Forecast Drought Condition for Belize is done using Standardized Precipitation Index (SPI)
The Standardised Precipitation Index (SPI), developed by T.B. Mckee, N.J. Doesken and J. Kleist (McKee et al. 1993) of Colorado State University is an index that, if used carefully, can provide early warning of an extended drought period and aid in assessing drought severity. It can also provide similar information at the other end of the spectrum- extremely high precipitation. SPI is basically a representation of rainfall in units of standard deviation. Positive values indicate greater than median rainfall; negative values indicate less than median rainfall. Belize is now using this tool for early drought warning.
Table SPI Classification (CIMH)
| SPI Value | Category | SPI Value | Impact |
|---|---|---|---|
| -0.50 to -0.01 | Normal | 0.50 to 0.01 | Normal |
| -0.80 to -0.51 | Abnormally Dry | 0.80 to 0.51 | Abnormally Wet |
| -1.30 to -0.81 | Moderately Dry | 1.30 to 0.81 | Moderately Wet |
| -1.60 to -1.31 | Severely Dry | 1.60 to 1.31 | Very Wet |
| -2.00 to -1.61 | Extremely Dry | 2.00 to 1.61 | Extremely Wet |
| -2.01 | Exceptionally Dry | 2.01 | Exceptionally Wet |
A three-month SPI analysis reflects short to medium term moisture and can give an indication of available moisture conditions at the beginning of the growing season. A six-month SPI analysis reflects medium term trends in rainfall and is effective in showing rainfall distribution over distinct seasons as well as being associated with anomalous stream flows and reservoir levels, which takes longer to manifest itself than does agricultural drought. A twelve-month SPI can indicate the potential periods of shortfall in groundwater amounts.
Disclaimer
The information is provided with the understanding that The National Meteorological Service makes no warranties, either expressed or implied, concerning the accuracy, completeness, reliability, or suitability of the Outlook. The information may be used freely by the public with appropriate acknowledgement of its source, but shall not be modified in content and then presented as original material.
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