2011 has been a deadly and devastating tornado year. Arguably one of the hardest hit areas has been Alabama, home of this year’s National Weather Association conference. I am currently in Birmingham attending the conference.
This morning, Dr. Greg Forbes of The Weather Channel discussed the April 27th tornado outbreak in the Southeast. From the hundreds of tornadoes that touched down, he drew some interesting conclusions. According to his research, the strongest tornadoes were all detectable on radar through the appearance of a ‘debris ball’. The debris ball, seen in this radar imagine as the small pink dot in the classic hook signature, is an area where the radar is literally seeing debris being thrown into the air by a tornado.
In each of the 3 EF-5 tornadoes recorded on the 27th, a debris ball was present on radar. A debris ball was also visible in 7/10 EF-4s, and 11/12 EF-3s. Debris balls were rarely visible for tornadoes weaker than EF-2s.
When considering tornadoes between April and June, that trend continued. 88% of EF-3, EF-4, and EF-5 tornadoes all featured a debris ball, while only 10-11% of weaker tornadoes did.
Given that 92% of tornado deaths occur with these strong tornadoes, this is an important finding for meteorologists. By knowing that a debris ball likely indicates a strong tornado is on the ground, meteorologists can issue warnings that are more dire when appropriate. That will limit ‘false alarms’, and will give the public a better idea of how much danger may really exist.
I’ll continue to post interesting information from Birmingham all week, both here, and on my personal blog.