Seasonal Outlook: July - September 2016

El Nino Southern Oscillation (ENSO)

The strong 2015-16 El Nino has ended giving way to ENSO-Neutral conditions.

During mid-June 2016 the Tropical Pacific Sea Surface Temperature (SST) anomaly was near zero, indicating ENSO-neutral conditions. The key atmospheric variables also indicate neutral ENSO condition. This includes near-average upper and lower level Tropical Pacific Winds, as well as near-normal cloudiness and rainfall patterns in the Central and Eastern Equatorial Pacific. Most ENSO prediction models indicate neutral ENSO conditions during June, with likely development of La Nina (of unknown strength, but likely weak) by late July or August, lasting through the 2016 Hurricane/Wet Season and into the 2017 Dry Season.

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

Expected Impacts on Rainfall and Temperatures

A shift towards above to normal rainfall is noted for the Caribbean due to reduced wind speeds in the upper atmosphere, which allows for stronger local showers to develop. A higher frequency of tropical storm likelihood during La Nina may also contribute to rainfall totals. Higher temperatures are probable for the region, which may also add to increased moisture uptake and lead to increase precipitation.

Climate conditions in the Tropical North Atlantic and Caribbean

Recent observations showed SSTs are 0.5 to 1oC above-average within the Caribbean and higher just to the north. Positive SSTs anomalies are expected throughout the Tropical Atlantic by July-August-September 2016. Trade wind strength is 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 July to September 2016

Rainfall Outlook

Rainfall Outlook
Rainfall Outlook

Slightly below to normal rainfall totals are forecast for Dominica for July-August-September 2016.


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

Wet Days and Wet Spells Outlook

Wet Days

JAS 2016 Wet Days Frequency Shift
JAS 2016 Wet Days Frequency Shift
Table 1: July to September Wet Days(>1.0mm) Frequency Shift
Station Climatology (Wet days) Forecast (Wet days)
Canefield Airport 51 to 65 55 to 70
Douglas-Charles 55 to 70 54 to 69

Forecast: Fewer (slight) wet days than normal (low to medium confidence).

Implication: Transitioning from the dry to wet season usually results in increasing surface wetness and disruptions of outdoor activities (however perhaps less often than usual).

7-Day Wet Spells

JAS 2016 7-day Wet Spells Frequency Shift
JAS 2016 7-day Wet Spells Frequency Shift
Table 2: July - September 7 Day Wet Spells Frequency Shift
Station Climatology (7 day wet spell) Forecast (7 day wet spell)
Canefield Airport 3.7 to 7.4 3.2 to 7.4
Douglas-Charles 2.9 to 6.9 2.2 to 6.1

Forecast: Fewer (slight) 7-day wet spells than normal (low to medium confidence).

3-Day Wet Spells

JAS 2016 frequency of extreme (1%) 3-day Wet Spells
JAS 2016 frequency of extreme (1%) 3-day Wet Spells
Table 3: July - September 3 Day Extreme Wet Spells Frequency Shift
Station Climatology (3 day extreme wet spell) Forecast (3 day extreme wet spell)
Canefield Airport 0 to 2.5 0 to 2.2
Douglas-Charles 0 to 1 0 to 1.1

Forecast: There is an increased chance of normal 3-day extreme wet spells (low confidence).

Implication: Flash flood potential developing.

Drought Outlook

Drought Outlook
Drought Outlook

There are no drought concerns for Dominica up to September 2016.

Temperature Outlook

Temperature Outlook
Temperature Outlook

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

Minimum/night-time temperature Probability

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

Maximum/day-time temperature Probability

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