30-Day Weather Outlook for June 15, 2019, to July 10, 2019
Summary- Focus of development of troughs and lows continues near the coast of central California and interior sections of California. Some showers of rain and snow are still possible in the high Sierra Nevada even at this late portion of the season.
El Niño continues to weaken, and cold water has continued to develop off S Baja California. El Niño is expected to reach minimum in July, then return to moderate intensity from Dec 2019 through Jan & Feb 2020.
An area of warm sea surface temperature anomalies (SSTAs) continues near Hawaii, and extends east-northeast to near N Baja California. This provides a weak zone of development for fronts extending west from N Baja.
A zone of development, which previously appeared robust off S California during late May, has subsequently weakened.
The area of colder than normal sea surface temperatures (cold SSTA) persists just west of the coast of south-central California. It will help to maintain a tendency for recurrent troughs through at least June 21. The size of this sea surface temperature anomaly has diminished during the past 2-3 weeks. The atmospheric response (water vapor at the surface to 6km above the surface) has also shown weakening.
Troughing will continue in the mid-Central Pacific near (north of) Hawaii. Thus far, the central Pacific trough appears to be deepening.
We have seen some hot days, including mid-90s in the coastal hills around Fortuna on the north coast. However, the cool troughs will be returning to SOCAL, and some cold fronts to NORCAL later this month.
In the Near Term – June 15-29… Salinas Valley-San Luis Obispo Co…Precipitation other than coastal drizzle is unlikely for the agricultural valleys. The central and S SierraNV receive TSTMS from June 16-19th. There is another small chance for a shower in the S Sierra about June 21-23rd.
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 on June 14-17th. Sunniest days with shallow marine layer are most likely on June 11-12th and again from the 19-21. Showers are possible in the SOCAL mountains from the 22-26th.
Summary – June 30 – July 14… The general synopsis for N, and Central California is upper low activity continues off southern California, and may begin to provide tropical moisture inputs for thunderstorms (TSTMS) in the SierraNV. Normal monsoonal TSTM activity is indicated for most of July.
Seasonal Outlook / El Niño Update... July 15 – September 15…Above normal temperatures, and near or a little below normal rainfall for the mid-summer monsoonal period. 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 with seasonably hot conditions (San Luis Obispo Co, San Joaquin Valley) and the usual TSTM frequency in the central SierraNV.
Sea surface temperatures continue cool to the south of Baja, so it will be difficult to achieve normal monsoonal rainfall for July and into early August. The lowering of sea surface temperatures will tend to discourage tropical cyclone development or persistence as the cyclones approach the Baja coast. However, tropical cyclones become more active and numerous in late August and early to mid-September, as we transition to a wet fall pattern for most of California.
For SOCAL, speeds of the westerlies will also decrease, and 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 until mid-August. We look for an up-tick in tropical cyclone activity, and moisture coming NNW from Mexico into SOCAL, the Sierras, and into the northern Sierras during the first part of September.
Alan Fox...Fox Weather, LLC
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