Cool Nighttime Temperatures Forecast For T&T Tonight

A cool and dry airmass with origins from North America settled across Trinidad and Tobago on Wednesday, leading to possible cooler-than-normal nighttime temperatures forecast for both islands for Thursday.

What’s causing the cool temperatures?

Over the last several days, an Atlantic High-Pressure system remained in place across the southern Windwards, including Trinidad and Tobago, channeling cooler and drier air toward the region. Ahead of this airmass, a shear line, which is a decaying or very weakened cold front, made its way across the entirety of the Eastern Caribbean and has moved across Trinidad and Tobago on Sunday through Tuesday, gradually dissipating and bringing showers and cloudy periods.

Now, In the wake of this shearline, a dry slot has developed with lower-than-usual relative humidities and little to no cloud cover, but low-level winds remain elevated.

This air mass is forecast to inhibit cloud formation at night, with little moisture (or water vapor), allowing for heat to escape from the ground at night.

This dry and relatively cooler airmass has been traced back to originating over North America and made its way down to the Caribbean due to the atmospheric circulations over the Atlantic – namely, a high-pressure ridge located northeast of the Caribbean, allowing for northeasterly to easterly prevailing winds.

While moisture and temperature increased on its journey to T&T, the conditions remained dry and stable enough to hinder clouds’ development. Situations like these are not frequent, but they tend to occur several times during our dry season.

Low temperatures during this time of year are normal, as the Northern Hemisphere experiences winter.

Cool temperatures across Trinidad result from several factors occurring:

• Calm/near-calm winds;
• Little to no cloud coverage;
• Winds originating from the northeast to the north at the lower levels of the atmosphere;
• Low amounts of low-level moisture (water vapor/relative humidity).

The dew point is the atmospheric temperature below which water droplets begin to condense, and dew can form. Meteorologists can determine the moisture content of the atmosphere near the surface and estimate the minimum temperature.

A lower dew point means that there is less water vapor in the air. Water vapor can absorb and radiate heat back to the surface. Hence, the lower the water vapor content, the more infrared radiation (i.e., long-wave radiation) can escape from the earth’s surface and cause rapid cooling.

Calm winds and no cloud coverage are due to a persistent sub-tropical high-pressure system that will begin to dominate the weather for much of January, causing dry air at mid and upper levels of the atmosphere and inhibiting cloud formation.

Lack of cloud coverage also leads to fairly warm days when temperatures reach 30-32°C.

For vulnerable persons, who might be especially susceptible to cooler temperatures, such as babies or people suffering from arthritis, it may be best to layer up as a way to keep warm at night.

Five-Day Temperature Forecast

For tonight (Wednesday into Thursday), generally, dry conditions are expected to persist, with minimal cloud cover expected. This would result in temperatures in the upper teens (18.5°C to 21°C) across Trinidad and lows near or at 22°C across Tobago. Temperatures are forecast to trend cooler in interior areas of Trinidad and Tobago, where winds are lighter, under clear skies, and away from urbanized areas.

A shearline north of T&T is forecast to continue its southward drift on Friday, bringing moisture to T&T with cloudy skies and showers mainly across Tobago and, to a lesser extent, the northern half of Trinidad into Saturday. This increase in cloud cover and moisture will lead to higher nighttime temperatures.

From Saturday night into next week, though dry air will be in place, pockets of low-level convergence within a moderate to strong low-level wind flow will lead to elevated winds, cloud cover, and passing showers, which will also lead to higher nighttime temperatures.

Temperatures are forecast to be far from the record lowest for January. The lowest minimum temperature on record at Piarco is 16.1°C, which occurred on the nights of January 21 and 30, 1964, followed by 16.4°C on the night of January 28, 1976. For Crown Point, Tobago, since 1980, the lowest minimum recorded temperature was 19.0°C recorded on February 4th, 1983, and February 1st, 1992. The lowest minimum temperature for January at Crown Point, Tobago, was on January 2nd, 1984, with a temperature of 19.6°C For T&T, the climate reference site for Trinidad is Piarco, where records have been kept since 1946, and Crown Point for Tobago, where records have been kept since 1969.