30-Day Weather Outlook for June 1, 2019, to June 25, 2019

  • May 31, 2019

Summary- Focus of development of troughs and lows continues near the coast of California from 32N (San Diego) to 40N (Cape Mendocino). Cold fronts coming into the Pacific Northwest tend to turn S then extend or expand SSW-ward then re-develop off the coast of California, consistent with the energy pattern set up by the sea surface temperature anomaly (SSTA) field near and west of California. 

El Niño continues to weaken slowly. Cold water has developed off S Baja California.

An area of warm sea surface temperature anomalies (SSTAs) extends from S California to central Baja California, then WSW-W towards Hawaii.

The area of colder than normal sea surface temperatures (cold SSTA) persists just west of the coast of central and N California. It will help to extend the cool and active spring pattern through the first half of June. The size of this area has expanded during the past two weeks.

High pressure will tend to develop near the Aleutians. Troughing will continue in the mid-Central Pacific near (north of) Hawaii. Another trough will anchor near the coast of N and Central California (San Luis Obispo-Pt Conception north to Cape Mendocino). This maintains the elevated risk for showers and recurrent cool weather in California, which should return about June 9-10th and continue off-on through the 20th (beginning of next MJO Cycle wet phase).

At a point during the first week or so of June, it will try to finally warm up, per start of summer season. We have seen some warming in nighttime temperatures.

In the Near Term – June 1-15… Salinas Valley-San Luis Obispo Co…Above normal precipitation, including continuation of cool conditions coincident with the wet periods.  Warm periods will not last long due to strong support for cool and showery conditions.

Only brief warm or hot periods continue most likely at this time. Days of precipitation are most likely on June 9-11 and 13-20. Watch for cool conditions with gusty SW-WSW winds during the periods from the 9-11 and 13-19th at times.

In the southern California avocado growing areas, from San Luis Obispo south, southern portions of the cold upper lows and cold fronts will affect SOCAL.   It will unusually be wet for the mountain areas (Ventura, LA and San Bernardino counties). From current model guidance, best estimate for rain days is June 10-20 (TSTMS).

Summary – June 16-30… The general synopsis for N, and Central California is that upper low activity continues off southern California, and may begin to provide tropical moisture inputs for thunderstorms (TSTMS) in the SierraNV.

Seasonal Outlook / El Niño Update... July 1 – August 31…As speeds of the westerlies continue to decrease, we should see a few of the usual upper low events, and south winds with a beginning of monsoonal TSTMS by mid-July. Latest indications are that upper low pressure will linger off the California coast, especially in the central and south-central areas (San Luis Obispo).

Sea surface temperatures have cooled a bit to the south of Baja, so we do not  look for a significant increase in TSTM activity until July. The lowering of sea surface temperatures will tend to discourage tropical cyclone development or persistence as cyclones move NW off the Baja coast.

For SOCAL, speeds of the westerlies will also decrease, and as the belt of westerlies gradually migrates  poleward, we should see a few of the usual upper low events, and south winds with a beginning of monsoonal TSTMS in July. Latest indications are that upper low pressure will linger near central and southcentral California on June 10-12, and this will be followed by development of upper high pressure and more of the normal summer hot periods for central and S California.

Increase in monsoonal TSTM (thunderstorm) activity will tend to assist development of tropical cyclones in August, after a near normal month for tropical cyclones in the western Mexico region. 

Alan Fox...Fox Weather, LLC
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