78 dBZ Storm in Alabama?
An extremely strong storm was tagged in northern Alabama last night. The KCBN Mississippi radar tagged it at 75 dBZ for several scans, and an unconfirmed 78 dBZ was reported in the WeatherMatrix StormMatrix, which also claimed "hail of over 4 inches in diameter" (the highest possible classification). (The WeatherMatrix StormMatrix reads storm cell data output by the government's NEXRAD radars).
Here are some reflectivity and velocity shots of the storm courtesy AccuWeather.com RadarPlus, and there is also a movie of the storm's trek across northern Alabama:
Storms over 70 dBZ are very rare and extremely dangerous. Even though neighboring radars tagged this storm at over 70 dBZ as well, there is some question as to the storm's actual strength, especially on the ground. Here are some interesting things that I observed:
The Echo Tops were not unusually high, which one would expect with a storm of this strength
The Vertically Integrated Liquid was also not extreme (only 62), considering that it is a hail indicator. I have seen storms in the Midwest top the VIL charts at over 80.
in diameter were received by the National Weather Service in Alabama.
What we may be looking at is the radar exaggerating the storm because of its distance from the scope. Near the edge of the NEXRAD scope is over 10,000 feet, so we might have been looking into the heart of the storm and picking up rain or hail reflectivities that would never reach the ground (thankfully).
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