BASIC PATTERN:
Large Scale Pattern –
- In the near term, we continue the influence of troughing in the north-central and northeastern North Pacific, related to the midlatitude sea surface temperature anomaly forcing (SSTA) patterns, indicated by our IVTinit™ system. The Madden Julian Oscillation (MJO) also currently adds a contribution, in the form of a stronger trough in the mid north Pacific (32-45N). Both the MJO and IVTinit influence the longwave circulation out 15-30 days, and affect the pattern and timing of day-to-day weather in California and the Pacific Northwest.
- In mid Oct – 13 Nov, rainfall continues below normal in central and south parts of California. Temperatures are well above normal in all of California during the rest of October, and continue persistently warm through Nov. There is good agreement from both models for above normal rainfall in central and N California, while S California is near normal for Nov. Arizona has had some good rains in early Oct. The rain in Arizona will be diminishing, but will be shifting to above normal in Nov.
- Mid Nov – mid Dec…it looks wet in central and northern California. The heavier rains begin in NW California first in late Oct and Nov per the CFSDaily and FoxCFSDailyAI™. Rains appear to spread south about the end of Nov through most of Dec. However, snow levels in Dec will continue unusually high, so the heavy rains will not help the snowpack or prospect for long term storage in Dec in Sierras.
- During Jan 2023, we return to near normal temperatures, but without the rains. The emerging pattern in Dec and Jan suggests that atmospheric rivers in Dec, followed by a more normal winter-type regime of showery cold front and the Usual snow levels reaching down to 3000 ft in the Sierras and NW California to the Bay Area.
- The only maps for Feb 2023 are from the NMME model. It appears that Feb returns us to drier than normal, but with frequent frost/freeze events, i.e. cold and dry. The risk of freeze will tend to have the greatest impact on central and S California agriculture, where frost-sensitive crops are grown, and will be starting their spring bloom cycle. So, places like the San Joaquin Valley (citrus), and Santa Maria/San Luis Obispo (winegrapes) in late Feb may see a larger impact.
- Precipitation Trend in California — Oct 15 – Nov 15 — Oct 22-26, Oct 31-Nov 1st (showery), Nov 2-4, Nov 7-10 and possibly also 14 per the CFSv2 short term climate model. The usual climatological trend gives us a good chance for rains in Nov during 16-23.
FORECASTS FOR CALIFORNIA
Forecast for Northern and Central California:
NORCAL Rains: Oct 22-26, 30-Nov 3 (shwrs),Nov 8-10, Nov 14, and Nov 15-23.
CENTRAL CALIF Rains: Oct 18-19 (S areas), 20-21 (S areas), Nov 9-10 and Nov 16-23.
WARM SPELLS: Oct 18-21, Nov 3-7 and Nov 10-15.
COOL SPELLS: Oct 23-25, 28-Nov 1, Nov 9-10 and Nov 16-19.
Forecast for Southern California:
SOCAL RAINS: Oct 15-17 (shwrs), Oct 18-19 (shwrs), Oct 21-23 (shwrs), and Nov 18-22.
SOCAL WARM AND HOT SPELLS: Oct 20-21, Oct 25-29 and Nov 3-15.
SOCAL COOL OR COLD SPELLS: Oct 19, 22-23 and Nov 17-23.
Forecast for Central Sierra Nevada:
Central Sierra Nevada Precipitation: Oct 18-19, 21, Nov 2-3, Nov 8-9 and Nov 16-19.
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The listings of dates normally included for hot and cold spells, and precipitation are very approximate. They are based on our CFSDaily and CFSDailyAI products; and present expected trends in precipitation and temperature (CFSDailyAI) to 4km. Our system gives some consideration to terrain and coastal influence. We consider the CFSv2 as one of the better ways to represent basic weather down in the sub-monthly time scale beyond the 15 –day GFS or monthly maps from CFSv2 or NMME.
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Southern California Deserts Outlook for October 15 – October 31, 2022
Highlights: This has been an active season for thunderstorms and rains in the southern deserts. It’s getting late in the tropical cyclone season now or Baja and Western Mexico. There will continue a tendency for troughs coming into north-central California to split apart, then secondary troughs intensifying near S California as active fronts or upper lows with thunderstorms. For the southern deserts, therefore, the season for tropical cyclone moisture is drawing to a close. In Nov, tropical cyclones focus mainly along Nayarit, and the southern Mexico coast Zihuantanejo and Manzanillo to the state of Michoacan.
Looking Ahead – Long Range Outlook
November 16 – December 31... NORCAL and Central California coastal valleys, and Central Valley: Above normal temperatures will continue through Nov across most of California, due to warm nights. The warm October is followed in Nov by a burst of above normal rainfall from the Bay Area north to Oregon, as well as interior N California, with near normal rainfall for central California. An expected up-tick in rainfall about Nov 16-23, is also warmer than normal. This combination suggests a persistently high or higher than normal snow level during the early season rains in Nov to first part of Dec. If a persistent trend for higher than normal snow levels occurs during the robust Nov – Dec rain periods, present a challenge for water supply and storage management during storms.
For SOCAL mountains westward to coast: Although cutoff lows may develop on occasion to bring rains to Southern California, the supply of water will be heavily dependent on strategic planning of water storage in Northern California and
Sierras. Despite some good early season rains that may occur, the challenge to make up for lack of Sierra snowpack water storage will continue to be an issue through this winter.
Alan Fox & Zane Stephens...Fox Weather, LLC
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