Thursday, July 06, 2017

Gradual Changes Continuing

The northwest portion of the Burro wildfire was burning actively yesterday afternoon, producing significant smoke over the Catalinas by evening.  Early this morning there was still some active fire, resulting in a small smoke column that became laminar with waves as it advected to the southeast. Photos above and below show this during about 15 minutes before sunrise. Conditions will be hostile again today with very high temperatures and increasing east winds at the fire location - but RH continues to slowly increase. 

Above graphic shows 24-hour CG flash density (from and Vaisala) for period ending at 07:00 am MST this morning. Little storm activity over Arizona, with most significant storms occurring over Sonora, as per the IR image below from 0600 UTC last night. The storms did reach westward to the northern GoC, enhancing the diurnal circulations and helping increase low-level moisture. The northern complex produced outflows that reached into southeastern Arizona.
The convective outflows passed by: Nogales about 06:30 pm; Ft. Huachuca and Yuma about 10:00 pm: Sasabe about 10:30 pm; and Tucson about midnight. All of this (heat low, diurnal circulations, and outflows) are fairly typical for a slow-onset monsoon.

Sounding plot for Tucson (above) this morning shows the moisture increases have brought PW up to 30 mm, however, little CAPE has developed at low elevations and afternoon BL mixed moisture has been only in the 6 to 7 g/kg range. Morning skewT plot for Phoenix below continues to be a dismal one.

The 500 mb anticyclone has shifted northward into southern Utah, where heights have built to nearly 6,000 m! This has resulted in strong, mid-level easterlies over southern Arizona. Temperatures at 500 mb have begun to increase, and temperatures of ~ -5 to to -7 C are advecting southward around the east side of the high.

The 06 UTC run of the WRF-GFS at Atmo forecasts little precipitation through midday on Sunday (above). Model forecasts highest amounts in the White Mountains and rim country, while storms across southern Arizona tend to be high-based and likely producing gusty winds and dry lightning.

However, the longer range model forecasts shift the 500 mb anticyclone eastward toward Colorado and Kansas. GEFS average and spaghetti forecasts below are valid at 144-hour from 00 UTC last evening (00 UTC on July 12th). This shifting allows several inverted troughs to move westward across northern Mexico and the Borderlands by midweek. The pattern shift also allows the next eastern Pacific TS to move on a more northward track. These changes should bring better low-level moisture and CAPE, allowing much increased storm activity. 

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