30-Day Weather Outlook for August 7, 2017, to September 7, 2017
Summary- In the basic pattern high pressure continues for S Oregon and N Calif to Idaho. Because there is abundant moisture in this storm track, significant rains are possible in Washington State and SW British Columbia. Upper low pressure near S Calif and N Baja gives more support for rain and TSTMS in central Calif and the SierraNV, but produces drier SW flow (more stable airmass), which tends to depress TSTM activity intermittently in SOCAL and W Arizona. Tropical cyclones should become more active again later this week and into mid Aug, to the W and SW of Baja. Warm SSTAs remain over the region near and west of Baja. This will provide a good energy source for developing tropical cyclones that move past S Baja. The warm sea surface will tend to support stronger tropical cyclone energies as they continue to the NW. This will help to maintain warmer than normal conditions as we head into fall.
In the Near Term – Aug. 10-24… In the southern California avocado growing areas from Santa Barbara County to San Diego County, it continues to be hot inland with persistently warmer than normal conditions thru August 12th. TSTMS occur in mountains and deserts on 12-13th and may spread to the Avocado region on late 13th with showers possible overnight 13-14th. Dry and warmer August 15-17th, then hot 18-19th. Cooler with deeper Marine layer and possible coastal eddy developing on the 20-24th.
Summary – Aug. 25-Sept. 7… In the southern California avocado growing areas, from San Luis Obispo south, hot periods return during August 25-31st, and Sep 1-7. TSTMS occur mostly in the afternoon-evenings in the mountains and deserts of S Calif. The 25-31th has potential for an increase in TSTMS again in SOCAL mountains and deserts. This appears to be an active period for tropical cyclones off S Baja Calif.
Seasonal Outlook / El Niño Update...September 8 – November 30, 2017… As normally occurs, there will be some monsoonal SE flow episodes with TSTMS in the mountains and deserts of SOCAL, and some early rains from cutoff lows occurring in central coast and central Calif during Oct and Nov.
El Niño is not present, with ENSO-neutral conditions thru mid-Fall to early winter. However, sea surface temperature anomalies in the mid-latitude Pacific favor development of a WSW-ENE storm track oriented toward northcentral and N Calif, producing a wet Oct -Dec in the N half of Calif. El Niño conditions are currently not indicated for Nov-Dec 2017, and above normal rainfall in SOCAL is generally not indicated, although a couple of wet storms are possible.
Wetter than normal conditions are more likely for the central and N SierraNV in Oct – Nov – Dec.
...Alan Fox, Fox Weather LLC...