Monday, June 29, 2015

Yesterday An Active Day - Less So Today

Yesterday was the most active storm day of the summer over eastern Pima County wrt to areal coverage of measurable rainfall. Webcam view from campus at about 3:45 pm MST shows a thunderstorm over the north part of the city. This storm was over the house at this time but was moving rapidly westward - net results: thunder, not much wind, and only 0.04" of rain. there have been thunderstorms here at the house for 5 consecutive days - quite something for June, but total rainfall those 5 days has been only 0.08".

Across the ALERT network 48 sites had measurable rainfall (0.04" or more), making this the highest percent coverage of the summer so far. Amounts were again mostly light - only 8 stations had a quarter of an inch or more, and Cargodera Canyon (near Catalina State Park on west side of Mt. Lemmon) measured 0.94".

The CG flashes detected through 10 pm last evening (below from Atmo and Vaisala) shows widespread thunderstorm activity across much of Arizona. Some storms did indeed make it all the way west to the Colorado River. Very noticeable though is the often-observed Phoenix doughnut hole and also little activity over Cochise County and southwest New Mexico.

This morning's skewT plot of the TWC 12 UTC sounding is shown above. Even though there has been a bit of middle-level warming and a down-trend in PW, CAPE appears similar to yesterday. The wind profile though indicates that storm anvils would spread to the south-southwest today. Thus, storms over the Catalinas could spew anvil out over the city. 

Things are complicated today by the significant gradient of PW from central Pima County to southwest New Mexico, with lower moisture lurking to our east. Graphic below shows 12 UTC blended PW from CIRA, with high PW from here west but with an area with less than inch over southwest New Mexico.

I have looked at the WRF forecasts from both the 00 and 06 UTC runs and can only say that the various forecasts for eastern Pima County are not consistent. Shown above is the 06 UTC WRF-NAM forecast of rainfall through midnight tonight, while below is same forecast from the WRF-GFS.

Basically, blending all the forecasts subjectively, it appears that we will be right in the battle zone of the moisture gradient. Initial storm developments could be anywhere from eastern edges of the ALERT network out to the western edges. As a half-empty rain-gauge meteorologist, I'd lean toward storms staying west today. But yesterday, it appeared that the 12 UTC WRF-NAM produced the best local forecasts, so we'll see what the new forecast runs show later this morning.

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