Saturday, March 27, 2021

Newnan, Georgia, This Morning: An Incredible Tornado Warning System Success

[Bumped to top, see new info at bottom]
Early this evening, this news about the northwest Georgia tornado broke. 
This tornado struck at 12:10am. It could easily have killed more than 200 people based on the population (33,000) and time of day; if there had been no warning. 

Thanks to the Wireless Emergency Alert (WEA) alarms, apps like AccuWeather's, and weather radios that sound an alarm during the night when programmed for your location.people were awakened in time to take shelter. But, none of these would work unless meteorologists had the science and technology to provide accurate and timely information. 

Various techniques showed a high risk of tornadoes over northwest Georgia which prompted the NWS's Storm Prediction Center to issue a "mesoscale forecast" (blue polygon). I combined that with the tornado warnings (red polygon), the location of the tornado (blue dot), and my text (below illustration that I included with my 11:30pm EDT update. I circled Newnan for ease of location. 
Bottom line: We were able to give more than 30 minutes of notification for the Newnan area where the F-4 occurred. 

As the tornado got closer, we switched primarily to radar to forecast and track the storm. I thought I would show you the types of radar (to illustrate one type of technology) meteorologists view when making tornado warning decisions. 
Above is what I was viewing at 12:06am Eastern this morning,
  • The reflectivity display (the type shown on television) showed a giant debris ball. That is a strong indication of a tornado.
  • The Doppler wind data was extraordinary. It indicated rotational winds of around 160 mph --  a very violent tornado.
  • The turbulence display shows the highly turbulent winds near the center of the tornado. 
  • Finally, a display known to meteorologists as "correlation coefficient" which displayed a huge area of lofted debris -- proof this was a major tornado tracking along the ground. 
We were able to give residents of the area minute-by-minute updates forty minutes before as this terrible storm swept into the area. Yes, there was one indirect fatality (medical emergency) but the the Newnan Tornado tremendous success in terms of lives saved. 

Addition: 3pm Saturday

The National Weather Service in Birmingham sent out an interesting comparison between Thursday's tornado before it struck Centreville and a tornado which struck Centreville in 1973 when a NWS WSR-57 radar was located in that city. 

The legend is the same as above except the lower left panel is storm relative wind velocity rather than turbulence (I prefer to display the latter, it is a matter of choice for a meteorologist). As with the Newnan Tornado, the storm is very easy to distinguish but I want you to focus on the "hook echo" in the upper left panel. That was all meteorologists had to go on before the Doppler radar network was installed in the 1990's.

As occurred Thursday, the towns of Brent and Centreville were devastated by a violent tornado in 1973. The radar was destroyed by that tornado. 

All we had to go on was the shape/intensity of the parent thunderstorm and its pendant hook echo. There wasn't even a map -- all we had were the concentric range rings. When tornadoes threatened, speed  was vital. So, one meteorologist would be reading the radar in a dark room while a second would mark down the range (distance from the radar) and azimuth (direction from the radar) of hooks and other vital features. 
       "Hook echo, 238°/11 miles" the radar meteorologist would shout. 
       "Tornado headed into Brent and Centreville," the warning
        meteorologist would reply and would then turn to the teleprinter. 
The warning meteorologist would "cut" a paper tape (something like an old stock ticker) with the warning info which would then be put into a paper tape reader. When the circuit was clear (two weather stations could not transmit at once), the warning meteorologist would begin to feed the tape through the reader and the warning would go out. The entire process -- and, why lives were lost due to delays -- is described here

American society is much safer as a result of these improvements in science and technology. 

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