20220812

 Previous Forecast

A mostly quiet day for the lower elevations.  It was active over much of the northern 1/2 of the state and in Cochise County, including my house.  1.9" and pea-size hail.  My neighbor had 2.05".

The WRFRR was too active in central Pima County and had too much activity early over southwestern Arizona.  This has been a reoccurring issue during very moist conditions as well as model instability and crashing, thus the missing panel.  The 12Z WRFHRRR was the best run and has been the best this monsoon season.  

Discussion

The 500mb synoptic pattern remains unchanged with the anticyclone located over eastern Colorado.  The steering flow is quite weak over the state, but temperatures have decreased a little and are as cold as -8C at El Paso.

This seems to be the year of the upper-level inverted troughs.  Another is on its way from far eastern NM and may be a factor tomorrow.  Another unusual feature is the center of the 300 anticyclone, which continues to be centered over Nebraska.  ly, it has moved south by now, resulting in upper-level SW flow over Arizona, eliminating the issue with anvil shading.  

A weak surge continues over SW Arizona as dewpoints at Yuma are again at tropical levels.  PW is in the low 40s for SE Arizona and from 47 to 53 mm for Phoenix to Yuma.  MLCAPE has improved and is nearly 900 J/kg at Phoenix.    There is a shallow moist layer and inversion, but it should mix out with sufficient heating.  Mid-level subsidence inversions are also minimal.   A negative is that steering flow is generally weak, from the S or SE.  So, the good outweighs the bad for the Phoenix area.

Tucson is looking favorable as well.  900 J/kg of MLCAPE, and only a very shallow near surface inversion is present.  There is a bit of a subsidence inversion at 500mb, but relatively weak.  The LFC is also quite low, at around 700mb.  Like Phoenix, the negative is weak steering flow.

Initializations

This morning is a complicated situation wted deep convection underway around the Yuma area.  Quite a few clouds are present over southeastern Arizona due to a MCV.  GOES CAPE is also quite high, especially where convection has fired up.  The 9 and 12Z WRFRR had the right idea with the morning convection, but in the wrong location, too far to the north.  This error shouldn't matter too much to the rest of the state.  6Z HRRR didn't have enough clouds, as usual.  The 6Z GFS was better.  The 9 and 12Z RR were too cloudy from Phoenix to Tucson, and the WRF runs were slow to burn them off.  The 12Z HRRR was pretty accurate with clouds.  Most of the initializations had the SE AZ MCV as an open wave.  Better than nothing.  The 12Z WRFHRRR looks to be the best initialized run today.

Day 1

(some parts of)Arizona on the left, Gulf Surge on the right.

A weak surge continues to advect very moist air into the state.  Perhaps today is the day for Phoenix as the past few days have been capped, cloudy, or both.

A lot of 15C dewpoints at 850mb.  If/when storms get going, they will produce extremely heavy rain.  One problem is that the surge flow pattern is shallow. Thus winds at 850mb are light and variable with no good low-level shear available.

CAPE is moderate to high over much of south to north-central Arizona.  Flash flooding is likely, again, at mid to high elevations.

Widespread storms are underway over the higher terrain this afternoon.

It looks favorable forrelativelyms in Tucson as CAPE is quite high, steering flow improves, anvil level winds are weaker, and the PBL is mixed deeply, nearly to the morning's LFC.

Despite the favorable vertical profile, no run has much activity in Tucson proper.   Most keep activity near or over the higher terrain.  I disagree with that and think there will be more in Tucson.

The forecast vertical profile at Phoenix also looks favorable.  By late afternoon, the PBL is mixed deeply, a weak inversion is present, some low-level shear, and relatively weak anvil-level winds.  CAPE is also good, at ~1300 J/kg.

Unlike Tucson, where the mode runs were wishy-washy with activity, almost every run has significant storms for Phoenix.  The 12Z WRFHRRR looks the best as it develops activity to the N and E of Phoenix and the south.  This results in outflow boundary collisions right over the valley.  Classic.

The threat of flash flooding is high as some storms cloud produce over 3" of rain.  There will likely be a few locations with severe winds due to wet microbursts.

Day 2

The forecast is very dependent on what happens later today/tonight.   Generally, PW decreases somewhat; as is typical, the lower deserts are quiet after a previously active day.

As expected, CAPE is less over central and west central Arizona.  It's pretty high for the Pima County and Mojave Counties, so I expect those to be the active areas tomorrow.