Wednesday, September 21, 2016

The Paine Lingers Mostly As Low-Level Moisture And Mid-Level Heat

The NHC issued its last advisory on Paine at 8:00 pm MST last evening, as the storm had rapidly crashed, much as they had predicted. No rain here from Paine, and the WRF-GFS two days ago was very good with its forecast keeping Paine's precipitation swath far to our west. The IR image above is from 14 UTC and indicates only low, warm cloudiness left in area where Paine's remnant circulation is (northern Baja). However, the CIRA blended PW analysis (below for 12 UTC) shows a large pool of high PW air extending northward over the lower Colorado Basin and eastward to El Paso. Forecast question for the last day of astronomical summer is whether or not there will be enough CAPE this afternoon to fuel thunderstorms over parts of southern Arizona.

The SPC skewT plot of TWC sounding data from 12 UTC looks very promising (above) - PW of 1.60", substantial CAPE, and a nicely veering, Plains-type wind profile. However, the 06 UTC WRF forecasts from Atmo do not indicate anything across southern Arizona this afternoon, except short-lived, small storms that are very isolated. The models forecast decreasing PW and CAPE diminishing due to warming in middle levels. So, the models forecast that all that low-level moisture out there will go for naught. The forecast soundings for early afternoon in both versions, however, do look a bit more favorable for storms than the forecasts indicate - can only watch and see what the mountains are able to boil up later.

Unfortunetly, Paine has also left behind a large pool of warm, middle-level air within the core of a rapidly weakening short wave at 500 mb (the remnant short wave is actually the melded result of Paine interacting with the pre-existing cyclone that had been present to its north - destructive interference in action. Shown here are 06 UTC WRF-GFS forecasts for 500 mb winds and temperature - above valid at 6:00 am this morning and below valid at 6:00 pm this evening. The forecasts indicate continuous warming at 500 mb over Arizona through the day, which acts to cap deep convection, especially at low elevations. So it goes - good riddance Paine.


  1. I heard on the radio that NWS Phoenix has 40 POPs for tomorrow! WRF has little or no activity. They must of been suckered by the high IPW and didn't see the warm mid levels.

  2. Looks like the 12Z WRFGFS does break out a few storms around Phoenix tomorrow afternoon after all.