Cooler Than Normal May for Antigua

30 06 2018

Dale Destin |

TempStmntGraphic_BelowNormalNotwithstanding being drier than usual, May was much cooler than normal, based on preliminary data record at the V.C. Bird International Airport (VCBIA), Antigua. The mean temperature of 26.4 °C (79.5 °F) was the lowest at VCBIA since 2012. Only six other Mays have been cooler on record dating back to 1969.

Further, at VCBIA, the mean daily minimum temperature (mean min) of 23.7 °C (74.7 °F), an indicator of night-time temperature, was well below normal. This is the lowest mean min for May since 1975 and only the third lowest on record dating back to 1969.

Additionally, the mean daily maximum temperature (mean max), an indicator of day-time temperature, was cooler than normal. The mean max of 29.3 °C (84.7 °F) tied with that of 2017 for the lowest temperature at VCBIA since 2014.

Looking deeper into the preliminary numbers at VCBIA, there was an above normal number of cold days (4) and cold nights (5). The most number of cold nights since 2008.

Clearly, the numbers indicated above, with respect to temperatures, differs from those recorded elsewhere across the island. We don’t have long enough datasets to speak definitively about temperatures for other areas of Antigua. However, it is believed that the rankings of temperatures are likely to be similar.

So, although other parts of Antigua had lower or higher temperatures, because temperatures are highly correlated, especially in a small island like ours, most if not all places had a cooler than normal May, relative to the given location. On average, some places across Antigua differ by as much as 5 °C (9 °F).

The reason for the cooler than normal temperatures is the same reason for the drought weather being experienced – cooler than normal sea surface temperatures across the tropical North Atlantic (TNA) Ocean. These temperatures are likely to remain cooler than normal for much of the rest of the year.

Tropical North Atlantic  (TNA) Index - Much Cooler Than Normal

Tropical North Atlantic (TNA) Index – a measure of the sea surface temperature between Africa and the Caribbean – much cooler than normal.

Based on record dating back to 1948, this past May was the coolest the TNA has been for the said month since 1989 and the sixth coolest on record.

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Record Low Cool Nights for Antigua

4 02 2016

Dale C. S. Destin |

2015 saw the fewest number of cool nights on record across much of Antigua. At the V. C. Bird International Airport (VCBIA), the number of cool nights – nights with the temperature falling to at least 22 °C (71.6 °F) – was the fewest on record in a series dating back to 1971.

CoolNightsAtOrBelow22C

Never before on record have there been so few days with the temperature falling to at least 22 °C. There were only 4% of days of the year when the temperature fell to 22 °C or lower. For an average year, this number is 11%, almost three times what was observed in 2015.

January and December, on average, are among the months with the highest number of cool nights. However, December had a record low number of cool nights – zero, and January had near record low – four.

Cool nights have been significantly declining over the years. The numbers at VCBIA have dropped from around 15% of days per year in the 1970s to around 7% at present.

This significant decline in cool nights is consistent with what is taking place globally, as our climate changes. According to the IPCC, “It is very likely that the number of cold…nights has decreased and the number of warm…nights has increased on the global scale.”

In general, cool places and times of the day are warming at a faster rate than warm places and times. In our case, nights are warming faster than days. Further, most of the warming being experienced across our area is due mainly to the nights warming at a significant rate.

The mean minimum temperature (mean-min-Temp) for 2015, a proxy for the mean night-time temperature, was at a record high level. The mean-min-temp of 24.5 °C tied with that of 2002 and 2001 for the record lowest.

Apart from cool nights trending downwards most likely due to climate change, the record low rainfall in 2015 contributed a lot to so few days with temperature falling through 22 °C. Evaporation is a cooling process and, when it rains, the water that is subsequently evaporated leads to cooling and reduced temperature. More rain did not fall than fell in 2015; hence, very little evaporative cooling.

On the other hand, the number of warm days – days with the temperature increasing to at least 31 °C (87.8 °F) – was fewer than normal. The year had 19% of days with 31 °C or higher temperature compared to the average of 25%.  These warm days are trending upwards but not significantly, at the moment.

Fewer cool nights have negative implications for our economy and ecosystem. The lack of cool or respite from our virtually year-round oppressive heat will likely hit us in the pocket as we burn more and more energy to keep our bodies from overheating. Heat stress is very costly to our health and well-being and that of our vital flora and fauna.

Follow this space as we bring you more highlights of our weather and climate of 2015. We can be followed on twitterfacebookinstagramtumblrflickrgoogle+, and youtube for education and information on all things weather and climate.

 








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