Sunday 5 July, 2020

May showers? Met Office warns of flash flooding in May-July outlook

After dry conditions and high temperatures in April, the public may experience above-average rainfall and even flash flooding events during the period May to July.

The Trinidad and Tobago Meteorological Service said in its Rainfall and Temperature Outlook for May to  July, 2020, that May is likely to be “slightly wetter than usual with slightly enhanced chances for above-normal rainfall”.

There is also a 60 percent chance of a three-day wet spell (that is, within the top one percent of the wettest three-day rainfall events on record) for the period May to July.

As a result, the Met Office said the potential for flash floods is a growing concern, particularly in June and July.

The Met Office said apart from parts of southwest Trinidad, the month of April produced rainfall deficits across most of the country.

The 3-month rainfall outlook for May to July (MJJ) 2020 shows a shift towards wetter than usual conditions with elevated odds for above-normal rainfall totals.

The Met Office said chances are also elevated for a possible rapid transition and onset to the wet season, particularly for Trinidad.

Temperatures are also set to be warmer than average.

“The temperature outlook for May to July tilts quite strongly, on average, towards above-normal temperatures; with warmer than average maximum day and minimum night temperatures likely. The chances of warmer than average temperature is greater than 70%”

“The forecast for MJJ reflects the consolidated influence of warmer than average sea surface temperatures in waters around Trinidad and Tobago and declining ENSO-neutral warm conditions in the tropical Pacific Ocean.”

Overall, May’s rainfall totals are likely to be above average with a greater than 45 percent chance for this to occur. Possible rainfall totals range from near 60mm to near 190 mm for May.

There is also a slightly enhanced chance for the occurrence of hot days (days with maximum temperatures being at least 34 degrees Celsius in Trinidad and 32 degrees Celsius in Tobago) and short duration hot spells (periods of consecutive hot days) during May.

 

Prepare for flooding

 As a result, the Met Office said an increase in ground water recharge rates, surface water flows and levels are likely.

The Met Office said there is an elevated flood risk for the months of June and July.

The Met Office advised that de-silting and cleaning of drainage areas, water channels, outlets and river mouths should be ramped up and people in flood-prone areas should begin their flood planning and preparedness efforts.

The Met Office said most of the country is likely to receive in excess of 530mm of rainfall over the May-July period.

Areas in the Northeast are likely to receive the highest rainfall totals at near 900mm (almost three feet) while areas in the northwest of Trinidad and southwest Tobago would receive the lowest totals (around 440mm).

The Met Office said the early rainfall outlook for August to October 2020 favours a much drier outcome over the eastern half of Trinidad with below-normal rainfall totals for the eastern half of Trinidad and extending southward to include Manzanilla and Mayaro.

However below normal rainfall in the wettest areas of Trinidad could still be substantial rainfall amounts.

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