Seasonal Outlook - January - March 2017

Influencing Factor

El Nino Southern Oscillation (ENSO)

Recent Observations

In recent months, sea-surface temperatures (SSTs) in the Equatorial Eastern Pacific (NINO3.4) hovered around 0.5°C below-average, which equates to borderline La Niña conditions.

 

Model forecast and guidance

Majority of models suggests a return to ENSO neutral conditions by January-February-March 2017 (with 55% - 75% confidence).

 

Expected Impacts on Rainfall and Temperatures

La Niña tend to shift rainfall chances for January-February-March 2017 to above to normal in the southern-most islands of the Caribbean, and below-normal in the Bahamas and Cuba. However, with the forecast ENSO conditions suggesting a weak La Niña at most, their effect on rainfall may not be dominant. With the absence of an El Niño, less solar radiation and more cooling by clouds and rain than last year, temperatures are expected  to be closer to normal in January-February-March 2017  and April-May-June 2017.

 

 

Climate conditions in the Tropical North Atlantic and Caribbean

Recent observations: showed SSTs up to 0.5°C above-average within the Caribbean and the Tropical North Atlantic east of the islands, however, after 2 years with (near-) record warm temperatures north of the Greater Antilles, SSTs are now near-average. Trade winds were at their usual strength.

 

Expected Conditions: Near normal SSTs are expected to return to the Caribbean Sea and further east by April-May-June 2017. Tradewind strengths are hardly predictable at seasonal time scales.

 

Expected impacts: A slight probability shift towards above- to normal rainfall is expected for January-February-March 2017 as positive SST anomalies in the Caribbean  Sea and Tropical North Atlantic tend to increase humidity in the region, which in turn can lead to increased rainfall. This influence will tend to subside by April-May-June 2017.

Regional Overview on Seasonal Forecasts for January-February-March 2017

Rainfall Outlook

 

Forecast:Above to normal rainfall totals can be expected for the season January-February-March 2017. (Normal range 150-400mm)

Probability:

  • 45% chance of above normal
  • 35% chance normal
  • 20% chance of below normal

Wet Days and Wet Spells Outlook

Wet Days

Table 1: January-February-March 2017 - Wet Days(>1.0mm) Frequency Shift
Station Climatology (Wet days) Forecast (Wet days)
Canefield Airport 29 to 46 26 to 54
Douglas-Charles 43 to 59 38 to 63

 

Forecast: Little change from the usual amount of wet days (very low confidence).

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

7-Day Wet Spells

Table 2: January-February-March 2017 - 7 Day Wet Spells Frequency Shift
Station Climatology (7 day wet spell) Forecast (7 day wet spell)
Canefield Airport 0 to 3 0.1 to 2.8
Douglas-Charles 0.4 to 2.1 0.6 to 2.2

 

Forecast: Little change from the usual amount of 7-day wet spells (very low confidence.)

Implication: Depletion of large reservoirs during dry season would likely be slower than in 2015.

 

3-Day Wet Spells

Table 3: January-February-March 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 (high confidence).

IMPLICATION: Flash flood potential is not a major concern until the end of  March.

Drought Outlook

 

There  are no drought concerns for Dominica both at the short term (October 2016-  March 2017) and long term (June 2016 –May 2017).

Temperature Outlook

 

FORECAST: Temperatures across the Caribbean are forecast to rise but generally continue to be comfortable until April, with the chance of heat waves appearing in May and June for many. (Maximum temperature normal range:  28-30°C) (Minimum temperature normal range: 21-22°C)

 

Probability:

Maximum/day-time temperature Probability

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

Minimum/night-time temperature Probability

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