Tuesday, June 30, 2009

Summary of Yesterday’s Storms

Thunderstorms were more widespread over southeastern Arizona yesterday afternoon. There was measurable precipitation at almost all reporting stations south and east of a line through Alpine – Saguaro RAWS – TUS – Sells RAWS. Many of these stations also had gusts of 30 mph or greater. There were two severe wind reports logged at the Storm Prediction Center this morning, and it gusted to almost 90 mph at the Atmospheric Sciences building (5th floor roof). Here at the house we had 40 to 50 mph winds that were carrying a heavy load of dust and grit – quite an ugly evening. No rain though, since there was little CAPE by afternoon at the lower elevations. A pronounced gust front raced into the lower desert northwest of Tucson but no new storms were triggered. Even though the steering winds were from the east-northeast, the cores of the heaviest storms propagated almost due south – they were propagating along and toward higher elevations where there was more CAPE available. In the Pima County ALERT network 36 stations had measurable rainfall in past 24 hours and these were mainly the eastern and southern sites.

Yesterday was the first day with widespread, heavy to severe storms occurring in a summer flow pattern! The visible satellite image above shows the impressive array of storms during the late afternoon.

Today’s TWC sounding appears to have similar CAPE to yesterday even though precipitable water is down a few mm. The morning steering level winds are srong from the east but NAM indicates the winds will weaken during the day. I don’t have time for an extended discussion since I’m on my way to several morning appointments.

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