Updraft: June 21, 2010 Archive

Weather psychology 101

Posted at 6:28 AM on June 21, 2010 by Craig Edwards
Filed under: Severe weather

I offered a mantra at the National Weather Service of a mission to tell people what we know when we know it. The sooner the better. There was a natural tendency to always wait for more confirming information. But if we had some knowledge of changing weather to share, we should promptly share it.

In the case of last weeks tornadoes, I was struck by the news stories of word of mouth warning of the approaching storms. Rural area residents were tuned into weather, already aware that storms had pounded parts of eastern North Dakota. It was old fashion communication of information of impending severe weather.

Advance warning from the National Weather Service allowed sufficient time for others to pass along the breaking weather alerts. In some cases, individuals raced to inform faimly and friends that a tornado was headed their way. Not surprisingly, I heard similar stories when I was a member on the NWS service assessment team of the 1999 Oklahoma City tornadoes.

While I didn't see many comments on warning sirens and NOAA Weather Radio, I know they were a part of the process as well as the broadcast media staying on top of developing weather.

I'm a believer that neighbor knowing neighbor and watching out for each other enhances the warning program. Sometimes I wonder how the warning process might be just slightly different in urban and suburbia regions, both at home and office.

On the day of the summer solistice we will experience warm and humid conditions. Some areas will get heavy downpours. A Flash Flood Watch is in effect through Tuesday for northwest Minnesota and eastern North Dakota. There should be a break in the thunderstorms and humidity at mid week.

The six to ten day temperature outlook indicates very warm weather continuing through the rest of June.
CE

More on the EF tornado scale

Posted at 2:58 PM on June 21, 2010 by Craig Edwards
Filed under: Severe weather

This image is courtesy of NOAA of the 199 F5 tornado that leveled the southwest suburbs of of Oklahoma City. EF scale established in February 2007.

The National Weather Service, working with experts skilled in engineering, developed an ehancement to document the historical damage category of the original Fujita (F) scale. It was not a surprisie to learn that Dr. Ted Fujita had anticpated a need to go beyond his original reserach work of the tornado intensity scale first used in 1971. His extensive field work was ground breaking on documenting the severity of tornado damage.

You may be interested in learning that the original tornado scale also included an assignment of what was called a P scale, referenced after Dr. Alan Pearson who was chief of the Storm Prediction Center at the time the F scale was implemented. The P scale was associated with the path and width of the tornado track.

NOAA meteorologists, working for the National Weather Service, are often accompanied by research experts from universities with departments of meteorology during assessments following strong, EF3 or greater tornadoes. A close inspection of the structure, not unlike a crime scene investigation, is conducted to determine strurctural integrity of a destroyed building. Cars airborne from a twister, wrapped around a tree, can be an indicator of winds of 200 mph or greater.

See more on the enhanced Fujita scale. There are a number of indicators used to make a final determination of the tornadoes intensity. in the case of the Oklahoma City tornado, the Severe Storm Laboratory had a Doppler on Wheels postioned to measure winds of greater than 300 mph in the Doppler velocity data.