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2020 Dry Season Likely To Be Less Dry Than Usual |
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Key Messages
- To date, the 2019 wet season has produced less rainfall than average in Trinidad and on par average rainfall totals in Tobago;
- December is likely to be slightly wetter than usual, with above normal rainfall totals expected;
- Flash flood risks remain up to early January 2020;
- Slightly wetter than normal conditions are forecasted for the 2020 dry season;
- The chances are highest for above normal rainfall accumulated totals from December 2019 to May 2020;
- Above normal rainfall during the dry season is usually not a significant amount of rainfall, since dry season rainfall typically accounts for only 20-25 % of the annual rainfall amounts;
- Both day and night temperatures are predicted to be warmer than normal over Trinidad and Tobago, however one or two nights during the season are likely to produce minimum temperatures below 22.0oC.
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Likely Impacts
- Existing below average accumulated rainfall totals during the 2019 wet season have negative implications for water resource management. Expect reduced water recharge rates and slower than average stream flows;
- Expected rainfall amounts during the 2020 dry season may not be sufficient to return water reservoir levels to their seasonal averages;
- Dry season conditions usually lead to an increase in the need to collect and store water in containers. This can increase breeding areas for mosquitoes if collected water is not stored adequately;
- Dry season conditions will increase bush and forest fire potential, especially during late February and March;
- Reduced air quality is likely during bush-, grass-, forest- and landfill-fires. This can negatively affect existing respiratory and other ailments.
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Early Actions & Preparedness
- Escalate water conservation programs and awareness messages;
- Revisit dry season contingency plans and upgrade based on historical extremes and not historical averages;
- Conserve, store and manage water in a safe and adequate manner;
- Take measures to lessen the impacts from dry season conditions. Be dry season ready. Stock up on water.
Figure 1: Category of rainfall likely for December 2019 to February 2020 (DJF 2019-2020) with the highest chance of occurrence expressed as probabilities and colour coded on the map. Blues indicate that it is more likely for above normal rainfall to occur than for below normal or near normal. Browns indicate it is more likely for below normal rainfall, while greens indicate it is more likely for near normal rainfall. Normal is defined by the rainfall that was observed in middle one-third of the DJF 2019-2020 period rainfall totals during the historical period used to produce the outlook.
- The DJF 2019/2020 rainfall outlook shows there are stronger chances for slightly wetter than usual conditions across the country, with above normal rainfall as the most likely category (high confidence);
- Above normal rainfall means rainfall totals that are greater than 125% of the long term average for the DJF period. For instance, at Piarco, normal rainfall for DJF is rainfall totals that are greater than 348.0 mm and at Crown Point totals that are greater than 311.0 mm;
- During the first half of the dry season, the month of February is likely to be the driest month.
Figure 2: The map shows the chances for extremely dry conditions over the next three months, December 2019 to February 2020 (DJF 2019-2020). Extremely dry conditions refer to the lowest 10% of December to January seasonal total rainfall amounts in the historical record.
- The chance for DJF 2019/2020 to be extremely dry is low (high confidence);
- The outlook indicates a 50-60% chance for at most, three 7-day dry spells during DJF, i.e. seven consecutive days with no measurable rainfall.
Figure 3: Possible accumulated rainfall totals with the highest chance of occurring during Deceembeer 2019 to February 2020 (DJF).
- Areas in northeast Trinidad, near Sangre Grande, North Oropuche and environs are likely to receive the largest rainfall accumulated totals, while areas near Port of Spain in the northwest are likely to receive the least rainfall totals during DJF;
- In Trinidad, accumulated rainfall totals are likely to range between 200.0 mm and 700.0 mm;
- In Tobago accumulated rainfall totals are likely to range between 100.0mm in the northeast to near 270.0mm in the vicinity of Mount Saint George;
- Trinidad and Tobago stands to get a delayed start to impactful ground dryness during the 2020 dry season.
Figure 4: Possible rainfall totals with the highest chance of occurring during December 2019.
- December is likely to be wetter than usual with a greater than 45% chance in most areas for rainfall totals in the above normal category (high confidence);
- Possible rainfall totals range from 55.0mm to 300.0 mm across the twin island Republic;
- Wet spells remain possible during December. The potential for flash flooding still exist.
Figure 5: Category of rainfall most likely for March to May 2020 (MAM) with the highest chance of occurrence expressed as probabilities and colour coded on the map. Blues indicate that it is more likely for above normal rainfall to occur than for below normal or near normal. Browns indicate it is more likely for below normal rainfall; while greens indicate it is more likely for near normal rainfall. Normal is defined by the rainfall that was observed in middle one-third of the MAM period rainfall totals during the historical period used to produce the outlook.
- The outlook for March to May 2020 indicates Trinidad and Tobago is likely to be as dry as usual with near normal rainfall totals likely.
The Temperature Outlook
- December 2019 to February 2020 daytime temperatures are very likely to be warmer than average for most of Trinidad and Tobago;
- The chance for warmer than average maximum temperatures is greater than 65% over Trinidad and greater than 60% over Tobago;
- Nights are also very likely to be warmer than average, with the chance for warmer than average nights exceeding 70%;
- Although warmer than average conditions are forecasted, uncomfortably high temperatures are not likely during the period, given that DJF is usually the coolest part of the year, locally;
- On one or two cloud free nights minimum temperatures are likely to cool well below 22.0oC.
Likely Implications
- Underperformance in rainfall amounts during the 2019 wet season has negative implications for water resource management;
- Expect reduced water recharge rates, slower and lower than usual stream flows and water levels;
- Above average rainfall totals during the 2020 dry season are not likely to be sufficient to restore water reservoir levels to their seasonal average conditions in Trinidad;
- Potential for an increase in the need to collect and store water in containers. This can increase breeding areas for mosquitoes;
- Expect increase browning of weeds, grass, bush and some forest species as the season progresses;
- Drying as the season progresses will increase bush and forest fire potential, especially during late February, March & early April;
- Reduced air quality is likely during bush, grass, forest and landfill fires. This can negatively affect existing respiratory and other ailments;
- Possibility of increased disruption in marine activities due to episodes of rough seas.
Early Actions & Preparedness
Water and Energy sector
- Escalate water conservation programs and awareness messages;
- Revisit dry season contingency plans and upgrade based on historical extremes and not historical averages;
- Harvest excess rainfall now and continue routine de-silting of reservoirs and riverine channels.
General Public
- Conserve, store and manage water safely and adequately. Take measures to lessen the impacts of dry season conditions. Be dry season ready. Stock up on water.
Disaster Risk Management Sector
- Sensitize vulnerable communities on the forecast, its negative impacts and actions to be taken;
- Review dry season contingency plans and early warning information dissemination channels.
Drainage
- Continue de-silting and cleaning drainage systems, water channels, outlets and river mouths.
Waste Management Sector
- Ramp-up contingency plans to mitigate the occurrence of landfill fires.
Health Sector
- Revisit contingency plans to manage spikes in vector-borne and dust/smoke-related respiratory ailments, as well as, contingency plans to manage impact on hygiene and sanitation.
Agriculture & Food Security Sector
- Raise awareness on agriculture pest and disease control measures and bushfires risk;
- Initiate contingency planning for expected drying as the dry season progresses.
Education Sector
- Put in place contingency plans for maintaining adequate water supply within schools.
Be vigilant and visit the Met. Service website at www.metoffice.gov.tt regularly to keep up to date with local weather changes and follow us on social media.
Climatic Influencers and Context of the Outlook
- Sea surface temperatures (SSTs) in waters surrounding Trinidad and Tobago are currently warmer than average. Multiple models surveyed by the MSD suggest the ongoing warming is likely to continue with above average temperatures during DJF and MAM.
- Warmer than average SSTs in waters east of Trinidad and Tobago are likely to be the primary driver of Trinidad and Tobago’s climate over the next 3 months.
- SSTs and atmospheric observations in the equatorial Pacific Ocean show El Niño-Southern Oscillation-neutral (ENSO-neutral) conditions exist during November. The consensus forecast suggests that ENSO-neutral conditions (neither El Niño nor La Niña) are likely to persist for the rest of 2019 and during early 2020.
- Typically, ENSO-neutral conditions at this time of the year have very little control over Trinidad and Tobago’s climate. ENSO-neutral is not likely to be a major influence on the southeastern Caribbean climate pattern, at least during DJF.
- After oscillating from its positive to negative phase during November, the North Atlantic Oscillation (NAO) is forecasted to return to its positive phase during most of December. A positive NAO tends to promote stronger trade winds and cooler than average SSTs in waters surrounding Trinidad and Tobago.
- The Madden Julian Oscillation (MJO) is known as the main feature driving fluctuation in tropical weather on weekly to monthly timescales. The MJO is likely to be present but weak during mid-to late December.
The precipitation and temperature outlook is based on statistical and dynamical seasonal climate models output and known seasonal climate influencers. The outlook is in reasonable agreement with several of the global climate models. Multiple climate influencers appear to be at play and can cancel out each other.
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