2009

Just a quick update this afternoon. Conditions have been relatively dry statewide over the past week, with only far NorCal seeing any significant precipitation (and even there, 7 day totals are below average for this normally very wet time of year). There will be a weak system tomorrow in NorCal that will probably produce wlight precipitation across far NorCal, with locally up to 0.50 inches in the northern mountains tapering to a few hundreths in the Bay Area, but in generally rainfall will be negligible to nonexistent. That will be the last opportinuty for precipitation, even in far NorCal, for quite some time–probably at least two weeks and potentially much longer than that. The culprit–a rather impressive ridge of high pressure that will anchor itself off the CA coast for the forseeable future–will bring very warm weather to much of the state for quite some time. One place that may stay dry yet languish under a layer of dense Tule fog may be the Sacramento Valley, where the strong temperature inversion aloft may prevent adequate mixing to occur. Therefore, while the southern parts of the Bay Area bask in 70-75 degree January weather and crystal clear skies, Sacramento may be stuck with highs in the 40-45 degree range and dismal misty skies all day. No matter what happens to temperatures, though, it will be dry everywhere. If this persists through the end of the month, we will have almost no chance of a normal season. We’re already in need of a Fabulous February, or a Miracle March. Hopefully, we’ll get at least one of the above…

One side note: La Nina, as has been noted by several experts in the past 48 hours, has not officially developed. The CPC has issued statements to the effect that La Nina conditions have developed in the equatorial Pacific, but SST anomaly amalgrams have not yet reached the official numerical threshold for La Nina. For all practical purposes, however, La Nina is back. It is still likely that La Nina will develop in a more “official” capacity later this winter.