Sunday, September 11, 2016
Tough Forecast Today
We have been away at Santa Rita Abbey since Friday afternoon - so a bit of catch-up here. Photo above is looking south from the Abbey a bit before 4:00 pm MST yesterday. Showers were bubbling up and down, and some produced bits of anvil and some light rain. The 24-hour flash density map (below from weather.graphics and Vaisala for 24-hours ending at 7:00 am this morning) indicates no CG flashes with this storm, and I saw none.
Regarding runoff for the Newton rains - I've added a new stream flow plot from the USGS gauge at the Rillito and Dodge, second below. The second pulse of runoff on Thursday, while not very large, did produce flow downstream from the gauge and past the Campbell Ave. bridge. The second pulse was probably from higher elevations and from greater distances - still little runoff from a fairly significant, widespread precipitation event.
We remain in the persistent pattern of a weak 500 mb trough affecting the Southwest - above analysis is from NCAR RAP/RAL for 12 UTC this morning.Of interest are the cooler temperatures in the trough beginning just out west of here.
The morning sounding plot for TWC (from SPC - below) indicates CAPE values of possibly 500 to 1000 J/Kg later today - if moisture remains at current levels. However, the 06 UTC runs at Atmo of the WRF model forecast PW and CAPE to decrease by early afternoon (forecast skewT at bottom is from the WRF-NAM and is valid at 3:00 pm) and both models fore today's storms to stay east and south of the metro area's lower elevations. The morning sounding has PW of 32 mm but the WRF forecast sounding below has only 23 mm and no CAPE. With colder air possible at mid-levels, perhaps we'll we'll see something a bit between conditions this morning vs the WRF forecasts?
Posted by Bob Maddox at 7:57 AM