Friday, July 03, 2009

Prospects for Today (Friday Jul 3 2009)

This morning’s TWC sounding indicates that considerable CAPe is again present. precipitable water remains near 40 mm, although drier air above 400 mb may inch its way across eastern pima County this afternoon – the upper-level dry line lies north to south across the county and has been fairly stationary this morning. The very thick cloud plume from Sonora has shifted eastward and covers only the southeast corner of Arizona but much of New Mexico. A distinct, but weak, shortwave is now positioned to the east of Tucson and winds below 500 mb are mostly from the north with very light speeds. Anvil level winds have become more westerly and this trend will continue according to models. Steering winds are weak and storms will go wherever their outflows and small-scale CAPE distributions take them.

The NAM 500 mb initial analysis – see above - indicates a string of 500 mb vorticity maxima along the east coast of the GoC (looks a bit like 2-delta noise) – but with no soundings from Mexico this morning, it is unclear how accurate this initialization might be, since it is primarily driven by the previous NAM forecasts. Interestingly, the NAM predicts a consolidation of the features over eastern Arizona and the GoC into a single shortwave that moves back to the northwest, making the weekend quite wet and stormy – at least in the model’s world.

As for today – definitely more sunshine to cook things up. Ample CAPE for storms that will drift about some given the lack of any clear steering flow. Heavy local rains possible in spots – a wet microburst or two also possible. Should be an interesting day and possibly weekend also. I’m going to guess that we have a 50-50 chance for rain here at house today since the weak northerly flow could let Catalina buildups drift our way.

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