30-Day Weather Outlook for June 26, 2017, to July 26, 2017

  • Jun 28, 2017

Summary- The basic pattern consists of high pressure to the west with hot N wind thru N and northcentral Calif during June 30th thru July 2nd. Troughing returns over Calif from July 4-7, and continues on July 8-11 off the coast, eventually moving W into N Calif and Oregon about July 12-15th. A pool of unusually cold water remains in the tropical region S thru WSW of southern Baja Calif. This will discourage development and intensification of tropical cyclones during the first part of summer 2017, continuing at least thru mid-July. It also contributes to below normal moisture into Baja Calif, resulting in drier than normal conditions in Baja and NW Mexico during most of July. El Niño is weak but still present along the equatorial east Pacific. Some redevelopment of El Niño may occur during Dec – Feb 2018, but forecasted results are currently inconclusive.

In the Near Term – June 30 – July 13…  In the southern California avocado growing areas from Santa Barbara County to San Diego County, coastal eddy conditions will exert the usual cooling influence during this period at the coast and into the coastal valleys, while seasonably warm or hot conditions occur in the inland valleys, e.g. Hemet, Riverside Valley, and Warner Springs.  Seasonably hot in the S and E Deserts.

Summary – July 14-28… In the southern California avocado growing areas, from San Luis Obispo south, a marine layer of normal depth is expected, with morning low clouds and sunny afternoons at the coast and seasonably very warm or hot inland. With sea surface temperatures below normal off S Baja and SW Mexico, tropical cyclone activity will tend to remain weak or below normal for nearly all of July. Seasonable occurrence of TSTMS in the mountains and deserts is indicated.

Seasonal Outlook / El Niño Update...August 1 – Fall 2017… The summer currently appears quiet, with regard to tropical cyclones. However, troughing will tend to continue off S and central Calif during the summer period, with dry SW flow into southcentral and S Calif.  As normally occurs, there will be monsoonal SE flow episodes.

El Niño continues subdued thru summer, but has a chance to intensify in the mid-fall. In addition, the SSTA pattern in the mid-latitude NE Pacific will continue to support troughing off the coast, centered about 130-140W.  This may actually promote a warmer than normal August, with usual development of TSTMS as the summer monsoon is near its maximum, and high pressure aloft over central and S Calif and the southern Rockies area.  There currently is no evidence in the CFSv2 for unusual rainfall anomalies.

For the late Fall, and December, as we enter winter in Dec above normal rainfall focuses into W Mexico, while drier than normal rainfall focuses in the Pacific Northwest.

...Alan Fox, Fox Weather LLC...

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