20220808

 Previous Forecast

It was a complex forecast situation due to the previous night's MCS, which left behind a modified lower troposphere.  The runs previous to 12Z were all going crazy for storms in and around the Phoenix area, while most backed off.  Only one rogue (severe) storm managed to move off the high terrain towards Phoenix.  The Tucson area and east of there saw a lot of action.

Despite getting Phoenix mostly correct, the runs struggled in southern Arizona.  They all had too much activity west of Tucson and not enough to the east.  In fact, a thunderstorm over in NM has knocked down the powerline to the Portal Paradise area, and I've been without power for over 12 hours.

Discussion

The 500mb ridge dominates CONUS, which is amazing.  One center is over the Four Corners and is providing optimal easterly steering flow.  Temperatures are moderate at -6 to -8C over the southwest. 

 There is a mid to upper-level IT located over the far northern Gulf of California. As it moves west, it will probably provide some stabilizing influence on Arizona's atmosphere.  The parade of ITs continues as another is moving onshore south of Brownsville.  This has been one of the best years for ITs in quite a while.

The Tucson 12Z sounding is the definition of "worked over."  MLCAPE is essentially zero, and the wind profile is unidirectional all the way up.

Phoenix doesn't exhibit the capping inversion and has a fair amount of MLCAPE, around 800 J/kg.  It's also moist with PW about 44mm.  An outflow-induced Surge is underway over southwestern Arizona, resulting in a dewpoint of 77F at Yuma!    The bad news is flow is light and variable below 500mb.  So, it is a mixed bag for today.  If (and it's a big if) there can be decent heating in and around Phoenix, perhaps a shot.  Tucson, probably not, at least during the afternoon and early evening.

Initializations

Besides all the clouds, there are some showers and weak storms ongoing.  An MCV is located over northwestern Arizona, while the larger IT spins south of Puerto Penasco.  There also appears to be another MCV just south of central Pima County.

None of the pre-12Z initializations had anywhere near enough clouds.  Both the 12Z HRRR and RR were mostly accurate.  They both had that MCV in far northern Mexico, but had the NW Arizona MCV as an open wave and too far south.  Either the 12Z RR or HRRR should perform well today.

Day 1

The brief outflow Surge ends by afternoon, but copius amounts of moisture remain over much of the state.   Despite downsloping flow, it's also moistened up over southern NM.    There is a bit of a low-level convergence zone over Cochise County, which may or may not help convective initiation.

850mb dewpoints continue to be juicy over central and southern Arizona.  

CAPE is quite high over Maricopa and western Pima Counties and up towards the higher terrain north of Phoenix.  Will storms be able "break on through to the other side" when the move into the Phoenix area this evening?  CAPE is also moderate over far SW NM and far SE Arizona.  Hopefully my power isn't going to go off for 12 hours again like it did last night.

Both the WRFHRRR and RR generally agree that storms form over the higher terrain and move to the west.  That's the easy part.

There is some trouble in store as the storms make their way to Tucson.  There is a strong subsidence inversion at 500mb, and the PBL isn't mixed very deeply.  The plus is the wind profile is much improved with good steering, low level shear, and weaker upper-level winds.  If storms can generate good outflow boundaries, they will be able to propagate into the lower elevations.

The WRFRR has strong storms in Tucson this evening, but the WRFHRRR skips them over the city proper.  IMO, either could happen.

The WRFHRR looks bad for Phoenix as it forecasts only 900 J/kg plus the mixed layer only goes to just above 850mb.  The WRFRR at least gives Phoenix a chance as it mixed deeper and has more CAPE.

Somewhat surprising is that the WRFHRRR has a little big of activity for Phoenix this evening.  The WRFRR kills of storms as they move into the lower elevations of Phoenix.

Day 2

You don't see this everyday!  Monsoon moisture makes it all the way Seattle tomorrow, thanks to the cutoff low off the coast.  Howard appears to be close enough to Baja to trigger a traditional Gulf Surge, along the entire length of the GofC.

The hotspots appear to be in and around Yavapai/Mojave Counties and southeastern Arizona.  SW Arizona may even have some action.

Both runs have storms in Yuma county tomorrow afternoon.  Maybe this is there one big event of the summer?  It seems they always get their entire summer's amount of rain from one event.

It's always risky forecasting out a day ahead, but saying that, the Tucson area seems to have another good chance for storms.  It's too hard to say for Phoenix.

The 250mb forecast does indicate weak difluence/divergence over far southern Arizon and into Sonora as an upper-level IT is located over Chihauaha.