Friday, February 01, 2013

First day Of February In Tucson


February dawns with beautifully clear skies here in Tucson and southeast Arizona. Low temperatures here in the north part of the city are again in the upper 20sF, so it's quite chilly out right now. Low at house was 28F and there is frost out there on roofs and cars, but it will warm up quickly.


The main forecast problem today and tomorrow will be the timing of high-level cloudiness coming by from west and southwest of Baja. Above is the water vapor image from 6 am this morning, showing a very large area of middle and upper-level cloudiness from south of 10 degrees north to about 30 degrees north.


The MIMIC blended precipitable water (above, from CIMSS in Madison, Wisconsin) for the eastern Pacific shows that PW values are low north of 20 degrees latitude (except far to the west). This means that the clouds of interest for the Southwest are high and that low-levels are dry. So, the main forecast impacts today and tomorrow will be the timing of cloudy periods and their impact on temperatures. Will look at the WRF-GFS forecast of OLR in next post.

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