30-Day Weather Outlook for January 14, 2018, to February 14, 2018
Summary- The MJO Cycle will be in its inactive phase until about 20-22nd. During the inactive phase, there will be support for more upper high pressure near the coast and into central California and S California, along with above normal temperatures. As the MJO becomes more active, we will see more of a normal increase in frontal passage through California, and at least a short period of seasonable rainfall during the last 9 days or so of January.
Support continues in the mid-latitude sea surface temperature anomaly (SSTA) field W of California for troughing at 140-145W, extending NE into Oregon-Washington coast and at times into N and northcentral California.
The El Niño Southern Oscillation (ENSO) continues in the cool (La Niña) phase. This leads to decreased energy in the subtropical westerlies, resulting in erratically moving cutoff lows near SOCAL and W Mexico.
For S California, warm sea surface temperatures are present to the west and southwest, but the La Niña pattern tends to discourage development of subtropical westerlies. Occasional lows and troughs develop in SOCAL as fronts move through central California.
In the Near Term – Jan. 19 – Feb. 1… In the southern California avocado growing areas, from San Luis Obispo County to San Diego County, we still have risk of warm and dry offshore flow with locally cold nights after mild or warm days. Best chances for rain will be on Jan 19th, 23-24th and 28-29th. A change to colder weather occurs from Jan 28th onward.
Summary – Feb. 2-14… In the southern California avocado growing areas, from San Luis Obispo south, rains will be mostly occurring in N California and the SierraNV. However, a cutoff low is always possible in such an erratic pattern, with some cold showers and low snow levels. Frosts and freezes will tend to be more frequent this period.
Seasonal Outlook / La Niña Update...Feb 15 – April 15… Latest solutions suggest continued cold and showery with low snow levels in the SierraNV during Feb, while coastal and valley areas are drier than normal from mid Feb onward.
Rains resume in March with some heavy rains possible in NW and central California coastal mountains, and N and central Sierra, with heavy snow in the central SierraNV and near Tahoe during March. Rainy and cold conditions possibly reach into Ventura and Santa Barbara Co’s.
In central California, the SierraNV has a better than even chance for above normal rain and snow, from about Placer Co to Madera Co in Feb, and across the entire Sierra in March. There is a chance for some frosts in the first week or so of April in coastal valleys, (Salinas/Pajaro/San Benito Valleys, Edna Valley, followed by a shift to warmer and drier than normal during April 8-15th.
For S California, there is support for a few cold Santa Anas in Feb, and accompanying wetbulb freezes. The first part of Feb is cold and mostly drier than normal in S California. The ensemble (NMME) model suggests more showers in the first half of March 2018 for the southern half of California. In April, SOCAL appears to turn warmer and drier than normal after 10th.
...Alan Fox, Fox Weather LLC...