Wednesday, July 06, 2016
Low level moisture is on the increase this morning and there will be a considerable upturn in thunderstorm activity this afternoon for southeast Arizona. The 12 UTC sounding for TWC is shown above. The PW is again above an inch and forecast CAPE for this afternoon is up around 1000 J/kg - quite an increase relative to yesterday. The wind profile is, however, a very negative factor, with mostly westerly flow and a chopped up profile below 300 mb.
The PW on the 5.4 km WRF grid is shown here from the o6 UTC forecast of the NAM version - top is at midnight last night and just below is valid at 6:00 pm MST this evening. The influx of higher precipitable water from the southern 2/3rds of the GoC directly into southeast Arizona is impressive.
At bottom is the forecast sounding for Tucson valid at 2:00 pm - also around 1000 J/kg.
The main forecast issue for the day is how west in Pima County will thunderstorm activity reach? The 06 UTC WRF forecasts differ some. The NAM version tends to keep storms just east and south of the metro area, with main action in Cochise County. The GFS version has activity extending out to the west of the metro area. Looking the forecast PW, I tend to go with the GFS version now, even with the poor wind profile. Will await Mike's discussion of the 12 UTC forecasts.
Posted by Bob Maddox at 7:37 AM