Friday, December 23, 2016

Wall Cloud West End Of Catalinas?

Photo above from Mike Leuthold yesterday at around 01:00 pm MST. There was some discussion among local weather watchers as to whether this might have been a wall cloud - a feature often associated with severe thunderstorms with rotation. It was certainly something to watch, but there did not appear to be rotation. There were definitely thunderstorms occurring - below is CG flash density for 24-hours ending at 07:00 am this morning.

Radar (base scan at 01:00 pm) above shows the line of strong echoes from I-10 north to west side of the mountains. The Doppler velocity at the same time (below) indicates radial velocities were all outbound - note that the height of the 1st tilt is well above what is shown in the photo at top. But there was probably not a deep updraft with rotation present.

Photo at bottom was taken by Art Rangno looking south from Catalina before the storms got to the mountains. There was a very pronounced shelf cloud leading the storms and it had a very low cloud base. So my guess about all this is that the photo at top shows the shelf cloud impinging onto the mountain. See Art's post about this event up where he was - link to right.

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