Saturday, June 23, 2012

Storms Today?

Yesterday's early run of the Atmo WRF-GFS forecast increased storms and PW today with some activity in Pima County. The forecast from today's early run is not nearly so active. The 4 pm forecast of PW for today (above) shows values remaining near 20 mm over eastern Pima County, with a plume of slightly higher amounts out to the west. The forecast sounding for TUS at 4 pm today is shown below. While there is a favorable wind profile (east-southeasterly mid-level winds veering to southwesterly at upper-levels), there is no CAPE available for convection - at least at low elevations. The model forecast only gets storms going over in the White Mountains and briefly along the borderlands. So today's model run indicates a fairly typical, hot late June day.

In fact, the model does not forecast much storm activity over southeastern Arizona for the next three days. The above graphic shows total accumulated precipitation forecast by WRF-GFS through 9 pm next Monday evening - pretty dismal. Our main hope for significant, low-level moisture influx will likely depend on how MCS activity evolves in Sonora the next two evenings - we need a significant thunderstorm complex closer to the border, with outflows making it north across Pima County.

Finally, the 700 mb analysis for 12 UTC this morning (below - from NCAR RAL) depicts both the large anticyclone covering the southern US, as well as a very large tropical low over the Gulf of Mexico. The long term models have different forecasts for how the GoM system will evolve. Both the GFS and ECMWF forecast intensification, with the GFS seeming to intensify the system to hurricane strength (at least some of the ensemble members). The ECMWF seems to indicate that it will become a westward-moving tropical storm. The GFS ensemble members are about split on whether this system will eventually head northeast or westward. If the system moves across northern Mexico, it could have a significant influence on the Southwest as July begins. Plenty of interesting features to follow during coming days.

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