused by strong thunderstorm winds. The crashes occurred because of wind shear--a sudden change in wind speed and direction. Wind shear is common in thunderstorms, due to a downward rush of air called a microburst or downburst. The TDWRs can detect such dangerous wind shear conditions, and have been instrumental in enhancing aviation safety in the U.S. over the past 15 years. The TDWRs also measure the same quantities as our familiar network of 148 NEXRAD WSR-88D Doppler radars--precipitation intensity, winds, rainfall rate, echo tops, etc. However, the newer Terminal Doppler Weather Radars are higher resolution, and can "see" details in much finer detail close to the radar. This high-resolution data has generally not been available to the public until now. Thanks to a collaboration between the National Weather Service (NWS) and the FAA, the data for all 44 of 45 TDWRs is now available in real time. We're calling them "High-Def" stations on our NEXRAD radar page, and they are denoted by a yellow "+" symbol. Only one TDWR radar (Las Vegas) remains to be added; this will happen in June. For more info on how to interpret the new TDWR images, see our radar FAQ page.
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