20200829 part 2

 Day 2

All the ingredients seem to be coming together for a major heavy rain event for many parts of the state.  It is a complex and unusual situation with the remnants of Hernan plus Iselle, moving slowly to the north, closer to the southern coast of Baja.  This location is favorable for the advection of additional moisture into Arizona.  It looks like it's going not just one, but two tropical systems to get it to rain in Arizona this monsoon season!

PW is about as high as it ever gets in Arizona with many areas exceeding 50mm!

The potential is certainly there as CAPE is very high.

The jet streak mentioned earlier is over northern Arizona, and theoretically providing synoptic scale lift in the vicinity of the right rear entrance region.

There is a weak inverted trough that moves into southern Arizona by tomorrow morning.  I'm not exactly sure where this comes from, but it seems to be the mid-level vortex left from Hernan.  The NAM sure sees it clearly.

There is no clear model agreement on when or where the heavy precipitation begins.  It's anywhere from 6am up until the early afternoon and from the Phoenix area, all the way to the Mexican border.

There sure are some crazy amounts of PW and CAPE.  Note that the mid-level circulation south of Tucson, apparently from Hernan, can be seen by the easterly flow.

Phoenix has a bit of directional and speed shear, thus some storms may be well organized.

Areas of organized deep convection generally move northward throughout the day.

Rain and thunderstorms continue into the evening.

With this airmass and the presence of some dynamical support, rainfall amounts are going to be extreme.  It will be great to catch up on the pathetic monsoon rainfall totals, but not to catch up in one event!  

Zooming up on Pima County indicates that some areas may see 4-6 inches of rain.  These amounts are likely at some other parts of the state too, especially in Maricopa and Pina Counties.