Review of Two Warnings for This Morning's Tornadoes

A destructive tornado struck Panama City, FL this morning starting at 5:29am CST. I suspect it will be rated upper EF-2 or EF-3. 

You can see video of the tornado here.

Damage video is here

I am puzzled however, by the short lead-time of the tornado warning. Let me stress there was advance warning -- by seven minutes. However, that amount of time was less than ideal both in terms of the published research (13-15, see here) and National Weather Service's (NWS) objective of 13 minutes. 
The tornado warning (above) was issued at 5:22am. The tornado crossed the coast at 5:29. That means the lead-time was just seven minutes. 

I congratulate the Tallahassee NWS for running their radar in 80-second "tornado mode." Thanks! Let's run the radar back to 5:10am. That would be about the time a decision would need to be made in order to get and distribute a tornado warning at 5:14, resulting in 15 minutes of lead-time.
At left is the reflectivity data, the type of radar you see on television. I've circled the "hook echo" which is a signature of a tornado. In addition, at right, the velocity data shows rapidly rotating winds which are circled. Ignore the rest of the velocity data, it is a form of false echo called a "side lobe" which is especially pronounced because of the storm's fast forward movement -- 70 mph. 

By 5:13, which may have been the latest data that could be used to achieve a lead-time of 13 minutes, things have changed very little. The side lobes have really scrambled the velocity data but it is clear enough that major rotation is in progress. 

At 5:20, which would have been radar data upon which the warning was based, things were extremely clear:
Classic hook echo.

Clear view of strong rotation, although it was still quite noisy due to side lobes. 

Below is the radar when the storm crossed the coast at 5:29am:
At left, the rotating winds have caused the hook to wrap around and form a donut. The tornado's circulation is spinning raindrops away, which creates the hole. At right is the strong rotation. 

There is very good news in that there were no fatalities. The advance notice would have allowed the emergency sirens along the coast to have been sounded. It is likely that played a role in saving lives. 

Dothan Eagle
However, we had the opposite problem with a fatal tornado that cut across far southeast Alabama later in the morning, The tornado warning was issued at the first sign of a tornado at 7:50am CST and expired at 8:15. But, the tornado continued on the ground after the warning had expired. 

At 8:14am, the velocity data (upper) clearly shows the rotation in the ongoing tornado while
the correlation coefficient data (lower) shows lofted debris. 

At 8:16, one minute after the warning expired, the tornado is still in progress. 

The tornado continued until at least 8:24. 
While weak rotation continued for another three minutes, it is unlikely the tornado was still in progress. By this time it had crossed into far southwest Georgia. 

So, there was a tornado that had earlier caused a fatality cutting its way through southeast Alabama for nine minutes without a warning. It is hard to understand how this could have occurred. 

Comments

  1. Isn't that the Lower Lagoon EF3 warned for like 7 minutes before making a landfall? And also, the Cottonwood EF2 tornado was apparently warned for like 20 minutes before it hit a town

    ReplyDelete

Post a Comment

Popular posts from this blog

Hilary's Forecast Path Shifts West; Updated 9:20am PDT

Dangerous Travel Conditions - People Reportedly Stranded

Dangerous Tornado Situation Developing Tuesday and Tuesday Night