Rainfall and Temperature Outlook for Trinidad and Tobago, December 2018 to February 2019



ISSUED AT: 03:20 PM

Date: Monday 3rd of December 2018

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Key Messages

  • December is likely to be drier than average with below normal rainfall likely;
  • The period December to February is likely to be drier than usual with below normal rainfall totals, as most likely (high confidence);
  • Wet spells remain possible for December; potential for flooding still strong;
  • Increased chance for drought, drought-like conditions or recurrent dry spells during February to March (high confidence);  
  • 60-70% probability for at least three 7-day dry spells during February to March;  
  • Most of Tobago experienced drier than usual conditions during June, July, August and September but above average rainfall during October and below average during November. An outlook for below average rainfall in the coming three months suggests recent improvement in rainfall deficit are likely to be eroded; 
  • Days and nights are likely to be warmer than average; Chance for hot days and hot spells are increased for February to March (high confidence); 
  • Drier than usual February to March 2019 is likely, due the potential development of El Niño.

Likely Impacts

  • Reduction in ground water recharge, surface water flow and faster depletion of large reservoirs;
  • Drier and hotter conditions will increase bush and forest fire potential;
  • Reduced air quality possible during bush, grass, forest and landfill fires;
  • Drier than average conditions enhance the chance for some agricultural pests and diseases to thrive;
  • Periods of excessive heat can increase heat-stress for persons with heat-sensitive ailments and for heat-exposed livestock, pets and other animals;


Rainfall and Temperature Outlook for Trinidad and Tobago, December 2018 to February 2019



ISSUED AT: 03:20 PM

Date: Monday 3rd of December 2018

Key Messages

  • December is likely to be drier than average with below normal rainfall likely;
  • The period December to February is likely to be drier than usual with below normal rainfall totals, as most likely (high confidence);
  • Wet spells remain possible for December; potential for flooding still strong;
  • Increased chance for drought, drought-like conditions or recurrent dry spells during February to March (high confidence);  
  • 60-70% probability for at least three 7-day dry spells during February to March;  
  • Most of Tobago experienced drier than usual conditions during June, July, August and September but above average rainfall during October and below average during November. An outlook for below average rainfall in the coming three months suggests recent improvement in rainfall deficit are likely to be eroded; 
  • Days and nights are likely to be warmer than average; Chance for hot days and hot spells are increased for February to March (high confidence); 
  • Drier than usual February to March 2019 is likely, due the potential development of El Niño.

Likely Impacts

  • Reduction in ground water recharge, surface water flow and faster depletion of large reservoirs;
  • Drier and hotter conditions will increase bush and forest fire potential;
  • Reduced air quality possible during bush, grass, forest and landfill fires;
  • Drier than average conditions enhance the chance for some agricultural pests and diseases to thrive;
  • Periods of excessive heat can increase heat-stress for persons with heat-sensitive ailments and for heat-exposed livestock, pets and other animals;
     

Figure 2: Category of rainfall likely for December 2018 to February 2019 (DJF) 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 DJF period rainfall totals during the historical period used to produce the outlook.

  • The December 2018 to February 2019 rainfall outlook shows there are stronger indications for drier than usual conditions across the country, with below normal rainfall category as the most likely (high confidence) ;
  • Below normal rainfall totals mean areas are likely to receive rainfall totals that are less than 75% of the long term average for the DJF. For instance, at Piarco, below normal rainfall for DJF is rainfall that is less than 278.9mm and at Crown Point less than 249.6mm
 

Figure 3: The map shows the chances for extremely dry conditions over the three months ending February 2019. Extreme refers to the lowest 10% of December to February accumulated rainfall in the historical record.

  • The chance for the DJF period to be extremely dry is moderate to slightly enhanced (high confidence);
  • The outlook indicates a 60-70% chance for at least three 7-day dry spells during DJF, i.e. seven consecutive days with no measurable rainfall;
  • Chance for drought, drought-like conditions or recurrent dry spells is increased for February to March
 

Figure 4: Possible accumulated rainfall totals with the highest chance of occurring during December 2018 to February 2019.

  • Areas in northeast Trinidad, near Sangre Grande, Valencia, North Oropuche and environs are likely to receive the largest rainfall accumulated totals close to 440.0mm, while areas near Port of Spain and Chaguaramas in the northwest are likely to receive the least rainfall totals, close to 150.0mm;
  • In Tobago accumulated rainfall totals are likely to range between 100.0mm in the northeast to near 270.0mm near Mount Saint George.
 

Figure 5: Possible rainfall totals with the highest chance of occurring during December 2018.

  • December is likely to be drier than average with a greater than 45% chance in most areas for rainfall totals in the below normal category (medium confidence);
  • Possible rainfall totals range from 55.0mm to 300.0 mm across the twin island Republic;
  • Extreme wet spells remain possible during December. Thus the potential for flooding is still strong.
 

Figure 6: Category of rainfall most likely for March to May 2019 (MAM) 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 MAM period rainfall totals during the historical period used to produce the outlook.

  • The outlook for March to May 2019 indicates large parts of Trinidad and Tobago are likely to be drier than average with rainfall totals likely to be in the below normal category. A few areas are also likely to be in the near-normal category (moderate confidence);
 

Temperature Outlook:

  • December to February daytime temperatures are very likely to be warmer than average for most of Trinidad and Tobago;
  • Chances of a warmer than usual maximum temperatures are greater than 65% over Trinidad and greater than 60% over Tobago;
  • Nights are also very likely to be warmer than average, with chances of warmer than average nights exceeding 70%;
  • Although warmer than average conditions are in the forecast, uncomfortably high temperatures are not likely during the period;
  • Few nights are likely to have minimum temperatures cooled below 22.0oC on cloud free nights.

Likely Implications

  • Expect a gradual reduction in ground water recharge, surface water flow and water availability;
  • Drier and hotter conditions will increase bush and forest fire potential, later in the season;
  • 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 can lead to late development of some agricultural crops and change in the harvest time;
  • Drier than average conditions and warmer than average temperatures tend to favour better quality in some fruits;
  • Drier than average conditions may favour some outdoor activities such as those in the Tourism industry;
  • Potential for periods of excessive heat, which can increase heat-stress for persons with heatsensitive ailments and for heat-exposed livestock and other animals;
  • Possibility of increased disruption in marine activities due to episodes of rough seas;
  • Reduced air quality during bush, grass, forest and landfill fires is likely.
 

Sectorial Early Action That Can Be Taken To Reduce Possible Disaster Effects!

Disaster Risk Management Sector

  • Sensitize communities and citizens on the forecast, its negative impacts and actions to be taken early;
  • Consider who may be most affected by the rainfall forecast of below-average rainfall;
  • Review your contingency plans and update as necessary;
  • Revisit early warning information dissemination channels.

Drainage

  • Continue de-silting and cleaning drainage systems, water channels, outlets and river mouths;

Waste Management Sector

  • Ramp-up contingency plans to mitigate landfill fire occurrence;

Health Sector

  • Clear bushes, open drainage systems, fumigate in and around residences;
  • Revisit contingency plans to manage spikes in respiratory, heat-related and vector-borne ailments.

Agriculture & Food Security Sector

  • Put in place pest and disease control measures; raise awareness on the risk of bushfire increases;
  • Initiate contingency planning for the likely drier than usual start to the upcoming dry season.

Water and Energy sector

  • Escalate water conservation awareness messages;
  • Conduct routine de-silting of reservoirs and riverine channels;
  • Harvest excess rainfall now and revisit contingency plans for drier than usual JFM.

General Public

  • Continue preparation especially for persons at risk. Stock up on water and emergency supplies for 3-7 days;
  • Clean drains and canals; conserve, store and manage water in a safe and adequate manner;
  • Take measures to lessen impacts from drier than usual conditions. Be dry season ready;

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

  • Waters in, and around Trinidad and Tobago warmed during October to November and are forecast to remain warmer than average during DJF;
  • During the last three weeks, SSTs in the equatorial Pacific Ocean continued to warm and were at El Niño levels, but not all the atmospheric variables have responded to the warming. The El Niño-Southern Oscillation (ENSO)-neutral conditions (neither El Niño nor La Niña) is maintained;
  • Current observations and model outlooks show increased chance (80-83%) for El Niño to develop during the December to February with a more than good chance for declaration of El Niño by the end of the period;
  • After being in its positive phase all of October, the North Atlantic Oscillation (NAO) fluctuated between the negative and positive phased during November and is likely to persist in negative phase during December. A negative NAO tends to aid in warming SSTs in waters around Trinidad and Tobago.
  • The Madden Julian Oscillation (MJO) is the main climate driver usually influencing fluctuation in the local weather on the sub-seasonal scale (weekly to monthly timescales). The MJO is likely to be in a favourable phase to influence local rainfall during the first two weeks of December but have little effects after that.

The precipitation and temperature outlook is based on statistical and dynamical seasonal climate models output and known seasonal climate influencers. Multiple competing climatic factors are at play but given the heightened chance for El Niño, its signal dominates the current outlook