Record-breaking Dry 12 Months

11 08 2022

Dale C. S. Destin |

The deficit in rainfall over the last 12 months ending July was record-breaking. August  2021 to July 2022 is now the driest such period on record, in a series dating back to 1928. The rainfall total of 727.2 mm (28.63 in) broke the previous record of 731.0 mm (28.78 in) measured over a similar period – August 1973 to July 1974, nearly 50 years ago.

During the last 12-month episode of drought, the six months ending January 2022 was the driest such half-year on record with 378.7 mm (14.91 in). Further, the last quarter of 2021, October to December (OND), had a record low rainfall of 127.3 mm (5.01 in). This displaced the previous OND record of 143.0 mm (5.63 in) observed in 1983, that fateful year in which we were forced to import water from Dominica, due to severe drought.

The rainfall total for the past 12 months was down an unprecedented 37 percent. This would have been much worse, if not for near normal rainfall in July of 99.3 mm (3.91 in), which is equivalent to 101 percent of the month’s average of  98.0 mm (3.86 in). The August-July year averages 1150.7 mm (45.3 in), which is similar to the annual average.

Since the deluge of November 2020, rainfall has been as scarce as gold. The rainfall for the past 20 months – December 2020 to July 2022, is the second lowest for such a period with 1082.8 mm (42.63 in). This is even less than the annual 12-month total and represents a deficit of over 38 percent. Only the 20-month period ending July 2016 was drier. Relative to all 20-month periods on record, the last 20 months rank seventh.

Happily, the impacts of the very harsh dry conditions continue to be masked by the adaptation measure of building more and more reverse osmosis (RO) plants to extract potable water from the ocean. If not for the plants, the socio-economic situation would be quite desperate. And to say that without the RO plants the country would have to be closed, leading to mass migration, is not hyperbolic.

According to the United Nations: “Water is at the core of sustainable development and is critical for socio-economic development, energy and food production, healthy ecosystems and for human survival itself. Water is also at the heart of adaptation to climate change, serving as the crucial link between society and the environment.”

Our poster child for droughts, Potworks Reservoir, remains dry land. Recall that in addition to meteorological droughts, there are also agriculturalhydrologicalecological and socio-economic droughts, which are currently, at varying intensities.

There is likely a number of factors responsible for the dryness; however, the main one seems to be the consistent stream of dry and dusty air from the Sahara Desert.

Examination of recent models reveals that there is no sustainable end to this dry weather. At best, rainfall for the rest of the year will be near normal, which will not erase the massive, accumulated deficit.

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Record-Breaking Dry 19 Months for Antigua

13 07 2022

Dale C. S. Destin |

The past 19 months is the driest such period on record for Antigua, dating back to at least 1928. Since the deluge of November 2020, December 2020 to June 2022 has yielded only a meagre 983.5 mm (38.72 in), for the island-average rainfall. This broke the record set for a similar period, December 2014 to June 2016, of 994.4 mm (39.15 in), which was also the record lowest for any consecutive 19 months.

Usually, 19 months ending June averages 1656.3 mm (65.21 in). This means that since December 2020 only 59 percent of the normal amount of rain fell. The 19-month total of 983.5 mm is less than that for 17 full years. The rainfall total for the last 19 months was less than what usually falls in 12 months – annually.

Rainfall total for Dec 2020-Jun 2022 – 983.5 mm (38.72 in) vs the normal total for the same period – 1656.3 mm (65.21 in). December 2020 to June 2022 is the driest 19 months on record.

Such an extremely low rainfall total for the last 19 months has a less than a 1 percent chance of occurring – 0.8 percent.  This translates to the dryness for December 2020 to June 2022 having a return period of 1-in-125 years, on average. It is unlikely that anyone alive has seen this kind of scant rainfall before and there is a less than 10 percent chance of a repeat in the next 13 years.

The last time we saw such dryness we were in the midst of the Great Drought of 2013-2016. At no time during that dearth of rainfall was the dryness this intense for any successive 19 months.

A lot of the dryness seems largely due to dry and dusty air from the Sahara Desert and or cooler than normal sea surface temperatures across the tropical North Atlantic Ocean. The high number of tropical cyclones in 2021 likely contributed, by steering clear of the area and pulling moisture away from the islands.

The dryness has been quite robust. Not only records were set for the last 19 months but also for the last 18, 17, 16 and 15 months respectively. It is also likely that more records will fall in the coming months.

As forecast, it was a drier than normal dry season for Antigua. The period January to June was the 20th driest in a series going back to 1928. The continued below normal rainfall means that drought continues to reign with no predictable end in sight.

With the rainfall at or near record-low levels over the past 19 months, one can appreciate the absence of virtually ALL water from surface catchments and the significant drop in groundwater. Potworks Reservoir, our billion-gallon surface catchment, has been totally dry since late October 2021. If not for water from the increasing number of reverse osmosis plants, “crapo would be smoking our pipes”, at the very least. And for those who say he is smoking our pipes, without the plants, it would be exponentially worse, in unimaginable ways.

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July Update: Below Normal Rainfall Still Most Likely for Antigua for 2022

9 07 2022

Dale C. S. Destin |

The prediction for rainfall remains unpromising. My latest updated forecast continues to call for most likely below normal rainfall for Antigua. The most likely total for the year is 1089 (42.9 in), up 9 mm (0.4 in) from the previous forecast. There is also a 70 percent or high confidence of the rainfall total falling in the range of 827 to 1405 mm (32.6 to 55.3 in).

The main reason for the below normal rainfall forecast is the cooler than average sea surface temperatures (SSTs) across the tropical North Atlantic (TNA), during the first half of the year, which led to a drier than normal dry season – January to June. Cooler than normal TNA SSTs favour suppressed rainfall conditions while the opposite enhances rainfall.

There is a La Niña underway, and this historically favours above normal rainfall for our area. Thus, the latter half of the year will most likely see near normal rainfall. However, because we are so deep in drought, normal rainfall is not going to cut it. Notwithstanding, below normal rainfall being most likely, there are relatively healthy probabilities for near or above normal totals – there is hope, think rain.    

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). Fall/autumn, September-November, accounts for 58 percent of the wet season total and 38 percent of the year’s total.

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.

This forecast will be updated during the first week of August.

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Near Record-Breaking Dry Year, Drought Reigns

18 01 2022

Dale C. S. Destin |

It was a near-record-breaking dry year (2021) for Antigua. The year produced a measly island-average rainfall of 600.7 mm (23.65 in), the second lowest on record behind 2015 with 574.5 mm (22.62 in). Officially, 2021 was easily the second most parched year in a series from 1928 and unofficially, since, at least, 1871.

The yellow broken line represents the rainfall anomaly trend, which indicates no significant change to wet (positive) or dry (negative) anomaly.

It was a year reigned by drought from beginning to end, and the reign is likely to go on through the upcoming months. The drought has a firm grip on the weather, being at the most intense category: severe, exceptional by some other standards. The normal annual total is 1156.7 mm (45.54 in), nearly twice the amount measured for 2021.

The rainfall deficit amounts to a whopping 556.0 mm (21.89 in) or 48 percent of the usual total for the year. This is more than the average for the first seven months of a year. Every month accrued a shortfall with the usually wettest month of the year–November, accounting for over 22 percent of the overall rainfall shortage.

This level of waterlessness for a year is extremely rare. There is only a 0.5 percent chance of the island-average being 23.65 inches or lower. This translates to the kind of dryness that has a return period of once in 200 years (1-in-200 years), on average.

Alternatively, there is less than a 10 percent chance of such harsh weather reoccurring in the next 20 years. One is, at least, twice as likely to see a hat-trick in a cricket match than experience the likes of such lacklustre annual rainfall.

268Weather accurately predicted a drier than usual year was likely. As early as May 2021, we indicated a 46 percent chance of below normal rainfall. The chance rose to 58 percent in June and peaked at 61 percent in August. There was also a peak of 19 percent for the year to rank among the top 10 driest.

The usually wettest consecutive pair of months, October-November, almost literally produced a speck in the bucket. The frequently rainiest duo was the record driest with the trivial amount of 63.8 mm (2.51 in) with each month recording less than an inch-and-a-half of rainfall for the first time, on record. Combined, the shortfall for the months accounted for 45 percent of the year’s deficit. The previous lowest for this period was 89.7 mm (3.53 in), in 1983.  

The last quarter (October-December) was also the driest on record, dating back to 1928. The total of 127.3 mm (5.01 in) shattered the previous record of 143.0 mm (5.63 in), for the last three months of the year, set in 1983. Usually, this period precipitates 397.5 mm (15.65 in), over thrice what actually fell.

It was essentially a year without a wet season (July-December). The dry season pretty much went on and on, for the whole year, resulting in a record-breaking dry wet season. The season’s total of 396.0 mm (15.59 in) retired the previous driest wet season of 1983, which accumulated 405.6 mm (15.97 in). Cumulatively, the third and fourth quarter rainfall represented just 53% of the normal amount of 746.8 mm (29.40 in). A typical dry season (January-June) averages more rainfall than occurred for the 2021 wet season.

While the island on a whole had near-record-breaking low rainfall, parts of the country actually had record dryness. Coolidge, in northeast Antigua, had a record low rainfall of 469.6 mm (18.49 in), crushing the previous record of 554.0 mm (21.81 in) set in 2015. This represents only 47 percent of the normal annual total of 1000.8 mm (39.40 in). This kind of rainfall scarcity occurs only once every 333 years, on average, or a less than 10 percent chance of occurring in the next 35 years or the next generation.

It is unclear as to what was responsible for this nearly unprecedented dryness. The usual culprit: El Niño was not only absent but his sister: La Niña, usually the rainmaker, was present, yet to little avail. The dryness may have been mainly the result of a consistent stream of dry and dusty air from the Sahara Desert along with a cooler than usually tropical North Atlantic.

There is the saying: “If rain does not fill a [water] drum, dew is not going to fill it.” Meaning, if the wet season did not end the droughts, particularly the hydrological and socioeconomic ones, how can the dry season, which we are in, do so? It can’t; hence, the sufferation from insufficient rainfall could continue through the next six months.

The last 10 years have been the driest decade for Antigua. Five of the last 10 years have had below normal rainfall with 2015 and 2021 ranking one and two, on record. Only one year (2020) has had above normal rainfall since 2011.

Other Caribbean islands are having similar challenges with rainfall or lack thereof. For example, the Henry Rohlsen Airport in St. Croix was said to be on track, in December, to record its third driest year, on record dating back 58 years. A number of other parts of the Caribbean were also on the way to record rainfall ranking among the top 10 lowest.  

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Drier than Usual August, Drought Continues

27 09 2021

Dale C. S. Destin |

Like every month of the year, except June, August was drier than usual. The month yielded only 81.0 mm (3.19 in) of rainfall. With continued below normal rainfall, drought continues. The rainfall for the last eight months ranks among the worst on record and there is still not much respite in sight.

The rainfall for August is the second lowest since 2015. The total for the month represents only 71 percent of the normal value of 114.8 mm (4.52 in), a deficit of 29 percent.

The period June-August was also drier than usual. The total of 202.2 mm (7.96 in) was the 18th lowest on record starting 1928. The last time this period was drier was 2015 with 95.0 mm (3.74 in).

We continue to witness one of the driest years on record. The last eight months is the fourth driest on record and the driest since 2015. January to August produced only a meagre 351.3 mm (13.83 in), only a little above half of the usual rainfall of 622.0 mm (24.51 in). Just three years have been drier through August: 2015, 2001 and 1939.  

Since the 2020 November’s deluge, the last nine months, December-August, is the fifth driest on record and the lowest since 2015. The period has only returned 61 percent of normal rainfall.

The upcoming three months, October to December, is likely to see further misery from lower than usual rainfall. Majority of models are forecasting the continuation of drier than normal weather. Hence, more rainfall deficits likely.

WMO Lead Centre for Long-Range Forecast Multi-Model Ensemble is forecasting 50-60% likelihood of below normal rainfall for Antigua and Barbuda. Also, below normal rainfall is likely for much of the rest of the northeast Caribbean.

As the meteorological drought goes, so go the other droughts: agricultural, hydrological and ecological. There is the continuing concern that this may precipitate a socio-economic drought, if it has not already done so. Our utilisation of the ocean for fresh water has made us drought resilient; however, obtaining potable water from this source is several time more expensive than from surface and underground catchments. Also, it has negative climate and environmental consequences, further adding to the overall expense of using the sea as a source for fresh water.  

Potworks Reservoir remains below extraction levels, along with most other surface catchments, according to the Antigua Public Utilities Authority (APUA), the country’s water authority. Water rationing is officially into its second month and with the rainfall outlook being gloomy, it is likely to continue for the foreseeable future.

Potworks Reservoir, Bethesda, Antigua, still on the verge of becoming totally dry – Sep 2, 2021. Picture courtesy Karen Corbin of the Humane Society

APUA water manager, Ian Lewis, told the media on August 31, that the Authority is only able to produce six million of the seven-and-a-half million gallons required to serve the country daily. There is not enough water to go around for everyone each day; hence, the rationing.

Antigua is not alone in experiencing significant rainfall shortages. The countries around us remain  thirsty for rainfall also. Deficit rainfall is occurring across the rest of the Leeward Islands, the northern Windward Islands, Hispaniola, Cuba and the Bahamas. And it is probable that it will worsen, over the upcoming months.

CMORPH 180-Day Total Rainfall Anomaly (mm) for the period 26 Mar to 21 Sep 2021

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Drier than Usual July, Drought Continues

27 08 2021

Dale C. S. Destin |

July was drier than usual like the first five months of the year. The month yielded only 65.5 mm (2.58 in) of rainfall. Although July took over from June as being the wettest month for the current year; it barely made a dent in the ongoing droughts. July has become the only month of the year, thus far, to clock over two-and-half inches of rain. The rainfall for the last seven months ranks among the worst on record and there is not much respite in sight.

Potworks Reservoir, Bethesda, Antigua, on the verge of becoming totally dry – July 7, 2021. Picture courtesy Karen Corbin of the Humane Society

The rainfall for July is the lowest since 2018, when the country had 39.6 mm (1.56 in). The total for the month represents only 67 percent of the normal value of 98.0 mm (3.86 in), a deficit of 33 percent.

The period May-July was also drier than usual. The total of 138.4 mm (5.45 in) was the 13th driest on record starting 1928. The last time this period was drier was 2015 with 74.4 mm (2.96 in).

We continue to witness one of the driest years on record. The last seven months is the fifth driest on record and the driest since 2015. January to July produced only a meagre 270.3 mm (10.64 in), only a little above half of the usual rainfall of 500.1 mm (19.69 in). Again, just four other years have been drier through July: 2015, 2001, 1977 and 1939.

Since the 2020 November’s deluge, the last eight months, December-July, is the seventh driest on record and the lowest since 2015. The period has only yielded 58 percent of normal rainfall. Our starving landscape and parched grounds continue to bear witness to the below normal rainfall.

The upcoming autumn, September to November, is likely to see us continue to suffer from a scarcity of rainfall. The majority of models are forecasting the continuation of lower-than-normal rainfall. Hence, the drought is likely to continue. Our largest catchment, Potworks Reservoir, along with others, are transitioning to dry land, again.

WMO Lead Centre for Long-Range Forecast Multi-Model Ensemble is forecasting 50-60% likelihood of below normal rainfall for Antigua and Barbuda. Also, below normal rainfall is likely for much of the rest of the northeast Caribbean.

Based on models which correlate our sea surface temperatures, across the tropics, with our rainfall, the medium and long term continue to look brown. The year will most likely remain drier than usual with a 61 percent chance of below normal rainfall; this is up 11 percent from last month.

As the meteorological drought goes, so go the other droughts: agricultural, hydrological and ecological. There is also the growing concern that this may precipitate a socio-economic drought, if it has not already done so. Our utilisation of the ocean around us for fresh water has made us resilient; however, this is expensive water, over seven times the cost of that from surface and ground water.  

Potworks Reservoir remain below extraction levels, along with most other surface catchments, according the Antigua Public Utilities Authority (APUA), the country’s water authority. Water rationing has officially started and with the rainfall outlook being gloomy, it is likely to continue for the foreseeable future.

Antigua is not alone in experiencing significant rainfall shortages. The countries around us remain  thirsty for rainfall. Deficit rainfall is occurring across the rest of the Leeward Islands, and it is probable that it will worsen, over the upcoming months.  

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





Wettest Month of the Year, Serious Drought Continues

21 07 2021

Dale C. S. Destin |

June has become the only month of the year, thus far, to clock over two inches of rain. This makes it esaily the wettest month of the year, to date; notwithstanding, serious meteorological drought continues for Antigua. The rainfall for the last six months rank among the worst on record. Despite the prayers for rainfall, the heavens look set to provide only sparing amounts, over the upcoming months.

Potworks Reservoir, Bethesda, Antigua, on the verge of becoming totally dry – July 7, 2021. Picture courtesy Karen Corbin of the Humane Society

The rainfall for June was 55.6 mm (2.19 in), the highest for the month since 2017, when the country had 84.8 mm (3.34 in). Notwithstanding, despite being the only month thus far with more than two inches of rain, relatively, June had near normal rainfall with the amount being below the month’s average of 68.1 mm (2.68 in).

Despite being the wettest month, so far, June continues to be the only month that is deemed to have a statistically significant drying trend, i.e. June has gotten drier over the years. The month went from a peak average of 98.6 mm (3.88 in) over 1931-1960 to a minimum of 55.6 mm (2.19 in) over 1971-2000, rebounding to 68.1 mm (2.68 in) over the last 30 years, 1991-2020.

The period April-June was very dry. The total of 111.8 mm (4.40 in) was the fourth driest since independence, 1981, and the eleventh lowest rainfall received for April-June, on record dating back to 1928. Interestingly, April-June 2020 was drier with 78.7 mm (3.10 in).

We continue to witness one of the driest years on record. The just ended dry season, January-June, is the fifth driest on record and the driest since 2015. The last six months yielded only a paltry 204.7 mm (8.06 in), only half of the usual rainfall of 410.0 mm (16.14 in). Just four other years have had a drier first half: 2015, 2001, 1977 and 1939. The record driest dry season is held by 2001 with 130.0 mm (5.12 in).

Our last wet month was November. It flooded severely across parts of the islands; however, the beneficial rainfall is becoming a distant memory, as indicated by our drying and empty catchments. Since November, the last seven months, December-June, was the sixth driest on record and the lowest since 2015. The period has only yielded 58 percent of normal rainfall. Our starving landscape and parched grounds continue to bear witness to the absent rainfall.

The upcoming season, August to October, is likely to see us continuing to suffer from a dearth of rainfall. The majority of models are forecasting the continuation of scarce rainfall. Hence, the drought is likely to continue. Our largest catchment, Potworks Reservoir, along with others, are trending toward becoming dry land, again.

WMO Lead Centre for Long-Range Forecast Multi-Model Ensemble is forecasting 50-60% likelihood of below normal rainfall for Antigua and Barbuda. Also, below normal rainfall is most likely for much of the northern islands.

Based on models which correlate our sea surface temperatures, across the tropics, with our rainfall, the medium and long term continue to look brown. The year will most likely remain drier than usual with a 50 percent chance of below normal rainfall; this is down 8 percent from last month.

As the meteorological drought goes, so go the other droughts: agricultural, hydrological and ecological. There is also the growing concern that this may precipitate a socio-economic drought, if it has not already done so. Our utilisation of the ocean around us for fresh water has made us resilient; however, at a very high cost, as potable water from this source cost at least seven times that from surface and ground water, I am told.  

In the last month, Potworks Reservoir fell below extraction levels, along with most other surface catchments, except for Donnings Reservoir, according the Antigua Public Utilities Authority (APUA), the country’s water authority. With the rainfall outlook bleak, we could be out of all surface water in weeks. Water rationing is imminent, if not already occurring.

Antigua is not alone in experiencing significant rainfall shortages. The countries around us remains  thirsty for rainfall. Deficit rainfall is occurring across the rest of the Leeward Islands, and it is probable that it will worsen, over the upcoming months before improving, based on recent forecasts.

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





Drought is Back

14 03 2021

Dale C. S. Destin |

Drought is back for Antigua. A slight meteorological drought is present as of the end of February. It is most likely to get worse over the next three months, as below normal rainfall is forecast by most models.

The rainfall for winter – December to February (DJF) 2020-2021, was 149.1 mm (5.87 in). This total is deemed below normal and beneath the drought threshold. Usually, DJF yields 225.8 mm (8.89 in) of rainfall, on average; hence, there is over a 75 mm (over 3 in) deficit or a 34 percent shortfall.

Rainfall for Antigua for the period December 2020 to February 2021. Picture in the background is Potworks Dam as of March 3, 2021 courtesy Karen Corbin of the Humane Society.
Rainfall for DJF is well below the slight or worse drought threshold, nearly at moderate drought. Rainfall for this period for Antigua shows no significant trend (black dashed line). Excess rainfall tends to be more extreme than drought rainfall.

The month that is mainly responsible for the scarcity in precipitation is January, which got only 41 percent of the normal amount of 67.3 mm (2.65 in). The rainfall for February was also lower than usual, accounting for 73 percent of the normal amount of 50.0 mm (1.97 in). The rainfall for December was near normal.

The two-month rainfall for January-February (JF) of 63.8 mm (2.51 in) is the lowest since 2001. Thus, the very dry start to the year continues. With this JF ranking the eighth driest on record, only seven other years have had a drier start on record dating back to 1928.

It normally takes a few months for the effects of a meteorological drought to descend to a hydrological drought and cause potable water issues. However, the effects are already manifesting themselves in the lowering of water in catchments. Yesterday, the APUA Business Unit Water Manager – Ian Lewis, said on Observer Radio News that the country has about three to four months of surface water remaining, at current extraction rate.  

We were last in a drought April to October last year. This was a severe drought that was more than meteorological; it resulted in surface catchments transforming into mud patches and then to grass lands. It is unclear, at this stage, whether there will be a repeat of similar rainfall absence this year.

The dry conditions last year, resulted in water rationing and almost a 100 percent reliance on desalinated water. Ian Lewis has already indicated that the absence of notable rainfall over the coming months would usher in return of the water conservation schedule better known as water rationing.

Antigua is not alone in experiencing notable rainfall deficits in the wake of winter. Much of the Caribbean is suffering a similar fate, from a drier than usual dry season, thus far. Short and long-term droughts are evolving across a number of islands and there is the potential of several others joining this drought-list.

Rainfall anomaly (departure form average) in mm for the Caribbean, based on CMORPH data

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Very Dry Start to 2021

16 02 2021

Dale C. S. Destin |

Antiguans have just witnessed the driest start to the year in over a generation. January 2021 was the driest January since 1977 for Antigua, with an island average of 27.4 mm (1.08 in).

Usually January yields 67.3 mm (2.65 in) of rain; however, this time, the total was down by 59%. This puts the rainfall for the month in the well below normal category – the bottom 10 percentile of the most recent climate period – 1991 to 2020.

Such low rainfall is rare for January. How rare? Once in every 27 years, on average, which translates to a 3.7 percent chance of such a low total annually. Usually, there is over a 96 percent chance of the month producing more rainfall.

From a historical standpoint, this is the third driest January on record dating back to 1928. Only January 1977 and 1931 have been drier. January 1931 is the driest on record with 16.3 mm (0.64 in) and January 2006 is the wettest with 2017.7 mm (8.57 in).

Despite the trickle of rainfall for January 2021, the rainfall for the month is usually the most reliable of all months with the lowest variability index of 0.83 or moderate, for the climate period 1991-2020. All other months have a variability index of 1 to 2.37 or moderate to extreme. The variability is obtained by dividing the difference in rainfall of the 90th percentile and the 10th percentile by the median.

Notwithstanding the drier than normal January 2021, the rainfall for January remains without any significant (statistical) trend. The mean rainfall over the past seven climates has not changed significantly, ranging between 65.8 to 79.5 mm (2.59 to 3.13 in), over the period 1928 to 2020.

As we look forward, the rainfall for February is lagging average by about 38 percent, and even if the averaged is reached, there is the high likelihood for rainfall to drop to drought levels by the end of February. About another 35 mm (1.38 in) of rain is needed to stave off drought. This or more rainfall for February 17-28 has only occurred 10 times in the last 55 years – 18 percent of the time.

January is unlikely to be this dry again under the next 27 years. By then, we will be at the middle of the 21st Century – millennials would have reach senior citizen age.

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The Hurricane Season in August Look Out You Must

8 08 2020

Dale C. S. Destin |

August is the second most busy month of the hurricane season, behind September. We in Antigua and Barbuda and the rest of the Caribbean have been impacted by tropical cyclones (TCs) – tropical depressions and named storms (tropical storms or hurricanes), many times in August. Hence, “look out you must” act to become hurricane strong.

Storms and hurricanes for August – 1851 to 2019. The 1899 Ciriaco Hurricane highlighted

The Atlantic Basin, including the Caribbean, averages in August: 3 to 4 named storms, including 2 hurricanes and 1 major hurricane – Category 3 intensity or more, based on the current climatological standard normal period, 1981-2010. The month sees a Category 5 hurricane every 7-8 years; the last one was Dorian of last year. Note that we credit TCs to the month in which they were formed.

Super Category 5 Hurricane Dorian in the northern Bahamas – Sep 1, 2019

The last hurricane to impact Antigua and Barbuda, in August, was Hurricane Earl of 2010. The centre of the hurricane passed within 40 km (25 mi) and 89 km (55 mi) north of Barbuda and Antigua respectively. At the time of impacting the islands, Earl was a Category 2 hurricane with maximum sustained winds of 169 km/h (105 mph). 

Category 2 Hurricane Earl with eye just northwest of Anguilla – August 30, 2010

Barbuda likely got close to the maximum impact from Earl. At the V. C. Bird International Airport in Antigua, maximum winds measured were 82 km/h (51 mph) gusting to 105 km/h (65 mph). The damage to both islands amounted to around US$13 million, and there was one fatality.

Earl also caused damage to the rest of the Leeward Islands, the Virgin Islands, Puerto Rico, the East Coast of the United States and Canada. The system caused a total of 8 fatalities and around US$45 million in damage.

The probability of Antigua and Barbuda being impacted by a storm or hurricane, in August, is around 18 percent, based on the current base period of 1981-2010. The probability increases to 38 percent for the active period being experienced by the Atlantic since 1995. This means that we have been impacted by a storm or hurricane every 2 to 3 years since the mid-1990s.

August Hurricane Climatology
The zones of origin and tracks of storms in August during the hurricane season

The probability of us being impacted by a hurricane, in August, is around 6 percent based on 1981-2010 data and around 11 percent for the current active period. This means that we are affected by a hurricane, in August, every nine years.

Antigua and Barbuda have been affected by 22 tropical storms and 18 hurricanes, in august, dating back to 1851. Our most powerful August hurricane was a Category 4 system nicknamed the San Ciriaco Hurricane of 1899. This is the longest-lived Atlantic hurricane on record – 28 days.

Since 1851, the Eastern Caribbean (EC) has been affected by 99 named storms; 37 were hurricanes and 10 were major hurricanes.

Storms to have pass through the Eastern Caribbean in August – 1851 to 2019

The last hurricane to impact the Caribbean in August was Dorian of 2019. It passed through the Windward Islands as a tropical storm, then turned north-northwest and brushed Antigua and most of the Leeward Islands. Dorian became a hurricane over the Virgin Islands. After leaving the Caribbean, it intensified into the second strongest Atlantic hurricane, tied with the Labour Day Hurricane of 1935 and (Wild) Gilbert of 1988, then literally flattened the northern Bahamas, over a three day period, in which it moved at a “snail’s pace”. It left in its wake 84 fatalities, 245 missing and US$4.6 billion. Dorian became the strongest hurricane, on record, to form in August.

Hurricane Dorian with centre near St. Croix, US Virgin Islands – August 30, 2019

The probability of at least a storm or hurricane impacting the EC annually, in August, is 41 percent; the probability of a hurricane is 15 percent and the probability of a major hurricane is 6 percent. It means that the EC is impacted by a storm or hurricane, in August, every 2-3 years; a hurricane every 6-7 years and a major hurricane every 16-17 years.

The probability of a storm or hurricane across the western Caribbean is around 33 percent. For the central Caribbean, this probability is around 26 percent.

August has produced 392 named storms of which 247 were hurricanes, 120 were major hurricanes and 14 were Category 5 hurricanes, based on NOAA. We note that there are likely storms that were missed prior to the Satellite era – prior to the mid-1960s. For climate period – 1981 to 2010, there have been 101 named storms of which 51 were hurricanes and 26 major hurricanes.

August has trice had a maximum of 8 named storms in a given year – 2012, 2011 and 2004. On two occasions, there were 3 hurricanes – 1966 and 1916. Further, on four occasions there were three major hurricanes – 1969, 1933, 1893 and 1886.

Like July, above normal tropical cyclone activity in August normally signals a busy hurricane season. What will this August bring? We can’t be sure, but the forecast is for an above normal to hyperactive season. Whatever it brings, let’s be prepared! Be hurricane strong!

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4th Driest May on Record for Antigua

5 06 2020

Dale C. S. Destin|

Potworks Dam, Antigua – June 1, 2020. Currently dry but when full, holds a billion gallons. Pic courtesy Karen Corbin – Humane Society

May 2020 was another very dry month for Antigua. The rainfall total of 20.8 mm (0.82 in) was the lowest since 2001 and the fourth lowest on record dating back to 1928. Only May 2001, 1939 and 1928 have been drier, with May 2001 being the driest with 6.4 mm (0.25 in).

Relative to the normal total for the month of 103.6 mm (4.08 in) only 20% fell; hence, the month had a rainfall deficit of 80%, based on the current base period of 1981-2010.

Such a low rainfall total for May is relatively rare. It happens once every 21 years, on average or has only 4-5% probability of occurring each year.

The rainfall for May is almost “bipolar” – you either get a lot or a little. This makes the rainfall for the month the most unpredictable with the highest variability index of all the months.

The dryness for May was not confined to Antigua. Most of the region from Hispaniola to Trinidad saw, at most, only 25% of the normal rainfall for the month.

The reason for the truant rainfall looks to be due mainly to higher than normal surface pressure and lower than normal relative humidity.  

Rainfall for the year has now fallen to below normal after an excellent start in the first quarter. There are some hopes for the return of seasonal or above seasonal rainfall over the upcoming months. The current forecast is for above normal rainfall for the period June to August.

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Driest April for Antigua in Over Two Generations

1 05 2020

Dale C. S. Destin|

Not since 1944 has an April been drier for Antigua than April 2020. It was the third driest April on record – the driest in 76 years or well over two generations. The last time April was drier, V. C. Bird Snr was president of the Antigua Trades and Labour Union and World War II was still raging.

Potworks Dam, May 1, 2020. Picture courtesy Karen Corbin – Humane Society

The island average for the month is 16.1 mm (0.63 in). Only April 1944, with 5.9 mm (0.23 in) and 1939, with 8.4 mm (0.33 in), have been drier in nearly 100 years.

The total for the month represents only 19% of the normal total of 85.6 mm (3.37 in) – a deficit of 81%, based on the current climatological standard period of 1981-2010.

Such a low rainfall total is very rare for April. How rare? It has only around a 4% chance of occurring or once every 25 years on average, based on record: 1928-2019. This would suggest that we were around 50 years overdue for such a parched April.

The reason for us going so many years overdue for such a near record low total is likely due to “positive” climate change. Rainfall for April has been on a steady wetting increase, rising from an average of 53.1 mm (2.09 in) for the period 1928-1957 to 80.8 mm (3.18 in) for the period 1990-2019.

So, if you were to segment the data, there is around an 11% chance of getting 16.1 mm during the years 1928-1957, as compared to just a 0.6% chance for the period 1990-2019. In other words, our current climate for April is over 18 times less likely to produce such a low rainfall total as compared to the past climate of 1928-1957.

Now, based on the segmented data, the return period for April’s rainfall of 16.1 mm is once every 9 years on average for the past climate. However, the return period for the same value in the current climate is once every 167 years on average. Hence, most persons alive along with their grand and great grand children are unlikely to see a similar or drier April in Antigua.

Compared to other months, this April is the driest since June 2018. And of all the 1108 months on record dating back to 1928, it ranks as the 23rd driest. This puts it in the top 2% of all time driest months.

Notwithstanding the miniscule rainfall for April, the rainfall for the year, thus far, is near normal.  However, if not for a wetter than normal first quarter, the situation would be much more dire.

The reason for the absentee rainfall for April looks to be due to a switch from a positive North Atlantic Oscillation (NAO) to a negative NAO. This is manifest in the swing from above normal pressure over the subtropical North Atlantic to below normal pressure. This switch or swing resulted in a reduction of moist unstable air flowing across the area and depositing rainfall.

The pressure over our islands also went from neutral, over the period January-March 2020, to above normal for April. Such a configuration of the pressure would usually also inhibit rainfall, which was evident.

April 2020 was a remarkably dry month. One that most of us have never seen and will likely never see again – happily.

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February 2020 to be Among the Wettest on Record

17 02 2020

Dale C. S. Destin

This February is on track to becoming one of the wettest on record for Antigua. Thus far, it is the wettest February, at the V. C. Bird International Airport (VCBIA) since 2005 and the wettest for Antigua since 2004.

It has been the wettest first two weeks of February, at the VCBIA, since 2002. The rainfall total of 55 mm (2.17 in), at the end of February 14, at the Airport, is well above normal – in the top 10 percentile on record dating back to 1962. It is more than twice the average – 25.4 mm (1.0 in), for the same period and the fourth wettest on record. Only three other times February 1-14 has been wetter, at VCBIA: 1997 – 66 mm (2.60 in), 1982 – 59.7 mm (2.35 in) and 2002 – 56.8 mm (2.24 in).

Heavy rainfall days (days with 10 mm – 0.40 in, or more) are fairly rare for February, at the Airport. There was none since 2009; however, already for this Feberuary, there have been three recorded. This ties with 2005, 1991, 1982, 1981 and 1976 February for the most number of heavy rainfall days, at VCBIA. The three heavy rainfall days tie with those of February 2005, 1991, 1982, 1981 and 1976. This record will likely be broken by the end of the month.

There is no daily breakdown of the island-average rainfall; however, based on the fact that the current island-average total of 59.9 mm (2.36 in) is already the most since 2004, and the average for the month is 55.9 mm (2.20 in), it is highly likely that the rainfall for the first two weeks of February was also well above normal for the island.

The cause of our wetter than usual February weather is the positive North Atlantic Oscillation (NAO) index. The NAO is a large-scale seesaw in atmospheric pressure between the subtropical (Atlantic) high and the polar low.

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The positive NAO index occurs when the subtropical high is higher (stronger) than usual and the polar low is deeper (lower) than usual. When this happens, it causes the winds across the area to be higher than usual (fresh to strong), which in turn destabilises the lower atmosphere by way of mixing and convergence – resulting in above normal rainfall for Antigua and likely other nearby islands.

When the NAO is above normal, the mean rainfall for Antigua for February is 62.7 mm (2.47 in) plus or minus 11.4 mm (0.45 in). These numbers are based on a 95% confidence interval and a probability value (p-value) of 0.009.

A positive NAO index also has implications for other places. For example, the United Kingdom, Ireland and northern Europe get more and stronger winter storms when the NAO index is positive, which have been happening. Thus far, there have been four named winter storms to significantly impact the area, the last being Storm Dennis.

The NAO index is forecast to remain above normal; hence, wetter than usual conditions are expected to continue. Unfortunately, the NAO index is not predictable beyond two weeks; thus, only short-range forecasting can be done using it as a predictor. Also, for some other months, a positive index is associated with below normal rainfall.

The wettest February for the VCBIA and Antigua, on record dating back to 1928, is 1982 with 110.5 mm (4.35 in) and 130.8 mm (5.15 in) respectively. The wettest February 1-14 at the VCBIA is 1997 with 66 mm (2.60 in).  

The average rainfall totals for February for the VCBIA and Antigua are 44.9 mm (1.77 in) and 55.9 mm (2.20 in) respectively. This February could be among the top three wettest on record.

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May’s Showers Ended Droughts

24 07 2019

Dale C. S. Destin |

The mini deluge at the end of May ended the droughts that were being experienced by Antigua, most of which started back in October 2017, after hurricanes Irma and Maria. May 2019 was the second wettest since 2011 and the 15th wettest on record dating back to 1928, with an island-average rainfall of 183.9 mm (7.24 in).

Following a wetter than normal May, June was drier than normal, yielding a meagre 26.1 mm (1.03 in) – only 38 percent of the usual total for the month. Meanwhile, July thus far is running below average, which is not a good sign.

Based on the last set of rainfall forecasts from regional and especially international sources, droughts are likely to return in the upcoming few months – August to October. However, things are looking less challenging for rainfall, as ENSO has returned to neutral state from the rainfall suppressing effects of El Nino.

Probabilistic multi-model ensenble forecast of rainfall for June-August 2019, based on 12 global models – 50 to 60% chance of below normal rainfall for Antigua and Barbuda

Recent projection is for a 50 percent chance of 2019 being drier than normal. This has happily dropped from 65 percent in May, likely, at least in part, due to the dissipation of El Nino. Further, around 1024 mm (41.0 in) of rain is forecast for the year, with a 70% chance of it falling in the range 741 to 1371 mm (29.2 to 54.0 in). The average annual rainfall is 1206.5 mm (47.5 in).

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Temporary Interruption to Dry Weather; Droughts Eased

29 04 2019

Dale C. S. Destin |

Drought Level is Slight

A drier than normal start to the year continues across Antigua; however, there was a temporary interruption – March turned out wet, relatively. The month had 59.6 mm (2.35 in), the most for March since 2013. Most of the rain fell on the 29 March – over 52%, otherwise the story for the month would have been quite different. The rainfall for March was 15% more that usual; notwithstanding, droughts continue, although eased a bit.

The last three-month period – January to March, upon which the assessment of the current intensity of the drought is based, was below normal. The period had 127.5 mm (5.02 in), while the normal amount of rainfall is 176.0 mm (6.93 in).

Rainfall totals for the past 24 months plus normals, anomalies 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, down from moderate. Recall that the overall description of the drought is based on the worst intensity achieved during its lifetime; however, over time, the intensity will fluctuate. Severe intensities were observed May-July and June-August of last year.

Potworks Dam, our billion-gallon surface catchment, has fallen below extraction levels – not potable water is currently available from the Dam. Water rationing is imminent but has been delayed by the presence of a number of desal plants operating in the country.  

Potworks Dam as of April 2, 2019 – drying up; picture courtesy Karen Corbin of the Humane Society

The eighteen-month period – October 2017 to March 2019, the duration of the drought thus far, is deemed severely dry. The total for the period of 1170.9 mm (46.10 in) is the fourth lowest on record, for such a period, dating back to 1928. This interval normally gets 1781.3 mm (70.13 in), which means a rainfall deficit of near 34% – close to one-third of the usual rain was absent.

Based on the last set of rainfall forecasts from regional and especially international sources, the news remains discouraging for rainfall. Overall, below normal rainfall is likely for the next six months – May to October 2019. Thus, there is every reason to believe that the droughts will not only continue but reintensify. The chance of the droughts ending is, at the very most, 30% or low.

Probabilistic multi-model ensemble forecast of rainfall for May-July 2019, based on 12 global models – 70 to 80% chance of below normal rainfall for Antigua and Barbuda

Early projections have us with a 60 chance of being drier than normal for the year, with a 45% chance of the rainfall total being in the bottom 20th percentile of all years. Further, around 977 mm (38.5 in) of rain is forecast for 2019, with a 70% chance it falling in the range 699 to 1321 mm (27.5 to 52.0 in).  

On average, our severe meteorological droughts last for around 16 months, but not continuously at severe intensity. At current, the drought is in its 19th month; the longest such drought on record lasted 38 months – Jul 2013 to August 2016.

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Continued Below Normal Rainfall; Droughts Loom Large for Antigua

1 03 2019

Dale C. S. Destin |

Rainfall

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

Antigua has had a drier than normal start to the year and the second consecutive drier than normal month. The rainfall for January was the driest since 2015 and the 14th driest on record dating back to 1928. Nearly half of the normal rainfall did not take place; the rainfall total of 40.4 mm (1.59 in) is only 59% of the average for the month. The near record rainfall of the first half of November 2018, is becoming a distant memory and the reintensification of the droughts looms large.

CurrentDroughtIntensityThe last three-month period – November to January, upon which the assessment of the current intensity of the drought is based, was slightly dry. However, the rainfall total fell in the near normal category. The three-month period had 310.1 mm (12.21 in), while the normal amount of rainfall is 422.7 mm (16.64 in).

We remain in a severe meteorological drought, the worst category on our drought scale. However, at the moment, the current intensity remains at slight, for the third month in a row. Recall that the overall description of the drought is based on the worst intensity achieved during its lifetime; however, over time, the intensity will fluctuate.

Potworks Dam, our billion-gallon surface catchment, is relatively close to falling below extraction levels. Water rationing is imminent or already occurring. This is indicative of the continued drought, which has no end in sight, at the moment.

The sixteen-month period – October 2017 to January 2019, the duration of the drought thus far, is deemed severely dry. The total for the period of 1083.8 mm (42.67 in) is the third lowest on record, for such a period, dating back to 1928. This interval normally gets 1673.9 mm (65.90 in), which means a rainfall deficit of 35% – more than one-third of the usual rain was absent.

Based on the last set of rainfall forecasts from regional and especially international sources, the news remains discouraging for rainfall. Overall, below normal rainfall is most likely for the next three months – March to May 2019. Beyond this period, there is notable uncertainty; however, the ECMWF IFS model, one of the more reliable models is forecasting continued drier than normal conditions being most likely for June to August 2019. Thus, there is every reason to believe that the droughts will reintensify. The chance of the droughts ending is, at most 25% or low.

Probabilistic Multi-Model Ensemble Forecast of Rainfall For Mar-May 2019, Based on 12 Global Models

On average, our severe meteorological droughts last for around 16 months, but not continuously at severe intensity. At current, the drought is in its 17th month; the longest such drought on record lasted 38 months – July 2013 to August 2016.

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Drier Than Normal December; Drought to Reintensify

30 01 2019

Dale C. S. Destin |

DCurrentDroughtIntensityecember was drier than normal for Antigua. The rainfall total of 65.8 mm (2.59 in) was below normal – 65% of the average for the month. This was the driest December since 2015. The month had very little positive impact on the droughts; hence, they will likely reintensify in the upcoming months.

The last three-month period – October to December, upon which the assessment of the current intensity of the drought is based, was slight dry. However, the rainfall total fell in the near normal category. The three-month period had 329.2 mm (12.96 in), while the normal amount of rainfall is 413.5 mm (16.28 in).

Rainfall for the past 24 months

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, for the second month in a row. 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.

Potworks Dam, our billion-gallon surface catchment, is again returning to critically low levels. The Authorities will be cutting back on extraction from the Dam and water rationing is imminent, if not already started. This is indicative of the continued drought; notwithstanding the ample rainfall of November.

The fifteen-month period – October 2017 to December 2018, the duration of the drought thus far, is deemed severely dry. The total for the last 15 months of 1043.4 mm (41.08 in) is the second lowest since 1969 and the fourth lowest on record, for such a period, dating back to 1928. This particular interval normally gets 1615.7 mm (63.61 in), which means a rainfall deficit of 35% – more than one-third of the usual rain was absent.

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 likely for the next six months – February to July 2019, with moderate confidence that the period February to April – 2019 having well below normal rainfall. Thus, there is every reason to believe that the droughts will reintensify. The chance of the droughts ending is, at most 20% or slight.

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

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

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

Last year – 2018, was the eighth driest on record, dating back to 1928. It was also the second driest since 1983; only 2015 has been drier since 1983 – 35 years ago.

accumulation_december2018

It is too early to say with any confidence whether the rainfall for 2019 will be below, near or above normal. However, early indicators suggest it could be another tough drought year for Antigua and Barbuda.

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Why Was It So Cold Night Before Last?

19 01 2019

Night before last was the coldest for Antigua and Barbuda for the year and the coldest for some areas in years. Some areas had temperatures as low as 15 °C (59 °F). Why was it so cold, relatively speaking, and is this unusual?

Min Temp for Antigua and Barbuda
Temperatures recorded January 17/18, 2019

The short answer to the question is radiational/radiative cooling. The long answer involves explaining what such cooling is and how it works. Radiational cooling is the process by which the ground and the adjacent air cool by emitting heat (infrared – IR energy).

The relationship between dew point (atmospheric moisture) and min temperature.
On a calm, clear night, the lower the dew-point temperature, the lower the expected minimum temperature. With the same initial evening air temperature (80ºF) and with no change in weather conditions during the night, as the dew point lowers, the expected minimum temperature lowers. This situation occurs because a lower dew point means that there is less water vapor in the air to absorb and radiate (heat) infrared energy back to the surface. More infrared energy from the surface is able to escape into space, producing more rapid radiational cooling at the surface. (Dots in each diagram represent the amount of water vapor in the air. Red wavy arrows represent infrared (IR) radiation.) Graphic courtesy Meteorology Today.

As we all know, as the sun goes down, the heat from it decreases. Consequently, at some point late in any given day, the ground and the air near it lose more heat that it receives.

The ground being denser than air cools more quickly than the air above it. Hence, after the sun goes down, the ground is cooler than the air directly above it.

For any two objects in contact with each other, heat will flow from the warmer to the cooler. Similarly, the warmer air above gives up heat to the ground, which the ground quickly emits away.

As the night progresses, the ground and the air near it continue to cool more rapidly. Air is a poor conductor (transferrer) of heat. As a result, it takes a while for the air to reach it coolest. However, this is normally reached just before dawn, in the Antigua and Caribbean context.

Now, radiational cooling happens 365 nights a year, so what was different last night? The main difference was the fact that the winds were calm, and the skies were clear – the main ingredients.

Additionally, we are in the Northern Hemisphere’s winter – shorter days, as the sun is away over the Southern Hemisphere; consequently, the coldest time of the year. So, we had almost the perfect recipe for radiational cooling to be at its optimum; thus, our colder than normal weather.

If you live at the bottom of a valley, you may have felt colder than most. This is because cold dense air, which originates from the cold hill tops, slowly flows down the hill slopes and settled in the valley – making for colder weather than non-valley areas.

If you live on a hill top you would have been coldest, as the higher you go, the cold it gets generally – 1 °C (1.8 °F) for every 100 metres (330 ft) you go up. Radiational cooling has a greater impact on hill tops that elsewhere.

There is nothing unusual with us having such cold night. No records were broken, which is indicative of the fact that we have had colder temperatures. Actually, as our climate warms like almost every other place on earth, these “extremes” temperature are occurring less frequently.

When I was a child, I recall that it was very common for my siblings and I to see our breaths in the mornings, at this time of the year – due the cold temperatures. We used to make the mirrors frosty with our breaths and then write stuff on them. That has become a rarity, at least for me – anecdotally indicating that our climate is warming and the reduced frequency of such low temperatures.

Radiational cooling operates at it maximum under clear skies, dry air, calm winds and long nights, which are synonymous with the winter months – December to February. So, we are in the period when radiational cooling operates at it best. The winds have the effect of disrupting the cooling; consequently, with the winds not likely to returning to calm over the next several days, a repeat of night before last is unlikely – fortunately or unfortunately.

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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

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All the best for 2019!





Near Normal Rainfall for September for Antigua, Droughts Eased Slightly

29 10 2018

Dale C. S. Destin |

SevereToSeriousThe rainfall for September was near normal for the second month in a row. The total of 107.2 mm (4.22 in) makes September the wettest month for the year, thus far; however, no month has yet had more than near normal. Notwithstanding, the consecutive months of near normal rainfall has led to the droughts easing slightly.

The total rainfall for the month – 107.2 mm was 74% of what normally falls – 144.0 mm (5.67 in). This was not very helpful, given the severe rainfall deficit we are experiencing.

The last three-month period – July to September, upon which the assessment of the current intensity of the drought is based, was seriously dry. In the last three months, only 249.7 mm (9.83 in) of rain fell. This is the 12th driest such period on record dating back to 1928.

Sep2018

Cumulatively, July, August and September normally yield 358.1 mm (14.1 in) of rain; however, a huge 30% of it did not fall. This means that we remain in a severe meteorological drought, the worst category on our drought scale.

So, overall, we remain in a severe drought that is currently at serious intensity. There has been a slight ease from last month – but nothing to shout about.  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.

Potworks Dam, Sep 29, 2018. Courtesy Veronica Yearwood - APUA

Potworks Dam, Sep 29, 2018. Courtesy Veronica Yearwood – APUA

Potworks Dam, with a billion-gallon capacity, has been totally dry for a few months now; however, it got in some water toward the end of August. Notwithstanding, the water levels remains well below extraction level and I am advised that the same is true for the other smaller catchments. These are indicative of the fact that the droughts are at very impactful levels.

The full brunt of the droughts continues to be masked by the presence of the desalination plants, which are virtually still the only source for potable water in the country. Notwithstanding, many impacts are starting to break through. Potable water is still being rationed; places have been left without water for days to weeks, at a time, especially when the sea is stirred up by swells, which negatively impacts the desalination process.

The twelve-month period – October 2017 to September 2018, the duration of the drought thus far, is deemed severely dry. The total for the last eleven months of 714.2 mm (28.12 in) is the third lowest on record and the lowest since 2001. The period normally gets 1202.2 mm (47.33 in) – a little less than twice the amount that fell.

Accumulation_Sep2018

Based on the last set of rainfall forecasts from regional and especially international sources, the news remains discouraging. Overall, below normal rainfall is likely for the next six months – November 2018 to April 2019. Thus, there is every reason to believe that the droughts will continue and likely worsen. The chance of the droughts ending is, at most 30% or low.

Probabilistic Multi-Model Ensemble Forecast of Rainfall For Nov 2018 - Jan 2019

Probabilistic Multi-Model Ensemble Forecast of Rainfall For Nov 2018 – Jan 2019

On average, our severe meteorological droughts last for around 16 months, but not continuously at severe intensity. Will this one go for another four months? Very likely, given the climate signals.

I now expected 2018 to be a drier than normal year with a confidence level of 80%. The best forecast for the amount of rainfall for the year is 845 mm (33.3 in) with a 70% chance of the amount ranging between 623 mm (24.5 in) and 1118 mm (44.0 in). Normally, we get 1206.5 mm (47.5 in) annually,

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