September 2017 Climate Forecast Discussion

September 2017 Climate Forecast Discussion for Oct-Dec through Jan-Mar

The SST forecast shows weak La Nina conditions for Oct-Dec through Jan-Mar, weakening slightly for Jan-Mar. The subtropical North Pacific SST and the SST in many of the other extratropical regions are predicted to be above average during all four forecast seasons. A slightly positive Indian Ocean Dipole is predicted for Oct-Dec through Dec-Feb, weakening for the later seasons. Slightly above-average tropical Atlantic SST is predicted for mainly Oct-Dec and Nov-Jan.

Enhanced probabilities for below-normal precipitation are predicted for Mexico and the southeastern U.S. from Oct-Dec through Jan-Mar, and in part of southeastern South America from Oct-Dec to Dec-Feb. A tilt of the odds toward below-normal is also forecast for part of southwestern Asia for Oct-Dec, for part of east coastal Asia from Nov-Jan to Jan-Mar, and much of Greenland for Nov-Jan and Jan-Mar. Enhanced chances for above-normal precipitation are forecast for northern South America and for most of Indonesia and parts of eastern Australia from Oct-Dec through Jan-Mar. A tilt toward above-normal is also predicted for northern and northeastern Asia for Oct-Dec and Nov-Jan.

An enhanced probability for above-normal temperature is predicted for Mexico and the southern U.S., as well as much of Asia and northeastern Europe, from Oct-Dec through Jan-Mar. Enhanced probabilities for above-normal are strongest and most widespread in Oct-Dec, when they appear also in much of northern North America, Greenland, central South America and parts of Australia and Africa. A tendency toward below-normal temperature is forecast in portions of mid-latitude North America Dec-Feb and Jan-Mar.