20190906

Initializations
The overall synoptic situation hasn't changed much as the center of the 500mb anticyclone continues to be over northern New Mexico accompanied by -6 to -3C temperatures.   The first in a series of troughs is coming onshore over the NW CONUS.   A broad IT appears to be located over NW Mexico as well as considerable clouds and moisture from the tropical system that moved inland south of Texas.   The Chihuahua Mexico sounding is interesting as it's nearly saturated, but little or no CAPE so in spite of all the moisture, there is little to show for it.   

Model initializations look accurate except the RR series has the morning clouds around Tucson, initialized too far west.  The 6Z GFS and 12Z NAM were more accurate.  Maybe that error will matter today, perhaps not, as deep convection may not form no matter how much heating occurs.  RR PW initializations are very good.  The NAM wasn't too bad except for over in southeastern NM. 

Day 1
PW has increased significantly over southern Arizona as PW is now almost 40mm in Tucson.  It is very moist over northern Sonora as well.  The forecast is for moist air to remain over much of the state today.  Part of the increase is from the old tropical system, and the other is just moisture trickling in from Sonora.

CAPE is forecast to be high to very high over western Arizona again, kind of reminding me of the other day when there were big storms out there.

I just looked at the RADAR reflectivity forecast for the various runs, and there is no deep convection, in any run, except for a little in the WRFGFS.

The forecast Skew-T indicates a strong cap in place at the top of the PBL.  The potential is certainly there as CAPE is around 1500 to 2000 J/kg and the PBL is mixed fairly deeply (for Yuma).

The situation isn't much better farther to the east as Tucson's PBL isn't mixed deeply at all and CAPE is only around 5-600 J/kg.  The vertical wind profile has a bit of shear, but steering is light.

A few storms may pop up near Tucson later this afternoon. 

Day 2
So, the reader is probably wondering "why bother with a discussion today"?  Well, tomorrow looks to be more active, mainly over southeastern Arizona as moisture remains.
At mid-levels, temperatures cool slightly as a second in a series of troughs moves into the western CONUS.  It's the beginning of the end of #nonsoon2019 as we move into transition season.

There is more storm activity over eastern and southeastern Arizona by later tomorrow afternoon.

 
Tucson's Skew-T is unimpressive with only limited CAPE and a poor wind profile; thus, most storms stay over the high terrain.

The WRFNAM and 15Z WRFRR do manage to develop a storm or two in the Tucson area by early evening.  It is unlikely that I will be writing a discussion tomorrow as I'm traveling.