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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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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Near Normal Rainfall for September, Drought Continues

27 10 2021

Dale C. S. Destin |

September joins June as the only two months of the year, thus far, to register near normal rainfall, all others had below normal figures. The month produced 122.2 mm (4.81 in) of rainfall, the highest total for any month since December 2020; notwithstanding, drought continues through September. The rainfall for the last nine months ranks among the worst on record, and it is still unclear as to when there will be significant respite.

The rainfall for September is the second lowest since 2015. However, the total for the month was a decent 90 percent of the normal value of 136.4 mm (5.37 in), only a deficit of 10 percent.

The period July-September was also drier than usual. The total of 268.7 mm (10.58 in) was the 18th lowest on record starting 1928. The last time this period was drier was 2015 with 168.1 mm (6.62 in).

We continue to witness one of the driest years on record. Thus far, this January to September is the sixth driest on record and the driest since 2015. The first three-quarters of the year has only a meagre 473.5 mm (18.64 in), only a little over 62 percent of the usual rainfall of 759.0 mm (29.88 in). The five drier January to September are 2015, 2003, 2001, 1939 and 1930. The year is on track to be among the top 10 driest or worst, on record.  

Since the 2020 November’s deluge, the last ten months, December-September, is the seventh driest on record and the lowest since 2015. The period has only returned 65 percent of normal rainfall.

The upcoming three months, November to January, has equal chance of below, near or above normal rainfall. Meanwhile, some of the more reliable models are still forecasting the continuation of below usual rainfall being most likely. Looking at the glass half full, near to above normal rainfall is more likely than not.

WMO Lead Centre for Long-Range Forecast Multi-Model Ensemble is forecasting equal chance of below, near or above normal rainfall for Antigua and Barbuda.

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. However, the rainfall of September did stabilise or eased the droughts a bit.

Our conversion of sea water to fresh water has built drought resilience; 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. Unfortunately, these “evils” are virtually unavoidable, for the foreseeable future.

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 continues and with the rainfall outlook unclear, an end is unforecastable, at this time. Daily water use continues to outstrip production by about one million gallons.

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

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2nd Driest May on Record, Serious Drought Continues

23 06 2021

Dale C. S. Destin |

We have just witnessed the second driest May, in Antigua, on record dating back to 1928. It was also the bottom 10 driest March-May and the bottom 4 driest January-May. With such significant rainfall shortage, the meteorological drought continues for Antigua, with a return to serious intensity. Much of the drought impacts are being mask; notwithstanding, the country is feeling it deep in the pocket and models indicate that this will continue for much of the upcoming three months.

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 Caribbean Basin.

The rainfall for May was 17.3 mm (0.68 in), the lowest since 2001, when the country had 6.4 mm (0.25 in). The total for the month was almost unimaginably low at 17 percent of the normal of 101.1 mm (3.98 in). Only eight other Mays have had less than an inch of rain. Overall, it was the 13th driest month of all 1121 on record.

The meteorological spring, March-May, was also very dry. The total of 85.3 mm (3.36 in) was the ninth lowest for the season. The last time we had a drier spring was 2015.  

We continue to witness one of the driest years on record and easily the driest since 2015. The year-to-date total is a meagre 149.1 mm (5.87 in), only 44 percent of the usual rainfall of 341.6 mm (13.45 in). The absent rainfall, 192.5 mm (7.58 in), is more than the annual average for January, February and March combined. Only three other years have had a drier start: 2015 with 140.2 mm (5.52 in); 2001 with 113.0 mm (4.45 in) and 1939 with 131.8 mm (5.19 in).

Our last wet month was November, which was floodingly wet. Since then, the last six months, December-May, is the fourth driest on record and the lowest since 2015. The period has only yielded 53 percent of normal rainfall. Our drying catchments and thirsty brownish landscape bear witness to the missing rainfall.

The upcoming season, July to September, is likely to be drier than normal. The majority of models are forecasting the continuation of deficit rainfall. Hence, the drought is likely to continue. Our largest catchment, Potworks Dam, along with others, could again revert to dry lands and shortcuts for vehicular traffic.

Based on models which correlate our sea surface temperatures, across the tropics, with our rainfall, the medium and long term continue to look brown. This dry season, January-June, is expected to be among the five driest on record. Meanwhile, the year is likely to be drier than usual with a 58 percent chance of below normal rainfall; this is up 12 percent from last month. There is a non-trivial 18 percent probability of the year’s rainfall falling in the bottom 10 percentile.

As the meteorological drought goes or worsens, so go or will 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.  

Potworks Dam is close to falling below extraction levels. With the rainfall outlook bleak, we could be out of surface water in weeks. Water rationing is imminent, if not already occurring.

Antigua is not alone in experiencing significant rainfall shortages. Much of the Eastern Caribbean remains  thirsty for rainfall. Deficit rainfall is occurring across many places, and it is probable that the it will worsen and or spread to other islands, over the upcoming months, based on recent forecasts, particularly the central Windward Islands to the Dominican Republic. For May, most of the Caribbean Basin had less that 50 percent of the usual rainfall, with some areas receiving less than ONE percent.

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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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Droughts Remain Slight, Despite Scarce April Showers

31 05 2019

Dale C. S. Destin |

Less than normal April showers fell across Antigua this year. The observed total rainfall of 42.2 mm (1.66 in), makes this April the second driest since 2006. Only 49 percent of the usual April showers fell, the rest added to our rainfall deficit; hence, droughts continue.

The last three-month period – February to April, upon which the assessment of the current intensity of the drought is based, was below normal. The period had 129.5 mm (5.10 in), while the normal amount of rainfall is 193.0 mm (7.60 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. 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 as of May 1, 2019 – drying up; picture courtesy Karen Corbin of the Humane Society

Potworks Dam, our billion-gallon surface catchment, has fallen below extraction levels – no 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.

The nineteen-month period – October 2017 to April 2019, the duration of the drought thus far, is deemed severely dry. The total for the period of 1213.1 mm (47.76 in) is the third lowest on record, for such a period, dating back to 1928. This interval normally gets 1866.9 mm (73.5 in), which means a rainfall deficit of near 35% – over 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 – June to November 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 June-August 2019, based on 12 global models – 70 to 80% chance of below normal rainfall for Antigua and Barbuda

Early projections have us with a 65 percent chance of being drier than normal for the year, with a 50% chance of the rainfall total being in the bottom 20th percentile of all years. Further, around 929 mm (36.6 in) of rain is forecast for 2019, with a 70% chance it falling in the range 664 to 1264 mm (26.1 to 49.8 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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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,

Keep following us 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.





9th Driest July on Record for Antigua, Droughts Continue

26 08 2018

Dale C. S. Destin |

July 2018 was the ninth driest on record for Antigua dating back to 1928. The last time we had a drier July was 2015, when we recorded our driest year in, at least, 145 years.

July2018

The total rainfall for the month of 39.6 mm (1.56 in) was a meagre 39% of what normally falls – 100.3 mm (3.95 in). Hence, there was a painful 61% rainfall deficit for the month.

From_mod_to_severe_droughtThis was also the third driest July or the third driest start to the wet season since 1977. Only 2015 and 2014 Julys were drier, with 33.3 mm (1.31 in) and 19.3 mm (0.76 in) respectively, in recent times.

The last three-month period – May to July, upon which the assessment of the current intensity of the drought is based, was severely dry. In that time, only 96.3 mm (3.79 in) of rain fell. This is the fourth driest such period on record and the second driest since 1977.

Cumulatively, May, June and July normally yield 273.1 mm (10.75 in) of rain; however, a massive 65% of it did not fall. This means that we are now in a severe meteorological drought, the worst category on our scale. Other droughts are believed to be at similar severity. Recall that there are, at least, five types of droughts.

RainfallForPast24Months_July2018

Rainfall (in) for the past 2 yrs. All periods showing well below or below normal rainfall.

So, overall, we are now in a severe drought that is currently at severe intensity. Last month, it was assessed to be a serious drought that was at moderate intensity. Recall that the overall description of the drought is based on the worst intensity achieved since it started; however, over time, the intensity will fluctuate.

Potworks Dam, with a billion-gallon capacity, has been totally dry for a few months now. The vegetation of the Island continues to struggle badly – grass has ceased growing in some locations. Many fields are bare, with some having large and dangerous cracks. Some animals are said to have perished due to insufficient food and water. These are indicative of the fact that the droughts, not just meteorological, are at severe levels.

Potworks_Dam_Aug22018

Potworks Dam – August 2, 2018. Picture courtesy Karen Corbin – Humane Society

Happily, the full brunt of the droughts continues to be held at bay by the presence of the desalination plants, which are virtually the only source for potable water in the country. Notwithstanding, many impacts are starting to break through. Potable water is being rationed, places have been left without water for days to weeks, at a time, notwithstanding a schedule issued by APUA – the water authority, to provide water to everyone, at least, three times per week.

The ten-month period – October 2017 to July 2018, the duration of the drought thus far, is deemed severely dry. The total for the last ten months of 504.2 mm (19.85 in) is the third lowest on record and the lowest since 2001. The period normally gets 945.1 mm (37.21 in) – nearly twice the amount that fell.

Based on the last set of rainfall forecasts from regional and especially international sources, the news remains discouraging. Overall, below normal rainfall is likely, if not expected, for the next six months – September 2018 to February 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.

SON_Aug2018

Probabilistic Multi-Model Ensemble Forecast of Rainfall For Sep-Nov 2018

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

The probability of 2018 being a drier than normal year remains high – 75%. The best forecast for rainfall amount for the year is 872 mm (34.3 in) with a 70% confidence of the amount ranging between 658 mm (25.9 in) and 1130 mm (44.5 in). Normally, we get 1206.5 mm (47.5 in) annually.

If you found this article informative, I would be very grateful if you would help it spread by emailing it to a friend, or sharing it on Twitter or Facebook.

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Very Dry March; Droughts Reintensify

26 04 2018

Dale C. S. Destin |

March 2018 was the driest since 2014 and the 12th driest March on record dating back to 1928. The island-average total for the month was 17.8 mm (0.70 in). This represents only 34% of the usual amount of 51.8 mm (2.04 in).

D&P_RainfallGraphic_Mar2018

Rainfall in inches for the past 24 months. Multiply by 25.4 to get mm.

The last three-month period – January to March, upon which the assessment of the current intensity of the drought is based, had 116.1 mm (4.57 in), only 66% of the normal total of 176.0 mm (6.93 in). This puts the meteorological droughts current intensity at moderate, down from slight.

DroughtGraphic: Slight_to_Moderate

With Potworks Dam about to go totally dry and the vegetation of the Island struggling, there is little doubt that other droughts are at moderate levels or worse. Thankfully, the full impacts of the droughts are being masked by the presence of the desalination plants.

Rainfall_Accu_Anu

Interestingly, in a negative way, the rainfall accumulation for the year, thus far, is not very dissimilar to that of 2015 and 1983 – the driest and second driest years on record, respectively. We make no conclusions here but it may be an ominous sign.

The six-month period – October 2017 to March 2018, the duration of the drought thus far, was seriously dry. The total for the period of 326.4 mm (12.85 in) is the fifth lowest on record dating back to 1928. It is also the lowest total for the given period since 2001. The rainfall deficit since the drought started is at 260.1 mm (10.24 in).

Based on the last set of rainfall outlooks, the news is not good for rainfall. Overall, below normal rainfall is most likely for the six-month period April to September. Thus, there is every reason to believe that the droughts will continue and likely worsen.

Even if the rainfall total turns out to be near average, it will not be enough, especially with respect to the hydrological drought, as the monthly evaporation rates significantly exceeds rainfall totals for most of the upcoming months. The chance of the droughts ending is slight – less than 30%.

Recall that the current drought started in October 2017 with the intensity at serious levels. On average, serious meteorological droughts, for Antigua, last for close to a year, but not continuously at serious intensity. We have just passed the six-month mark. Will it go another six months? The answer looks more likely to be yes rather than no.

Keep following us for more on this developing story and all things weather and climate. Follow us here on wordpress and also via twitterfacebookinstagramtumblrflickrgoogle+, and youtube.





2nd Wettest February In Years, Yet Less Than Usual Rainfall

1 04 2018

Dale C. S. Destin|

February 2018 was the second wettest since 2011, yet the rainfall total for the month was below the usual.  The island-average total was 35.8 mm (1.41 in); however, the usual amount for the month is 55.9 mm (2.20 in). Clearly, with only 64% of February’s rains falling, there was no positive impact on the drought situation being experienced.

Slight Meteorological Drought

Rainfall in inches for the past 24 months. Multiply by 25.4 to get mm. For records, the year given marks the start of the period.

The three-month period – December to February, upon which the assessment of the current intensity of the drought is based, had 198.6 mm (7.82 in). This puts the meteorological droughts at slight. However, with Potworks Dam about to go totally dry and the vegetation of the Island struggling, there is little doubt that other droughts are at moderate levels or worse. Of course, and thankfully, the full impact of the droughts is being masked by the presence of the desalination plants.

Drought Level is Slight

Based on the last set of rainfall outlooks, the news is not good for rainfall. Overall, below normal rainfall is most likely for the six-month period March to August. Thus, there is every reason to believe that the droughts will worsen. Even if the rainfall total turns out to be near average, it will not be enough, especially with respect to the hydrological drought, as the monthly evaporation rates significantly exceeds rainfall totals for most of the upcoming months. The chance of the droughts ending is slight – less than 30%.

Recall that the current drought started in October 2017 with the intensity at serious levels. On average, serious meteorological droughts last for close to a year, but not continuously at serious intensity. We have just passed the six-month mark in the drought. Will it go another six months? Unfortunately, the answer looks more like yes than no.

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A Severely Dry February for Antigua

22 03 2017

Dale C. S. Destin |

February 2017 was a severely dry month for Antigua. It is the fourth driest February on record, dating back to, at least, 1928. Only one other February has been drier since 1983 – that of 2013.

Top4DriestFebForAntigua

On average, such an extremely low rainfall only occurs once in around every 33 years for February. In other words, there is only a 3% chance of such little rainfall taking place for the month.

The island-average for the February was just 14.0 mm (0.55 in). This makes it the driest and first below normal rainfall month since October 2016.

One month of dryness does not say anything about the rainfall for the upcoming months. However, with the probability of an El Nino rising, this dryness may be a sign of unwelcome things to come.

Recall the El Nino reduces rainfall activity across our area, mainly during the wet season, while the opposite – La Nina has reverse effect. It is still early days as to whether El Nino will develop but not too early for us to start to put contingency plans in place.

On average, February is our second driest month on, with an island-average of 55.9 mm (2.20 in).

Based on rain gauge measurement and satellite estimates, Barbuda fared slightly better with a total in the range of 12.7 to 38.0 mm (0.5-1.5 in).

Thus far, March is on track for, at least, near normal rainfall.

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Antigua’s Unenviable Record Worst Drought Continues

25 04 2016

Dale C. S. Destin |

Notwithstanding the significant rainfall of the past week, our unenviable record worst drought continues. However, the rains did bring some much-needed relief, as many residents got their cisterns and other catchments replenished. The precipitation also brought some relief to our farming community and landscape.

No sign of water in Potworks Dam, Antigua, April 22, 2016. Photo courtesy Karen Corbin – President of the Humane Society

No sign of water in Potworks Dam, Bethesda, Antigua; April 22, 2016. Photo courtesy Karen Corbin – President of the Humane Society

Recall that there are, at least, four types of droughts – meteorological, agricultural, hydrological and socioeconomic, which is the worst. Antigua has been in these droughts for around two months shy of three years. Of the mentioned droughts, the rains had the greatest impact on the meteorological and agricultural droughts.

For the week ending April 23, the island-average rainfall for Antigua was 63.3 mm (2.49 in). To have ended at least the meteorological drought, we needed over 100 mm (4 in); much more was need to end the other droughts.

Based on a mixture of rain gauge measurements and radar estimates, the rainfall across the island was quite variable, ranging from 25 mm (1 in) in the west to 152 mm (6 in) in the northeast. Notwithstanding, most areas got 40-100 mm (1.5-4 in).

24-hr Estimated Rainfall, From 8 pm April 17, 2016 to 8 pm April 18, 2016

24-hr Estimated Rainfall: From 8 pm April 17, 2016 to 8 pm April 18, 2016

At the V. C. Bird International Airport (VCBIA), the 42 mm that fell on April 18 makes it the wettest day since October 28, 2014. It was also the wettest April 18 at VCBIA since 1992 and 15th wettest of 1620 April days on record since 1962.

VCBIA also had a near record wet spell for April – six consecutive days with at least 1 mm (0.04 in), second only to the seven recorded in 1970. The six-day (April 17-22) total of 70.4 mm (2.77 in) at VCBIA, is now the fourth wettest for the month. With respect to a week, it’s the wettest for April since 2010 and the wettest for all weeks since October 23-29, 2014.

As of Sunday morning, April 24, the island-average rainfall for Antigua for the month was 80.5 mm (3.17 in). Thus far, this is the wettest April since 2013, when we had 132.1 mm (5.20 in). It is also our fourth wettest month since December 2014. On average, April is the fifth driest month with 85.6 mm (3.37 in).

The wet week was all due to a cold front preceded by an associated trough. Both systems have since been replaced by high pressure.

The wet weather has eased the meteorological drought to slight levels; however, not much has changed regarding the more serious hydrological and socioeconomic droughts. Follow us as we continue to monitor our rainfall closely.





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.





Near Record Dryness for the First Half of May

17 05 2015

Dale C. S. Destin |

The first half of May 2015 is over and the Met Office, located at the V. C. Bird International Airport, Coolidge, Antigua, has measured only 1.7 mm (0.07 in) of rainfall. This represents the second driest such period on record. The only time May 1-15 was drier was back in 2001.

May 1-15 Rainfall at the V. C. Bird Int'l Airport

We are clearly not having a normal May or year but normally we would have received around 37.8 mm (1.49 in) by now. Instead, we have had near record dryness.

The rest of the country has not fared better. In fact, there are a few areas that are yet to see measurable rainfall for the month. Neighbouring islands are also experiencing similar rainfall deficits.

This severe dryness for the first half of May is very rare. On average, this happens once every 250 years, which translates to a 0.4% probability of May 1-15 being this dry.

The near record low rainfall seems largely connected with the anomalous cooling of the tropical North Atlantic which is associated with a positive North Atlantic Oscillation (NAO). Another significant driver of the dryness is the above normal flow of very dry, dusty air from the Sahara Desert to the region.

A dry start to the month does not always imply a dry month; however, of the six other times we have had 10 mm (0.40 in) or less for the first half of May, the eventual month’s total has never exceeded 56 mm (2.20 in). Only once such a dry start did not signal a dry month.

Overall, the second half of May has produced as little as 3.9 mm (0.15 in) and as much as 434.7 mm (17.1 in). Hoping to be wrong, but it would not be “tempting fate” to say that we absolutely will not get anywhere remotely close to 434.7 mm over the next two weeks.

Climatologically, the past 30 years show that rainfall on a whole for May is not changing. However, May 1-15 is trending positively (wet) while May 16-31 is trending negatively (dry). These trends are not considered significant, at the moment, but May 1-15 is not far away from being so.

The driest May on record at the Airport, dating back to 1928, is May 2001 with 7.6 mm (0.30 in). This record appears to be in jeopardy.

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Record Breaking Rainfall over the Past Two Years

29 03 2012

As we continue to see a drying trend across our area, the record shows that the past two years ending February 2012 was the wettest on record. The total for the period March 2010 to February 2012 was 129.80 inches; the previous highest was 129.72 inches recorded over the period March 1951 to February 1953; this was 59 years ago. The normal rainfall for this period is 93.88 inches. Recall that prior to the past very wet period, we had a serious drought during the second half of 2009 through early 2010. We may be heading into another Meteorological Drought over the next few months.








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