30-Day Weather Outlook for February 19, 2018, to March 19, 2018
Summary- The MJO Cycle was in another maximum on Feb 18-19th. The expected increase in the number of frontal passages has occurred, and precipitation amounts started to increase in the Sierras (snow).
Support continues for a westward relocation of troughing from 115W to about 130-140W over the next two weeks.
As the focus of troughing relocates westward, wetter conditions will develop along the California coast and higher rain amounts will focus into northcentral and N California during March 5-15.
The El Niño Southern Oscillation (ENSO) continues in the cool (La Niña) phase. This continues to support decreased energy in the subtropical westerlies from about 140W in the Pacific to S California.
In the Near Term – Feb. 23 – March 10… In the southern California avocado growing areas, from San Luis Obispo County to San Diego County, after frosts on Feb 20-21st, the next chance for showers occurs on the 22nd. After some frosty mornings on Feb 25th and 26th, more rains are suggested in the extended range model solutions for the 28th – March 4th and about March 7th. This appears to be a breezy, cold and rainy period with snow in the mountains.
Frost occurrence will continue mitigated some by unusually warm sea surface temperatures near the coast of central and S California.
Summary – March 11-25… In the southern California avocado growing areas, from San Luis Obispo south, this period appears to have a chance for rains or showers overall in SOCAL.
A drier and warmer period appears to develop during March 12-17th. Moderate rains are currently suggested by our CFSDailyAI system for March 18-23. These also potentially affect both Ventura Co (fire burned areas of Ventura City and foothills), and SE Santa Barbara Co mountains (Montecito).
Seasonal Outlook / La Niña Update...March 25 – May 25… Latest solutions suggest another rain in California, including both N and S portions of the state about the last week of March. Otherwise, near or a little below normal rainfall is suggested by consensus of cFSv2 and NMME for the last week of March. April turns sharply warmer and drier per both NMME and CFSv2 solutions.
As mentioned in previous reports, unusually warm sea surface temperatures west of central and S California have been inhibiting the usual occurrence of cold and frosty nights in midwinter, with exception of the current cold spell from Feb 18-26th. This trend may redevelop in late March and middle of spring frost season for NW California vineyard regions. The main issue of concern that begins to develop in the long range guidance (CFSv2) is unusually warm conditions in late April, followed by a hot May.
In central California, there is a chance for rains in the first week or so of April in coastal valleys, including Salinas, Pajaro, San Benito Valleys, and Edna Valley. A shift to warmer and drier than normal is suggested during April 12-25.
For S California, the ensemble (NMME) model suggests showers then some cold nights in SOCAL during late March – early April. After the first week of April, SOCAL appears to turn warmer and drier than normal.
...Alan Fox, Fox Weather LLC...