Declaration of the end of the Meteorological Drought in Trinidad And Tobago

Stemming from the definition of a Meteorological Drought, recent rainfall events have signified that the Meteorological Drought is officially over in Trinidad and Tobago. However, the positive impacts on water reserves may not be immediately reflected. 

In an effort to comply with standards being developed by the WMO, the Meteorological Services have been using the Standardized Precipitation Index (SPI) to determine conditions, with respect to rainfall, ranging from extremely wet to extremely dry.  The index is negative for drought and positive for wet conditions. As the dry or wet conditions become more severe, the index becomes more negative or positive.

The Standardized Precipitation Index was designed to explicitly express the fact that it is possible to simultaneously experience wet conditions on one or more time scales, and dry conditions at other time scales, often a difficult concept to convey in simple terms to decision-makers.

The SPI was used to monitor the drought affecting Trinidad and Tobago. A time scale of 1 to 6 months was looked at to determine the extent of the drought being experienced.  Preliminary results, using the SPI for Piarco, Trinidad, show that moderately to very dry conditions were experienced for 4 to 6 months leading up to April 2010. For a shorter time scale of 1 to 3 months leading up to April 2010, the SPI indicated that conditions were gradually improving to near normal conditions. The month of April 2010 had rainfall amounts totaling above normal. The precipitation forecast for the next three months indicates that rainfall will be near normal to above normal which should lead to a gradual improvement in the agricultural and water resources.

The table below represents a simple guide as to SPI and the category each range represents.

SPI                              Category

2.0 +                           Extremely wet

1.5 to 1.99                   Very wet

1.0 to 1.49                   Moderately wet

-0.99 to 0.99                Near normal

-1.0 to -1.49                Moderately dry

-1.5 to -1.99                (Severely) Very dry

-2.0 and less                 Extremely dry

Rainfall patterns recently are indicating therefore that the meteorological drought has ended. However, a hydrological imbalance continues to exist and as such reserves may not reflect positively in the immediate future.