30-Day Weather Outlook for June 8, 2019, to July 3, 2019
Summary- Focus of development of troughs and lows continues near the coast of California from 32N (San Diego) to 42N (Oregon state line). 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 N Baja California WSW towards Hawaii. This provides a zone of development for fronts.
A new zone of development west of central California, which slowly increased during May 25-June 3 supports formation of cold upper lows near the California coast.
The area of colder than normal sea surface temperatures (cold SSTA) persists just west of the coast of central California. It will help to maintain the tendency for recurrent troughs through at least June 25th. The size of this sea surface temperature anomaly has expanded during the past three weeks.
Troughing will continue in the mid-Central Pacific near (north of) Hawaii.
Hot days will occur at times in the inland valleys, and San Joaquin Valley, followed by active troughs. Troughs occur about June 14-16th, and again from the 21-24th producing cooler conditions and some showers mainly in the SierraNV.
In the Near Term – June 8-22… Salinas Valley-San Luis Obispo Co…Precipitation other than coastal drizzle is unlikely for the agricultural valleys. The Yolla Bolly Mountains may receive a thunderstorm (TSTM) about June 5-6th, and about the 22nd. Hot and dry periods are suggested from the 9-12th, and 18-20th.
In the southern California avocado growing areas, from San Luis Obispo south, night and morning coastal low clouds and local fog, with mostly sunny afternoons inland. Coolest and cloudiest days are most likely from June 6-7-8th, and again from the 15-17th. Sunniest days with shallow marine layer are most likely from the 10-12th and again from the 19-22nd.
Summary – June 23 – July 7… 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. S Baja and S Mexico, as well as Central America (Guatemala, Honduras, Nicaragua, and Mexico states of Chiapas, Michoacán, Guerrero, and Oaxaca will tend to see below normal rainfall during this normally wet monsoonal period of mid-June through mid-July.
Seasonal Outlook / El Niño Update... July 7 – 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 continue cool to the south of Baja, so it will be difficult to achieve normal monsoonal rainfall for July and at least a portion of early August. The lowering of sea surface temperatures will tend to discourage tropical cyclone development or persistence as the cyclones approach 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, S-SE winds, and occasional periods of monsoonal TSTMS in July and August. However, this does not appear to be a season of active tropical cyclones due to the depressed sea surface temperatures near Baja and the southern Mexico coast.
Alan Fox...Fox Weather, LLC
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