Wetter Than Normal November Eases Drought to Slight

31 12 2018

Dale C. S. Destin |

DroughtMeterNovember’s rainfall was higher than usual – 135% of the average for the month. The total of 204 mm (8.03 in) makes this November the 21 wettest on record. The very welcome rainfall has ease the meteorological drought to slight levels and have also eased or eliminated other droughts.

Over 95% of the rainfall for November fell during the first 15 days of the month, making it the second wettest such period on record. The rainfall was caused by a cold front and a series of troughs.

The last three-month period – September to November, upon which the assessment of the current intensity of the drought is based, was slight dry. Notwithstanding a wetter than normal November, the last three months, as a time interval, had below normal rainfall with 370.6 mm (14.59 in) recorded. This is the lowest since 2015 and the second lowest since 2009.

RainfallAccuForPast24Months

Rainfall for the past 24 months for varying time intervals compared to the normal/average and records

We remain in a severe meteorological drought, the worst category on our drought scale. However, at the moment, the current intensity is slight. Recall that the overall description of the drought is based on the worst intensity achieve during its lifetime; however, over time, the intensity will fluctuate. Last month the intensity was at serious levels.

Potworks Dam, with a billion-gallon capacity, has moved from near totally dry to being one-third full, two-third empty – depending on your perspective. The water levels have gone above extraction height and I am advised that the same is true for the other smaller catchments.

Potworks Dams Nov13_2018_KarenCarbin

Potworks Dam – Nov 13, 2018. Complements Karen Corbin of the Humane Society

Potable water has become more readily available and water rationing has apparently cease, for now. This is indicative of huge dent November’s rainfall made on the droughts.

The fourteen-month period – October 2017 to November 2018, the duration of the drought thus far, is deemed severely dry. The total for the last 14 months of 977.6 mm (38.49 in) is the second lowest since 2001 – only the similar period October 2014 to November 2015 was drier. October of one year to November of the next normally gets 1514.6 mm (59.63 in), which means that there is a large rainfall deficit of around 35% – more than one-third of the usual rain did not fall.

Based on the last set of rainfall forecasts from regional and especially international sources, the news is discouraging with respect to rainfall. Overall, below normal rainfall is most likely for the next six months – January to June 2019, with relatively high confidence that the period January to March 2019 will be drier than normal – possibly well below normal. Thus, there is every reason to believe that the droughts will continue and likely reintensify. The chance of the droughts ending is, at most 30% or low.

MultimodelEnsembleRainfall_JFM_2019

Probabilistic Multi-Model Ensemble Forecast of Rainfall For Jan-Mar 2019, based on 12 global model

On average, our severe meteorological droughts last for around 16 months, but not continuously at severe intensity. At current, the drought is in its 15th month; the longest such drought on record lasted 38 months – Jul 2013 to August 2016.

I now expected 2018 to be among the top 10 direst years on record with the island-average total less than 900 mm or less than 35 inches. We normally get 1206.5 mm or 47.5 inches.

AccumulationJan_Dec2018

Keep following me for more on this developing story and all things weather and climate. If you find this article useful, please share it with your family and friends. I am also available to follow on TwitterFacebook and Instagram.

All the best for 2019!





Needed Showers but Unwelcome Hazardous Seas for Much of the Caribbean

7 03 2016

Dale C. S. Destin |

A cold front is sweeping the Caribbean, bringing much-needed showers but unwelcome strong winds and hazardous seas.

Rainfall

Already, more than an inch of rain has fallen in parts of Cuba and Hispaniola over the past 72 hours. Meanwhile, winds have reached near 20 knots (23 mph) with stronger gusts across Cuba. Seas are near 3 m (10 ft.) and rising, mainly across the northern waters of the Bahamas.

The front is expected to reach Trinidad by around Thursday/Friday, which is very unusual for such a system to go so far south into the Caribbean.

As it moves across the region, showers will spread to the Virgin Islands today; the Leeward Islands late Tuesday/Wednesday; the Windward Islands and Barbados Wednesday/Thursday and Trinidad and Tobago Thursday/Friday.

Most of these islands will likely see rainfall totals in the range of 10-40 mm (0.40-1.60 in). At least minor inland flooding is possible across some islands.

FcastRain

Forecast 5-Day Rainfall Total for the Period March 7-11, 2016

Strong winds and rough seas will reach the various islands within 24 hours after the arrival of the front and continuing for up to 120 hours after the front passes. Thus, by Friday, most of the waters of the Caribbean will be having hazardous seas and will require the requisite warnings for mariners and sea bathers. Seas could peak near 3.5 m (12 ft.) across some areas.

Seas.png

Most areas will see sustained winds in excess of 20 knots (23 mph) with gusts across a few islands reaching gale force strength of near 40 knots (46 mph). Higher elevations can expect higher speeds.

WindGusts.png

With the combination of strong winds, sea swells and wind-driven waves, flooding of low-lying coastal areas due to large breaking waves is possible. Damage to coastlines can also be expected.

The strong winds could also render some routine outdoor activities uncomfortable if not hazardous.

We will continue to follow the progress of this system and keep you posted. Meanwhile, pay attentions forecast coming from your local meteorological office for information specific to you location.





Record Breaking Dry Year for Antigua

28 01 2016

Dale C. S. Destin |

2015 will go down in meteorological history as the driest year on record for Antigua in nearly 150 years. The island-average rainfall was a paltry 574.5 mm (22.62 in), the lowest in a series from, at least, 1871. 2015 has shattered the previous record driest year – 1983 – by some distance, when we had 681.5 mm (26.83 in).

RainfallAccu

Never before on record has a year’s rainfall deficit or the rain that did not fall (rain-not-fall) was greater than the rain that did fall (rainfall). So the rain-not-fall, 628.6 mm(24.75 in), was greater than the rainfall – 574.5 mm. Of course, the rainfall deficit is the difference between what we got and what we usually get.

Avgvs2015Rain

Looking at the deficit another way, the rain-not-fall is roughly equivalent to the rainfall we would normally get from the first seven months of a year.

Such a dry year, as 2015, is extremely rare. It happens only once every 500 years on average. That translates to a 0.2% chance of a given year getting so little rainfall. It is quite possible that the last time it was this dry Christopher Columbus was still sailing the Caribbean.

If we were still in the pre-desalination-era, it would not be a stretch to say that the Antigua and Barbuda’s economy would have collapsed due to lack of sufficient potable water. As has been the case for months now, over 90% of potable water is coming from the ocean via desalination.

Interestingly, no month had record low rainfall. So, the record low rainfall for 2015 came about due to persistent low rainfall throughout most of the year. Five of the 12 months not only had below normal, but well below normal rainfall. Further, all months had below normal rainfall except September and November, which had near normal rainfall.

MonthlyRain

Most areas of the country had record or near record low number of wet days – WDs – (days with at least one mm) for the year. At the V. C. Bird International Airport (VCBIA), there were 97 WDs, the third lowest behind 2001 with 94 and 1983 with 93. However, the total rainfall from WDs of 495.8 mm (19.52 in) was at a record low for 2015. Normally, WDs yield around 1019.3 mm (40.13 in).

Heavy rainfall days – HRDs –  (days with at least 10 mm) was also at record low numbers at many places during 2015. At the VCBIA, they were at a record low total of 12, tying 1983 and 1973. Normally, there are 26 HRDs annually. Meanwhile, the rainfall total from HRDs of 217.1 mm (8.55 in) was the second lowest behind 207.4 (8.16 in) measured in 1983. Usually, it’s around 665.5 mm (26.20 in).

The dismal rainfall for the year was due largely to two factors. Firstly, dry and dusty air from the Sahara Desert which hampered rainfall mainly during the first half of the year. Secondly, a record strong El Nino, which suppressed rainfall mainly over the latter half of 2015.

Follow us on twitterfacebookinstagramtumblrflickrgoogle+, and youtube as we provide you with further analyses of the historic rainfall year for Antigua. We will also provide you with observed and forecast rainfall totals for 2016, as we keep close eyes on our climate.





A Tropical Wave to Shower the Leeward Islands

21 06 2015

Dale C. S. Destin |tropwaveJun21

A tropical wave is expected to raise our rainfall total over the next 24 hour. It will likely shower the island with 5 to 10 mm (0.20 to 0.40 in) of rain as it traverses the region. It’s possible that rainfall total could reach as high as 25 mm in some places.

forecast_June22

Already, the system has dumped over 25 mm of rain on parts Barbados with more rain in the forecast. The Windward Islands and the rest of the Leeward Islands are also in for some much needed showers, from the tropical wave.

Many of the islands are in the midst of droughts and are thirsty for rainfall. For example: as of the end of May, Antigua only had two more months of surface water remaining, according to Ian Lewis, Water Production Manager of the water authority. Meanwhile, the Government of St. Lucia has declared a “water emergency”.

The wave will also cause a surge in the winds and seas across the Eastern Caribbean. Winds are expected to rise to near 20 knots, mainly over open water and elevated places. Wind gusts to near 28 knots will also take place.

Seas_June 21

In response to the strong winds, the seas will become hazardous with heights reaching 2.4 m (8 ft), especially on the eastern side of the islands.

The winds alone will make some outdoor activities, such as working at heights, uncomfortable if not dangerous.

While the rain is expected to subside by the end of tomorrow (Monday), strong winds and rough seas will continue until Wednesday. Given the situation, mariners should really stay near shore until winds and seas subside to safe levels.

Given the rainfall deficits across much of the region, the possible rainfall totals from the tropical wave are only “drops in the bucket”. However, we are in a very desperate position; hence, we will cheer for every and any shower.








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