Tuesday, June 30, 2015

Moisture Prevailed Yesterday - Sunrise Storms This Morning

A small MCS has been moving westward across the Borderlands this early morning - as per 1330 UTC IR satellite image above (another is also active in northwest Sonora). Composite radar below from TUS is for 1300 UTC. When I walked before sunrise skies were very dark to the south, but I saw no lightning flashes. When the sun rose there was a partial morning rainbow - no camera unfortunately. Regardless, this morning thunderstorm activity throws a monkey wrench into today's situation.

Yesterday the moisture hung in over eastern Pima County and by evening there was a surprisingly high amount of CAPE detected by the evening sounding - over 1500 m2/s2. This helped support several severe thunderstorms just to the south and west of the metro area. It was a very unusual situation since these storms produced large hail rather than the expected downbursts - see SPC report plot above and the Kitt Peak webcam shot of hail falling at the observatory. 

Given the unusual morning storms, I am showing two CG flash charts (from Atmo/Vaisala). The plot above shows widespread activity yesterday through 07 UTC. The back edge of the storms was again close to the western boundary of Cochise County, with more intense lightning storms indicated north to west to south of the metro area. There were several thunderstorms that impacted northern Maricopa County, and I see that Sky Harbor airport in Phoenix reported 0.05" of rainfall. The plot below shows CG flashes though 13 UTC this morning and is focused on the early morning MCS activity - the warm colors (orange to white) essentially show flashes that occurred after midnight.

The two periods of storms makes for a complicated situation across the ALERT network. For the 24-hours ending at 7:00 am MST this morning, 53 of 92 sites had rainfall (nudging out yesterday for highest coverage so far this summer). However, 17 of these sites had all or most of their rainfall during the past 6-hours as the morning MCS moved across southern portions of the network - for example, at Tubac 24-hour rainfall was 1.22" (most in network) but with 0.94" of that during past 6-hours.

Here at the house we had thunder again and a shower before dark that produced 0.06". The last week of June has a chance to produce thunder here every day. But what happens today is a difficult forecast. The WRF runs at both 00 and 06 UTC did not forecast the morning MCSs at all and their forecasts can not be given much weight for this afternoon.. The morning TWC sounding reflects mostly the mesoscale environment of the MCS and is likely not representative of the larger-scale. I'll take a closer look at the morning observations to try to get a better feel for what the afternoon might bring. A special noon sounding from the NWS would certainly help clarify the complicated situation!

No comments:

Post a Comment