Tuesday, June 16, 2015

High-Based June Thunderstorms - Part II

A number of years ago I used to do subjective analyses of the standard level charts on most days of the summer. Haven't had time for that in recent years, but I took the time this morning. Chart above is my quick analysis of the 12 UTC 500 mb observations. A fairly classic summer pattern is in place with an anticyclone located to our north-northeast. The air within this anticyclone is cool and also moist - a situation that is actually better than many days that occur later in the summertime. There is a substantial inverted trough from the Big Bend Country that extends to the south end of the GoC - this should be pushed a bit westward as "Bill" comes ashore in south Texas. However, it will have to do battle with a weak trough over the lower Colorado River Basin.

At 700 mb (12 UTC analysis above) moist air covers most of New Mexico and is trying to advect westward, but again the two troughs are butting against each other. Very hot and drier air dominates over Arizona. At the surface (below is analysis for 8:00 am MST this morning) moist low-level air is mixed deeply enough to be advecting westward across the Continental Divide to the north of a weak, backdoor front. The moisture gradient is fairly strong from Deming west to Tucson area. Some low-level moisture is also sneaking north up the river valleys in northern Mexico that are to the south of Cochise and Santa Cruz Counties.

The two 12 UTC soundings here are from El Paso (above) where PW is a fairly healthy 31 mm and from Tucson (below) where PW is 22 mm. Although the 500 mb pattern is favorable, the BL is very deep here at Tucson. I have modified each sounding for conditions during mid-afternoon, assuming little adevtion, with heating and BL mixing dominating. The El Paso sounding exhibits CAPE through a deep layer; however, the Tucson sounding is quite anemic. Steering flow around Tucson would be from the north, if storms were to develop over the Catalinas. Storms have little chance of moving into low elevations - unless cooling occurs in a layer around 400 mb or a considerable increase in BL moisture makes into low elevations.

I would say that winds and dust are most likely here in the metro Tucson area, with thunder and even some showers over higher terrain between here and New Mexico. 

1 comment:

  1. Nice to see a thorough hand analysis of all the crucial features. Yes, I also did a daily analysis like this up into last summer. It goes well after a brisk (pace not temperature) morning walk and with a cup of coffee. Very therapeutic and enlightening. Up here along the southern edge of the Sonoran foothills in northern Maricopa County spring has brought good rains and some thunder: YTD rain is 6.86inches and 3.17inches during the past 60 days. This year's summer monsoon will be quite unique as the recent and current atmospheric circulation is far from average. More later, Jack