Friday, June 08, 2018

Thunderstorms Again - Aletta Now Category 4

Afternoon thunderstorms in Cochise County again yesterday - third consecutive day. Looks like the summer thunderstorm season has already begun in far southeast Arizona. Image above shows CG flashes detected yesterday afternoon through midnight last night (from Atmo and Vaisala).

Hurricane Aletta (IR image above from 13 UTC this morning) has become a Cat 4 storm (sustained winds of 120 kt). Another example of how difficult it is to forecast strength of tropical storms - yesterday's NHC am forecast kept Aletta at and below speeds of 80 kt. The track forecasts have also been shifting somewhat to the north and east (am forecast below).

The global models continue to forecast that Aletta will trigger the first GoC moisture surge of the summer. The forecast of PW (valid at 5:00 pm MST on June 14) above is from the 06 UTC WRF-GFS run at Atmo - the push of low-level moisture into all of southern Arizona will be quite remarkable for early June, if forecast verifies. In response the same model run increases precipitation (below) and threat for dry thunderstorms, or more, over much of the state for same time period.

Forecast at bottom (from 00 UTC run of the ECMWF) is valid at 00 UTC on June 14 (500 mb left and surface right) indicates the storm (Bud) following Aletta to be approaching the south end of Baja!

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