Following a cool and sunny start to Tuesday, temperatures are forecast to dip below 20°C on Tuesday night into Wednesday, with slightly warmer temperatures across Tobago.
What’s causing the cool temperatures?
Cool and dry air from the north Atlantic has gradually moved towards the Southern Windward Islands, embedded within the large sub-tropical Atlantic high-pressure system.
This high-pressure system has brought brisk winds across the region. While moisture and temperature increased on its journey to T&T, the conditions remained dry and stable enough to hinder clouds’ development, leading to our mostly sunny days and clear nights.
As we head into the latter half of the week, moisture from South America may return to T&T, increasing cloudiness and showers across the country, particularly on Thursday.
Why the cool temperatures? It all has to do with the dew point, which is the atmospheric temperature below which water droplets begin to condense and dew can form, meteorologists can determine both the moisture content of the atmosphere near the surface, as well as an estimate for 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.
A trough system east of the Lesser Antilles has also weakened the pressure gradient, allowing calm winds to occur. With little to no cloud coverage, due to a persistent sub-tropical high-pressure system that began to dominate the weather for much of January, causing dry air at mid and upper levels of the atmosphere, inhibiting cloud formation.
Low temperatures during this time of year are normal, as the Northern Hemisphere experiences winter.
Cool temperatures across Trinidad result of several factors occurring:
- Calm/near calm winds overnight (though over the last 3 days, it has been quite windy across T&T);
- Little to no cloud coverage;
- Winds originating from the northeast to the north at the lower levels of the atmosphere (over Trinidad);
- Low amounts of low-level moisture (water vapor).
Lack of cloud coverage also leads to fairly warm days, where temperatures can 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.
Forecast Into This Week
For tonight and tomorrow, generally dry conditions are expected to persist, with minimal cloud cover expected. This would result in temperatures in the upper teens (19°C to 21°C) across Trinidad and lows near or at 22°C across Tobago. Mostly clear skies are expected overnight into Wednesday.
However, models indicate an increase in moisture Thursday and persist into the weekend due to a series of low-level perturbations affecting the Windward Islands. With this increase in moisture, lows are forecast to be in the low twenties (22°C to 24°C) across Trinidad, with lows near or at 24°C across Tobago.
The coldest March temperature ever recorded at Piarco is 17.2°C on March 2nd, 1962 while the coldest ever temperature was 16.1°C occurred in January 1964. The record hottest, in the last 30 years, was 35.7°C on March 8th, 2010.