As anticipated, not much storm activity for the state. There was a large MCS over southern Sonora last evening as well as another one yesterday morning. I'm puzzled why there hasn't been an outflow induced gulf surge yet.
The WRFNAM appears to have the best forecast for once. The other 12Z models didn't have enough precipitation while the 15Z WRFRR had too much over in southern NM, SE Arizona, and east of El Paso. I just happened to have a question emailed to me today why the WRFNAM has typically been the poorest performing model. A few years back, it was usually the best. I think the main issue is the non-assimilation of the GPSIPW data as I'm always mentioning how significant the errors are in the NAM initial conditions. I contacted NCEP about the problem, and the reply was that they had some temporary issue with assimilating GPSIPW data incorrectly; thus, it was turned off. Before they were able to fix it, the NAM was locked down, and no further changes were allowed, so the GPSIPW data was never turned back on. The other reason is that the RR (and HRRR) were updated last summer and to me, their initial conditions have improved. Before the update, frequently the WRFRR was the worst-performing model run.
Initializations
So much for the 500mb high center consolidating over southern Utah. There is a large area of near-constant heights and light and variable winds over Arizona and western NM. Empalme upper-air data hasn't been available for the past few day, and I hope they haven't run out of consumables. It's not apparent in the maps, but there is an IT just south of Baja which seems to be helping with deep convection over NW Mexico. A weak MCV is over the northern Gulf of California, which is responsible for some clouds and showers.
It is mainly clear over Arizona which was also initialized well except for the far south where there where cloud cover was too thick due to an area of convection over NW Sonora. The initializations have quite a strong MCV/IT initialized, but the satellite imagery doesn't show strong rotation. The NAM and GFS do have some moderate PW errors over Arizona and into NW Mexico. The favored run is the WRFRR, but the others should be OK too.
Day 1
Both the WRFGFS and WRFNAM are forecasting the start of a gulf surge. I was wondering where it was! PW is forecast to increase for much of southern Arizona throughout the day. I would think that the moist air is also going to be somewhat cooler and with the warm air aloft, we might be capped again.
There is a considerable difference between the model CAPE forecasts as the WRFGFS has around 3000 J/kg for parts of SE Arizona by this afternoon. The WRFRR has much less, 500-1000 J/kg. The WRFNAM is between the two and has some areas as high as 2000 J/kg. The difference is due to the amount of low-level moisture as the WRFRR has only dew-points of around 9C while the WRFGFS has 13 or 14C. It's hard to say what is going on as there is no operational GPSIPW station. The 15Z WRFRR just became available, and it's similar to the 12Z run.
All runs forecast the 500mb high center to consolidate over northern Arizona, which results in favorable E to NE steering flow over southern Arizona. However, 500mb temperatures are around -6 to -5C with even warmer air over in NM, unfavorable for deep convection.
Even with the enormous CAPE, the WRFGFS has only isolated storms around far SE Arizona this afternoon. Will WRF again have an issue with not forecasting enough deep convection? I don't know.
The surge makes its appearance by later in the afternoon as seen on the model forecast sounding with the increase of moisture below 800mb. CAPE increases resulting in around 700-1200 J/kg. The vertical wind profile also looks good with some easterly flow, low-level shear, and upper winds in a different direction from the steering flow. However, some sort of outflow is going to be required to trigger deep convection.
Storms develop farther west than usual, perhaps due to the hot mid-level air in NM. By late afternoon, thunderstorms are in the Tucson vicinity and east of Phoenix.
CAPE is looking rather anemic for Phoenix at only around 300-700 J/kg. However, the other night, CAPE was only around 700 J/kg, and this was sufficient. The wind profile is very good, like in Tucson.
The convective planetary boundary layer is quite deep and displaying a significant inverted V pattern. Strong outflow winds move toward both Tucson and Phoenix during the later afternoon hours. Will the lift provided and CAPE sufficient for storms?
The 15Z WRFRR manages to only eke out a few showers and weak storms. There may be more activity for both cities than depicted as WRF has been having issues with not enough convection in situations like this.
What I'm concerned about is the forecast of strong southwesterly winds associated with the surge interacting with the outflows from the north. Seems to me like a classic outflow intersection situation to me and with some CAPE, I don't understand why there aren't more storms. (or any!)
Day 2
The MCV/IT is responsible for a lot of morning cloud and showers, which may significantly reduce heating. A weak surge continues to advect moisture into the state, so that isn't a problem.
Temperatures at around -5C are going to be a problem though. Steering winds are also quite light over eastern Arizona.
Storms are restricted to mainly the higher elevations of eastern Arizona.
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