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



ISSUED AT: 01:31 PM

Date: Tuesday 1st of October 2019

Key Messages
 
  • Near normal to slightly above normal rainfall totals were observed across Trinidad and Tobago  during September 2019;
  • October to December (OND) 2019 rainfall outlook indicates Trinidad and Tobago is likely to be as wet as usual for this time of the year. Rainfall totals are likely to be near normal across all of the country for the 3-month period OND 2019 (medium confidence);
  • An outlook with increased chances for near normal rainfall totals over the next three months suggests rainfall relief is likely to continue, while the risk of flooding remains elevated;
  • October is likely to be just as wet as usual with possible rainfall totals in the near normal category (medium confidence);
  • OND 2019 is likely to be warmer than usual with both day and night temperatures likely to exceed their averages;
  • October is usually the end of the local heat season. October 2019 is likely to be the warmest of the three months;
  • Concerns remain heightened for short duration hot-spells and a number of hot days (days with maximum temperature greater than 33.9oC in Trinidad and greater than 32.0oC in Tobago) during October.
 

 

 

 

 

 

 
 

Likely Impacts

  • Flash flooding is expected to be of general concern for the country throughout the period, but particularly in October and November;
  • Increased risk for riverine flooding, landslips and landslides during prolonged rainfall periods;
  • More reliable rains for water management & agriculture can be expected during the period;
  • Increases in surface water ponding can promote mosquito breeding, leading to higher risk for spikes in vector-borne diseases;
  • Several days during October are likely to feel far from comfortable due to high temperatures and high humidity values.
 
 

 

 


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



ISSUED AT: 01:31 PM

Date: Tuesday 1st of October 2019

Reasonable Chance For  Wet  As Usual Conditions During October to December 2019

Risk of Flooding Is Elevated
 
 

Key Messages

  • Near normal to slightly above normal rainfall totals were observed across Trinidad and Tobago  during September 2019;
  • October to December (OND) 2019 rainfall outlook indicates Trinidad and Tobago is likely to be as wet as usual for this time of the year. Rainfall totals are likely to be near normal across all of the country for the 3-month period OND 2019 (medium confidence);
  • An outlook with increased chances for near normal rainfall totals over the next three months suggests rainfall relief is likely to continue, while the risk of flooding remains elevated;
  • October is likely to be just as wet as usual with possible rainfall totals in the near normal category (medium confidence);
  • OND 2019 is likely to be warmer than usual with both day and night temperatures likely to exceed their averages;
  • October is usually the end of the local heat season. October 2019 is likely to be the warmest of the three months;
  • Concerns remain heightened for short duration hot-spells and a number of hot days (days with maximum temperature greater than 33.9oC in Trinidad and greater than 32.0oC in Tobago) during October.

 Likely Impacts

  • Flash flooding is expected to be of general concern for the country throughout the period, but particularly in October and November;
  • Increased risk for riverine flooding, landslips and landslides during prolonged rainfall periods;
  • More reliable rains for water management & agriculture can be expected during the period;
  • Increases in surface water ponding can promote mosquito breeding, leading to higher risk for spikes in vector-borne diseases;
  • Several days during October are likely to feel far from comfortable due to high temperatures and high humidity values.

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 and excessive heat. Be sand-bag ready.
 

Figure 1: Category of rainfall likely for October  to December  (OND) 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 OND period rainfall totals during the historical period used to produce the outlook.

  • The rainfall outlook indicates that OND 2019 is likely to be just as wet as usual with near normal rainfall totals likely (medium confidence);
  • The percent chance for as wet as usual conditions over the 3-month period OND 2019 is at least 41% across the majority of Trinidad and Tobago;

  • Near normal means areas are likely to receive 3-month rainfall totals between 75% and 125% of the long term averages. For instance, this means possible accumulated OND rainfall totals between 450.5 mm and 750.8 mm at Piarco and between 384.4 mm and 640.6 mm at Crown Point.

 

Figure 2: The map shows the chances for extremely dry conditions over the next three months, October  to  December  (OND) 2019. Extremely dry conditions refer to the lowest 10% of October to December accumulated rainfall totals in the historical record.

  • There is a low to moderate chance for OND 2019 to be extremely dry (medium confidence);
  • The chance for OND 2019 accumulated rainfall totals to be in the lowest 10% of historical OND rainfall totals ranges between 8% and 20%;
  • Even though the odds for OND 2019  rainfall totals to be in the lowest 10% on record are low to moderate, should it occur, it can have far reaching negative impacts on water resources in the upcoming dry season.
 

Figure 3: Possible accumulated rainfall totals with the highest chance of occurring during  October tto December (OND) 2019.

  • Largest rainfall accumulated totals for OND 2019 are likely to be as much as 1050.0 mm in Valencia, Sangre Grande, North Oropuche and surrounding environs in east Trinidad; while the smallest totals are likely to be as low as 453.0 mm, near Icacos, Cedros  and other areas in southwest Trinidad;
  • Across in Tobago the largest totals are likely to be near 800.0 mm in the vicinity of Hillsborough and other northeastern areas, while smallest totals are likely in the southwestern areas near Crown Point, Mount Irvine and environs;
  • October and November are likely to be the wettest of the three months. 
 

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

  • The country is likely to receive near normal rainfall totals during October 2019 (medium confidence);
  • Possible rainfall totals range from near 110.0 mm to near 300.0 mm in Trinidad and near 170.0 mm to near 275.0 mm in Tobago.
 

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

  • Rainfall is likely to be above normal across most of the country for the early 2020. January to March 2020 is likely to be wetter than usual with a greater than 35% chance for accumulated rainfall totals to be in the above normal category.
 

The Temperature Outlook

  • Usually, the month of October is considered as the end of the annual heat season in Trinidad and Tobago;
  • Both daytime and night temperatures are very likely to be above normal across all of Trinidad and Tobago during the October to December period;
  • There is a greater than 70 % chance for maximum daytime and minimum night temperatures to be warmer than normal;
  • Concerns for short duration hot-spells and of hot days (days with maximum temperature greater than 33.9oC in Trinidad and greater than 32.0oC in Tobago) are elevated for the October;
  • There is a risk for high heat exposure during the month of October. The risk is highest in the cities and urban built-up areas.

Likely Implications

  • 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 months of October and 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  during October are likely to feel far from comfortable because of warmer  than average temperatures and high humidity values;
  • Excessive heat in October has the potential to cause: discomfort and illness in vulnerable persons; crops and livestock to suffer; and increase cooling needs.
 

Early Actions & Preparedness

General Public

  • Persons living in flood risk areas are urged to 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 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 and excessive heat. 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;
  • Clean and 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 are currently warmer than average. A number of models surveyed by the MSD indicate ongoing warming is likely to produce much above average temperatures during OND in most waters to the east of Trinidad and Tobago.
  • Warmer than average SSTs in waters east of Trinidad and Tobago are likely to be the primary driver of Trinidad and Tobago’s rainfall climate over the next 3 months.
  • El Niño-Southern Oscillation-neutral (ENSO-neutral) conditions exist in the tropical Pacific Ocean as SSTs in the east-central Pacific continue to cool.
  •  ENSO is likely to remain neutral (neither El Niño nor La Niña) for the remainder of 2019 and early 2020.
  • Typically, ENSO-neutral condition has very little control over Trinidad and Tobago’s climate.
  • After oscillating from positive to negative phase during September, the North Atlantic Oscillation (NAO) is forecast to remain in its negative phase during most of October. A negative NAO tends to promote warner 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 influence local rainfall favourably during October.

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. This reduces our confidence in the OND outlook to medium.