Rainfall and Temperature Outlook for Trinidad and Tobago, June to December 2019



ISSUED AT: 10:47 PM

Date: Friday 7th of June 2019

Key Messages
    • The Rainfall Outlook for the overall 2019 Wet Season indicates near normal rainfall totals (that is totals between 75% and 125% of average) have the most likely chance of occurring, when compared with the chances for below normal and above normal totals (High confidence);
    • The June to August (JJA) 2019 Rainfall Outlook shows the best chance is for less wet than usual conditions. That is, accumulated rainfall totals are likely to be in the below-average category (rainfall totals less than 75% of the long term mean) (High confidence);
    • The forecast indicates fewer wet days than usual and  fewer wet spells during JJA (High confidence);
    • June 2019 rainfall is likely to be less than usual (High confidence);
    • September to November Rainfall Outlook shows the best chance is for  above-normal rainfall (Medium confidence);
    • Both day and night temperatures are forecasted to remain higher than average;
    • Episodes of dust-haze outbreaks are expected during JJA.
 

Likely Impacts

    • Possible gradual increase in rainfall in both islands as the season progresses;
    • Possible slower than usual stream flow and lower than usual water levels;
    • Possible slower than usual recharge rates at water reservoirs/dams;
    • Loss of vegetation, ground cover and altered top soil structure due to recent bushfires have the potential to elevate soil erosion, runoff, and the volume of sediment entering streams. This can lead to increased turbidity and degraded water quality;
    • Flooding potential associated with heavy rainfall and short duration wet spells is enhanced for flood prone areas;
    • Flooding risk is elevated for the September to November period.
     
 

 

 


Rainfall and Temperature Outlook for Trinidad and Tobago, June to December 2019



ISSUED AT: 10:47 PM

Date: Friday 7th of June 2019

Near Normal Wet Season 2019

June to August Likely To Be Drier Than Usual

September to December Likely To Be Wetter Than Usual

Key Messages

  • The Rainfall Outlook for the overall 2019 Wet Season indicates near normal rainfall totals (that is totals between 75% and 125% of average) have the most likely chance of occurring, when compared with the chances for below normal and above normal totals (High confidence);
  • The June to August (JJA) 2019 Rainfall Outlook shows the best chance is for less wet than usual conditions. That is, accumulated rainfall totals are likely to be in the below-average category (rainfall totals less than 75% of the long term mean) (High confidence);
  • The forecast indicates fewer wet days than usual and  fewer wet spells during JJA (High confidence);
  • June 2019 rainfall is likely to be less than usual (High confidence);
  • September to November Rainfall Outlook shows the best chance is for  above-normal rainfall (Medium confidence);
  • Both day and night temperatures are forecasted to remain higher than average;
  • Episodes of dust-haze outbreaks are expected during JJA.

Likely Impacts

  • Possible gradual increase in rainfall in both islands as the season progresses;
  • Possible slower than usual stream flow and lower than usual water levels;
  • Possible slower than usual recharge rates at water reservoirs/dams;
  • Loss of vegetation, ground cover and altered top soil structure due to recent bushfires have the potential to elevate soil erosion, runoff, and the volume of sediment entering streams. This can lead to increased turbidity and degraded water quality;
  • Flooding potential associated with heavy rainfall and short duration wet spells is enhanced for flood prone areas;
  • Flooding risk is elevated for the September to November period.

Early Actions & Preparedness

  • Proper preparation especially for persons in at risk areas. Stock up on emergency supplies for 3-7 days;
  • Persons in flood prone areas should pack a flood-ready go-bag with clothes and essentials;
  • Develop an emergency communication plan, which includes a place to stay;
  • Clear dry branches/tree-overhang near residence; Guard against the effects of excessive heat;
  • Clean drains, canals and guttering; Conserve, store and manage water in a safe and adequate manner;
  • Take measures to lessen impacts from flooding. Be sand-bag ready.
 

 

Figure 1: Category of rainfall likely for the 2019 Wet Season (June to December) 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 June to December rainfall totals during the historical period used to produce the outlook.

 

  • The overall 2019 Wet Season Rainfall Outlook (June to December) is indicating that Trinidad and Tobago is likely to receive near-average rainfall (High confidence);
  • Currently, there is no strong signal for an overall wetter or drier than average wet season;
  • This means the usual number of extreme wet spells are expected;
  • At least one prolonged wet spell (3 or more extremely wet days) is expected.
 

Figure 2: Category of rainfall likely for June to August  2019 (JJA) 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 JJA rainfall totals during the historical period used to produce the outlook.

  • The outlook for the early wet season (June to August) shows less wet than usual conditions are likely with below-average rainfall totals expected across both island (High confidence);
  • A gradual increase in rainfall occurrence is likely over the period, but July is likely to be the wettest month of the JJA period;
  • Even though less than the usual amount of rainfall is expected, concerns for flash flooding during heavy and prolonged rainfall events still exist.
 

 

Figure 3: Possible accumulated rainfall totals with the highest chance of occurring during June to December 2019.

  • The largest rainfall accumulated totals are likely to be near 2260 mm in Valencia and surrounding environs in northeast Trinidad while the smallest obverall totals are likely to occur  in Port of Spain and surrounding areas  and the extreme southwestern end of Trinidad;
  • Tobago’s largest totals are likely to be near 1800 mm near the Mt. Saint George/Hillsborough area while the smallest totals are likely in the extremee southwestern area, near Crown Point.
 

Figure 4: Possible rainfall totals with the highest chance of occurring during June to August 2019.

  • For JJA 2019, accumulated rainfall totals are likely to range from near 950 mm to near 540 mm in Trinidad and from  near 670 mm to near 400 mm in Tobago;
  • The largest totals in Trinidad are expected in northeastern areas while in Tobago largest totals are likely near the Mt. Saint George/Hillsborough area.
 

Figure 5:  Category of rainfall likely for September to November  2019 (SON) 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 SON rainfall totals during the historical period used to produce the outlook

  • September to November (SON) 2019 shows a shift towards much wetter than usual conditions is likely, with accumulated rainfall totals favoured to be in the above normal category, across both islands (Medium confidence);
  • This suggests that concerns for flooding are elevated during this period.

 

 

 

 

 

The Temperature Outlook Favours Warmer Than Usual Temperatures During JJA 2019

  • Trinidad and Tobago is likely to receive warmer than usual conditions during JJA and SON;
  • There is a 72% chance for maximum day-time and minimum night-time temperatures to be above  average;
  • Concerns for short duration hot-spells and an increase in the number of  hot days (days with maximum temperature greater than 33.9 degrees Celsius in Trinidad and greater than 32.0 Celsius in Tobago) are elevated for the August to October period;
  •  The chance for an increase in the number of hot days is higher in Port of Spain and built-up areas, than elsewhere.

Likely Implications

  • Possible gradual increase in rainfall in both islands as the season progresses;
  • Possible slower than usual stream flow and lower than usual water levels;
  • Possible slower than usual recharge rates at water reservoirs/dams;
  • Loss of vegetation, ground cover and altered top soil structure due to recent bushfires have the potential to elevate soil erosion, runoff, and the volume of sediment entering streams;
  • Possible increased turbidity and degraded water quality;
  • Increased risk of flash and riverine flooding, landslips and landslides on heavy rainfall days and short duration wet spells;
  • Flooding risk is elevated for the September to November period;
  • Warmer than average temperatures can aid more intense showers, which can increase the risk for flash floods on hot days, especially in the cities, built-up areas and flood prone areas;
  • Increased surface water ponding can promote mosquito breeding, leading to  higher risk for spikes in vector borne diseases;
  • Increased rainfall, mixed with warm and humid conditions tend to promote rapid multiplication of some agricultural pests, diseases and fungal growth;
  • More rainfall than normal is associated with more flies and flies are known to carry and spread diseases such as Gastroenteritis and Salmonella infection;
  • Increased  rainfall could  lead to slower traffic flows, disruptions in localized travel, longer travelling times, which may require earlier start times for commute.

 

 

 

 

 

 

 

Early Actions & Preparedness

General Public

  • Proper preparation is encouraged, especially for persons lining in at-risk areas.
  • Stock up on emergency supplies for 3-7 days;
  • Persons in flood prone areas should pack a flood-ready go-bag with clothes and essentials;
  • Develop an emergency communication plan, which includes a place to stay;
  • Clear dry branches/tree-overhang near residence; Guard against the effects of excessive heat;
  • Clean drains, canals and guttering;
  • Conserve, store and manage water in a safe and adequate manner;
  • Take measures to lessen impacts from flooding. Be sand-bag ready.

Water and Energy sector

  • Conduct routine de-silting of reservoirs and riverine flooding channels;
  • Harvest excess rainfall during the wet season;
  • Review contingency plans for increased turbidity and degraded water quality;
  • Remove dry branches, trees and overhang near electrical wires, especially in landslip and landslide prone areas.

Agriculture & Food Security Sector

  • Ready pumps for clearing waterlogged drainage;
  • Clear or clean poorly maintained and choked surface drains to prevent waterlogging.

Disaster Risk Management Sector

  • Sensitize communities on the forecast and its negative impacts or its opportunities;
  • Revisit early warning information dissemination channels;
  • Alert communities and citizens in flood and landslide prone areas to act early.

Drainage

  • De-silt drainage systems, canals, drains and river mouths;
  • Perform maintenance on sluice gates;
  • Clean and clear choked surface drains to allow fast drainage and to reduce flash flood;

Health Sector

  • Revisit contingency plans to manage spike in vector borne deseases;

Waste Management Sector

  • Ramp up efforts to prevent waste from entering drains and water courses in order to reduce flooding and water pollution;
  • Implement anti-litter activities to raise awareness on the impacts of poor solid waste management.

Be vigilant and visit the Met. Service website at www.metoffice.gov.tt regularly to keep up to date with local weather changes and download our free mobile app on the Google Play Store or Apple iStore.

 

 

 

 

Climatic Influencers and Context of the Outlook

  • A mixture of cooler than average, near-average and warmer than average sea temperatures currently exist in waters in, and around, Trinidad and Tobago. The forecasts indicate that warming is likely to produce near to above average temperatures during the wet season;
  • Current weak El Niño in the tropical Pacific Ocean is expected to persist throughout the early wet season. Most of the climate models reduces the chance for El Niño  as the season progresses;
  • El Niño conditions during most of the local wet seasons in the past, tended to favour less than average rainfall totals for Trinidad and Tobago;
  • Since mid-April, the North Atlantic Oscillation (NAO) has mostly been in its negative phase. A negative NAO tends to aid in warming SSTs in waters around Trinidad and Tobago. Warmer than usual SSTs usually have a positive influence on local rainfall;
  • The Madden Julian Oscillation (MJO) is usually the main feature driving fluctuations in tropical weather on weekly to monthly timescales. The MJO is likely to be in a favourable phase to influence local rainfall during the last week of June and first week of July.
  • The precipitation and temperature outlook is based on statistical and dynamical seasonal climate models output and known seasonal climate influencers. The outlook is in good agreement with most of the global climate models, which favour either below average or near average rainfall in the Caribbean region for the same period. This increases confidence in the totall forecast.