Seasonal Outlook - April - June 2017

Looking back at the January - March 2017 Season

The dry season runs from December to May when the seas are cooler and thunderstorms and rainfall activities are relatively low. Rainfall accumulated at both the Canefield and Douglas-Charles Airports for the season January - March 2017 was above normal. Above to normal maximum and mean temperatures were recorded with the Douglas-Charles Airport recording cooler than normal night time temperatures.

Table 1: January - March (JFM) 2017 Season
Climatological Normal (30 Years)
Rainfall
  Canefield Airport Douglas-Charles Airport
Normal
179.3 to 259.1 mm
301.0 to 397.3 mm
JFM 2017 Total
300.3 mm (above normal)
426.9 mm (above normal)
Temperature
Average Maximum Normal
29.5oC to 30.1oC
28.1oC to 28.6oC
JFM 2017 Average Maximum
30.3oC (above normal)
28.6oC (normal)
Average Mean Normal
25.8oC to 26.3oC
25.0oC to 25.6oC
JFM 2017 Average Mean
26.5oC (above normal)
26.2oC (above normal)
Average Minimum Normal
21.7oC to 21.9oC
22.0oC to 22.3oC
JFM 2017 Average Minimum
21.8oC (normal)
21.6oC (below normal)

 

El Nino Southern Oscillation (ENSO)

Recent Observations

ENSO-neutral conditions continued during February, with near-average sea surface temperatures (SSTs) across the central equatorial Pacific and above-average SSTs in the eastern Pacific.

Model Forecast and Guidance

Most models predict the continuation of ENSO-neutral (3-month average Nino-3.4 index between -0.5oC and 0.5oC) through the Northern Hemisphere summer. However, some dynamical models anticipate an onset of El Nino towards the end of the dry season into the wet season (dry season-December to May, wet season-June to November).

Expected Impacts on Rainfall and Temperatures

ENSO neutral conditions have little effect on rainfall or temperatures. However, if El Nino manifests during the first half of the wet season, odds are in favour of drier weather with less extreme rainfall than usual for that part of the wet season.

Mid March 2017 Plume of Model ENSO Predictions
Mid March 2017 Plume of Model ENSO Predictions
Mid March IRI/CPC Model Based Probabilistic ENSO Forecast
Mid March IRI/CPC Model Based Probabilistic ENSO Forecast


Climate conditions in the Tropical North Atlantic and Caribbean

Recent observations: Recent observations showed SSTs up to 0.5oC above-average in the eastern part of the Caribbean Sea. Although recently cooling, SSTs in the far northwest of the region remained above average. Elsewhere, SSTs have been close to average. Trade winds have been slightly stronger than usual over the Tropical North Atlantic.

Expected Conditions: SSTs are expected to warm in the Tropical North Atlantic until September 2017, but the warm anomalies are forecast to be less extreme than in previous years. Note also that episodes of Saharan dust blowing into the region are likely at least until July 2017, increasing the likelihood of reduced rainfall but they are hardly predictable at this time.

Expected impacts: A slight probability shift towards above to normal rainfall is expected as positive SST anomalies in the Caribbean Sea and Tropical North Atlantic tends to increase humidity over the region which in turn can lead to increased rainfall. This influence may subside by June-July-August.

Regional Overview on Seasonal Forecasts for October to December 2016


Rainfall Outlook

Rainfall Outlook
Rainfall Outlook

Forecast: There are uncertainties at this time for the expected rainfall for the season April to June 2017. However, beyond June with the anticipation of a transition to El. Nino phase, below normal rainfall are forecast. (Normal range for April to June- approximately 250 to 400mm) (Normal range for July to September- approximately 600 to 900mm).

Probability for April - June 2017:

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

Probability for July - September 2017:

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


Wet Days and Wet Spells Outlook


Wet Days

April - June 2017 Wet Days Frequency Shift
April - June 2017 Wet Days Frequency Shift
Table 2: April - June 2017 Wet Days(>1.0mm) Frequency Shift
Station Climatology (Wet days) Forecast (Wet days)
Canefield Airport 27 to 45 28 to 51
Douglas-Charles 41 to 63 43 to 69


Forecast
: An increase in the amount of wet days (low to medium confidence) is expected.

Implication:

  • Disruptions of outdoor activities will become more frequent
  • Decreasing surface dryness across the region, especially after April


7-Day Wet Spells

April - June 2017, 7-day Wet Spells Frequency Shift
April - June 2017, 7-day Wet Spells Frequency Shift
Table 3: April - June 2017, 7 Day Wet Spells Frequency Shift
Station Climatology (7 day wet spell) Forecast (7 day wet spell)
Canefield Airport 0.9 to 3.4 1.3 to 5.5
Douglas-Charles 0.9 to 4.7 1.7 to 5.9


Forecast
: An increase in 7-day wet and very wet spells frequency (medium to high confidence).

Implication: The build-up of usual dry season impacts on water availability should be slower than usual.


3-Day Wet Spells

April - June 2017 Frequency of Extreme (1%) 3-Day Wet Spells
April - June 2017 Frequency of Extreme (1%) 3-Day Wet Spells
Table 4: April - June 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 2 0 to 1.2


Forecast
: There is little indication of change in frequency for 3-day extreme wet spells (low confidence).

Implication: Flash flood potential is becoming a concern mostly after April.


Drought Outlook

January - June 2017 Drought Outlook
January - June 2017 Drought Outlook


Forecast
: A short term (January to June 2017) drought watch has been issued for Dominica. This means that drought conditions are possible within the next 3 months. Continue to monitor the situation and conserve water.


Temperature Outlook

April - June 2017 Temperature Outlook
April - June 2017 Temperature Outlook


Forecast
: Temperatures across the Caribbean are forecast to gradually rise and become more uncomfortable throughout the period. Heat discomfort will probably grow more slowly in the Windward than at this time in the past couple of years. The chances of heat waves are appearing in May and June for many islands. (Maximum temperature normal range: 30-32oC) (Mean temperature normal range: 27-28oC) (Minimum temperature normal range: 23-24oC).

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