Wet Weekend for the Northeast Caribbean

28 04 2022

Dale C. S. Destin |

A trough system is poised to cause wet weather across the northeast Caribbean, including Antigua and Barbuda. Several of the more reliable weather models are forecasting the potential (10 percent chance) for rainfall totals exceeding 25 mm (over 1 in) to fall over the period Friday to Sunday of this weekend.

The potential total for over 25 mm in 72 hours is not in and of itself a high figure. However, relative to April and the fact that we are in a severe drought makes this worth “writing home about”.

Whereas all models consulted are forecasting rainfall for the weekend, the forecast totals differ, as can be expected. At the lower end of the potential rainfall scale some are projecting a 10 percent chance of over 25 mm (over an inch), while others are suggesting potentially higher totals, a 10 percent chance of over 75 mm (3 in) for the weekend.

GFS 24hr precipitation total exceedance forecast probabilities showing all areas with at least a 10 percent chance of getting over 50 mm (2 in) of rainfall from 2 am Saturday, 30 April to 2 am Sunday, 1 May 2022

The wet weather is expected from Dominica to Hispaniola. The highest totals are likely across Puerto Rico and the Virgin Islands Saturday/Sunday. Most of the rainfall for Antigua and the rest of the Leeward Islands is likely Friday/Saturday and for Hispaniola Sunday/Monday.

If the models prove right, and the upper end of the rainfall potential materialises, some places across the northeast Caribbean could see the average total for April falling in one weekend, if not one day. The possible rainfall total for the area is 25 to 100 mm (1 to 4 in). With this kind of rainfall possible, depending on the intensity and duration, flash flooding and associated impacts are of concern.

Deterministic rainfall accumulation forecast by the GFS model from Thursday, 28 April to Sunday, 1 May 2022

The rainfall of this weekend could, at least, put a dent or further dent in the droughts across the area, particularly the Virgin Islands and Puerto Rico. It will certainly have a big impact on domestic catchments, temporarily easing the stress and demand on water resources authorities.

There is no doubt that these showers will be welcome by all; however, they could prove disruptive to weekend plans leading up to Labour Day Monday celebrations. Good news though: The weather should just about be back to normal by Monday.

The system has already caused wet weather across the southern Caribbean with some areas receiving over 75 mm (3 in). The trough also prompted flash flood warnings for some islands.

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Early Prediction: Below Normal Rainfall Most Likely for Antigua

21 04 2022

Dale C. S. Destin |

The year will most likely be another drier than usual one for Antigua. My early forecast calls for the rainfall total for 2022 to most likely be 1105 mm (43.50 in) with a 70 percent or high confidence of it being in the range of 811 to 1463 mm (31.93 to 57.60 in).

The main reason for the most likely below normal rainfall forecast is the current cooler than normal sea surface temperatures (SSTs) across the tropical North Atlantic (TNA), which should last, at least, into the second half of the year. Cooler than normal TNA SSTs favour suppressed rainfall conditions while the opposite enhances rainfall.  

The year started out with a severe drought brought forward. This drought started in the winter of 2020/2021 and continues through the present. January 2022 was wetter than January 2021, but it was still only 72 percent of the normal total. The last two months, February and March, have been wetter than normal resulting in the intensity of the meteorological drought easing to slight. This easing is likely to be a brief respite, given the forecast.  

The dry season, January to June, will likely be below normal with a 60 percent chance. The forecast is for 298 mm (11.73 in) with high confidence of it ranging between 182 to 459 mm (7.17 to 18.07 in). This dry season could also be one of the top 10 driest. There is a 33 percent chance of this happening with the possibility of the total falling below 254 mm (10 in). Currently, the total stands at less than 203 mm (8 in) with April running well below normal at less than 25.4 mm (1.0 in) and the forecast indicating a better than 70 percent chance of May-June being drier than normal.

WMO Lead Centre for Long-Range Forecast Multi-Model Ensemble is forecasting 70-80% likelihood of below normal rainfall for Antigua and Barbuda for May to July. Also, below normal rainfall is likely for much of the rest of the Eastern Caribbean.

A typical year, based on the new standard climate period 1991-2020, averages 1156.7 mm (45.54 in). The dry season averages 410 mm (16.14 in) and the wet season, July to December, averages 746.8 mm (29.40 in). The fall/autumn, September-November, accounts for 58 percent of the wet season total and 38 percent of the year’s total.

Rainfall-wise, last year–2021, will be most remembered for being the second driest on record with some parts of the country having record-breaking dry weather. There were likely significant socio-economic impacts but unfortunately, this has not been quantified.

This forecast will be updated monthly around the 21st of each month until August. The first update will be issued around May 21.

Regardless of the forecast, we all need to conserve water and be as efficient with its use as much as possible. Reducing our personal water footprint will literally redound to our individual and collective socio-economic benefit. Minimising your water footprint is also good for the climate and good for our environment.

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Early Prediction: Very Busy 2022 Atlantic Hurricane Season Forecast

14 04 2022

Dale C. S. Destin |

This hurricane season will likely be another very busy one, exhausting the primary list of named storms, once again. My early forecast for the 2022 Season is out, and it calls for 21 named storms, 9 hurricanes and 4 major hurricanes.

In addition to being a very busy season, it is most likely to be an active season. Recall that the accumulated cyclone energy index (ACE) is the universally accepted metric used to classify the overall activity of a hurricane season. The ACE forecast for this year is 182, 30 above the threshold for an active season, based on 1991-2020 data.

A super hyperactive season is also possible. There is a 36 percent chance of the ACE exceeding 223. Further, there is a 49 percent chance of more than 19 named storms; 30 percent chance of more than 11 hurricanes and 29 percent chance of more than 6 major hurricanes.

If the forecast pans out, this season would be the third most active since 2017, in terms of ACE, and the tied with 1998 for the 10th most active on record dating back to 1851. It would also tie 2021 for the third highest number of named storms.  

According to other forecasts surveyed, the consensus is for an ACE of 161, 19 named storms, 8 hurricanes and 4 major hurricanes, a busy and active season. This is generally consistent with my forecast but with a notable 21 less ACE. However, regardless of the forecast, you should always be well prepared each season, as it only takes one hurricane to ruin your year and or life.

The main reason for the above normal forecasts is the current La Niña, which should last into the first half of the hurricane season and maintain favourable conditions for tropical cyclone formation even beyond August, into the peak of the hurricane season.

A typical season, based on the new standard climate period 1991-2020, has 14 named storms, 7 hurricanes and 4 major hurricanes. Major hurricanes have sustained wind speeds of at least 178 km/h or 111 miles per hour (e.g., Category 3 or higher), according to the Saffir Simpson Hurricane Wind Scale.

The last Atlantic hurricane season–2021, will be most remembered for being a very busy season with 21 named storms. Collectively, the season caused 103 deaths and over US$80 billion in damage. Major Hurricane Ida alone caused 55 deaths and over US$75 billion in damage.

This forecast will be updated monthly around the 14th of each month until August. The first update will be issued around May 14.

The Atlantic hurricane season officially begins on June 1 and concludes on November 30; nevertheless, in the last six years, there have been preseason tropical cyclones–be prepared!

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