Disclaimer

The information contained herein is provided with the understanding that The Caribbean Institute for Meteorology and Hydrology (CIMH) 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.

Background

The Precipitation Outlook for the Caribbean is prepared by the Caribbean Institute for Meteorology and Hydrology with contributions from some regional Meteorological Services.

The outlook is produced by combining objective input (climate model output) and subjective input (experience). Precipitation forecasts from the Climate Prediction Tool (CPT - a statistical model) in the form of probabilities of above-, near-, or below normal rainfall, are balanced with similar output from dynamical climate models - i.e. general circulation models. Both model types predict seasonal rainfall based on the latest observed climate state (e.g. tropical sea surface temperatures). Currently output from climate models from the International Research Institute for Climate Prediction (IRI, including CPT), the United Kingdom meteorological Office (UKMO), and the European Centre for Medium-Range Weather Forecasts (ECMWF) are examined.

Precipitation probabilities are estimated for a number of sub-regions based on the model forecasts, the level of agreement between the different models, and a subjective confidence in the different predictions based on current conditions and a knowledge of the local climatic conditions. In addition, the probabilities provided by the various contributors are consulted to present a consistent forecast.

The precipitation outlook is issued in the form of a map of tercile probabilities showing regions having homogeneous forecast probabilities for below, near, and above normal precipitation. The terciles separate the possible outcomes into three categories (terciles) based on the historical precipitation record. The probabilities add up to 100.

Tercile probabilities separate the possible outcomes into three categories/ terciles (thirds) - based on the historical precipitation record. The three categories are:

The tercile probabilities are presented in the form:

20 Percentage likelihood of above normal rainfall
45 Percentage likelihood of normal rainfall
35 Percentage likelihood of below normal rainfall
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