Sunday, September 06, 2015

Another Very Quiet Day Yesterday - Saturday September 5th

Yesterday brought another round of morning showers and rain to eastern Pima County. It was dreary and damp much of the day, as per morning view of Catalinas above. Widespread morning rains are usually the kiss of death for afternoon storms and that was certainly the case yesterday. Plot below (from Vaisala and Atmo) shows CG flashes through midnight last night and almost no thunderstorm activity over all of southern Arizona - there might have been two flashes in Cochise County.

The rains, however, were widespread across eastern Pima County - 90 of 93 ALERT stations measured 0.04" or more. so virtually another 100% event - the second in four days. But, amounts were very light with nothing recorded over 0.20", except 0.55" at Mt. Lemmon site and 0.28" at Manning Camp. Here at the house we had 0.09".

Today has dawned bright and sunny, with just some middle cloud around (above). The forecast for today will be a bit difficult. There may be a weak short moving moving toward southeastern Arizona this evening - or the feature forecast by the NAM model this morning may be a mesoscale response to significant, heavy thunderstorms over north Sonora. The NAM forecasts very heavy rainfall over the borderlands of northeastern Sonora and southeastern Arizona during coming 24-hours. The 06 UTC forecasts from Atmo were a bit of a mixed bag - the WRF-NAM forecast isolated storms over higher elevations of southeast Arizona, with heavier activity along the border; while the GFS version forecast more widespread thunderstorm activity over eastern Pima County and Cochise County - definitely something to keep an eye on.

The morning sounding from TWC (below from SPC) indicates substantial moisture with slight to moderate CAPE. However, low elevations need to heat and mix to about 700 mb, and it may not get that hot. However, the higher elevations will be much more unstable, but storms that develop in the strong southwesterly winds will be heading away from metro Tucson.

Finally, the NHC expects to declare the TD south of Baja has become Tropical Storm Linda this morning. They forecast Linda to become a hurricane during next few days, but to stay well southwest of Baja.

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