Updated Prediction: Below Normal Rainfall Most Likely for Antigua for 2022

31 05 2022

Dale C. S. Destin |

The prediction for rainfall remains discouraging. My latest forecast continues to call for most likely below normal rainfall for Antigua. The most likely total for the year is 1080 (42.5 in), down 25 mm (1 in) from the previous forecast. There is also a 70 percent or high confidence of the rainfall total falling in the range of 590 to 1695 mm (23.2 to 66.7 in).

The main reason for the below normal rainfall forecast is the current trend of cooler than average sea surface temperatures (SSTs) across the tropical North Atlantic (TNA), which should last through summer (June-August). 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. This May has been wetter than the last one; notwithstanding, it will end with well below normal rainfall. Year-to-date is drier than normal. Further, since the deluge of November 2020, the start of the current drought, there has been 943.1 mm (37.13 in) of rainfall, for December 2020 to May 2022. This total is so far below normal that it is the second driest such period on record.

The dry season, January to June, is on track to be drier than usual. Summer, June to August, is also likely to be drier than normal. Further, the first three quarters of this year (January to September) is likely to see deficit rainfall with a most likely total of 645 mm (25.4 in) compared to the usual amount of  759 (29.9 in). There is also a 29 percent chance of January to September having top 10 dryness.

WMO Lead Centre for Long-Range Forecast Multi-Model Ensemble is forecasting 40-50% likelihood of below normal rainfall for Antigua and Barbuda for June to August. Also, below normal rainfall is likely for much of the rest of the 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.

This forecast will be updated monthly around the 25th of each month until August. The next update will be issued around June 25.

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, good for our environment and good for rainfall.

Please share this blog, if you found it useful, and follow me for more on the evolving drought and for all things weather and climate – TwitterFacebook and Instagram.





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.

Please share this blog, if you found it useful, and follow me for more on the evolving drought and for all things weather and climate – TwitterFacebook and Instagram.





Drought Continues Almost Everywhere

20 04 2019

Dale C. S. Destin |

We continue to see red almost everywhere across the Caribbean region – indicative of drought, severe in some places. The red has spread from the last blog on the subject, suggestive of the drought spreading, one may say, like a wild-fire.

Dec 2018 – Feb 2019 SPI index, characterising rainfall across the Caribbean. More red seen above than below – the last three months drier than the previous three.

Nov – Dec 2018 SPI index, characterising rainfall across the Caribbean

According to data from the latest Caribbean Climate Outlook Newsletter, over the past three months – December to February, rainfall deficits have resulted in the development or continuation of drought across many parts of the Caribbean. The few exceptions include the Bahamas, the Cayman Islands and the western parts of Cuba.

El Nino, warmer than usual sea surface temperature across the eastern tropical Pacific Ocean, is likely to have been the main cause of the deficit in rainfall over the past three months. Regression analysis shows that El Nino normally causes negative rainfall anomalies – below normal rainfall, across much of the region, especially across the Eastern Caribbean during December to February (DJF).

Rainfall and El Nino – The gray areas indicate the places that receive below normal rainfall during an El Nino during the period December-February.

For much of the region, the Newsletter indicates just a low chance of drought-busting rainfall over the period April-June. Beyond June, there is just a slight chance of drought-busting rainfall over the period July-September. Rainfall will most likely be the scarcest across the Eastern Caribbean.

So, unfortunately, we will continue to see mostly red across the area – it is going to be another tough year for rainfall, with eastern area getting the driest end of the atmosphere.

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Drought Almost Everywhere

9 03 2019

Dale C. S. Destin |

Red is a beautiful colour but not when it is on a rainfall map. On such a map, red is bad news – it is a warning that something very unwelcome is happening – severe drought.

According to data from the Caribbean Climate Outlook Newsletter, over the past three months – November to January, rainfall deficits have resulted in severe drought across many parts of the Caribbean. This includes, parts or the whole of Barbados, Cuba, Hispaniola, St. Vincent and Trinidad and Tobago.  

Beyond the last three months – longer term drought is seen across Antigua and Barbuda and much of the rest of the northeast Caribbean, the Cayman Islands, parts of the Dominican Republic, northeast Guyana, much of the Windward Islands, Trinidad and Tobago.

El Nino, warmer than usual sea surface temperatures across the eastern tropical Pacific Ocean, is likely to have been the main cause of the deficit in rainfall over the past six months.

Regression analysis shows that El Nino normally causes negative rainfall anomalies – below normal rainfall, cross much of the region, especially across the Eastern Caribbean during September to November (SON) and December to February (DJF).

El Nino and rainfall – It normally results in negative (-) rainfall anomalies or below normal rainfall across the Caribbean during SON. Graphic courtesy U.S. Climate Predicttion Centre.

El Nino and rainfall – It normally results in negative (-) rainfall anomalies across the Eastern Caribbean and positive anomalies across the Western Caribbean during DJF.
Graphic courtesy U.S. Climate Predicttion Centre

The Newsletter indicates that there is just a little bit of distant light at the end of the tunnel for most of the Caribbean with respect to the end of the drought. How distant is this light? Three to six months down the road for the northeast Caribbean, including Antigua and Barbuda, at which time, the forecast is for rainfall to be most likely above normal. However, this light could go dark, if El Nino continues, as is most likely from this vantage point.

Usual rainfall totals for the Caribbean for March to May

The exceptions to the rule are Cuba and Jamaica, which are most likely to have above normal rainfall during the upcoming three months.

Unfortunately, we will continue to see mostly red for the rest of the next three months with a glimmer of hope for friendly, calming colours – blues, thereafter.

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The Driest Year for Antigua since at Least 1871

21 12 2015

Dale C. S. Destin |

Earlier this year, we indicated that Antigua could see its driest year on record. Regrettably, this is coming to past. The country is on its way to having the driest year on record dating back to at least 1871 or 145 years ago.

Up to the end of November, the rainfall total stood at 525.8 mm (20.70 in). Based on measured rainfall, it’s the lowest on record for any January-November period dating back to 1928. Further, based on statistical analyses, we are almost 100% certain that this is the driest such 11 months since 1871.

Annual Rainfall for Antigua. Blue line - rainfall; heavy grey line - normal rainfall using base period 1981-2010

Annual Rainfall for Antigua. Blue line – rainfall; heavy grey line – normal rainfall using the base period 1981-2010.

It would take perhaps a miraculous deluge to prevent the 1983 record (681.5 mm or 26.83 in) from being broken. Over six inches of rain is required in December to prevent the record from being broken. Thus far for the month, the rainfall total is less than an inch.

There have been only 11 times in 88 years when the rainfall for December has exceeded 155.7 mm (6.13 in) – the amount required to prevent the record from falling. The probability of this happening is around 12%, El Nino or not. Currently, we are at least 70% certain that this rainfall will not materialize.

We could also see our record driest wet season (July-December). Statistically, there is a very low chance of this happening – around 8%; however, given the near record low rainfall for the month thus far, the chance is increasing.

We do not actually have data from our current stations going back beyond 1928. However, with the use of regression analysis, we were able to use other datasets to successfully extend our record back to 1871. So we now have very high quality datasets of annual and some seasonal rainfall totals dating back 145 years.

Like Antigua, most of the eastern half of the Caribbean could also see record-breaking low rainfall for 2015.

Caribbean Rainfall - Dec 2014 to Nov 2015

Nov 2014-Dec 2015 SPI. The darker the reds, the drier the weather; the darker the blues, the wetter the weather. Record or near record low rainfall for much of the eastern half of the Caribbean basin.

El Nino, Saharan dust and a positive North Atlantic Oscillation are the main culprits for the parched weather conditions for this year.

Keep following this “space” for more insights into the rainfall for Antigua and the Caribbean. Unfortunately, we have additional undesirable statistics to share with you on this subject.





Significant Rainfall Deficits Across Much of the Caribbean

25 04 2015

Dale C. S. Destin|

Rainfall totals across most of the Caribbean has been lower than normal for various time intervals going back a year. For some islands, rainfall deficits have been at or near record levels.

The time interval that shows the greatest deficits is the past 12 months (April 2014 to March 2015); while, over the past three months, there have been some improvements.

One way of expressing rainfall is by way of the standard precipitation index (SPI) and most of the Caribbean has been having negative values which translate to below average rainfall.

Basically, the SPI is an expression of how far away the rainfall was from the average. Positive values of 0.5 or greater (blues on the maps) indicate more rainfall than normal and negative values of -0.5 or less (yellows & reds on the maps) indicate lower than normal rainfall.

By general definition, all areas with an SPI of minus 0.5 or less are experiencing drought. This includes the Virgin Islands to Martinique. Hence, most of the northeast Caribbean is in drought, of some kind. According to the Caribbean Drought Bulletin, drought also exists across Eastern Jamaica and Haiti.

2015 first-quarter rainfall

Lower than normal first-quarter rainfall has not only been experienced by Antigua but also by most of the rest of the Leeward Islands, the Virgin Islands and the Windward Islands north of St. Lucia, according to the graphic (click for larger view) from the Caribbean Institute for Meteorology and Hydrology (CIMH).

SPI for Jan-Mar2015

Credit: @CIMHbb

First-quarter deficits were most extreme across St. Martin and nearby islands such as Saba and St. Barthelemy; the rainfall totals were at record low levels or in the bottom 2% of all totals for January-March.

Surplus rainfall took place across parts of Puerto Rico and the Dominican Republic; rainfall totals were at record high or in the top 5% of all rainfall for this time of the year.

Rainfall for the past six months

Over the past two quarters (October 2014-March 2015), more areas than the first-quarter experienced significant rainfall deficits. The “bullseye” dry spot remained over Dominica, where rainfall totals were in the bottom 5% of the historical record.

SPI Oct2014-Mar2015

Credit: @CIMHbb

Nearby islands – Guadeloupe, Dominica and Martinique, had rainfall totals ranked in the bottom 10% of the historical record.

Meanwhile, Tobago enjoyed surplus rainfall with totals in the top 10% for this period.

Rainfall for the past year

Of the three time scales, the past 12-months saw the greatest area under significant rainfall deficits.  A “bullseye” dry spot is again evident over Dominica; rainfall deficits were near record high levels.

SPI for Apr2014-Mar2015

Credit: @CIMHbb

Rainfall totals were also ranked in the bottom 10 percent for Guadeloupe, Dominica, Martinique and parts of St. Lucia.

Coastal areas of parts of Guyana, Puerto Rico and Jamaica had surplus rainfall.

The Cause

Much of this dry weather is due to the presence of El Nino and a positive North Atlantic Oscillation (NAO). Both phenomena are known to suppress rainfall activity across most of the region.

Outlook

According to CariCOF, the outlook is for most areas for April-June is for above normal rainfall which would ease the deficits. However, with El Nino developing and SSTs cooling in response to the positive NOA, the long term outlook is for the increase and spread of rainfall deficits.

Increasing rainfall extremes, mainly deficits, are likely to increase across the region once El Nino develops and persists. It is likely to be a drought year for much of the Caribbean; how bad would depend on the eventual duration and strength of El Nino and how cool the Atlantic gets.

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