There was quite a bit of activity over southeastern Arizona yesterday and into the evening. As anticipated, WRF didn't have nearly enough storms in spite of a decent looking Tucson forecast Skew-T. Also, the forecast track of the significant inverted trough was poor as it moved up into southern Arizona rather than out along the Colorado River valley. It is responsible for the rains overnight and up till now.
There was really no good run. The WRFGFS was the least bad as it had marginally more precipitation.
I took a look at the HRRR 24 hour accumulated precipitation to see if it did andy better. It's similar to the WRF runs as there isn't nearly enough precipitation. Whatever is wrong with the WRF is also wrong with the HRRR.
The WRF also did poorly in Sonora where a large cluster of thunderstorms was present into the early morning hours. Some very high precipitation amounts were estimated by MRMS.
Initializations
It is a complicated situation this morning as a broad IT is located over southern Arizona into NW Mexico. Satellite imagery indicates the center of the IT is located north of Tucson, which is responsible for widespread clouds and a large area of showers. Note the -4C at Tucson!
All three have initialized the location of the IT well, but with varying intensity. The RR has up to 25-knot winds at 600mb which seems a little strong. All of the initializations have clouds initialized OK, and only the RR had sufficient shower activity. A big issue is going to be heating, so I checked how well the T@2m forecasts are doing and I was quite surprised to see that the WRFRR is 7F too warm at Phoenix. The other two forecasts have much better temperature forecasts so far this morning. RR and GFS PW initializations are generally accurate. It looks like the GFS initialized the best so the WRFGFS should be the better run today.
Day 1
It was sure a nice walk to work with all the clouds and temperatures in the low 80's. Unfortunately, the cool air and clouds are going to be an issue with the heating and with -4C at 500mb, it's going to be tough to get convection going. The Tucson 12Z sounding displays an "onion" type sounding with a modified surface layer, dry air from 850 to 700mb, and saturated above. Steering winds are not good as they are southwesterly as Tucson is on the backside of the IT. Phoenix isn't quite as modified, but only has 319 J/kg of MLCAPE.
A weak surge continues to advect moist air into the state with PW in the 40-45mm range this afternoon.
CAPE is very low and probably insufficient to support much deep convection except for the far eastern parts of the state. Saying that it doesn't take much to develop storms with the atmosphere so moist.
Model forecasts vary widely with the afternoon moisture/CAPE for Tucson. The WRFGFS has hardly any CAPE while the WRFRR and WRFNAM have quite a bit. The wind profile becomes mainly unidirectional from the south, which isn't very favorable.
There is a big difference with regards to late afternoon storm activity too. The WRFGFS hardly has any while the other runs are more active, but activity mainly remains over the higher terrain of southern Arizona. With the amount of CAPE forecast for Tucson, some storms may form late this afternoon or evening as outflow boundaries move through.
Day 2
CAPE is forecast to be extremely high along the border. This will support strong to severe storms tomorrow afternoon.
There is plenty of CAPE for the Tucson area, but winds are not favorable as the steering is out of the southwest. Plus, activity from the south will likely result in Tucson being covered by anvil clouds by later in the afternoon, suppressing deep convection.
The WRFRR does manage to move a few strong to severe storms into the Tucson area later in the afternoon anyway.
Phoenix has some CAPE, so it's not out of the question that there could be some activity near during the evening. However, no model forecasts predict any activity for the valley tomorrow.
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