Hot and humid, how long will the heat last?

Sweltering temperatures continue to grip Trinidad and Tobago, with the official climate site for Trinidad, at Piarco, recording its second-highest temperature for 2020 at 34.2°C. Piarco also recorded this maximum high temperature on April 13th, April 14th, May 20th, and May 24th (today).

Maximum high temperature recorded at Piarco International Airport, the second-highest temperature recorded for the year to date at Piarco. Data: Trinidad and Tobago Meteorological Service.
Maximum high temperature recorded at Piarco International Airport, the second-highest temperature recorded for the year to date at Piarco. Data: Trinidad and Tobago Meteorological Service.

On Sunday, across most of the country, temperatures between ranged between 30.0°C and 33.0°C, with isolated areas between 33.0°C and 37.0°C, mainly across Trinidad. In urban areas and areas where development is prevalent, temperatures trended higher.

Maximum high temperatures recorded across Trinidad and Tobago on Sunday 24th May 2020. Data: Trinidad and Tobago Meteorological Service.
Maximum high temperatures recorded across Trinidad and Tobago on Sunday 24th May 2020. Data: Trinidad and Tobago Meteorological Service.

Some low-level moisture is present across Trinidad and Tobago, which not only makes outside feel more humid, but makes the heat index, or what temperature outside feels like higher.

Maximum Heat Indices Across Trinidad and Tobago, with most of the "feels like" temperatures in the extreme caution to danger category.
Maximum Heat Indices Across Trinidad and Tobago, with most of the “feels like” temperatures in the extreme caution to danger category.

The Heat Index

Several persons across the country took to social media to complain about the heat, or more so what outside felt like. This is called the heat index and is a combination of air temperature and relative humidity, determining what the air feels like to a person i.e., how hot it actually feels.

The heat index is important because of sweating. Your body sweats to cool the skin and maintain a constant, healthy body temperature. This cooling process means that the sweat has to evaporate off the skin to remove heat. However, if the sweat is unable to evaporate, the body isn’t able to regulate temperature.

With high volumes of moisture in the air, also known as high relative humidity, which T&T regularly experience due to its tropical climate, the rate of sweat evaporation decreased. This is because the atmosphere is unable, or has limited potential to hold additional moisture in the atmosphere.

This results in you feeling warmer in humid conditions and cooler in less humid conditions i.e. when relative humidity decreases. As temperature increases, the heat index increases. As relative humidity increases, so does the heat index.

 Heat Index Values Explained
Heat Index Values Explained

Heat index is generally classified into four categories: caution, extreme caution, dangerous, and extremely dangerous. Generally, across Trinidad and Tobago, we experience heat indices of caution to extreme caution in times of hot days, with isolated areas experiencing dangerous heat indices such as urban areas.

Temps in cities, such as Port of Spain, tend to be much higher than surrounding locations due to a phenomenon called the Urban Heat Island Effect. There are several causes, but the main instigator for this phenomenon tends to be increased dark surfaces such as roads and pavement in cities, which absorb solar radiation more than surrounding areas.

Is this record heat?

Where do these temps stand compared to our records? The hottest recorded in Trinidad, based on data from the Global Historical Climatology Network (pre-1980) and the Trinidad and Tobago Meteorological Service (1980-2019) stands at 37.8°C recorded on April 20th, 1946 at Wallerfield.

At Piarco International Airport, where the new official records began, the hottest temperature for the year was recorded on September 25th, 1990, at 36.5°C but the hottest May temperature occurred on May 11th, 2010 at a scorching 35.9°C.

Is this a heatwave?

Not Yet.

For a hot spell (or heat wave) to be declared in Trinidad and Tobago by the Trinidad and Tobago Meteorological Service, a period of hot temperatures, characterized by maximum temperatures of at least 34.0°C in Trinidad and 32.0°C in Tobago, lasting five or more consecutive days. A short-duration hot-spell is three or more consecutive hot days.

Maximum high temperatures at Piarco, Trinidad over the last 10 days, with a number of days recording the top five highest temperatures recorded for 2020 at the site. Data: Trinidad and Tobago Meteorological Service.
Maximum high temperatures at Piarco, Trinidad over the last 10 days, with a number of days recording the top five highest temperatures recorded for 2020 at the site. Data: Trinidad and Tobago Meteorological Service.

To date, while we have had sporadic days where the official temperature at Piarco and Crown Point come in at or above the threshold temperatures, for the TTMS to declare a hot spell would require these oppressively hot maximum temperature to occur at least three consecutive days.

Maximum high temperatures at Crown Point, Tobago over the last 10 days, with a number of days recording the top five highest temperatures recorded for 2020 at the site. Data: Trinidad and Tobago Meteorological Service.
Maximum high temperatures at Crown Point, Tobago over the last 10 days, with a number of days recording the top five highest temperatures recorded for 2020 at the site. Data: Trinidad and Tobago Meteorological Service.

High Temperatures To Continue

At least one more day of high temperatures is forecast for Monday 25th May 2020, ahead of the passage of our next tropical wave. Currently, tomorrow’s forecast maximum high temperature is forecast to be near 34.0°C in Trinidad and 32.0°C in Tobago. Heat indices will be between 35°C and 45°C across Trinidad, with indices higher in urban areas and lower across Tobago.

A weak tropical wave, with a large moisture envelope is forecast to begin moving across Trinidad and Tobago on Tuesday. Based on current (12Z May 24th) models, increased cloudiness is forecast to keep temperatures below the 34.0°C in Trinidad and 32.0°C in Tobago – the threshold for a short-duration hot spell, given that it would be the third day in a row with these maximum temperatures materialize on Monday and Tuesday.

Again, based on current models, isolated to scattered showers are forecast on Wednesday which is forecast to keep temperatures down near the 30-degree mark across both islands. However, following the passage of this tropical wave, on Thursday, the hot temperatures return, in addition to a surge of Saharan Dust.

https://ttweathercenter.com/peak-concentrations-ongoing-more-saharan-dust-forecast/
Saharan Dust is forecast to return by late Wednesday, following the passage of Tropical Wave 02 Tuesday into Wednesday.

In the Trinidad and Tobago Meteorological Service’s (TTMS) Rainfall and Temperature Outlook for Trinidad and Tobago, issued on Tuesday 19th May 2020.

In fact, according to the TTMS, the “above-normal temperatures are likely with warmer than average maximum day and minimum night temperatures expected. The risk for hot days and short-duration hot-spells is elevated for the August to October period.”

“There is a 75% chance for warmer than usual maximum daytime temperatures and nighttime minimum temperatures, especially during June to October 2020,” based on the TTMS’s outlook.

Heat Safety

Graphic: Beat the Heat. Heat related deaths are preventable.

Graphic: Beat the Heat. Heat-related deaths are preventable. Source: MEMA

Heat Safety Tips and Resources
Heat Safety Graphic. Source: Heat Safety Tips and Resources
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