Dale C. S. Destin |
The first half of May 2015 is over and the Met Office, located at the V. C. Bird International Airport, Coolidge, Antigua, has measured only 1.7 mm (0.07 in) of rainfall. This represents the second driest such period on record. The only time May 1-15 was drier was back in 2001.
We are clearly not having a normal May or year but normally we would have received around 37.8 mm (1.49 in) by now. Instead, we have had near record dryness.
The rest of the country has not fared better. In fact, there are a few areas that are yet to see measurable rainfall for the month. Neighbouring islands are also experiencing similar rainfall deficits.
This severe dryness for the first half of May is very rare. On average, this happens once every 250 years, which translates to a 0.4% probability of May 1-15 being this dry.
The near record low rainfall seems largely connected with the anomalous cooling of the tropical North Atlantic which is associated with a positive North Atlantic Oscillation (NAO). Another significant driver of the dryness is the above normal flow of very dry, dusty air from the Sahara Desert to the region.
A dry start to the month does not always imply a dry month; however, of the six other times we have had 10 mm (0.40 in) or less for the first half of May, the eventual month’s total has never exceeded 56 mm (2.20 in). Only once such a dry start did not signal a dry month.
Overall, the second half of May has produced as little as 3.9 mm (0.15 in) and as much as 434.7 mm (17.1 in). Hoping to be wrong, but it would not be “tempting fate” to say that we absolutely will not get anywhere remotely close to 434.7 mm over the next two weeks.
Climatologically, the past 30 years show that rainfall on a whole for May is not changing. However, May 1-15 is trending positively (wet) while May 16-31 is trending negatively (dry). These trends are not considered significant, at the moment, but May 1-15 is not far away from being so.
The driest May on record at the Airport, dating back to 1928, is May 2001 with 7.6 mm (0.30 in). This record appears to be in jeopardy.
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