Wednesday, July 31, 2013

Heavy Cloud Cover Early This Morning


First - there is a new Tropical Storm in the eastern Pacific this morning, TS Gil (see above). Gil is forecast to become a hurricane during part of its life, as it moves generally off to the west. TS Flossie dissipated over the Hawaiian Islands on Monday. Apparently the storm was weaker than forecast, as per headline in Hilo newspaper - "Flossie Fizzles."

Suppressed conditions continued yesterday - graphic below shows lightning strikes through 5 am MST this morning - note that there were several strikes out in central Pima County. However, most of the CG lightning occurred over northeast Sonora, south of the border. This morning at 6 am none of the ALERT stations in eastern Pima County reported any rainfall during the past 24-hours (third consecutive day with no rain at all over the network).



This morning skies are clouded over with middle and high clouds from the activity over northern Mexico - above is visible satellite image at 6:15 am MST. At that time there were still some light showers moving westward along the Borderlands.

A skew-T plot of the 12 UTC TUS sounding is shown below. Even though PW is now up to around an inch and a half, there is little CAPE available at low elevations. Winds are easterly in mid-levels and southerly at high-levels and a bit stronger in the upper-troposphere.


No forecast from the early WRF-GFS this morning. The latest (12 UTC) NAM analysis at 500 mb is shown below. The model analyzes a weak trough over northwestern Mexico. This feature does not show up in the analyses above 400 mb, nor below 700 mb, and it is thus hard to assess what exactly might be there. There has been substantial cloud cover and storm activity over northern Mexico the last two days, so something is likely there. The NAM forecasts this feature to move northward and be nearly over Tucson by midnight tonight. The NAM also forecasts most significant storms and rain to occur along the Borderlands this afternoon and evening. Considerable uncertainty present today.



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