Monday, July 05, 2010

Another Clear and Hot Day On Tap

Yesterday was deathly clear and was the second day with no precipitation reported in southeast Arizona; today will be the third with very dry conditions prevailing. This morning's 500 mb analysis from Univ. of Wyoming indicates dry, northwesterly flow from the Pacific over most of the western US and northwestern Mexico. The bottom image shows the GPS PW (and the TWC raob PW) for the past 30 days - from the GPS group at NOAA/Boulder. The observed PW has only flirted briefly with the important 3 cm threshold that some use to define the onset of monsoon conditions. Certainly a dismal start so far to the summer. Although Alex looked promising for a while, the storm's remnants stalled out over central Mexico, eventually pulling north-northeastward into the Plains. The NAM had predicted, at least for a while, that the 700 mb circulation with Alex would continue westward out over the lower GoC, but those forecasts did not verify. At this time, I don't see any feature in the model forecasts out to 6 or 7 days that would provide an impulsive northward push to the subtropical moisture - which at this time is quite far to the south down the GoC. There is quite a bit of activity in the Atlantic, Caribbean, and Gulf of Mexico to keep an eye on later in the week. After 3 or 4 days the mid-level, subtropical high build back westward across the Southwest and by 6 or 7 days conditions appear favorable for MCSs in Sonora to move into GoC during the nights. But that's about it - appears that we may have a very gradual development of the summer storm season here in southern Arizona.

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