Monday, October 19, 2009

Art Douglas Reports from Ash Canyon

10 pm MST radar last night from NCAR RAP web site - see second note below

Two nights of thunderstorms here in Ash Canyon (SE Huachucas) with T and 0.01 on the rain amounts..........but spectacular lightning SW to S to SE and East. Heavy rainshafts in Mexico to my SSE much of the evening which got illuminated by the cloud to ground strikes. Saturday's line was active 10PM to midnight and yesterday afternoon Cananea area started popping early and by 7PM to Midnight great lightning display with a good number of leaders coming out of the mid layer of the CBs cloud and back in at 20,000 to 30,000'. Even more spectacular were the positive strokes...very orange and blinded me for a few seconds and the thunder afterwards was incredible. Clouds topping the ridges now with dew point 54F. Models show nothing! No Guaymas sounding since October 17 and Tucson must have failed this morning. LAP MZT and CHIH all have pretty light winds up to about 400mb........not like with Jimena or Olaf. Rick might need a little ventilation to compensate for the drier air from the NW. ECMWF and NAM don't recurve Rick......and it looks like the lower layer system is still moving NW while the upper deck is moving NNE.


Note that Art mentions the fact that the NWS operational models shear out some of Rick's middle-level vorticity but keep the circulation in the lower half of troposphere drifting slowly around near the south end of Baja. This alternate scenario is mentioned in this morning's 8am NHC discussion, but the official forecasts remain that Rick will turn the corner and accelerate rapidly inland over west-central Mexico.
Note 2 - The NCAR RAP web site provides easy access to NWS radar reflectivity plots but, because the base scan data are used for both the site and regional displays, the products are seriously flawed across the western US. This is because of severe terrain blockage problems around most sites. The Tucson base scan figure above illustrates the many sectors that are completely blocked. This is why one should always try to examine composite reflectivity products for western US radars.

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