TTMS: Observed Dryness Likely To Spread Across T&T

The Trinidad and Tobago Meteorological Service (TTMS) is forecasting dry conditions to spread across Trinidad and Tobago through April 2021, through the 2021 Dry Season.

According to the TTMS, most of Trinidad’s northern half experienced borderline dry to slightly dry conditions based on rainfall measurements across the country. These measurements were compiled into the Standardized Precipitation Index and converted into a map using the TTMS’ Dryness Indicator.

Observed dryness levels based on the rainfall differences from average, which have been standardized and expressed as the number of standard deviations less than average over November 2020 to January 2021 compared to the historical average for the same 3-month period. (TTMS)
Observed dryness levels based on the rainfall differences from average, which have been standardized and expressed as the number of standard deviations less than average over November 2020 to January 2021 compared to the historical average for the same 3-month period. (TTMS)

During the 90 days between November 2020 and January 2021, T&T’s Dryness Indicator ranged between -0.5 to -1.0 across the northern half of Trinidad, with an area of -0.5 across south-central Trinidad. Most locations across Central and Southern Trinidad experienced near-average rainfall with values greater than -0.5.

Predicted dryness levels for February to April 2021 based on the standardized rainfall difference between what is forecasted and the historical average rainfall, for the period of the forecast, while also considering actual observed rainfall for the last three months. (TTMS)
Predicted dryness levels for February to April 2021 based on the standardized rainfall difference between what is forecasted and the historical average rainfall, for the period of the forecast, while also considering actual observed rainfall for the last three months. (TTMS)

The TTMS’ Dryness Outlook from February through April 2021 indicates borderline dry to dry conditions are likely to spread over larger areas of the country, with dryness levels strengthening in some locations. Notably, all areas across T&T, according to the Met Office, are likely to remain below the dry-spell level on the Dryness Indicator or less than -1.25 on the Standardized Precipitation Index.

The expected drying is likely to increase bush and forest fire potential, especially during late February and March. Reduced air quality is also expected during bush-, grass-, forest- and landfill-fires. This can negatively affect persons with existing respiratory and other ailments.

In the TTMS’ Rainfall and Temperature Outlook issued in January 2021, the Office called for “less dry than usual” for the 2021 Dry Season with high chances for above-normal rainfall. The Office also indicated many sunny days with typical dry season weather expected, including typical dust events, but more so during March and April.

What is the Dryness Indicator?

The Dryness Indicator is a tool for keeping track of the level of dry conditions, rainfall deficit, and length of the dry period across Trinidad and Tobago. It is based on the TTMS’s Dry Spell and Meteorological Drought Policy which uses the Standardized Precipitation Index (SPI) to indicate dryness levels. The SPI is a simple measure of dryness based solely on the total rainfall for a given period, for example, over the last 60 days, compared with the long-term average rainfall for that period.

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