On this date in 2009, a tornado intermittently caused damage to homes and businesses along with trees and power lines starting southwest of the interstection of Republic and Scenic extending northeast to the intersection of Fremont and Catalpa. Winds up to 100 mph…or EF1 on the enhanced fujita scale…was indicated by the damage.
 |
 |
Ordinary radar echoes at 10:45 pm and 10:49 pm on 2/10/2009 |
 |
 |
Storm-Relative Velocity images at 10:45 pm and 10:49 pm on 2/10/2009 |
 |
 |
Normalized Rotation (NROT) at 10:45 pm and 10:49 pm on 2/10/2009 (standard MDA settings) |
A tornado watch was in effect but Greene County was not under a warning of any type when this tornado occurred! The reason has to do with the type of tornado which occurred.
Small tornadoes can occur if rotation which exists at ground level finds itself under the updraft of a storm. The updraft stretches the column of air and decreases the radius of rotation. Since angular momentum must be conserved, the speed therefore must increase (cue obligatory ice skater example).
In theory, this can happen under any updraft. As a practical matter however, meteorologist look for certain areas in thunderstorms that are favored for tornado development and would likely examine such areas more closely to see if there was rotation.
In this case, the rotation was overlooked because the radar signature gave no cause for concern (I call it a pimple on the radar screen!) and the rotation was so broad and short-lived that computer algorithms simply didn’t register it as a threat. Even if perchance I had seen this rotation, I might have raised an eyebrow but I don’t think I would have pulled the warning trigger if I were the one with the warning responsibility! Moreover if I had some magical gift of radar interpretation or inside knowledge and decided to cry tornado, would it have done any good? The twister was on the ground for a total of five minutes!
Recent Comments