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Sample Forecast for USA (West Coast)

Summary for California, Nevada, Washington and Oregon

Synopsis: El Niño is expected to remain strong through the Northern Hemisphere winter 2015-16, with a transition to ENSO-neutral anticipated during late spring or early summer 2016.

A strong El Niño continued during November as indicated by well above-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean. The Niño-4, Niño-3.4 and Niño-3 indices rose to their highest levels so far during this event, while the Niño-1+2 index remained approximately steady. The subsurface temperatures in the central and eastern Pacific, while still well above average, decreased slightly due to the eastward push of the upwelling phase of an equatorial oceanic Kelvin wave. Low-level westerly wind anomalies and upper-level easterly wind anomalies continued over the most of the tropical Pacific. The traditional and equatorial Southern Oscillation Index (SOI) values remained negative. These conditions are associated with enhanced convection over the central tropical Pacific and suppressed convection over Indonesia. Collectively, these atmospheric and oceanic anomalies reflect a strong El Niño episode that has matured.

Most models indicate that a strong El Niño will continue through the Northern Hemisphere winter 2015-16, followed by weakening and a transition to ENSO-neutral during the late spring or early summer. The forecaster consensus remains nearly unchanged from last month, with the expectation that this El Niño will rank among the three strongest episodes as measured by the 3-month SST departures in the Niño 3.4 region dating back to 1950. El Niño is expected to remain strong through Northern Hemisphere winter 2015-16, with a transition to ENSO-neutral anticipated during the late spring or early summer 2016.

El Niño has already produced significant global impacts and is expected to affect temperature and precipitation patterns across the United States during the upcoming months. Seasonal outlooks indicate an increased likelihood of above-median precipitation across the southern tier of the United States, and below-median precipitation over the northern tier of the United States. Above-average temperatures are favored in the West and northern half of the country with below-average favored in the southern Plains and along the Gulf Coast.

Temperature

January

Cooler than normal across nearly the entire four state region with only Central Washington and southern Nevada and southeastern California near normal to slightly and in the case of Central Washington moderately warmer than normal.

February

Cooler than normal across nearly the entire four state region with only Central Washington and southern Nevada and southeastern California near normal to slightly and in the case of Central Washington slightly warmer than normal.

Precipitation

January

In California, most of the state should be near normal to slightly wetter than normal in the south and slightly drier than normal in the Northern Sierra and east of Sacramento up to the border with Oregon. Nevada should be slightly drier in the northern half and near normal to slightly wetter in the south. In Oregon, the coast should be near normal and the central area near normal to slightly wetter and the southeast should be slightly drier than normal. For Washington almost all the state should be slightly wetter than normal to near normal to the west of the Cascades.

February

In California, most of the state should be near normal to slightly wetter than normal in the south and slightly drier than normal in the Northern Sierra and east of Sacramento up to the border with Oregon. Nevada should be slightly drier in the northern half and near normal to the south. In Oregon, the coast should be near normal and the central area near normal to slightly wetter and the southeast should be slightly drier than normal. For Washington almost all the state should be slightly to moderately wetter than normal to near normal to the west of the Cascades.