Tuesday, June 28, 2011

Shorter Term Weather Situation

The large area of high precipitable water (see above) west of Baja has diffused horizontally and spread to the west and southwest during the last two days. While not as impressive as it was at time of the last post about it, it still appears that this pool of low-level moisture has begun (note its northward spread to southern California coast) interacting with the digging 500 mb short wave off the Northwest Coast.

This morning skies here were partly to mostly clouded over with middle-level cloudiness (see visible image above). IR satellite loops indicate that these clouds are debris from yesterday evening's deep convection over the mountains of Sonora. The debris cloudiness spread westward to the GoC and then turned north-northeastward, advecting into Arizona.

The El Paso morning sounding (12 UTC 28 June 2011 - see above) remains fairly dry (PW about 19 mm), but winds below 700 mb are quite strong and from the southeast. Something to watch, as the tropical disturbance in the GoM is very moist.

The morning sounding from NWS TUS (above) is very dry with indicated PW of 13 mm - however, the data are too dry wrt GPS data by about 5 mm (note that there are no local GPS data with which to compare El Paso's PW). There is a shallow layer of south-southwest to south-southeast winds around 500 mb, which has brought the Mexican cloud debris overhead. The winds are westerly above and L/V below this layer. Unfortunately, there are still no soundings from Guaymas, and this morning Mazatlan has also gone missing - leaving a big data void right we'd like to know what's happening.

The forecasts from the Atmo, high-resolution version of the WRF model (from run initialized at midnight last night - above) are very interesting. As the Pacific short wave moves ashore tomorrow into the Great Basin, the WRF forecasts a continuing influx of low-level moisture from the GoC (see forecast of PW above, which is valid at 4 pm tmorrow afternoon (Wednesday the 29th). The model predicts a very substantial increase of PW across all of southern Arizona, with the Tucson value predicted to reach 42 mm!

The WRF's total predicted precipitation is shown above for the period ending at 1200 UTC on 30 June. The model forecasts 1/2 an inch at Tucson (most of which falls during thunderstorms on Wednesday afternoon). This would be a the most substantial rainfall in many months. Hope that the model forecast verifies.
The longer term situation is also very interesting - I'll address this later today after a dentist appointment. I note that the NWS forecast looks very summer-like, with Tucson metro area POPs of 10 to 30% for each of the 12 12-hour forecast periods beginning tomorrow.

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