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Weather Outlook

June 21, 2017

Summary- A trough will redevelop over Calif for June 26th thru July 2nd. High pressure will rebuild into Calif during July 4-8th. Another period of showers appears to develop during July 19-20 in N Calif, mostly apparently associated with mountain TSTMS. 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 into early July. It also contributes below normal moisture into Baja Calif, resulting in drier than normal conditions in Baja and W Mexico during late June thru most of July. El Niño has become weak as is normal in our summer. Some redevelopment in El Niño may occur during Dec – Feb 2018, but forecasted results are currently inconclusive.

June 13, 2017

Summary- The occurrence of active westerlies will decrease, and strong warm upper high pressure will build from the Pacific into most of Calif. A pool of unusually cold water has retreated further west of Calif, and its influence is diminished. 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 into early July. It also contributes below normal moisture into Baja Calif, resulting in drier than normal conditions in Baja and W Mexico during late June thru most of July. El Niño has become weak, as it usual does, in our summer. Some redevelopment in El Niño may occur during Dec – Feb 2018, to produce above normal rainfall in Central and S Calif.

June 6, 2017

Summary- Occurrence of active westerlies will decrease, and troughing will focus in the Rockies and Great Basin, with dry NNW flow recurring in Calif. A pool of unusually cold water will retreat further to the west of Calif. 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 into early July. Though weak and intermittent during summer, the basic signature of El Niño continues in the equatorial Pacific. The bottom line is that we will need to deal with El Niño again in the fall and next rainy season when it redevelops. The usual result for El Niño is above normal rainfall during winter and early spring months in central and S Calif.