20220715

Previous Forecast

It was an active day for many parts of Arizona.  A weak IT moved across NW Arizona during the afternoon, and PW was high, resulting in some heavy precipitation.  Storms developed in central and eastern Pima County and moved northwest into Phoenix.

WRF forecasts were generally accurate with locations and timing but didn't have enough precipitation in NW Arizona.  

Discussion

The center of the 500mb anticyclone has moved a bit to the NW and is located around NW NM.  As mentioned yesterday, a possible inverted trough was in the making, and one is now moving westward over the Big Bend area.  It's quite apparent in the WV imagery.

The trough responsible for all the NW Arizona Activity is over Las Vegas.

PW in central and western Arizona has remained about the same, around 35-45mm.  Southeastern Arizona has decreased and is around 30-35mm as dry air advection is occurring from southern NM.  The Tucson upper-air data indicates a fair amount of MLCAPE, around 650 J/kg, despite the slight drying trend.  Winds are mostly southeasterly up to 300mb where they are easterly, so there might be some issues with anvils.  It may be an interesting day around Tucson with the approach of the IT.

The Phoenix sounding has the green onion look indicating it's been worked over.  MLCAPE is only 220 J/kg.  They also have a low-level easterly flow, which may result in some dry air advection.  

Initializations

Clouds were initialized well, except for the 12Z RR.  It had too much coverage, along with too many showers and thunderstorms.  It really has struggled with situations like this.  The mid/upper IT seems to be initialized too weak by some, as, from satellite imagery, it has a closed circulation.  

Day 1

The IT moves slowly westward, and by afternoon, southeastern Arizona is on the nose of a weak jet, along with upper difluence and some divergence.  This will help organize and support storms.

The dry air from NM has made significant inroads into SE Arizona and is setting up another boundary over Tucson.  PW is relatively high from Tucson westward, so it's plenty moist.

850mb dewpoints are also supportive of activity from Tucson westward.

CAPE is impressive just west of Tucson, perhaps 1500-2000 J/kg.  This is the best setup for strong to severe storms thus far this monsoon season.

The 15Z WRFRR has low-level moist and unstable westerlies making it as far as Tucson.  The result is 11-1700 J/kg of CAPE.  It might be difficult to get deep convection to go in the lower elevations, but the surrounding high terrain is very likely to experience strong to severe storms.

All runs develop strong and severe storms across eastern Pima County by mid-afternoon.  The various RR runs have storms in or close to the valley.

The WRFHRRR runs have severe storms just west of Tucson.

Storms continue to propagate to the WNW.  Most runs have them dying out as they approach Phoenix.

Deep convection can't be ruled out for Phoenix as CAPE is around 1200 J/kg by early evening.  The wind profile is also good, with low-level shear and OK mid-level SE steering.  The PBL isn't mixed very deeply, but with some good outflows to provide meso lift, it could happen.

Day 2

I don't have much time to look, but it seems like a favorable situation for severe storms in far southern Arizona in the afternoon again.  Also, for the Phoenix area.