30-Day Weather Outlook for October 2, 2017, to November 2, 2017
Summary- Troughing will continue in the central Pacific with fronts approaching Washington-Oregon, with rain. For California, including the north, continued drier than normal overall with recurrent dry windy events, interrupted by windy cold fronts with scant or small precipitation through October 19th.
Support exists in the sea surface temperature anomaly (SSTA) field for a long wave trough in the central North Pacific near 150W, an intermittent storm track extending east into the Washington and the Oregon coast and S British Columbia. These subtropical rains will have difficulty reaching N California.
High pressure will extend from the E North Pacific 130W to the N and central California coast. Cold fronts coming south from Washington move into the Great Basin, mostly bypassing California. This will produce a tendency for offshore flow in N and central California and coastal eddies in S California. Some Santa Ana winds are possible also in S California on a few brief occasions.
Rains appear to develop during October 19-25th into N and northcentral California.
In the Near Term – Oct. 6-20… In the southern California avocado growing areas, from Santa Barbara County to San Diego County, a marine layer with coastal eddy occurs on October 5-6th, then breezy or windy, with locally cold early mornings and warmer days on the 7-9th. A deeper marine layer is possible with coastal drizzle on the 10-12th.
Summary – Oct. 21 – Nov. 3… In the southern California avocado growing areas, from San Luis Obispo south, persistently dry and mild days and cool or cold nights are suggested for this period. For southern California, we will start to see the alternation between Santa Anas and marine drizzle events. However, it also means a greater potential for some cold nights with wetbulb temperatures dipping into the 30s in late Oct and around the first of Nov.
Seasonal Outlook / La Niña Update...November 4 – December 31, 2017… November still appears to continue the drier than normal trend in N and Central California, and drier than normal in S California. The best chances for rains or showers in Nov are usually the 10-20th, and again around 28-30th. Our CFSDaily guidance currently suggesting a rainy period for November 5-11.
Dec still looks wetter than normal for N and Central California. A period of heavier rains and storm events often occurs during December 18-23rd and 27-30.
Southern California also appears to turn wetter than normal during Dec in Santa Barbara and Ventura Counties.
In agreement with the current La Niña, there is suggestion of colder and wetter than normal conditions developing for California in mid to late December, followed by a very dry spell through most of January, 2018.
...Alan Fox, Fox Weather LLC...