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The Precipitation Outlook for the Caribbean is prepared by the Caribbean Institute for Meteorology and Hydrology with contributions from the regional Meteorological Services and the Climate Research group at UWI, Mona.

The precipitation outlook provides probability distributions indicating the likelihood of below-, near-, or above normal rainfall for the various sub-regions of the Caribbean. For this purpose, ‘normal’ is defined as the climatological mean. The Outlook is generated through analysis of historical records throughout the region, data available from the global climate monitoring system, and computer models of the evolution of the global sea surface temperature field.

The outlook is produced by combining objective input (dynamic model output) and subjective input (experience). The process starts with an examination of the sea surface temperature and precipitation forecasts from the climate models. Currently the output from four climate models are examined; three - ECHAM, CCM3, NCEP - from the International Research Institute for Climate Prediction (IRI) and one from the United Kingdom meteorological Office (UKMO). Tercile probabilities are then estimated for a number of sub-regions based on:

• Forecast anomalous precipitation from the IRI models

• Probabilities from the UKMO model

• The level of agreement between the models

• Subjective confidence in the model forecasts based on current conditions in the region and knowledge of the local climatic conditions

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

• Above normal - wettest third of the record
  

• Near normal - middle third of the record
  

• Below normal - driest third of the record
  

The tercile probabilities are presented in the form:

A few words of caution. This outlook is relevant only to seasonal time scales and relatively large areas; local variations should be expected, and variations within the 3-month period should also be expected. It is also emphasized that the boundaries between the sub regions are only qualitatively defined, and should be considered as transition zones rather than sharp boundaries. Consequently users of this Outlook are strongly advised to contact their National Meteorological Services for interpretation of this Outlook and for additional guidance.

Disclaimer
The information contained herein is provided with the understanding that The Caribbean Institute for Meteorology and Hydrology 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

The northern and western parts of the Caribbean is expected to experience normal to slightly above rainfall totals for the period forecasted. These areas include Cuba, the Bahamas and Belize. Jamaica and Cayman Islands are expected to experience below normal totals. This is especially the case within the first 2 months of the forecast.

The rainfall totals in the eastern part of the region is forecasted for below normal totals. The northern part of the Eastern Caribbean chain is expected to normal to below normal totals.

The rainfall totals in the southern part of the Caribbean is forecasted for below normal totals.

 El Niño conditions are expected to persist throughout the forecasted time.

Precipitation Outlook for Central America from

August to October,2010

The trimester August to October(ASO) is usually characterized as the main part of the rainy season.The two months of September and October represent the most active part of the the hurricane season. The most recent seasonal forecast prepared by Messrs. Klotzbach/Gray from Colorado State University(CSU) is suggesting a very active hurricane season. Klotzbach and Gray are forecasting  eighteen(18) named storms, ten(10) hurricanes and five(5) intense hurricanes for the 2010 Atlantic hurricane season. This forecast compares will with the efforts from the University College of London(TSR).Their seasonal forecast is suggesting nineteen(19) named storms, ten(10) hurricanes of which five(5) will become intense hurricanes. The forecast prepared by Cuba's Institute of Meteorology predicts sixteen(16) named storms, nine(9) hurricanes with four(4) named storms occurring within the Caribbean. The National Oceanic and Atmospheric Administration's(NOAA) seasonal forecast is also calling for an active Atlantic hurricane season. Their forecast  is suggesting fourteen(14) to twenty three(23) named storms, of which eight(8) to fourteen(14) will become hurricanes. Three(3) to seven(7) of these hurricanes will intensify to major hurricane status. The analogous years selected by Klotzbach and Gray for this year's hurricane season are:1958,1966,1969 and 2005.

Composite analysis is based on current results of the strength of the sea surface temperatures(SST) measured at several locations of the central and eastern Pacific Ocean. Climate model forecasts from the International Research Institute (IRI) have  indicated an increase La Niña  conditions over the eastern equatorial Pacific. Sea surface temperatures (SST)continue to decrease much of the central and eastern Pacific Ocean.

Most of the dynamical and statistical forecast models from the International Research Institute (IRI) indicate a persistence of the ENSO cold phase conditions through the remainder of 2010.There is a 80% probability of the cold phase conditions persisting for the August-October(ASO) trimester. 

Precipitation    

Tercile probability forecasts (see map above) for the country are all suggesting rainfall amounts in the Normal (N) for greater part of the country. There is a tendency for rainfall amounts to range between Normal (N) to Above Normal (AN) for the extreme northwest corner of  Belize. Rainfall amounts will range from 180mm (7.00”) in the north  then increasing to near 250mm to 280mm (9.90-11.00”) for central and coastal  Belize. In the south rainfall amounts will peak near 550mm (22”) for Punta Gorda town.

Analogous years

To prepare the set of analogous years for this trimester the data set for the Oceanic Niño Index (ONI) were used to find the closest comparison to this year’s ONI values. These years are: 1970,1973,1988,1995 and 1998.

Prepared by: Frank Tench Jnr. (weather forecaster)

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