Met Office predicts near normal wet season with high flood potential

The Meteorological Office says the 2023 wet season will be near-normal but the potential for flooding remains high.

In a release, the Met Service said the first half of the wet season, from June to August 2023, is likely to be mostly wet as usual. It said there is a greater than 32 per cent chance for near-normal rainfall to occur over most areas during this period, with a 51 per cent chance for above-normal rainfall in pockets across western Trinidad.

It said there are high chances for flash flooding during heavy and prolonged rainfall events.

It said the three months of July to September are likely to get near normal rainfall totals across the majority of areas with chances ranging between 31 per cent to 63 per cent, while August to October are likely to get mostly near normal rainfall totals across most areas with a chance greater than 31 per cent. There are growing pockets that will receive below-normal rainfall totals with chances ranging between 61-67 per cent.

The Met Office said there is a moderate probability that the September to November rainfall totals will be near normal. It said there are developing and shifting pockets across Trinidad that will receive below-normal rainfall totals with chances ranging between 36 and 69 per cent.

Overall, the 2023 wet season is likely to be usual (near normal), with a greater than 36 per cent probability for near-normal accumulated rainfall totals across TT for the 2023 wet season.

The Met Office said the country is likely to get 10-18 heavy rainfall days during the season, ie, days with rainfall equal to or exceeding 25 mm. It said Trinidad and Tobago is likely to get four to ten extremely heavy rainfall days (rainfall reaching or exceeding 50 mm), with at least two days likely to produce over three inches or 75 mm of rainfall.

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 2,076 mm in northeast Trinidad, in the vicinity of Sangre Grande, Vega De Oropouche, and Plum Mitan and environs.

The wet season usually produces 102 to 106 wet days, ie, days with rainfall less than 1.0 mm. However, 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 three-day wet spells with three-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 five-day wet spells with five-day totals exceeding 80 mm of rainfall. At least one of the five-day wet spells is likely to exceed 100 mm.

In August, the outlook shows that Sangre Grande, Navet, Rio Claro and environs have the highest chance for rainfall to exceed 250 mm in August.

The Met Office said flood risk potential exists across the whole wet season, with the areas of greatest risk for flooding including the Caroni, North Oropouche and South Oropouche river basins. It said the local flood season is likely to expand as the season progresses.

It said there is a much 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. Similarly elevated potential exist in the South Oropouche River Basin, Penal, Debe, Princes Town and parts of Couva.

The Met Office said the 2023 Saharan Dust haze season is likely to peak between July and August, 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 is also likely to be more prolonged than earlier in the year, with increased odds for higher dust haze concentration during plumes visitation.

Temperature-wise, the wet season temperature outlook favours warmer than average temperatures, particularly in western areas. There is a greater than 45 per cent chance for maximum day temperatures and minimum night temperatures to be above normal, with maximum temperatures reaching or exceeding 34 degrees Celsius during the season.

Chances are also elevated for five-day short-duration hot spells and three-day heat surges, ie maximum temperatures greater than or equal to 34.0 degrees Celsius to develop during September, and early October.