August 2018 Climate Forecast Discussion for Sep-Nov 2018 through Dec-Feb 2019
The SST forecast shows weak El Nino conditions developing for the initial Sep-Nov season, intensifying to moderate strength (>1.0C in the Nino3.4 region) by Nov-Jan and Dec-Feb. Much of the subtropical and extratropical North Atlantic and North Pacific SST, as well as the SST in much of the mid- to high-latitude Southern Hemisphere, are predicted to be above-average during all four forecast seasons. Exceptions are noted in the very high latitudes north of North America and south of South America, where below-average SST is predicted for all four forecast seasons. Slightly below-average SST is also predicted at lower latitudes in various locations for the Sep-Nov season. A positive Indian Ocean Dipole is predicted for all four forecast seasons. Near-average SST is predicted for the north and south tropical Atlantic for all four seasons.
Moderately strong tilts of the odds toward below-normal are forecast for northern South America, Indonesia, the Philippines and parts of Australia for all four forecast seasons (Sep-Nov through Dec-Feb). Slightly enhanced probabilities for below-normal precipitation are also predicted for Central America, the Caribbean islands, parts of the immediate southeast Asia coast, and central Chile for Sep-Nov, and for the Caribbean islands, central Africa for Sept-Nov and Oct-Dec, and for southern Africa for Dec-Feb. The chance for below-normal also returns to Central America and the Caribbean for Dec-Feb. Enhanced chances for above-normal precipitation are forecast for parts of the southern U.S./northern Mexico, part of central-southwest Asia and northern Asia for all four forecast seasons (Sep-Nov through Dec-Feb), southeastern South America and eastern equatorial Africa for Sep-Nov through Nov-Jan, and the African Gulf of Guinea for Sep-Nov and Oct-Dec.
Enhanced probabilities for above-normal temperature are predicted for varying parts of Greenland, Asia, eastern Europe, northern or southern Africa, Australia, North America and South America from Sep-Nov through Dec-Feb. However, the above-normal signal is mainly absent from southern Africa in Sep-Nov and from the southern half of North America in Dec-Feb. Enhanced probabilities for below-normal temperature are very scant, and appear just weakly in part of central Asia in Dec-Feb. An enhanced likelihood for near-normal temperature is predicted for a part of northeastern South America in Sep-Nov and in central and/or western Africa from Sep-Nov through Dec-Feb.
