This velocity radar grab (courtesy of Weather Underground) shows the low level rotation in the storm relative to my position at the red “X”.  This was just before I pulled up stakes and moved a couple miles eastward to get out of the rain shaft.   At 2056 UTC (9 minutes before this radar grab) the local airport KEZF – located ~4 miles west of the “X” –  recorded a 5 mph wind backing to the south, which lasted for over 3 hours before the wind direction veered to southwest.  (The winds for over 2 hours prior to this time were recorded being from the west at 5-8 mph.)  Barometric pressure was steady for several hours before and after this event as was the temperature / dew point, which was recorded as 76/75 degrees F in the 2056 UTC observation.
     Thus the only appreciable change in the meteorological parameters being recorded at the local airport was a wind shift that coincided with the passage of this storm and lasted for several hours.  NWS Sterling had issued a tornado warning on this cell at 2037 UTC, so the rotation was already evident on radar by the time the storm reached its closest approach to the airport location.   So, did the storm itself create the wind shift, or was there a localized boundary that increased the low level rotation that resulted in the rotating wall cloud and funnel that I witnessed?  Hmmmmm…….

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