Trinidad and Tobago Dryness/Drought Indicator, Monitor and Outlook By End of December 2023



ISSUED AT: 11:26 AM

Date: Friday 23rd of December 2022

Dryness Indicator from September to November 2022 & 3-month Dryness Outlook for December to February 2023

Key Message:

Trinidad and Tobago received copious amounts of rainfall during September to November, with torrential rainfall in October and November 2022. Piarco, Trinidad monthly September-October-November totals range from about 205.8mm, 359.4mm and 469.9mm respectively, while Crown Point, Tobago monthly totals September-October-November range from about 162.8 mm, 491.1mm and 259.6 mm respectively. There is no concern for dryness at this time. The outlook for the next three months, December-January-February 2023 shows all areas are likely to be free from dryness in the short-term.

Dryness Indicat...


Trinidad and Tobago Dry/Wet Spell Monitor and Outlook by End of December 2023



ISSUED AT: 11:26 AM

Date: Friday 23rd of December 2022

Dryness Indicator from September to November 2022 & 3-month Dryness Outlook for December to February 2023

Key Message:

Trinidad and Tobago received copious amounts of rainfall during September to November, with torrential rainfall in October and November 2022. Piarco, Trinidad monthly September-October-November totals range from about 205.8mm, 359.4mm and 469.9mm respectively, while Crown Point, Tobago monthly totals September-October-November range from about 162.8 mm, 491.1mm and 259.6 mm respectively. There is no concern for dryness at this time. The outlook for the next three months, December-January-February 2023 shows all areas are likely to be free from dryness in the short-term.

Dryness Indicator for September to November 2022

During September, normal rainfall amounts occurred over Trinidad and Tobago. Trinidad had fifteen relatively wet days (>1.0 mm) and eight wet days (>10.0 mm) while Tobago had sixteen relatively wet days (>1.0 mm) and five wet days (>10.0 mm) and zero excessively wet days (>50.0mm). The month of October had above normal rainfall for both Trinidad and Tobago. Trinidad had fifteen relatively wet days (>1.0 mm), six wet days (>10.0 mm) and two excessively wet days (>50.0mm) which gave a monthly totally of 359.4 mm. Tobago had thirteen relatively wet days (>1.0 mm), ten wet days (>10.0 mm) and three excessively wet days (>50.0mm) which gave a monthly tally of 491.1 mm beating the previous extreme of 379.3 mm and being the wettest October on record (1969-2021) for Tobago. The month of November was another above normal rainfall month for Trinidad but normal for Tobago. Trinidad had twenty-one relatively wet days (>1.0 mm), sixteen wet days (>10.0 mm) and two excessively wet days (>50.0mm) which gave a monthly tally of 469.9 mm beating the previous extreme of 442.9 mm and being the wettest November on record (1946-2021). Tobago had eighteen relatively wet days (>1.0 mm), eight wet days (>10.0 mm) and zero excessively wet days (>50.0mm) which gave a monthly total of 259.5 mm which is within the normal range.

The 3-month dryness indicator for September to November shows dryness indicator values that range from +0.1 to +3.5, which is within the no concern for impactful dryness category (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 period used to compute the dryness is  the  3-month period September to November 2022 compared to the historical average for the same 3-month period. The yellow to red colours on the map are used to 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 December to February 2023:

The accumulated rainfall received nationwide during the wet months of June to November 2022, together with the predicted volume of rainfall for December to February 2023 has definitely remove any chances of dryness. Frequent rainfall events are expected to continue into January-February 2023. The Dryness Outlook shows dryness indicator values between +0.28 and +0.35 are likely to develop across the vast majority of Trinidad and Tobago by February month end (see Figure 2). The outlook is based solely on rainfall and should be used only as a guidance tool.

Figure 2. The colours on this map show the predicted levels of dryness for the period December to February 2023.  It is based on the difference between standardized accumulated rainfall (observed and predicted) from December to February 2023 and the historical average rainfall for the same period. The yellow to red colours indicate borderline dry to extremely dry levels of dryness. The grey colour indicates areas where there is 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 larger 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.