Seasonal Forecast: September - November 2020

Influencing Factors

El Nino Southern Oscillation (ENSO)

Recent observations
Sea Surface Temperatures (SSTs) in the eastern Pacific SSTs cooled during May from slightly above average to between -0.7oC and 0oC. This resulted in neutral to borderline La Nina conditions.
Model forecast and guidance
The models slightly favour a transition to La Nina through December-January-February 2020/21 (with around 50-60% confidence) over maintaining ENSO neutral (35-45% confidence).
Expected impacts on rainfall and temperatures
La Nina tilts the odds to more rainfall, more extreme rainfall and stronger tropical cyclone activity. In addition, temperatures tend to be tempered by the added moisture and more frequent showers in areas that are wetter than usual.

Climate conditions in the Tropical North Atlantic and Caribbean

Recent observations
SSTs along the shores of the Caribbean and in parts of the Tropical North Atlantic (TNA) and sub-tropical North Atlantic are around 0.5oC to 1oC above average.
Expected conditions
Most models sustain warm SST anomalies of around +0.5oC across the Caribbean Sea, the TNA and the sub-tropical North Atlantic throughout September-October-November and December-January- February 2020/ 21.
Expected impacts
Continued warm SSTs throughout the Caribbean tends to contribute to above average humidity, seasonal rainfall totals, wet spell frequency and Atlantic Hurricane Season activity across the region. In addition, warm SSTs favours warmer night-time temperatures and where rainfall does not increase warmer daytime temperatures.


Currently some uncertainties exist as it pertains to accumulated rainfall amounts by the end of November. However, it is anticipated that at least as wet as usual condition is expected. Models indicate no significant changes from the usual number of wet days and wet spells for the season. At least 1 to 2 extreme 3-day wet spells are expected which increases flash flooding potential. There are no short-term drought concerns (covering June to November 2020). However, the possibility for a hydrological/ long term drought (covering December 2019 to November 2020) remains as the island continues to record less rainfall than usual. An increase in rainfall activity is expected towards the end of 2020 into 2021. Keep updated.


Warmer than to usual temperatures are expected for the September to November 2020 season. Very high probabilities for having 7 to 14 heatwaves days in September exists. These heatwaves are expected to continue into October. Some cooling is expected by November as the island transitions out of the heat season (May to October).

A heatwave is two or more consecutive hot days with peak temperatures of 32.8oC and higher at Canefield and areas along the west coast and 31.5oC for Douglas-Charles and surrounding areas.

Climatological Normal/ Averages

September-October-November Season
Climatological Normal (30 years)
Rainfall Canefield Airport Douglas-Charles Airport
Normal 466.4 to 746.7mm 737.4 to 1077.1mm
Wet Days Normal 42 to 54 days 57 to 69 days
7-Day Dry Spells Normal N/A 0 to 1
Temperature (15 years average)
Average Maximum 31.5oC to 31.9oC 30.6oC to 30.8oC
Average Mean 27.5oC to 27.8oC 27.2oC to 27.4oC
Average Minimum 23.4oC to 23.8oC 23.6oC to 24.0oC

Disclaimer: The Dominica Meteorological Service makes no warranties, either expressed or implied, concerning the accuracy, completeness, reliability or suitability of these products and will not be held liable for any actions taken in reliance thereon. The information is free for use with the understanding that content may not be modified and presented as original material.

Source: Dominica Meteorological Service (DMS) in collaboration with the Caribbean Institute for Meteorology and Hydrology (CIMH) & National Oceanic and Atmospheric Administrative (NOAA).