BASIC PATTERN:
Large Scale Pattern –
- In the near term, we continue under the influence of troughing in the central Pacific, related to both the midlatitude sea surface temperature anomaly forcing (SSTAs) indicated by our IVTinit system, and also influenced by the Madden Julian Oscillation (MJO). Both the MJO and IVTinit influence the longwave circulation out 15-30 days, and affect the pattern and timing of day-to-day weather here in California and the west coast.
- In the latter part of August, in California it looks a little less hot and mostly dry. There is chance for above normal rainfall in southern California mountain and desert areas about 24-25th, and above normal rainfall in Arizona. This will be caused by a trough of low pressure near the California coast. S-SSW-SW flow around the trough will draw moisture from tropical cyclones, the Gulf of California and Tropical Pacific into Arizona.
- In September, there is a chance for showers coming into far southern SOCAL and to Arizona from the SSW-SW, with some rains into SE California as well, with focus on San Bernardino Co deserts eastward.
- The moist easterly flow from the Caribbean brings tropical waves and cyclones (possible hurricanes) across southern Mexico to Baja around Sep 1 and 9-12th. These regenerate into new tropical cyclones over the warm waters of southern Gulf of California and S Baja.
- During early Sep, and possibly again mid Sep, we should begin to see some upper lows and fronts bring rains into far NW California and the Pacific Northwest, as the westerlies start to strengthen and begin to migrate slowly south.
- For mid to late Sep and Oct, our maps (posted at the end of our PDF report), from the CFSv2 short term climate model predict warmer than normal conditions for California. S California has near or a little above normal rain in Sep, There currently is below normal rain in N California for Sep but a possible up-tick of rain within the first half of Oct. Southern California is a little wetter than normal in Sep, but near normal in Oct. A combination of cutoff lows and tropical moisture over central and S Baja California add some uncertainty to our Oct 2022 portion of this outlook in N/Central California.
- Precipitation Trend—through Sep 23....Most TSTMS will be focusing into S Nevada and Arizona. The next period of TSTMS would be about Aug 30-Sep 5. Thereafter, next period of rains is suggested by CFSDaily about Sept 19-22. There is a small hint of come possibly significant rains into N and Northcentral California mountain areas during the first part of Oct, but nothing more can be said about it at this time.
FORECASTS FOR CALIFORNIA
Forecast for Northern and Central California:
NORCAL Rains: Very dry thru Sep 14. Light rain 15-16 and 21-23.
CENTRAL CALIF Rains: Sep 14-16 (showers) and 22-24.
WARM SPELLS: Aug 25-26, 30-Sep 3, 6-10, and 15-18.
COOL SPELLS: Aug 27-28, Sep 5, 12-13 and 21-24.
Forecast for Southern California:
SOCAL RAINS: Aug 24-25 (SE areas), Sep 3-6 and 19-21.
SOCAL WARM AND HOT SPELLS: Aug 24-27, 29-Sep 6, 11-15 and 21-24.
SOCAL COOL OR COLD SPELLS: Sep 8-10 and 17-18.
Forecast for Central Sierra Nevada:
Dates of mountain showers-TSTMS (Central & S Sierra): Aug 31-Sep 1, 5-6 and 11-24 (heavier 18-22).
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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 August 14 – September 14, 2022
Highlights: Hot weather alternates with usual monsoonal TSTM conditions during August and early Sept. Watch for a possible tropical cyclone-associated heavy rain event that covers the southern deserts 24-25 Aug and in early Sept. The rains then drift north into southern and central Nevada, and the east slopes of the Sierras.
Looking Ahead – Long Range Outlook
September 26 – November 26... NORCAL and Central California coastal valleys, and Central Valley: Above normal temperatures will continue from late Sep thru Nov across most of the state. Near normal temperatures across northern California in Nov with seasonable to warm across central California. Latest CFSv2 Model solutions suggest an up-tick in rainfall about Nov 15-20, followed by a shift to above normal rainfall during the first 20 days or so of Dec 2022. This is a significant change, and it may be worth watching. Trying to specify rain dates for Dec this early is not reasonable, but we can certainly mention forecast trend changes in the CFSv2 and NMME when we see them.
For SOCAL mountains westward to coast: A bit wetter in Sep, especially 2nd and 3rd to 4th weeks of Sep occur in rain events that last 1-2 days. A dry beginning for Oct. What we have seen in the CFSv2 and our terrain-adjusted simulations for late Nov to early Dec are some interesting rain events for N and central California as far south as San Luis Obispo, but not yet anything of interest for SOCAL.
(Terms and Definitions Used In This Weather Outlook)
Alan Fox & Zane Stephens...Fox Weather, LLC
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