Grand Cayman is experiencing the driest year in recorded history, possibly because of the El Niño event in the tropical Pacific Ocean.
John Tibbetts, chief meteorologist of the Cayman Islands National Weather Service, said that through 25 August, there had only been 7.67 inches of rain in 2009.
‘The 7.67 inches recorded so far for the year is the driest over that period on record,’ Mr. Tibbetts said. ‘In fact, the second driest [year through August] on record was 1974 with 18.62 inches, which was more than twice as much rainfall as we have experienced this year.’
The average amount of rainfall on Grand Cayman through the end of August is 30.3 inches.
‘The rainfall total, so far, represents 25 per cent of the normal rainfall,’ Mr. Tibbetts said.
Mr. Tibbetts said pinpointing a reason for the dry year was difficult.
‘The dominant pattern over our region is a developing El Niño pattern,’ he said. ‘Under this pattern, the Caribbean countries all experience diminished rainfall. In discussions with forecasters from the region, they all confirm this is occurring.’
Mr. Tibbetts said Cayman’s two driest years on record, in 1986 and 1997, both corresponded with years of strong El Niño events. El Niño is a cyclical weather phenomenon in the tropical Pacific Ocean where sea surface temperatures rise above average. Its effects can cause more rain in some places – like California – and less rain in places like the Caribbean.
Mr. Tibbetts said every month so far this year has had rainfall amounts below the long-term average. The summer months, however, have been particularly drier than average.
May’s 0.67 inches of rain was well below the average of 5.53 inches, and was the lowest since the 0.03 inches of rainfall measured in May 1983.
Not only was July’s 0.38 inches of rain far below the average rainfall of 5.81 inches for the month, it was the lowest total for July on record.
August will likely also set a record for the lowest rainfall total on record. Through Thursday morning, only 0.45 inches of rain have fallen at the airport in August, far below the 6.7-inch average for the month. It’s also more than two inches below the 2.48 inches that fell in August 1993, the lowest amount on record for the month.
Depending on what happens in September and October – Grand Cayman’s wettest two months historically – 2009 could very well turn out to be the driest year ever recorded.
The lowest rainfall for an entire year in Cayman’s recorded history is 35.61 inches in 1997, Mr. Tibbetts said. If only the statistical average amount of rain falls between now and the end of December, Cayman will easily set a record for the lowest amount of rain in a year.
According to the Caribbean Institute of Meteorology and Hydrology’s Standardised Precipitation Index forecast, there is a good chance – 45 per cent – the area around Cayman will experience below normal rainfall through the end of September, and only a 20 per cent chance of above normal rainfall.
Grand Cayman’s annual average of rainfall, which Mr. Tibbetts said has been calculated from data from 1971 through 2000, is 56.41 inches.
Although El Niño is the most likely culprit for this year’s drier-than-usual rainy season, Mr. Tibbetts said there could be another factor inhibiting rainfall in Cayman.
‘The Saharan Air Layer is an intensely dry, warm and sometimes dust-laden layer of the atmosphere, which often overlies the cooler, more humid surface air of the Atlantic Ocean,’ he said. ‘Special satellite pictures confirm that this layer has been spreading over the Caribbean at times.’