Seasonal Forecast: May to July (MJJ) 2023

Date of Issue: May 7, 2023

What are the usual MJJ conditions?

  Canefield Airport Douglas-Charles Airport
Normal Accumulation 333.6 to 593.2mm 445.2 to 729.8mm
Number of Wet Days 36 to 61 days 43 to 69 days
Number of 7-day Wet Spells 3 to 7 2 to 6
Number of 7-day Dry Spells - -
Average Maximum 31.8°C to 32.4°C 30.4°C to 30.7°C
Average Mean 27.9°C to 28.5°C 27.4°C to 27.8°C
Average Minimum 24.0°C to 24.5°C 24.4°C to 24.9°C

What is the forecast for this MJJ season?

  • Rainfall:
    • May marks the transition of the dry season into the wet season;
    • Uncertainties remain in the rainfall totals forecast at this time; however, a general increase in rainfall amounts is usual during this season;
    • A slight decrease in the number of wet days is likely, however, the frequency of outdoor activity disruptions due to rainfall should be increasing;
    • A faster than usual increase in the number of very wet spells (with medium confidence) which could result in flash floods is expected;
    • At this time, there is no concern for drought, however some parts of the island may continue to experience extended dry spells;
  • Temperature:
    • The Caribbean Heat Season begins in May;
    • Temperatures are forecast to be high enough to be uncomfortable to many;
    • Daytime and night-time temperatures are likely to be higher than usual;
    • This may manifest in recurring heatwaves and rapidly increasing heat stress;

What factors are influencing this forecast?

  • El Niño Southern Oscillation (ENSO)
    • Recent observations: Sea Surface Temperatures (SSTs) in the eastern Pacific have risen from La Niña to slightly above average (ENSO neutral conditions) by mid-April;
    • Model forecast and guidance: The forecast models indicate a likely transition to El Niño conditions in MJJ (60-70% confidence) and ASO (80% confidence);
    • Expected impacts on rainfall and temperatures: ENSO neutral offers little contribution to seasonal forecasting, but a transition into El Niño more often than not is marked by a delayed onset of the wet season, a drier summer season and reduced tropical cyclone activity, especially in September and October;
  • Climate conditions in the Tropical North Atlantic (TNA) and the Caribbean Sea
    • Recent observations: SSTs have hovered around 0.5°C above average in much of the sub-tropical North Atlantic and eastern Tropical North Atlantic (TNA), but are near average in the Caribbean Sea;
    • Expected conditions: Models are confidently forecasting increasingly warm SST anomalies of 0.5°C to 1°C (or more) above average across the Caribbean Sea and the TNA;
    • Expected impacts: Warm SSTs in and around the Caribbean tend to contribute to higher air temperatures with above-average humidity and an increased frequency of heatwaves, but also higher Atlantic Hurricane Season activity, seasonal rainfall totals and an increased frequency of extreme rainfall during the wet season;

Note: The level of forecast accuracy and certainty decreases as the time increases. This is inherent to all model projections. Therefore, there is less confidence after 48 hours. Model projections may change significantly daily.