August 2021: “Extremely Unsettled & Consistently Wet” Across T&T

August 2021 brought severe floods, landslides, funnel clouds, a waterspout, and even a damaging tornado. Unfortunately, Trinidad and Tobago also recorded two weather-related fatalities during this month.

August 2021 was a wet, cloudy, and relatively cool month across Trinidad and Tobago. The Trinidad and Tobago Meteorological Service minced no words, calling it “extremely unsettled and consistently wet” across much of the country.

A Cool August

T&T’s mean temperature for August as a whole was 28.0°C, which was 0.2°C cooler than the 1991-2020 long-term average. This was the second coolest August in the last 13 years in terms of mean temperature. However, looking at our long-term climate records, August 2021 tied with 2006 as the eleventh warmest mean August temperature in the 76-year record. The mean August temperatures of 29.1°C in 2015 and 2011 remain the warmest on record at 0.9°C above the long-term average, followed closely by 2016 at 0.8°C above average.

T&T’s mean maximum daytime temperature for August 2021 was 32.2°C, which was 0.4°C cooler than the long-term average. August 2021 tied with 2004, 2006 & 1988 as the 13th warmest mean maximum temperature on record according to the Chief Climatologist at the Trinidad and Tobago Meteorological Service (TTMS), Kenneth Kerr. Eight of the ten warmest Augusts have occurred since 2008 with August 1998 and 1989 still ranking in the top 10 warmest August on record.

T&T’s highest maximum temperature recorded for August 2021 was 33.8°C, ranking 17th in the record for warmest August temperature at a full 2.0°C less than the record warmest August maximum temperature of 35.8°C, which occurred in 2017. According to the TTMS, August 2021 was also the second-lowest extreme maximum temperature in the last 19 years, for August. Only August 2019, with an extreme temperature of 33.5°C, was lower.

T&T’s mean minimum temperature for August 2021, at 23.8°C, according to the TTMS, was below average by 0.1°C. However, it was still in the top 10 warmest mean minimum temperatures for August, and tied with 2012 & 1997 as the eighth warmest minimum temperature for August on record.

T&T’s Wet Month

August 2021 was the 7th wettest August in the 76-year record at Piarco and was the second wettest in the last decade.

At Piarco, August 2021 accumulated 368.6 millimeters (mm) of rainfall at Piarco, coming in at 132.5 mm more than the 255.3 mm 1991-2020 long-term average, or 151% above average. Only August 2020 was wetter in the decade, while August of 1949 remains the wettest August on record with 464.7 mm.  August was also the wettest month for the first eight months of the year.  Rainfall was also above average at Crown Point, Tobago according to the TTMS. 

81% of the month’s total, or 314.6 mm of rain, fell between August 12th through August 24th. Significant rainfall events, where 20 mm or more of rain, fell on the 8th, 12th (64.1 mm), 14th (47.8 mm), 15th, 17th (53.8 mm), and 18th.

On August 18th, with 92.4 mm of rainfall, Piarco recorded its wettest August day in the last 27 years and it became the 5th wettest August day on record. August 15th, 1993 remains the wettest August day on record with 144.2 mm. 

According to the Met Office, rainfall surpluses were consistent across Trinidad but varied across Tobago. Areas further northeast than Piarco and southern Trinidad received between 104% and 139% of average rainfall. 

August 2021’s Severe Weather Events

The Met Office tracked nine tropical waves across Trinidad and Tobago during August with the Intertropical Convergence Zone moving across the country mainly during the latter half of the month. During August 2021, of the 12 tropical waves (Tropical Wave 28 to Tropical Wave 40) that could have moved across the country based on our tracking, Tropical Wave 33 formed into Tropical Storm Grace and Tropical Wave 37 dissipated. There were four significant weather events in August.

On August 3rd, localized heavy rainfall caused a severe flash flood event in northwestern Trinidad. Severe flash flooding affected St. Ann’s, Cascade, Maraval, and Port of Spain with a number of rivers, including the St. Ann’s River (or East Dry River) and the Maraval River overtopping their banks.

Multiple vehicles were damaged, with some being swept into the Cascade River. One fatality was recorded as a socially displaced man in the St. Ann’s River was swept into the Gulf of Paria and drowned.

This event was associated with trailing moisture and instability following the passage of Tropical Wave 27. Isolated heavy showers continued to trigger localized street/flash flooding through August 5th.

On August 14th, feeder band activity from Tropical Storm Grace brought widespread heavy rainfall to Trinidad and Tobago. An Adverse Weather Alert (Yellow Level) was in effect for the country. According to the TTMS, up to 50 mm (or two inches) of rainfall triggered floods across low-lying communities within some river catchments and urban areas with easily overwhelmed storm-water drainage systems, as well as caused deadly landslides.

Funnel clouds were spotted in Cunupia and east of Piarco, and a waterspout was spotted at Vessigny, southwestern Trinidad. An oil spill was also reported in Erin.

Several areas in northern and southern Trinidad reported landslides, including one at Rancho Quemado that resulted in one death and another at Buenos Ayres that caused the roadway to be impassable, while landslides were reported in Belmont, St Ann’s, Morvant, Malick, Santa Cruz, San Juan, and Petit Bourg. Across in Tobago, a landslide was reported along the Bloody Bay Road.

The month also spawned a tornado on August 17th that damaged homes and vehicles in the village of Los Iros, South Trinidad.

On August 17th and 18th, a complex tropical weather system consisting of Tropical Wave 34 and the Intertropical Convergence Zone brought sustained heavy and at times torrential rainfall across most of the country. At Piarco, close to 100 mm fell in 24 hours on the 18th and in excess of 50 mm on the 17th leading to close to 150 mm (6 inches) in 48 hours. This led to riverine and widespread flash flooding across the country. During this period, Trinidad and Tobago was under an Adverse Weather Alert (Yellow Level), and a Riverine Flood Alert, which was upgraded to Orange Level.

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