2007

That interesting and rather impressive-looking upper level low currently spinning west of Baja CA is bringing some copious mid and upper-level tropical cloudiness to the southern half of CA. The models indicate that the low will bring significant to heavy precipitation to parts of the Baja Peninsula and possibly Arizona, leaving most of SoCal out of the loop once more. However, systems such as this one are notoriously hard to predict and the models already have shown inadequate modeling of the current entrainment of tropical moisture. So…some showers are certainly possible from about Los Angeles south Fri/Sat., with the outside chance of some convective activity. If the low takes a more northerly track than expected, some more siginificant rainfall could occur north of the CA/Mex. border; if the low moves south, it will take any chance of rain with it. In any case…the low will lift out of the region by later this weekend. Some mostly dry cold fronts will sweep south into NorCal over the next few days bringing windy conditions and much cooler temperatures as a result of cold air aloft (nearly -3C at 850 mb). A few showers are possible, mainly over the mountains and out over the open ocean on account of the steep lapse rates. The zonal jet breakthrough that has been progged for next week currently looks unimpressive, esp. for CA. A dose of moderate rainfall appears likely for far NorCal and possibly as far south as the Bay Area, but nothing spectacular will occur, and SoCal looks like it will stay high and dry once again. The 16 day deterministic model runs, in fact, show a very eerie pattern setting up–one where rain will be nonexistent, and pattern changes will be hard to come by. Hopefully next week’s rain helps at least a little bit up here. Othewise, NorCal may begin to see an exhanced wildfire risk in December. I don’t think I’ve ever experienced that before.