Saturday, August 16, 2014

More Storms At Low Elevations Today?

Yesterday there were many thunderstorms around, but storms stayed mostly at higher elevations - although there was moderate CAPE at low elevations there apparently wasn't enough in way of organized outflows to force storms in the low deserts. Plot of CG flashes above is through 3 am MST today (August 16th) and MesoWest rain reports (below) are for 24-hours ending at 7 am this morning. Here at the house we had several thunderstorms, beautiful rainbows, but no rain. Across the ALERT network 35 of 92 sites reported rainfall for 24-hours ending at 7 am, 11 sites reported over 1/2 an inch and 2 sites reported over 2 inches. The Rillito wash was flowing again this morning.

Skies are clear this morning, except along the south-central border region (visible image above is from 8:30 am), so there will be good heating today. The morning sounding from NWS (plot below from SPC) indicates moderate CAPE again; PW of 42.9 mm (1.68"); some moistening above 500 mb; and most importantly the development of stronger, easterly steering winds. The morning sounding indicates a good shear profile through convective cloud depth for more organized storms and outflows today. The model forecasts do indicate weakening upper-level winds by afternoon. The forecasts also hint at some mid-level cooling coming in from the northeast. So there is a mix of more positive features today balanced against some possible negatives later in the day. Note that the Yuma dewpoint has gone into the upper-70s early this morning - see their time series of T and Td at bottom.

The early WRF forecasts are quite different this morning. The NAM version again keeps storms mostly at high elevations and to the south, while the GFS forecasts a line of severe storms to impact the metro area during the late afternoon. Will wait to see what the new model runs forecast and of course keep an eye on how storms develop today.

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