Rainfall and Temperature Outlook for Trinidad and Tobago, October to December 2020



ISSUED AT: 02:00 PM

Date: Friday 25th of September 2020

Key Messages
  • Preliminary analysis suggests rainfall performance for September is on track to produce more than average rainfall for most of Trinidad and less than average rainfall in Tobago;
  • The month of October is likely to produce near-normal rainfall totals in  most areas, but will be particularly wet during the first half;
  • The rest of the year, October to December (OND) 2020, is likely to be wetter than usual overall with above-normal rainfall in most areas and near-normal rainfall in a few areas;
  • 39-50 wet days out of the 92 days during OND and at least two (2) heavy-rainfall days (50.0 mm or more rainfall in 24 hrs.) are likely;
  • October to December is likely to be warmer than usual with both day-time maximum and night-time minimum temperatures likely to exceed their averages;
  • October is likely to be typically hot, but will bring the heat season to a close. Expect at least five (5) hot days (days with maximum temperatures in excess of 33.9oC).

 

 

 

Likely Impacts

  • Above-normal rainfall during September would have maintained already swollen streams, high river levels and soil moisture content;
  • As such, riverine flood potential increases while flash flooding concerns remain elevated during the forecast period, particularly for known flood-prone areas and new/recent flood risk areas;
  • Increased risks exist for landslips and landslides in hilly areas during prolonged rainfall periods and heavy rainfall days;
  • Hot days are likely to bring excessive heat  and very humid conditions during October;
  • Increases in surface water ponding can promote mosquito breeding, leading to higher risk for spikes in vector-borne diseases;
  • Farmers should expect some farming fields to become flooded and water-logged during prolonged rainfall periods.
 


Rainfall and Temperature Outlook for Trinidad and Tobago, October to December 2020



ISSUED AT: 02:00 PM

Date: Friday 25th of September 2020

October to December 2020 Likely to be Wetter Than Usual

 Significant Fllod Risks Exist

 
 
 
Key Messages
  • Preliminary analysis suggests rainfall performance for September is on track to produce more than average rainfall for most of Trinidad and less than average rainfall in Tobago;
  • The month of October is likely to produce near-normal rainfall totals in  most areas, but will be particularly wet during the first half;
  • The rest of the year, October to December (OND) 2020, is likely to be wetter than usual overall with above-normal rainfall in most areas and near-normal rainfall in a few areas;
  • 39-50 wet days out of the 92 days during OND and at least two (2) heavy-rainfall days (50.0 mm or more rainfall in 24 hrs.) are likely;
  • October to December is likely to be warmer than usual with both day-time maximum and night-time minimum temperatures likely to exceed their averages;
  • October is likely to be typically hot, but will bring the heat season to a close. Expect at least five (5) hot days (days with maximum temperatures in excess of 33.9oC).

 
 

 Likely Impacts

  • Above-normal rainfall during September would have maintained already swollen streams, high river levels and soil moisture content;
  • As such, riverine flood potential increases while flash flooding concerns remain elevated during the forecast period, particularly for known flood-prone areas and new/recent flood risk areas;
  • Increased risks exist for landslips and landslides in hilly areas during prolonged rainfall periods and heavy rainfall days;
  • Hot days are likely to bring excessive heat  and very humid conditions during October;
  • Increases in surface water ponding can promote mosquito breeding, leading to higher risk for spikes in vector-borne diseases;
  • Farmers should expect some farming fields to become flooded and water-logged during prolonged rainfall periods.
 

 

 

 

Early  Actions & Preparedness

  • Closely monitor the  Trinidad and Tobago Meteorological Service weather forecasts;
  • Strengthen community coordination with disaster management personnel;
  • Prepare contingency plans for adverse weather events, including high wind events;
  • Persons living in flood risk areas should continue or maintain 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 be 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: The category of rainfall most likely for October to December (OND) 2020 with the highest forecast chance of occurrence, expressed as probabilities, is coloured on the map. The most likely category for above-normal, near-normal and below-normal is shown in blue, green and brown shadings respectively. The baseline period is 1981-2010. Normal is defined by rainfall totals observed in middle one-third of the OND season during the baseline period.

  • October 2020 is likely to have near-normal rainfall in most areas across Trinidad and Tobago;
  • At the sub-monthly scale, the first two weeks of October are likely to be wetter than average for both islands;

  • Overall, October to December is likely to be wetter than usual with above-normal rainfall totals for most areas in Trinidad and near-normal totals in a few areas in Trinidad and most areas in Tobago;  

  • Both islands are likely to get the usual number of wet days and heavy rainfall days. Usually the islands receive between 39-50 wet days out of the 92 days from October to December and on average 2 heavy-rainfall days (a day with 50.0 mm or more rainfall).

Figure 2: The map shows the percent chances for extremely dry conditions over the next three months, October to December (OND) 2020. Extremely dry conditions refer to the lowest 10% of October to December accumulated rainfall in the historical record.

  • The chance for extremely dry conditions during OND 2020 is low;
  • The chance ranges from 6-8% for OND 2020 accumulated rainfall totals to be in the lowest 10% of historical OND rainfall totals.

Figure 3: Possible accumulated rainfall totals with the highest chance of occurring during October to December (OND) 2020.

  • Accumulated rainfall totals for OND are likely to be the highest in northeastern and eastern Trinidad with totals close to 1150.0 mm possible near Sangre Grande, North Oropouche and surrounding areas;
  • The smallest rainfall totals are likely to occur along the extreme western and southwestern areas of Trinidad, near  Icacos, Cedros  and Granville;

  • Most areas in northeastern Tobago are likely to receive rainfall totals close to 900.0 mm, with the highest values expected in the vicinity of Hillsborough and other areas near Mount Saint George, Moriah, and Golden Lane;

  • November is likely to be the wettest of the three months in both islands. 

     

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

  • Possible rainfall totals  for October range from near 120.0 mm in areas close to the west coast of Trinidad to 300.0 mm near the foothills of the northern range and areas along the east coast;

  • Most of Tobago is expected to receive possible rainfall totals between 200.0 to 325.0 mm during October 2020.
  •  

    Figure 5:  The category of rainfall most likely for January to March (JFM) 2021 with the highest forecast chance of occurrence, expressed as probabilities, is coloured on the map. The most likely category for above-normal, near-normal and below-normal is shown in blue, green and brown shadings respectively. The baseline period is 1981-2010. Normal is defined by rainfall totals observed in middle one-third of the JFM season during the baseline period.

  • The start of 2021 is likely to be wetter than usual with the 3-month period January to March having a greater than 50% chance for accumulated rainfall totals in the above normal category.
  •  

    October  to  December 2020 Temperature Outlook

    • Usually, October brings the heat season to a close in Trinidad and Tobago. October 2020 is likely to typically hot;
    • Days during October to December are likely to be warmer than usual with above-normal temperatures;

    • Nights are also likely to be  warmer than average;

    • Day-time maximum temperatures and night-time minimum temperatures have a 72 % chance to be above average, with October days and nights likely to be the warmest during the period.

             

    Figure 6: The map shows the percent chance of the colour-coded category (below-normal, above-normal, or near-normal) of maximum and minimum temperatures that is most likely to occur across Trinidad and Tobago for the OND 2020.  The colour-coded bar-graph with the numbers to the right gives the probability for each forecast category to occur.

    • Concerns for hot days and short duration hot-spells remain elevated  for early October (hot days: days with maximum temperature greater than 33.9oC in Trinidad and greater than 32.0oC in Tobago);
    • Concerns for extremely hot days and nights are more enhanced for cities and urban areas.

    Likely Implications

    • High potential for flash and riverine flooding continue until December in Trinidad in view of the possible number of wet days, wet spells and heavy rainfall days;
    • The risk of landslides is high along the North Coast Road, Naparima-Mayaro Road and other known land-slippage areas of Trinidad and along the North-side and Windward Roads in Tobago;
    • Localized moderate to heavy rainfall days and prolonged wet spells particularly during October and November increases flood potential in high-risk/flood-prone areas, new flood risk areas and within watersheds with narrow valleys and steep hill-sides;
    • Stream and surface water flows, river levels and ground recharge rates are likely to increase;
    • Possible increased turbidity and degraded water quality on heavy rainfall days could disrupt water supplies in some areas;
    • Possible flooding and waterlogging of agricultural fields;
    • Increased rainfall, mixed with warm and humid conditions tend to promote rapid multiplication of some agricultural pests, diseases and fungal growth;
    • An increase in surface water ponding can promote mosquito breeding, which can lead to higher risks for spikes in vector-borne diseases;
    • Increased rainfall could lead to reduced traffic flows, disruptions in localized travel, and longer travelling times, which may require earlier commute start-times;
    • Increased adverse weather events are likely to also produce an increase in high wind events;
    • Higher than usual and extreme temperatures can lead to relatively excessive heat during October, which can intensify existing health conditions in vulnerable persons and worsen chronic health conditions in others.
     

    Early Actions & Preparedness

    General Public

    • Closely monitor the Trinidad and Tobago Meteorological Service weather forecasts;
    • Strengthen community coordination with disaster management personnel;
    • Prepare contingency plans for events, including high wind events;
    • Persons living in flood risk areas should continue their flood planning and  preparedness;
    • Avoid parking cars where they are likely to be hit by falling trees or power lines;
    • 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.

    Drainage

    • Continue de-silting and cleaning of drainage systems, water channels, outlets and river mouths.
    • Pay attention to areas of rock fall which may be indicative of potential landslides.

    Disaster Risk Management Sector

    • Continue with the necessary measures to ensure communities are sensitized;
    • Continue prepositioning of resources for quick response to weather-hazard impacts;
    • Continue to review contingency plans and early warning information dissemination channels;
    • Engage vulnerable communities in disaster plans and strategies;
    • Continue to engage the media for delivery of suitable messaging and advice on the outlook.

    Water and Energy sector

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

    Health Sector

    • Revisit contingency plans to manage possible spikes in vector-borne diseases;
    • Improve the usage of early excessive heat climate outlook information in plan of action.

    Agriculture & Food Security Sector

    • Raise awareness on agriculture pest and disease control measures;
    • Escalate flood mitigation action plans and removal of rotten trees.

    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

    • La Niña conditions currently exist with below average sea surface temperatures (SSTs) across the equatorial central and eastern Pacific Ocean and the Nino-3.4 index is currently at -0.8oC.
    • The majority of models and the consensus forecast favour (approximately75% chance) La Niña to continue through to the end of the year and into early next year;
    • La Niña conditions during the second-half of the local wet season is known to tilt the odds in favour of increased rainfall occurrence in Trinidad and Tobago and usually influence increased tropical cyclone activity in the North Atlantic hurricane basin;
    • SSTs in waters in relatively close proximity to Trinidad and Tobago remained warmer than average for this time of the year;
    • Several international model predictions indicate warming is likely to continue during OND and this will maintain above average temperatures in the waters to the east and around Trinidad and Tobago.
    • Warmer than average SSTs in waters to the east of Trinidad and Tobago tend to have a positive influence on local rainfall.
    • Between August 01st and September 20th the North Atlantic Oscillation (NAO) moved from being in its positive phase during the first half of August to its negative phase during the second half and back to positive phase during most of September.
    • The forecast is for transition back to negative phase during the first half October. The pattern of oscillation between negative and positive phases of the NAO is likely to aid maintenance of 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 most dominant source of short-term fluctuations in tropical climate variability affecting tropical convection on weekly to monthly timescales. The enhanced rainfall (wet) phase of the MJO is set drive an influx of moisture to the area, and initiate and positively influenced rainfall activity within the region during the first two weeks of 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 moderate model consistency which somewhat favour near-normal rainfall in the vicinity of Trinidad and Tobago.