2009

Just a quick update this evening. A glance at the satellite imagery of the E Pac indicates a much more active than usual setup. Moisture from former TS Dolores and from convective complexes over the Sonoran desert is moving up the CA coast and has now reached the Bay Area. Occasional showers and possible thunderstorms continue to pop up in this plume, and I would not be totally surprised to see isolated showers or thunderstorms anywhere in the state over the next 24 hours or so. Mountain and desert areas are likely to see more widespread activity, as usual. Also of note are the very hot temperatures inland across the entire state. Widespread 100-110 readings in the Central Valley have occurred for five consecutive days, with similar readings over much of SoCal away from the immediate coast. Readings in the 110-120 degree range have been widespread in the deserts, with Death Valley clocking in in the 120-125 degree range (with overnight lows in the 100-105 range). This heat will continue for at least another day or two before subsiding somewhat towards the middle of the week (though temperatures are still expected to be well above average inland).

This is where things get even more interesting. The models have been indicating the potential for a very strong high pressure area to build into CA from the SE beginning around day 5. Flow aloft begins to back to the S/SE and then E/SE later in the week, transporting very hot and rather moist air from the deserts and the Gulf of California into the state. Some GFS runs are bringing 850 mb temps over 30 C during the peak of the upcoming heat wave, even surpassing 33 C on the 12z. This would bring record-breaking high temperatures to many areas, which is especially significant because this is climatologically the hottest part of the year. In addition, surface dewpoints will be on the rise during this event, and this may have the combined effect of bringing convective chances to the lowlands and also making heat indices even higher. This has the potential to be the most significant heat event since 2006, but may be significantly more prolonged (especially considering the present magnitude of the heat already ongoing). Stay tuned…