Seasonal Outlook - November-December 2016-January 2017

El Nino Southern Oscillation (ENSO)

Recent Observations

During early November 2016 the tropical Pacific Sea surface temperature (SST) anomaly was slightly cooler than -0.5C, the threshold for weak La Niña. Also, most of the atmospheric variables across the tropical Pacific have been consistent with weak La Niña conditions.

Model Forecast and Guidance:

The collection of ENSO prediction models indicates SSTs near or slightly cooler than the threshold of La Niña during the remainder of 2016 and into early 2017, then weakening to cool-neutral by the end of the first quarter of 2017.

Expected impacts on rainfall and temperatures:

Atmospheric circulation patterns during La Niña periods may contribute to increased frequency of developing storms and cyclones. This, in turn, can contribute to higher rainfall totals, both in the wet and dry season around the end of a calendar year and the start of the next calendar year.

Climate conditions in the Tropical North Atlantic and Caribbean

Recent observations showed SSTs 0.5°C above-average within the Caribbean and the Tropical North Atlantic east of the islands, but 1°C warmer north of the Greater Antilles. Trade winds were at their usual strength.

Expected Conditions:

Near normal SST are expected to return to the Caribbean Sea and further east by February-March-April. Tradewind strengths are hardly predictable at seasonal time scales.

Expected impacts:

A probability shift towards above- to normal rainfall is noted for much of the Caribbean for November-December -January due to positive SST anomalies in the Caribbean Sea and Tropical North Atlantic. Those warmer temperatures enhance humidity in the region, which in turn can lead to increased rainfall. This influence will tend to subside by February-March-April 2017.

Regional Overview on Seasonal Forecasts for November-December 2016-January 2017

Rainfall Outlook

ND 2016-J 2017 Rainfall Outlook

Forecast: Below to normal rainfall totals can be expected for the season November-December 2016-January 2017.

Probability:

  • 25% chance of above normal
  • 35% chance normal
  • 40% chance of below normal

Wet Days and Wet Spells Outlook

Wet Days

NOVEMBER-DECEMBER 2016-JANUARY 2017 WET DAYS(≥1.0MM) FREQUENCY SHIFT
Station Climatology (Wet days) Forecast (Wet days)
Canefield Airport 40 to 54 40 to 56
Douglas-Charles 55 to 67 53 to 69

Forecast: No significant shift in wet days (medium to high confidence).

Implication: Regular disruptions of outdoor activities due to rainfall events.

7-Day Wet Spells

NOVEMBER-DECEMBER 2016-JANUARY 2017 7-DAY WET SPELLS FREQUENCY SHIFT
Station Climatology (7 day wet spell) Forecast (7 day wet spell)
Canefield Airport 1.8 to 3.8 1.7 to 4
Douglas-Charles 1.7 to 4.7 1.8 to 4.8

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

3-Day Wet Spells

NOVEMBER-DECEMBER 2016-JANUARY 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 1 0 to 0.3
Douglas-Charles 0 to 1 0 to 1.2

Forecast: No change in the amount of 3-day extreme wet spells (medium to high confidence.)).

Implication: Flash flood potential developing.

Drought Outlook

Forecast: There are no drought concerns for Dominica both at the short term (August 2016- January 2017) and long term (December 2015 –November 2016).

Temperature Outlook

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

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