Thursday, January 21, 2010

Couple of Comments and Question

Bob, The map (the NWS rainbow product map below) would have you belive we are in for a blizzard in the city! They really need to create new mountain zones for our area. Jack

Reply from Mike Hardiman - Not sure that new zones are the answer (they're sort of an outdated concept), but I agree the maps are misleading. They should be based on the Hazard Grids, which can be created by elevation. It is probably in the works, but I haven't heard anything definitive.

I think that I agree with Mike - there are so many variations of elevation and weather within just eastern Pima County that breaking it down into smaller zones would probably be more confusing. Elevations within TUS NWS zone 33 "Metro Tucson" range from below 2000 ft MSL to over 9,000 ft MSL. Makes the zone 33 forecast seem like strange gibberish unless you go into the interactive click mode and examine the grid point forecasts. These forecasts are roughly adjusted for altitude. Bob

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Jack also asks - Forgive what may be a silly question, but on the U of A model runs, Tucson seems to be always in a relative minimum of precip? Is the valley rain shadowed under most atmospheric flow situations? I did not think the Tucson mountains were nearly high enough to do this.

Often the valley is rain-shadowed - but usually under weaker flow regimes/dynamics. Given the current situation with strong forcing for vertical motion and a very deep, nearly saturated layer, I think that the terrain to the southwest should have minimal impacts on the precipitation distribution. Consider the map above - the terrain within the area bounded by a line from Three Points, to Sells, then down to a bit south of the border, east to Nogales, north to Green Valley, and then back to Three Points seems to be the terrain related to the Tucson/U of A rainfall minimum. The Tucson Mountains are probably not in play. Perhaps when things quiet down a bit we get Mike Leuthold to address this question?


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