Tuesday, May 25, 2010

Supercells In Western Kansas ... Again!

The above is a shot of the Goodland, KS (KGLD) dopper radar, reflectivity mode (showing precipitation echoes), taken shortly after 8 o'clock this evening Central time.  Note the strong "hook echo" signature on the eastern-most storm, to the North-Northeast of Scott City, KS.  This is a classic indicator of a rotating, likely tornadic, thunderstorm.

Below is a shot of the same storm using the "storm relative velocity" mode (showing wind motion toward & away from the radar) taken at the same time.  Remember that on any kind of velocity image, wind blowing toward the radar is depicted by the green and blue colors, while wind blowing away from the radar is shown by the red and yellow colors.  In this case, the radar is located in the upper left hand corner of the image.  With that in mind, note the broad circulation located near the reflectivity hook echo (depicted by the arrows inside the white circle).  This is called the "mesocyclone", which is the first sign of organized rotation and tornado potential within a supercell thunderstorm. 

If you look closely, right beneath the upper-most arrow within the mesocyclone, there is another (very small by comparison) spot where the red and green touch abruptly.  That is the "tornado vortex signature" (TVS), or most likely where the ground-level rotation (tornado) is located.  The TVS is highlighted by a smaller circle on the image below.

The Vortex 2 teams deployed on the storm located to the West (left) of this storm earlier in the evening, and observed from 3-5 tornadoes.  It appears that that storm is either weakening or "cycling" (changing from one phase/intensity to another) while the storm to the North-Northeast of Scott City is strengthening and organizing at this time.

One more thing I'd like to point out.  A Severe Thunderstorm Watch was issued for most of Western Kansas earlier this afternoon.  The events that have unfolded this evening prove that just because a Tornado Watch is not issued doesn't mean that tornadoes can't (or won't) form.  After all, the tornado doesn't know that it isn't forming inside a tornado watch area.  Folks in tornado alley know to keep an eye to the sky regardless of what type of weather watch is in effect for the area.  The local NWS offices in Goodland, Dodge City and Pueblo have done a good job warning on the tornadic potential of the affected storms, despite the earlier "forecast" of the Severe Thunderstorm Watch.

*** Updated at 9:55pm:  The Storm North-Northeast of Scott City indeed went on to produce additional tornado reports, including a "large" tornado in Gove and Trego Counties:

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