• What can we usually expect during this period?
  • Climatically, December to February forms the first half of the Dry Season in the Caribbean Islands, Belize, and the far interior of the Guianas. The historical record shows that the first half of the Caribbean Dry Season in the Bahamas, Belize, the Greater and Lesser Antilles is usually characterised by a steady decrease in the frequency of wet days and in the intensity of heavy showers. Conversely, the number of dry days and dry spells is high westwards of Puerto Rico throughout the period while, further east, their frequency increases towards the end of February. The resulting drier surface and foliage increase wildfire potential and the concentration of airborne particulates and local dust levels. Access to more detailed forecast information on dust and air quality in the Caribbean may be found here: http://dafc.cimh.edu.bb/.
  • By contrast, the coastal Guianas are in their secondary Wet Season until early February, then moving into their secondary Dry Season. Hence, wet days and wet spells are usually frequent while dry spells are few in December and January.
  • In this period, flood and flash flood potential (i.e., the chance of occurrence of an excessive rainfall event that can trigger floods and cascading impacts – such as land slippage, rock fall, soil erosion, river damming, mud flows – in flood-prone areas) is typically high (i.e., occurs at least once every two years) to extremely high (i.e., occurs in most years) in the Guianas and southern Belize, but slight (i.e., occurs once every five to ten years) to moderate (i.e., occurs at least once every five years) elsewhere.
  • The 2024 Atlantic Hurricane Season officially ended on November 30th, but the historical record shows that storms and hurricanes have occurred after the official end date (including an unnamed sub-tropical storm in January 2023).
  • December to February further marks the return of the entire Caribbean region to the Cool Season. Generally, more comfortable temperatures and decreasing humidity are the historical norm for this period.
  • Across the region, swells, surges and rip currents from large, mostly extratropical cyclones in the North Atlantic can be hazardous to life and engender beach erosion. (Seven-day forecasts of swell heights may be found here: WaveWatch III (cimh.edu.bb)
  • Notwithstanding that it is the coolest part of the year, there remains a high risk of skin damage due to intense ultraviolet (UV) light emitted by the sun. The UV index will be high in the northern Bahamas (7-8) and very high (9-10) elsewhere in the Caribbean until January, and then increase to very high and extremely high in those areas, respectively, by February.
  • The frequency of Saharan dust incursions into the Caribbean tends to be low during this period. However, in recent years, an increase in significant episodes as early as February has been observed.
• What is different this year?
  • This year, a strong El Niño event faded in May, with near- to just below-average sea surface temperatures in the eastern tropical Pacific Ocean observed since then. The forecast models forecast more likely than not La Niña conditions (approx. 50-70% confidence) in December-January-February. La Niña conditions are often associated with increased heavy shower activity and rainfall totals in the southeastern Caribbean – including the Guianas -, but the opposite in the northwestern Caribbean.
  • By contrast, near record-high temperatures in the North Atlantic Ocean and the Caribbean Sea contribute to higher air temperatures, but also to increased air humidity and rainfall throughout the Caribbean, as well as the frequency of severe weather during the early Dry Season.
  • As compared to the historical norm, the unusually warm waters in the Tropical North Atlantic Ocean will increase air temperatures and humidity during the Cool Season which runs throughout the three-month period, but unlikely to the point of significant heat stress.
• In light of the very warm North Atlantic, the forecast for December 2024 to February 2025 suggests:
  • Seasonal rainfall amounts are forecast to be close to the usual or even less in the Bahamas, the Cayman Islands and Cuba, whereas the ABC Islands, Barbados, the Guianas, Trinidad & Tobago and the Windward Islands should record seasonable rainfall amounts – or more – during this period (medium confidence).
  • Especially where less than the usual rainfall totals have been recorded in previous months, such rainfall deficits increase the chances of drought.
  • As such, short-term drought is expected to be a significant concern by the end of February 2024 in the extreme northwest Bahamas, southwest Belize, most of Cuba, southeast Puerto Rico, and the U.S. Virgin Islands (medium to high confidence), but also possible in central Cuba, Dominica, southern Dominican Republic, eastern Jamaica, western Puerto Rico and Saint Lucia (medium confidence). Short-term drought may impact food production, water quality and quantity from small streams, small ponds and other surface sources. Long-term drought is evolving by the end of May 2024 in southwest Belize, southeast Puerto Rico and the U.S, Virgin Islands (high confidence) and might possibly develop or continue in southwest Puerto Rico (medium confidence). Long-term drought (on a 12 months timescale) affects water availability across a multitude of socio-economic sectors in countries where the main freshwater resource is from very large rivers, large reservoirs or groundwater.
  • Despite the return to the Caribbean Cool Season, seasonal night-time and day-time temperatures in the region are expected to be warmer than usual (high confidence) and accompanied by higher than usual levels of air humidity (medium confidence).
  • Whereas tropical cyclone activity typically decreases after mid-October, severe weather systems related to tropical cyclones, as well as heavy showers can still affect Caribbean territories, particularly during December. The warm Atlantic and possible La Niña conditions increase flood and flash flood potential from high to extremely high in Belize and Guyana, high in the Windward Islands, and moderate to high Persons should keenly monitor weather advisories issued by the National Meteorological Services and other information provided by the Caribbean Disaster Emergency Management Agency (http://cdema.org/) and the US National Hurricane Center (https://www.nhc.noaa.gov/).
  • Zooming in on the first half of December, prototype sub-seasonal forecasts suggest that relatively dry conditions are expected across most of the region. By contrast, this forecast suggests there is only a 30% chance or less for severe weather and resulting heavy rainfall in most areas until then, except in parts of northern Guyana, western Jamaica, eastern Cuba where severe weather is more likely, as well as, to some extent, southern Belize and Curaçao. In addition, these forecasts suggest that persons located in inland parts of Guyana, the west coast of Dominica and parts of Jamaica may still experience days of excessive humid heat.

This Bulletin provides a broad overview of climate conditions up to 3 months in advance. It is based on insights drawn from CIMH’s suite of technical climate information products and epidemiological insights from CARPHA and PAHO. The information contained herein is provided with the understanding that the CARPHA, the PAHO and the CIMH make no warranties, either expressed or implied, concerning the accuracy, completeness, reliability or suitability of said information. The Bulletin may be freely used and disseminated by the public with appropriate acknowledgement of its source but shall not be modified in content and then presented as original material.