Seasonal Outlook - October to December 2016

El Nino Southern Oscillation (ENSO)

Observations done in August 2016 showed Nino3.4 Sea Surface Temperatures (SSTs) anomalies at weak La Nina (-0.54). The probabilities for La Nina are between 50% and 70% from September-November through to December-February 2016-17, then drops into the 40s during the latter and below 25% from March-May 2017 onwards. The probability for neutral conditions rises to 50% for November-January and December-February, and still higher thereafter.

Mid September 2016 Plume of Model ENSO Predictions (Click to enlarge)
Mid September 2016 Plume of Model ENSO Predictions (Click to enlarge)
Mid September 2016 IRI/CPC Model (Click to enlarge)
Mid September 2016 IRI/CPC Model (Click to enlarge)

Expected Impacts

Average circulation patterns during La Nina periods may contribute to increased frequency of developing tropical storms which can contribute to higher rainfall totals.

Climate conditions in the Tropical North Atlantic and Caribbean

Recent observations showed SSTs 0.5oC above-average within the Caribbean and the Tropical North Atlantic. Trade winds were calmer than usual.

Expected Conditions: Slightly positive SST anomalies are expected throughout the Tropical North Atlantic by October – December 2016. Tradewind strengths are hardly predictable at seasonal time scales.

Expected impacts: Warm Atlantic temperatures increases evaporation and local deep atmospheric convection, potentially increasing precipitation.

Regional Overview on Seasonal Forecasts for October to December 2016

Rainfall Outlook

October - December 2016 Rainfall Outlook (Click to enlarge)
October - December 2016 Rainfall Outlook (Click to enlarge)

There is a low predictability for rainfall amounts for Dominica for the period October- November-December 2016. Chances are that rainfall totals will most likely be that of climatological averages.

Probability:

  • 33% chance of above normal
  • 33% chance normal
  • 33% chance of below normal

Wet Days and Wet Spells Outlook

Wet Days

October - December 2016 Wet Days (Click to enlarge)
October - December 2016 Wet Days (Click to enlarge)
Table 1: October to December 2016 - Wet Days(>1.0mm) Frequency Shift
Station Climatology (Wet days) Forecast (Wet days)
Canefield Airport 58 to 69 61 to 78
Douglas-Charles 25 to 35 27 to 46

Forecast: More wet days than normal (high confidence).

Implication: Increased disruptions of outdoor activities due to increase rainfall days.

7-Day Wet Spells

October - December 2016 - 7 Day Wet Spells (Click to enlarge)
October - December 2016 - 7 Day Wet Spells (Click to enlarge)
Table 2: October to December 2016 - 7 Day Wet Spells Frequency Shift
Station Climatology (7 day wet spell) Forecast (7 day wet spell)
Canefield Airport 3.0 to 5.8 3.7 to 7.1
Douglas-Charles 2.6 to 4.9 2.8 to 5.9

Forecast: More 7-day wet spells and very wet spells (medium confidence).

3-Day Wet Spells

October - December 2016 - 3 Day Wet Spell (Click to enlarge)
October - December 2016 - 3 Day Wet Spell (Click to enlarge)
Table 3: October to December 2016 - 3 Day Extreme Wet Spells Frequency Shift
Station Climatology (3 day extreme wet spell) Forecast (3 day extreme wet spell)
Canefield Airport 0 to 1.2 0 to 1.5
Douglas-Charles 0 to 2 0 to 1.3

Forecast: No significant shift in the amount of 3-day extreme wet spells (medium confidence).

Implication: Flash flood potential developing.

Drought Outlook

July - December 2016 Drought Alert (Click to enlarge)
July - December 2016 Drought Alert (Click to enlarge)
2016 Drought Alert Map - End of Hurricane Season (Click to enlarge)
2016 Drought Alert Map - End of Hurricane Season (Click to enlarge)

There are no drought concerns for Dominica both at the short term (July - December 2016) and long term (December 2015 – November 2016).

Temperature Outlook

October - November 2016 - Temperature Outlook (Click to enlarge)
October - November 2016 - Temperature Outlook (Click to enlarge)

Air temperatures are expected to be above to normal. Night and day-time temperatures are expected to be warmer.

Maximum/day-time temperature Probability

  • 70% chance of above normal
  • 20% chance normal
  • 10% chance of below normal

Minimum/night-time temperature Probability

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