Seasonal Outlook - December 2016 - January - February 2017

El Nino Southern Oscillation (ENSO)

Recent observations:

La Niña conditions persisted during November, with slightly below -0.5°C sea surface temperature (SST) anomalies present across most of the central and eastern equatorial Pacific.

Model forecast and guidance:

The multi-model averages favour La Niña to continue through December – February(DJF) 2016-17. A transition to ENSO-neutral is favoured during January – March(JFM) 2017.

Expected impacts on rainfall and temperatures:

La Niña increases chances of wetter than usual conditions in much of the region during December-January-February. It increases flash flood, long-term flooding and landslide potential until the end of the year, but cools the dry season and dampens the intensity of its dryness.

 

Regional Overview on Seasonal Forecasts for December 2016 to January-February 2017

Rainfall Outlook

 

Forecast: Above to normal rainfall totals can be expected for the season December 2016-January-February 2017. (Normal range 250-400mm)

Probability:

  • 50% chance of above normal
  • 30% chance normal
  • 20% chance of below normal

 

Wet Days and Wet Spells Outlook

Wet Days

 

Table 1: December 2016 - January- February 2017 - Wet Days(>1.0mm) Frequency Shift
Station Climatology (Wet days) Forecast (Wet days)
Canefield Airport 36 to 54 35 to 53
Douglas-Charles 48 to 62 45 to 64

 

Forecast: No significant shift in the number of  wet days (low confidence).

Implication: Disruptions of outdoor activities by rainfall will become fewer as the months progress..

7-Day Wet Spells

 

Table 2: December 2016 - January - February 2017 - 7 Day Wet Spells Frequency Shift
Station Climatology (7 day wet spell) Forecast (7 day wet spell)
Canefield Airport 0.8 to 3.9 0.5 to 3.7
Douglas-Charles 0.8 to 3 0.7 to 3.3

 

Forecast: No significant shift in the number of 7-day wet spells (low confidence).

Implication: Recharge of large water reservoirs by rainfall to slow down by the end of the year. Depletion of large reservoirs during the dry season is likely to be slower than usual. .

3-Day Wet Spells

 

 

Table 3: December 2016-January–February 2017 - 3 Day Extreme Wet Spells Frequency Shift
Station Climatology (3 day extreme wet spell) Forecast (3 day extreme wet spell)
Canefield Airport 0 to 0 0 to 0
Douglas-Charles 0 to 0 0 to 0

 

Forecast: Low chances for 3-day extreme wet spells beyond December (high confidence) .

Implication: Flash flood potential mostly disappearing by the end of the year.

Drought Outlook

Forecast: There are no drought concerns for Dominica both at the short term (September 2016- February 2017) and long term (June 2016 –May 2017).

 

 

Temperature Outlook

Forecast: More comfortable temperatures than in recent months are expected during that time of year. However, temperatures are expected to be above to normal. Heat waves very unlikely throughout the period. (Maximum temperature normal range: 28-30°C) (Minimum temperature normal range: 21-22°C)

Probability:

Maximum/day-time temperature Probability

  • 60% chance of above normal
  • 25% chance normal
  • 15% chance of below normal

Minimum/night-time temperature Probability

  • 50% chance of above normal
  • 30% chance normal
  • 20% chance of below normal