Arizona WRF Discussion: 20160809

Previous Day

Activity was restricted to far southeastern and eastern Arizona. The WRFGFS and RR runs were quite good. The WRFNAM had a bit too much activity over eastern Pima and other than that, not bad.

12Z WRFRR

Initializations
It's going to be a tough day forecasting as all previous runs missed the morning activity in SE Arizona. The 12Z WRFRR has very little activity this morning. The 12Z WRFNAM is a bit better as it at least has some activity over Pima county, but not nearly enough. The WRFGFS is terrible.

There is a broad 700mb IT located over far northern Sonora that is responsible for the widespread overnight activity in northern Sonora and now in SE Arizona. Oh yeah, and the 50mm of IPW at Tucson from Javier might have helped too. The 12Z NAM and RR have this feature initialized. Speaking of Javier, it seems to of taken a more westerly track and did not go into the GofC like a few of the runs from yesterday were saying. All 12Z initializations have it about right with location and intensity.

Remarkably, all 3 initializations have IPW initialized well.

Again, model confidence is low today. That saying, it seems that the WRFNAM has the best handle on activity. It's a few hours behind relative to actual events and much better than the WRFGFS.

Day 1
It's a bit hard to concentrate on the discussion this morning as a major flash flood event is underway in Tucson. The WRFNAM moves the morning convection slowly to the north and approaching Phoenix by mid-day.

IPW increases to around 50mm at Phoenix with a well-mixed PBL and a large amount of CAPE. Any outflow boundaries should set off deep convection at any time. Like Tucson, steering is very weak so storms won't move much once they form.

Very high CAPE is present over much of the southern 1/2 of the state (where it isn't convecting already).

Strong to severe storms over much of central Arizona this afternoon. The various model runs do keep the heaviest rain west of Phoenix, but with so much CAPE and outflows around, Phoenix could just as well see heavy rain.