Hot Start To September

First two days in September have hit 100 and 102F. But with the very dry air, it was a pleasant 62F here at house at sunrise this morning. Lots of fluffy middle cloud around 550 mb floating about this morning (top image) - nice start to a day that will get uglier as the sun heats things up.

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The backdoor cold front from the Plains has pushed into far southeastern Arizona this morning and will do battle with the hot Sonoran air today. Unfortunately, neither air mass has much moisture in it. The bulk of the very moist air behind the front (see satellite image in middle) appears headed for the Big Bend country and northeastern Mexico. The winds will kick up, perhaps some dust too, and it will heat up rapidly, but it's not clear that there will be much cooling or moistening today. The Tucson morning sounding (bottom graphic) indicates a hot, very dry, and deep residual boundary layer from yesterday. So, if a layer of cooler more moist surface air makes it in behind the front, it will have a very strong cap above it.

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If things are to turn up a bit tomorrow, we'll need some influx of moisture from the south. Tropical Depression Ten-E is south of the tip of Baja but is forecast to move to the west. MCS activity in western Mexico last night remained far south in Sonora and Sinaloa. So, we should keep an eye to the south this evening to see if more extensive storm cover develops to help push some moisture to the north.