ISSUED AT: 06:00 PM

Date: Friday 17th of January 2025

Key Message: 

No concerns for impactful dryness across Trinidad and Tobago over the next three months.

Dryness concerns have lessened overall from the previous three months across Trinidad and Tobago. The dryness indicator improved for October to December 2024 and shows the majority of Trinidad was borderline dry to no concern, while portions of Tobago were borderline dry, in particular southwest Tobago. There were fewer concerns of significant dryness observed by late December as decent and beneficial rainfall amounts rebounded across Trinidad and Tobago.

Trinidad experienced near normal rainfall October, November and December. The rainfall totals for October, November and December consecutively are 181.1 mm (93.9% of average), 196.0 mm (87.9% of average) and 132.6 mm (89% of average). 

Meanwhile, Tobago experienced much below normal rainfall in October, and then gradually rebounded through November to reach above normal rainfall amounts in December.

The rainfall totals in Tobago for October, November and December consecutively are as follows 85.4 mm (48% of average), 177.7 mm (81.3% of average) and 176.1 mm (129% of average). Although Trinidad in particular received rainfall deficits from November to December 2024, the 3-month dryness levels nationwide was for no concern by the end of December 2024.

In October, Trinidad had four wet days(>10.0mm) and eight relatively wet days (<10.0mm) and Tobago had three wet days (>10.0 mm), eleven relatively wet days (<10.0 mm) and the rest of month was a mixture of relatively dry days (< 1.0 mm) and dry days (0.0 mm). In November, both islands each observed six wet days (>10.0mm), twelve relatively wet days (< 10.0mm with the rest of days mixture of relatively dry days (< 1.0 mm) and dry days (0.0 mm).In December, Trinidad had four wet days(>10.0mm), eleven relatively wet days (<10.0 mm) while Tobago had also had four wet days (>10.0 mm) with seven relatively wet days (<10.0mm) and the rest of days were a mixture of relatively dry days (< 1.0mm) and dry days (0.0 mm).

The 3-month dryness indicator October to December 2024 shows dryness indicator values that ranged from -0.96 to +0.74, so the dryness category is no concern (see Figure 1). The colour-coded dryness indicator map showing observed level of dryness is based solely on rainfall and can be used for decision-making or for heightening awareness on dryness. 

Figure 1. The colours on this map show 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.  The 3-month period used to compute the dryness is October to December 2024 compared to the historical average for the same 3-month period. The yellow to red colours on the map indicate areas with borderline-dry to extremely dry levels of dryness. The grey colour indicates areas where there is no significant dryness concerns.

Dryness Outlook for January to March 2025:

The dryness outlook shows that the dryness concern will lessen for Trinidad and Tobago through January and February, as most areas will experience no concerns of significant dryness in the short-term. Although there is an overall rainfall deficit for 2024, near to above-normal rainfall forecast January, February and March is expected to delay the usual drying trend during the early dry season.  The recent cooling of eastern Pacific Ocean and the onset of La Nina conditions is expected to increase rainfall intensity and amount through January and February. 

The predicted volume of rainfall from January to March 2025 will likely increase soil moisture to raise streams and river levels within catchment areas and begin to replenish reservoirs. 

The Dryness Outlook shows dryness indicator values between +0.31 and +0.47 are likely to develop across the vast majority of Trinidad and Tobago by the end of March (see Figure 2).

Figure 2. The colours on this map show the predicted levels of dryness for the January to March 2025.  It is based on the difference between standardized accumulated rainfall (observed and predicted) from January to March 2025 and the historical average rainfall for the same period. The yellow to red colours indicate borderline dry to extremely dry levels. The grey colour indicates areas where there are no significant dryness concerns.

Standardized Precipitation Index:

The Standardized Precipitation Index (SPI) is an index showing the severity and rarity of dryness or wetness of an area. Negative values of SPI indicate less than median rainfall and drier conditions; positive values indicate greater than median rainfall and wetter conditions. In general, dryness impacts are expected when the value of the 3-month SPI lies near-1.0. As the negative SPI value becomes smaller in amount than -1.0, the severity of impacts increases. For Trinidad and Tobago, extreme dryness occurs in the dry season when negative SPIs are larger than -1.25.