Rainfall and Temperature Outlook for Trinidad and Tobago, August to October 2019



ISSUED AT: 12:14 PM

Date: Friday 26th of July 2019

Key Messages
 
  • The outlook for  August to October  (ASO) 2019 indicates Trinidad and Tobago is likely to be as wet as usual with near average rainfall totals expected (medium confidence);
  • An outlook with increased chances for near average rainfall totals over the next three months suggests rainfall relief is likely to continue;
  • The outlook indicates  at least three (3) wet spells are likely during ASO 2019 (3 or more continuous days with rainfall totals greater than 10 mm);
  • August is likely to be as wet as usual with rainfall totals in the near average category (medium confidence);
  • Usually, Trinidad and Tobago's second heat season runs from August to October. In most years September is the hottest month and the peak of the heat season;
  • ASO is likely to be warmer than usual with both day and night temperatures likely to exceed their averages;
  • Concerns for short duration hot-spells and an increase in the number of hot days (days with maximum temperature greater than 33.9oC in Trinidad and greater than 32.0oC in Tobago) remain elevated for the August to October period.
 

 

Likely Impacts

  •  

      • Flash flood potential is expected to be of general concern for the country throughout the period, but particularly in August and October.   Flash flood  risk is further elevated for November;
      • Increased risk for riverine flooding, landslips and landslides during prolonged rainfall periods;
      • Many days  between August and October  are likely to feel far from comfortable because of high temperatures and high humidity values;
      • More reliable rains for water resource management and agriculture can be expected  with enhanced chances for wet as usual conditions;
      • Increases in surface water ponding can promote mosquito breeding, leading to higher risk for spikes in vector borne diseases.

       

 

 

 


Rainfall and Temperature Outlook for Trinidad and Tobago, August to October 2019



ISSUED AT: 12:14 PM

Date: Friday 26th of July 2019

Near Normal Rainfall  Likely During August to October 2019

 Risk of Flooding Remains High

Key Messages

  • The outlook for  August to October  (ASO) 2019 indicates Trinidad and Tobago is likely to be as wet as usual with near average rainfall totals expected (medium confidence);
  • An outlook with increased chances for near average rainfall totals over the next three months suggests rainfall relief is likely to continue;
  • The outlook indicates  at least three (3) wet spells are likely during ASO 2019 (3 or more continuous days with rainfall totals greater than 10 mm);
  • August is likely to be as wet as usual with rainfall totals in the near average category (medium confidence);
  • Usually, Trinidad and Tobago's second heat season runs from August to October. In most years September is the hottest month and the peak of the heat season;
  • ASO is likely to be warmer than usual with both day and night temperatures likely to exceed their averages;
  • Concerns for short duration hot-spells and an increase in the number of hot days (days with maximum temperature greater than 33.9oC in Trinidad and greater than 32.0oC in Tobago) remain elevated for the August to October period.
Likely Impacts
  • Flash flood potential is expected to be of general concern for the country throughout the period, but particularly in August and October. Flash flood  risk is further elevated for November;
  • Increased risk for riverine flooding, landslips and landslides during prolonged rainfall periods;
  • Many days  between August and October  are likely to feel far from comfortable because of high temperatures and high humidity values;
  • More reliable rains for water resource management and agriculture can be expected  with enhanced chances for wet as usual conditions;
  • Increases in surface water ponding can promote mosquito breeding, leading to higher risk for spikes in vector borne diseases.
 

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 August to October (ASO) 2019 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 ASO period rainfall totals during the historical period used to produce the outlook.

  • Less rainfall than the average was observed across most areas in July; however, the latest forecasts for the country as a whole suggest that the country is likely to be as wet as usual during the three months August to October with near average rainfall totals likely (medium confidence).
  • This means the country is likely to receive 3-month rainfall totals that are between 75% and 125% of the long term averages. For instance, at Piarco, this means possible accumulated ASO rainfall totals between 495.0 mm and 825.0 mm and at Crown Point possible totals between  368.0 mm and 614.0 mm;
  • Trinidad is likely to receive 32-48 wet days during ASO while Tobago is likely to 40-55 wet days (Usually out of 92 days in ASO the average is 37-52 wet days for Trinidad and 43-56 for Tobago). Both islands are likely to get at least 3 wet spells (3 or more continuous days with rainfall totals greater than 10 mm).
 

Figure 2: The map shows the chances for extremely dry conditions over the next three months, August to October 2019. Extreme dry conditions refers to the lowest 10% of  August  to October accumulated rainfall in the historical record.

  • The chance for the ASO  period to be extremely dry is low to moderate (medium confidence);
  • The chance for accumulated rainfall totals over ASO 2019 to be in the lowest 10% of historical ASO rainfall totals ranges between 9% and 20%;

  • Even though the odds for this to occur is low, should it occur, it can have far reaching negative impacts on water resources later on;

  • There is a 30- 40 % chance for at least two (2) periods of seven (7) consecutive dry days during ASO.

 

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

  • Largest rainfall accumulated totals  for ASO are likely to be near 845.0mm in Sangre Grande, North Oropouche and surrounding environs in east Trinidad with the smallest totals likely near Icacos, Cedros  and other areas in southwest Trinidad;
  • Tobago’s largest totals are likely to be near 784.0 mm in the vicinity of Kings Bay and other northeastern areas, while smallest totals are likely in the southwestern areas near Bon-Accord, Mount Irvine and environs.
 

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

  • The country is likely to receive near average rainfall totals during August with most areas having an enhanced chance for August to be as wet as usual (medium confidence);
  • Possible rainfall totals range from near 181.0 mm to near 360.0 mm in Trinidad and near 160.0 mm to near 240.0 mm in Tobago.
 

Figure 5:  Category of rainfall most likely for November 2019 to January 2020 (NDJ) 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 NDJ period rainfall totals during the historical period used to produce the outlook.

  • November 2019 to January 2020 (NDJ) is likely to be wetter than usual with a greater than 35% chance for accumulated rainfall totals to be in the above  average category, across both islands;
  • November is likely to be particularly wet.  As such, the risk for flooding remains elevated.
 
 

The Temperature Outlook

  • In most years, August to October is  considered as the second heat season in Trinidad and Tobago, with September often being the hottest month;
  • August to October in Trinidad and Tobago will likely be warmer than usual with potentially risky heat exposure during very hot dry spells between August and October.
  • There is greater than 55 % chance for maximum day-time and minimum night-time temperatures to be above average, with  September days and nights likely to be the warmest during the period;
  • The chance for increases in the number of hot days is higher in Port of Spain and built-up areas;
  • Concerns for short duration hot-spells and increase in the number of hot days (days with maximum temperature greater than 33.9oC in Trinidad and greater than 32.0oC in Tobago) are elevated for the August to October period.
Likely Implications
  • Increased risk of flash and riverine flooding, landslips and landslides, on heavy rainfall days and short duration wet spells. Flooding risk is further elevated for the month of November;
  • Increase in recharge rates at water reservoirs associated with as wet as usual conditions. Possible increased turbidity and degraded water quality on heavy rainfall days;
  • More reliable rains for water resource management and agriculture;
  • Warmer than average temperatures can aid more intense showers, which will increase the risk for flash floods on hot days, especially in the cities, built-up areas and flood prone areas;
  • Increases in 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;
  • Increased rainfall is often associated with more flies and flies are known to carry and spread diseases such as gastroenteritis and salmonella infection;
  • Increased rainfall could lead to reduced traffic flows, disruptions in localized travel, longer travelling times, which may require earlier start time for commute.
  • Many days  between August and October  are likely to feel far from comfortable because of warmer  than average temperatures and high humidity values
  • Excessive heat can cause discomfort and illness in vulnerable persons, increase in cooling needs, and cause crops and livestock to suffer; hence can reduce food production.
     
 

Early Actions & Preparedness

General Public

  • Persons living in flood risk areas should prepare now. 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 tree-overhang near residence; Take measures to lessen impacts from 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 now;
  • Review contingency plan for increased turbidity and degraded water quality;
  • Remove dry branches, trees and overhang near electrical wires, especially in landslip prone areas.

Agriculture & Food Security Sector

  • Ready pumps for clearing waterlogged drain;
  • 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. 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;
  • Clear choked surface drains to allow fast drainage and to reduce flash flood;

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.

Health Sector

  • Revisit contingency plans to manage spike in vector borne incidences.

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

  • Sea surface temperatures (SSTs) in waters close to Trinidad and Tobago continue to warm and are now much warmer than average while SSTs further east are near average and cooler than average in some spots. Several model predictions indicate ongoing warming is likely to produce near to above average temperatures during ASO in waters to the east of Trinidad and Tobago.
  • Weak El Niño conditions continue in the tropical Pacific Ocean as SSTs in the east-central Pacific declined during early July, but are still above average.
  •  El Niño  is predicted  to  transition to neutral El Niño-Southern Oscillation or ENSO during the forecasts period with most dynamical climate models predicting ENSO-neutral as the year progresses;
  • El Niño conditions during the local wet seasons in the past tend to favour less rainfall than usual  for Trinidad and Tobago, but not always, especially during weak El Niño events;
  • Since May, the North Atlantic Oscillation (NAO) has mostly been in its negative phase and is predicted to continue in its negative phase during the first two weeks of August. A negative NAO tends to aid warmer SSTs in waters around Trinidad and Tobago. Warmer SSTs usually have a positive influence on local rainfall;
  • The Madden Julian Oscillation (MJO) is the main feature driving fluctuation in tropical weather on weekly to monthly timescales. The MJO is unlikely to influence local rainfall during August.

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, which favour either near to above average rainfall in the vicinity of Trinidad and Tobago. Multiple climate influencers appear to be at play and can cancel out each other. This reduces our confidence in the ASO outlook.