Rainfall and Temperature Outlook for Trinidad and Tobago, April to June 2020



ISSUED AT: 12:24 PM

Date: Thursday 2nd of April 2020

Key Messages
  • The month of March produced rainfall deficits across all of Trinidad and Tobago;
  • April 2020 is likely to be drier than average nationwide but the occurrence of rainfall is expected to increase during April to June (AMJ) 2020;
  • The rainfall outlook for the three month period, April to June 2020 shows a mixed picture. Below-average rainfall totals are likely across much of the country with near-average conditions favoured in small areas in both islands;
  • The chance of an early onset to the 2020 wet season is low;
  • April and May are usually two of the warmest months of the local heat season and this is likely to continue during 2020;
  • Maximum day and minimum night temperatures are likely to be warmer than average during AMJ;
  • Chances are enhanced for hot days (greater than or equal to 34oC in Trinidad and 32.0oC in Tobago) and hot spells (5 or more consecutive hot days) during April to May.

Likely Impacts

  • A near to below-average AMJ means little easing of the dryness until at least late May;
  • Near to below-average rainfall and warmer than average temperatures are likely to maintain low surface water flows and water levels;
  • Periods of excessive heat can increase heat stress for persons with heat-sensitive ailments, as well as for heat-exposed livestock, pets and other animals.

 


Rainfall and Temperature Outlook for Trinidad and Tobago, April to June 2020



ISSUED AT: 12:24 PM

Date: Thursday 2nd of April 2020

 

Mixed Conditions Likely Drier Than Average Conditions Favoured Across Most Areas For April to June 2020

 
 

Key Messages

  • The month of March produced rainfall deficits across all of Trinidad and Tobago;
  • April 2020 is likely to be drier than average nationwide but the occurrence of rainfall is expected to increase during April to June (AMJ) 2020;
  • The rainfall outlook for the three month period, April to June 2020 shows a mixed picture. Below-average rainfall totals are likely across much of the country with near-average conditions favoured in small areas in both islands;
  • The chance of an early onset to the 2020 wet season is low;
  • April and May are usually two of the warmest months of the local heat season and this is likely to continue during 2020;
  • Maximum day and minimum night temperatures are likely to be warmer than average during AMJ;
  • Chances are enhanced for hot days (greater than or equal to 34oC in Trinidad and 32.0oC in Tobago) and hot spells (5 or more consecutive hot days) during April to May.
 

 Likely Impacts

  • A near to below-average AMJ means little easing of the dryness until at least late May;
  • Near to below-average rainfall and warmer than average temperatures are likely to maintain low surface water flows and water levels;
  • Periods of excessive heat can increase heat stress for persons with heat-sensitive ailments, as well as for heat-exposed livestock, pets and other animals.
 

Early Actions & Preparedness

  • Continue water conservation programs and  awareness messages;
  • Revisit contingency plans to take advantage of the expected increase in fequency and amount of rainfall;
  • Ramp-up desilting of major river courses and reservoirs;
  • Start early preparation for the upcoming wet season.
 

Figure 1: Category of rainfall likely for April to June 2020 (AMJ) 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 AMJ period rainfall totals during the historical period used to produce the outlook.

  • April to June (AMJ) 2020 rainfall outlook shows a mixed picture;
  • AMJ 2020 is likely to eventually bring typical April type showers and transitional rainfall in May, but overall, rainfall during these two months is not likely to reduce the recent dryness, significantly;

  • The April to June 2020 rainfall outlook indicates below-average rainfall across much of the country is favoured with near-average conditions likely in a few areas (high confidence);

  • There is a 70-80% chance for at least three 7-day dry spells during April to June 2020 and a 60% chance for at least one 15-day dry spell.

 
 

Figure 2: The map shows the chances for extremely dry conditions over the next three-month period, April to June  (AMJ) 2020. Extremely dry conditions refer to the lowest 10% of  March to May accumulated rainfall totals in the historical record.

  • The chance for April to June to be extremely dry is low to moderate (medium confidence);
  •  All areas have less than 12% chance of receiving rainfall in the lowest 10% of historical April to June rainfall on record;

  • Overall, this means the odds for serious rainfall deficiency is slight.

 

Figure 3: Possible accumulated rainfall totals with the highest chance of occurring during  April to June 2020.

  • Much of Trinidad and Tobago is likely to receive accumulated rainfall totals in excess of 320.0 mm, but less than 530.0 mm over the next three months (see figure 3);
  • Rainfall totals are likely to range between 250.0 mm and 530.0 mm with the lowest totals likely in southwest Tobago, southwest and western Trinidad, while the highest totals are expected in northeastern areas of both islands.
 

Figure 4: Possible rainfall totals with the highest chance of occurring during April  2020.

  • Rainfall totals for April 2020 are likely to  be below average with a greater than 40% chance for this to occur (high confidence);
  • Possible rainfall totals range between 19.0 mm and 60.0 mm (see figure 4).

 

Figure 5:  Category of rainfall most likely for Julyto September 2020 (JAS) 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 JAS period rainfall totals during the historical period used to produce the outlook.

  • early outlook for July to September 2020 indicates above average rainfall totals are likely nationwide.
 

The Temperature Outlook

  • April and May are usually two of the warmest months in the local heat season and a similar pattern is expected for 2020;
  •  April to June average day-time maximum and night-time minimum temperatures are very likely to be warmer than average for all of Trinidad and Tobago;

  • The chance for warmer than average maximum and minimum temperatures is greater than       90 % for Trinidad and greater than 65% for Tobago;

  • There are increased chances for hot days (days with maximum temperatures being at least 34.0oC in Trinidad and 32.0oC in Tobago) and short duration hot spells (periods of consecutive hot days).

Likely Implications

  • Current rates of ground water recharge and surface water flows are likely to be maintained;
  •  Drier than average conditions can increase the need to collect and store water in containers which can increase breeding areas for mosquitoes;
  • Drier than average conditions does not mean no rainfall, and can have significant individual rainfall events which can lead to flash flooding, especially during late May and June;
  • Increase rainfall frequency and amount can lead to increased ponding of rainwater which tend to encourage mosquito breeding;

  • Periods of excessive heat can increase heat-stress  for persons with heat- sensitive ailments and for heat-exposed livestock and other animals;

  • Increased heat may increase the need to access cooling, which requires energy.
 

Early Actions & Preparedness

Water and Energy sector

  • Continue water conservation programs and  awareness messages;
  • Revisit contingency plans to take advantage of the expected increase in rainfall;
  • Rain water harvesting should also be encouraged to boost water availability in residential and commercial properties;
  • Ramp-up de-silting of major rivers and reservoirs.

General Public

  • Conserve, store and manage water safely and adequately. Take measures to lessen the impacts of the continuation of dryness early in the period and excessive heat, overall;
  •  Start preparedness for the expected increase in rainfall and take early action in preparing for the upcoming wet season.

Disaster Risk Management Sector

  • Put  in place the necessary measures to ensure communities are sensitized
  • Start preparedness for the expected increase in rainfall and the associated negative impacts;
  • Review contingency plans and early warning information dissemination channels.

Drainage

  • Ramp-up de-silting and cleaning drainage systems, water channels, outlets and river mouths.
Health Sector
  • Revisit contingency plans to manage possible spikes in vector-borne diseases due to the expected increase in the frequency and amount of rainfall.

Agriculture & Food Security Sector

  • Take  advantage  of  the  expected  increase in rainfall  and  maximize  crop  yield  through  appropriate land-use management;
  • Raise awareness on agriculture pest and disease control measures;
  • Initiate contingency planning for transition to, and the upcoming wet season.

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

 1. Waters in and around Trinidad and Tobago continue to show sea surface temperatures (SSTs) that are currently warmer than average for this time of the year. This warming is forecasted to continue during AMJ.

     Warmer than average waters to the east of Trinidad and Tobago generally means more clouds than normal and this can lead to increased rainfall over the islands.

2. Across the equatorial Pacific Ocean, the El Niño-Southern Oscillation remains neutral (ENSO-neutral) but on the warm side with near-to-above average SSTs in most areas.

3. The consensus forecast suggests that ENSO-neutral-warm conditions (neither El Niño nor La Niña) are likely to persist throughout the rest of the dry season and the start of the wet season.

    ENSO-neutral on the warm side tends to inhibit rainfall in the vicinity of Trinidad and Tobago.

 The existing and forecast conditions for these two major climate influencers suggest the possibility exists for each to cancel out the other’s influence.

4. After remaining mostly in its positive phase since January 2020, the North Atlantic Oscillation (NAO) moved into its negative phase towards the end of March and is predicted to remain in its negative phase during April.

5. A negative phase NAO tends to promote weaker trade winds, which can lead to enhanced warming of SSTs in waters surrounding Trinidad and Tobago.

6. During the last two weeks of March, the Madden Julian Oscillation (MJO) which is usually the main climate feature that influences variability in tropical weather on weekly to monthly timescales, had a negative influence on rainfall in the region.

7. The MJO is forecasted to move into a phase, which is likely to positively influence local rainfall during the second to third week of April.

The rainfall and temperature outlook is based on statistical and dynamical seasonal climate models outputs 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 at varying time scales and can cancel out each other.