May 2021 Climate Forecast Discussion

May 2021 Climate Forecast Discussion for Jun-Aug through Sep-Nov

The SST forecast indicates that the La Niña event has transitioned to ENSO-neutral and will likely remain so through the boreal summer. This collection of models suggests a re-emergence of cool SST anomalies in boreal fall that are just cool enough to meet the La Niña condition threshold of -0.5 C below average. SST forecasts in the tropical Indian and Atlantic Oceans are primarily for normal conditions in the coming seasons; however, some warming over the western equatorial Indian ocean is predicted with the re-emergence of La Niña.

Precipitation forecasts show enhanced probabilities of above-normal precipitation over the Maritime Continent and much of Australia for all forecasted seasons, with probabilities increasing in later seasons. Enhanced probabilities of below-normal precipitation are forecast over northwestern United States, parts of Central America, and much of southern South America for the Jun-Aug and Jul-Sep seasons. Forecasts suggest enhanced likelihood for below-normal precipitation during Aug-Oct and Sep-Nov over northern South America and Africa’s Ivory Coast. Below-normal precipitation is likely over much of Chile for all forecasted seasons.

In Jun-Aug enhanced probabilities of above-normal temperatures are forecast for the Western United States, Eastern Canada, Greenland, Southern Europe, and Northern Russia. The probabilities weaken through Aug-Oct. In Sep-Nov, high probabilities for above-normal temperatures reappear over the northernmost land areas and much of Central Asia.