ISSUED AT: 02:13 PM

Date: Friday 12th of May 2023

Rainfall and Temperature Outlook for Trinidad and Tobago, June to December 2023

Figure 1: Category of rainfall likely for June 2023 with the highest chance of occurrence expressed as probabilities represented on the map. Blue areas indicate places with an increased chance for above normal rainfall, brown areas show an increased chance for below-normal rainfall, while green areas show an increased chance for near normal rainfall. Normal is defined by the rainfall that was observed in the middle one-third of the June period rainfall totals during the historical period used to produce the outlook.

• The June 2023 rainfall outlook indicates that there are enhanced chances for usual to wetter than usual conditions to occur across Trinidad, and usual for Tobago,
• The outlook suggests a 36% to 57% chance for above-normal rainfall in June across western Trinidad.

Figure 2: Category of rainfall likely for the June to August 2023 (JJA) with highest chances of occurrence expressed as probabilities represented on the map. Blue areas indicate places with an increased chance for above normal rainfall, brown areas show an increased chance for below normal rainfall, while green areas show an increased chance for near normal rainfall. Normal is defined by the rainfall that was observed in the middle one-third of the JJA period rainfall totals during the historical period used to produce the outlook.

• The  first half of the wet season, June-July-August (JJA) is likely to be mostly wet as usual, with near normal rainfall totals.
• There is a greater than 32% chance for near normal rainfall totals to occur over most areas.
• The outlook suggests a 51% chance for above normal rainfall in JJA in pockets across western Trinidad.
• High chances for flash flooding during heavy and prolonged rainfall events.

• The three (3) months July to September are likely to get near normal rainfall totals across majority of areas with chances ranging between 31%-63%.
• The three (3) months August to October are likely to get mostly near normal rainfall totals across most areas with a chance greater than 31%.
• There are growing pockets that will receive below normal rainfall totals with chances ranging between 61%-67%.

Figure 3: Category of rainfall likely for July to September 2023 (JAS) and August to October 2023 (ASO) with the highest chance of occurrence expressed as probabilities and colour coded on the map. Blue areas indicate that it is more likely for above normal rainfall to occur than for below normal or near normal. Brown areas indicate that it is more likely for below normal rainfall, while green areas indicate that it is more likely for near normal rainfall. Normal is defined by the rainfall that was observed in middle one-third of the JAS and ASO periods rainfall totals during the historical period used to produce the outlook.

Figure 4:  Category of rainfall likely for September to November 2023 (SON) with the highest chance of occurrence expressed as probabilities and is colour coded on the map. Blue areas indicate that it is more likely for above normal rainfall to occur than for below normal or near normal. Brown areas indicate that it is more likely for below normal rainfall, while green areas indicate that it is more likely for near normal rainfall. Normal is defined by the rainfall that was observed in middle one-third of the SON period rainfall totals during the historical period used to produce the outlook.

• The outlook indicates a moderate probability (33%-62%) exists that the September to November (SON) rainfall totals will be near normal.

• There are developing and shifting pockets across Trinidad that will receive below normal rainfall totals with chances ranging between 36%-69%.

Figure 5. Category of rainfall most likely for the Wet Season 2023 with the highest chance of occurrence expressed as probabilities and colour coded on the map. Blue areas indicate that it is more likely for above normal rainfall to occur than for below normal or near normal. Brown areas indicate that it is more likely for below normal rainfall; while green areas indicate that it is more likely for near normal rainfall. Normal is defined by the rainfall that was observed in the middle one-third of June to December rainfall totals during the historical period used to produce the outlook.

• Overall, the 2023 wet season is likely to be usual (near normal).
• Probabilities are greater than 36% for near normal accumulated rainfall totals across the entire Republic of Trinidad and Tobago for the 2023 wet season.
• There is 40% chance for normal number of heavy rainfall days (days with rainfall equal to or exceeding 25 mm). The country is likely to get 10-18 heavy rainfall days during the season.
• A 27% chance exists for above-normal, extremely heavy rainfall days. These are likely to be days with rainfall reaching or exceeding 50.0 mm.
• The country is likely to get 4 to 10 extremely heavy rainfall days, with at least 2 days likely to produce in excess of 3 inches or 75 mm of rainfall.

Figure 6: Possible accumulated rainfall totals with the highest chance of occurring during the 2023 wet season.

• Possible rainfall volumes for the 2023 wet season are likely to range from 887 mm in most areas of Tobago and areas along the west coast of Trinidad, with higher volumes that are closer to 2076 mm in northeast Trinidad, in the vicinity of Sangre Grande, Vega De Oropouche, Plum Mitan and environs.
• The wet season usually produces 102 to 106 wet days (days with rainfall > 1.0 mm).
• The 2023 wet season is likely to have a reduced number of wet days, with 85 to 107 wet days most likely.
• There is also a high chance for at least six, 3-day wet spells, with 3-day totals exceeding 50 mm and at least three of these wet spells are likely to produce above 75 mm of rainfall.
• The outlook favours at least two, 5-day wet spells, with  5-day totals exceeding 80 mm of rainfall.  At least one of the 5-day wet spells is likely to exceed 100 mm.

Figure 7: Chance of exceeding 250 mm of rainfall during August 2023.

•  The chance of exceeding 250 mm of rainfall during August, the wettest month of the year, is low to moderate.
• The outlook shows there is a 20% to 60% chance of reaching and exceeding 250 mm across Trinidad and Tobago during August 2023, which is more than the average for the month in most areas.
• The outlook shows that Sangre Grande, Navet, Rio Claro and the environs have the highest chance for rainfall to exceed 250 mm in August.

Figure 8: Chance of exceeding 250 mm of rainfall during October 2023.

• The chance of exceeding 250 mm of rainfall during October is low to moderate.
• The outlook shows there is a 4% to 60% chance for October’s rainfall to reach or exceed 250 mm, across most areas, with the higher chances to occur in pockets in north, northeast and central Trinidad.

Figure 9: The 2023 Wet Season flood risk potential outlook with categories of flood potential colour coded on the map. Blue indicates a much higher than normal flood potential. Brown indicates it is more likely for moderately higher normal flood potential. Yellow indicates a slightly higher than normal flood potential. Green indicates a near normal flood potential.

Seasonal Flood Potential Outlook:

• Overall, flood risk potential exists across the whole wet season. The areas of greatest risk for flooding include the Caroni, North Oropouche and South Oropouche river basins. The local flood season is likely to expand as the season progresses. 

• There is an elevated flood potential, with a higher than normal flood potential in northeast Trinidad, near Valencia, Sangre Grande, including Vega de Oropouche, Fishing Pond, Sangre Chiquito and environs. Similar elevated potentials exist in the South Oropouche River Basin, Penal, Debe, Princes Town and parts of Couva.

• Flood potential is moderately higher than normal for St Helena and environs, Plum Mitan and environs, parts of Mayaro, the city of Port of Spain, Maraval and lower Diego Martin.

• Tobago has a slightly higher than usual flood potential in the western half of the island.

• Areas which are not colour-coded also have flood risks, but the chances are not as high as those that are colour-coded.

Saharan Dust Haze Season Outlook:

The 2023 Saharan Dust Haze Season is likely to peak during JJA, with the number of Saharan dust haze days expected to increase significantly in frequency. The duration of plumes of Saharan dust haze visiting both islands are also likely to be more prolonged than earlier in the year, with increased odds for higher dust haze concentration, during plumes visitation.