Rainfall and Temperature Outlook for Trinidad and Tobago, July to September 2021



ISSUED AT: 04:50 PM

Date: Wednesday 30th of June 2021

Key Messages

  • Overall wet as usual (near -normal) conditions are forecast for the July to September (JAS);
  • July to September is likely to receive near-normal rainfall. Concerns for flooding still exist;
  • July is likely to be as wet as usual;
  • October to December is likely to receive much more rainfall than usual with above-normal totals most likely - Potential for flooding is elevated;
  • Slightly and moderately higher than normal flood potential exist for all well-known flood prone and some occasionally flooded areas;
  • Both day and night temperatures are expected to be much warmer than average during the wet season;
  • A few hot days (maximum temperatures ≥34.0oC) and  at least one short duration hot spell (5 or more consecutive hot days) are likely during August and September;
  • Cities and urban areas are likely to get the most intense heat;
  • The Madden Julian Oscillation (MJO) is likely to suppress local rainfall during the fortnight of July 6th -19th.
 

 

 

Likely Impacts

An outlook with increased chances for wet as usual conditions suggest:

  • Elevated risks of heavy rainfall days and prolonged wet periods.
  • Heightened concerns exist for persons in occasionally flooded and flood prone areas.

Hotter than average maximum day and night temperatures suggests:

  • Heightened concerns for persons with heat-sensitive ailments, vulnerable persons exposed to excessive heat, and heat-stress in livestock and other animals, as well as, in young and transplanted crops.


Rainfall and Temperature Outlook for Trinidad and Tobago, July to September 2021



ISSUED AT: 04:50 PM

Date: Wednesday 30th of June 2021

Near-normal rainfall likely for July to September

Flood Potential Remains Elevated

Key Messages
  • Overall wet as usual (near -normal) conditions are forecast for the July to September (JAS);
  • July to September is likely to receive near-normal rainfall. Concerns for flooding still exist;
  • July is likely to be as wet as usual;
  • October to December is likely to receive much more rainfall than usual with above-normal totals most likely - Potential for flooding is elevated;
  • Slightly and moderately higher than normal flood potential exist for all well-known flood prone and some occasionally flooded areas;
  • Both day and night temperatures are expected to be much warmer than average during the wet season;
  • A few hot days (maximum temperatures ≥34.0oC) and  at least one short duration hot spell (5 or more consecutive hot days) are likely during August and September;
  • Cities and urban areas are likely to get the most intense heat;
  • The Madden Julian Oscillation (MJO) is likely to suppress local rainfall during the fortnight of July 6th -19th.

 Likely Impact

An outlook with increased chances for wet as usual conditions suggest:

  • Elevated risks of heavy rainfall days and prolonged wet periods.
  • Heightened concerns exist for persons in occasionally flooded and flood prone areas.

Hotter than average maximum day and night temperatures suggests:

  • Heightened concerns for persons with heat-sensitive ailments, vulnerable persons exposed to excessive heat, and heat-stress in livestock and other animals, as well as, in young and transplanted crops.
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Early  Actions & Preparedness

  • Strengthen community coordination with disaster management personnel;
  • Persons living in flood risk areas should quicken their flood planning and preparedness efforts;
  • Purchase emergency supplies and pack a grab and go-bag with clothes and essentials and have these on standby;
  • Get acquainted with your flood prone areas, shelter locations and become sand-bag ready;
  • Develop an evacuation plan that outlines the safety of family members and pets;
  • Update contact information for the local disaster officials and other emergency services.
 

Figure 1: Category of rainfall likely for July to September 2021 (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.

  • A slight  increase in rainfall amounts is expected for July to September with wet as usual conditions  likely;
  • Rainfall for July to September is likely to be near-normal for all of Trinidad and Tobago with most of the eastern half of Trinidad and more than three-quarters of Tobago showing a greater than 40% chance for this to occur;
  • Near-normal rainfall for JAS is  usually substantial amounts of rainfall;
  • Periods of prolonged rainfall interspersed by a number of dry days are likely during JAS;
  • Concerns remain for flash flooding during heavy and prolonged rainfall events;
  • There is a reasonable chance that September will get a Petite Careme this year.

 

 Figure 2:  Percentage of average rainfall totals likely for July to September 2021.

  • The pattern for the percentage of average rainfall for July to September remains close to average 100% , and ranges between 90% and 111%, though the lowest percentage of average is expected in a few areas in eastern Trinidad.

Figure 3: The map shows the chance for extremely dry conditions over the three months, ending September 2021. Extreme refers to the lowest 10% of July to September accumulated rainfall totals in the historical record.

  • The chance for JAS 2021 accumulated rainfall totals to be among the driest 10% of July to September is relatively low to moderate amd ranges between 8% and 15%.
 

Figure 4: Possible accumulated rainfall totals with the highest chance of occurring during July to September 2021.

  • Possible accumulated rainfall totals for JAS in Trinidad are likely to range between 520 mm and 879 mm;
  • Areas in the eastern half of Trinidad are likely to be the wettest areas and expected to receive in excess of 723 mm of rainfall;
  • Possible JAS rainfall totals likely for Tobago range between 520 mm and 828 mm.

Figure 5: Possible rainfall totals with the highest chance of occurring during July 2021.

  • July is likely to be as wet as usual with near-normal rainfall totals likely to range between 138.0 mm and 318.0 mm in Trinidad and between 162.0 mm and 232.0 mm in Tobago;
  • The chance for near-normal rainfall is greater than 40%, which is larger than the chance for above-normal or below-normal totals.

Figure 6: Category of rainfall most likely for October to December (OND) 2021 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 outlook for  October  to  December  2021 (OND) favours much wetter than usual conditions with above-normal rainfall likely;
  • October and November are likely to be the wettest months.

Temperature Outlook:

  • Maximum temperatures for July to September are likely to be above average for all of Trinidad and Tobago;
  • Cities, urban and developed areas have the highest chance for warmer than normal  temperatures;

  • Minimum temperatures for July to September are very likely to be above average for Trinidad and likely for Tobago, which shows slightly lower chances over most areas;

  • The period August to September forms part of the second peak of the local heat season during which there are likely to be a few hot days (maximum temperatures ≥34.0oC) and at least one short duration hot spell (5 or more consecutive hot days);

  • The risks for hot days and hot spells are highest for September.

Figure 9: The map shows the colour-coded category (below-normal, above-normal, and near-normal) of maximum and maximum temperatures that is most likely to occur across Trinidad and Tobago for the July to September 2021. The colour-coded bar-graph with the numbers to the right gives the likelihood for each forecast category to occur.

Likely Implications

  • Near-normal rainfall for JAS can still have sufficient heavy rainfall days that are high risk enough to cause severe flooding. Flash flood risk remains elevated in occasional and well-known flood prone areas;
  • Localized moderate to heavy rainfall days could trigger flash-flooding in high-risk/flood-prone areas and within watersheds with narrow valleys and steep hill-sides;
  • Expect an increase in recharge rates, surface water flows and river levels;
  • Possible increased turbidity and degraded water quality on heavy rainfall days;
  • More reliable rains for agriculture but the excess rainfall can lead to water logging of agricultural fields;
  • Increased rainfall, mixed with warm and humid conditions will likely promote rapid multiplication of some agricultural pests, diseases and fungal growth;
  • Increased rainfall could lead to reduced traffic flows, disruptions in localized travel, and longer travelling times, which may require earlier commute start-times;
  • An increase in surface water ponding can promote mosquito breeding, which can lead to higher risks for spikes in vector-borne diseases;
  • Higher than usual and extreme temperatures can lead to relatively excessive heat for Trinidad and Tobago during the peak of the local heat season, which can amplify existing health conditions in vulnerable persons and worsen chronic health conditions in others;
  • Increased heat may increase the need to access cooling, which requires energy;
  • Hot days and spells can cause heat stress in livestock and wilting in newly transplanted and younger crops;

  • Warmer than usual temperatures can lead to warmer than usual water-temperatures, which are particularly important for the health of aquaponic fishes  and plants;
  • Water temperatures much warmer than 30.0oC can affect warm-water fishes such as tilapia.
 

Sectorial Early Actions  and Preparedness That Can Be Taken To Reduce Possible Impacts

General Public

  • Persons living in flood risk areas should continue their flood planning and preparedness efforts;
  • Maintain emergency supplies and a grab and go-bag with clothes, medicnes and essentials and have these on standby;
  • Get acquainted with your flood prone areas, shelter locations and become sand-bag ready;
  • Develop an evacuation plan that outlines the safety of family members and pets;
  • Update contact information for the local disaster officials and other emergency services.

Disaster Risk Management Sector

  • Continue sensitization and awareness building in vulnerable communities;
  • Start preparedness for the expected increase in rainfall and the associated negative impacts;
  • Test and re-check emergency check-lists, contingency plans and warning dissemination channels;
  • Enhance outlook messages and distribute appropriate advice on the outlook through the media.

Water and Energy sector

  • Update flood action plans and continue water conservation awareness messaging;
  • Revisit contingency plans and ramp-up de-silting of major rivers and reservoirs;
  • Remove dry branches and tree-overhang near electrical power wires.

Drainage & Infrastructure

  • Continue de-silting and cleaning of drainage systems, water channels, outlets and river mouths;
  • Visit and pre-check areas known for rock fall which may be indicative of potential future landslides.

Agriculture & Food Security Sector

  • Raise awareness on agriculture pest and disease control measures. Revisit flood action plans.

Waste Management Sector

  • Review contingency plans and operational practices (such as diverting rainfall water-flows away from waste heaps) used for mitigating/preventing leachate and contamination of ground/surface water.

Health Sector

  • Revisit contingency plans to manage spikes in vector-borne and excessive heat ailments;
  • Review fumigation plan and programme.

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

Climatic Influencers and Context of the Outlook

  • During the last four weeks, changes in sea surface temperatures (SSTs) in waters surrounding Trinidad and Tobago have been positive, maintaining warmer than average conditions over most areas and this is also forecast for the JAS period.  
  • El Niño–Southern Oscillation (ENSO) is currently neutral amd this is predicted to persist for JAS and the rest of the wet season.

  • Since late May, the North Atlantic Oscillation (NAO) has been in its positive phase but is forecast to be in its negative phase during July;
  • The rainfall suppression phase of the Madden Julian Oscillation (MJO) is expected to track across the western hemisphere, including over Trinidad and Tobago during the  July 6th to 19th forthnight.

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.