Drier Than Normal May for Antigua, Droughts Reintensify

28 06 2018

Dale C. S. Destin |

The rainfall for May 2018 was below normal for Antigua. The total of 43.9 mm (1.73 in) was only 42% of what normally falls – 103.6 mm (4.08 in). Thus, there was a 58% deficit of rainfall for the month.

DroughtDial-Slight_to_ModerateThe last three-month period – March to May, upon which the assessment of the current intensity of the drought is based, had 135.1 mm (5.32 in), only 56% of the normal total of 240.8 mm (9.48 in). This puts the meteorological droughts current intensity at moderate, declining from slight.

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

The eight-month period – October 2017 to May 2018, the duration of the drought thus far, is deemed severely dry. This means that the total is in the bottom 5% of the historical data; such dryness is unusual – it happens, at most, once every 20 years, on average. The total for the period of 451.9 mm (17.79 in) is the lowest since 2001 and the fourth lowest on record dating back to 1928. The period normally gets 775.7 mm (30.54 in).

TemporalRainfall

Based on the last set of rainfall outlooks, the news is not good for rainfall. Overall, below normal rainfall is most likely for, at least, the next three months – July to September. Further, recent outlooks from global models indicate that the next six months will see below normal rainfall. Thus, there is every reason to believe that the droughts will continue and likely worsen.

The rainfall total for the year thus far – January to May, is well below normal. The 365.3 mm (14.38 in) is only 66% of what normally falls. Of the 91 years on record, only 17 have been drier to this point.

RainfallAccumulations_May2018

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 will significantly exceed rainfall totals for most of the upcoming months. The chance of the droughts ending is around 20% or slight.

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 eight-month mark. Will it go another four months? The answer still looks more like to be yes than no.

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.

Follow us for all you need to know about the current drought and all things weather and climate. Follow us on twitterfacebookinstagramtumblrflickrgoogle+, and youtube. Thank you!

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No End in Sight for Drought-Hit Antigua

22 06 2018

Dale C. S. Destin |

There is no end in sight for the current drought affecting Antigua. Not only there is no end in sight but it is expected to get worse, perhaps much worse.

Potworks Dam, a Billion Gallon Dam - Jun 5, 2018.

Potworks Dam, our billion gallon dam, is empty. Pic taken Jun 5, 2018, courtesy Karen Corbin – Humane Society.

Analyses done for the upcoming months, for as far as the (forecasting) eyes can see – through December 2018, suggest a moderate drought or worse will continue. For the drought to end, we need a very wet month or a few months of above normal rainfall – it’s possible but highly unlikely, based on projected climate signals.

LikelihoodOfRainfallForAntigua

The period with the highest likelihood of getting less than usual rainfall is July to September. It is near 100% certain that this period will be, at least, moderately dry i.e. rainfall in the bottom 20% of the historical record. This means that such dryness occurs no more than once every five years.

Already, June 1-20 is tied for the second driest across some parts of the island in over a generation. Further, the year, thus far, is the driest since 2015 and the second driest since 2003.

Meanwhile, the rainfall for the year has a 60% chance of being below normal. The projection is for the year to get around 965 mm (38 in) with a 70% likelihood of it being in the range 686 to 1295 mm (27 to 51 in).  On average, Antigua gets 1194 mm (47 in).

Rainfall For Anu 2018

Ongoing or potential impacts of the drought include the following:

  • Crop or pasture damage or losses
  • Decreased food production and crop scarcities
  • Financial losses primarily to farmers and related sectors
  • Water shortages and restrictions
  • Higher than usual grass and bush fires
  • Environmental degradations

The current and projected dry weather is largely due to the ongoing cooler than normal tropical North Atlantic, which is projected to remain this way through much of the rest of the year. The dryness could be intensified by El Nino, which is now likely to develop by October.

Recall that drought is not the absence of rainfall but rather lower than usual rainfall or a deficit in rainfall. Thus, relatively dry weather conditions will prevail for the drought period.

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.

Follow us for all you need to know about the current drought and all things weather and climate. Follow us on twitterfacebookinstagramtumblrflickrgoogle+, and youtube. Thank you!





Usual Rainfall for April, Droughts Eased

31 05 2018

Dale C. S. Destin |

The rainfall for April 2018 was near normal; however, is the driest April since 2015. The island-average total for the month was 71.6 mm (2.82 in). This represents 84% of the usual amount of 85.6 mm (3.37 in).

Potworks_Apr282018

The last three month period – February to April, upon which the assessment of the current intensity of the drought is based, had 126.2 mm (4.97 in), 65% of the normal total of 193.0 mm (7.60 in). This puts the meteorological droughts current intensity at slight, improving from moderate. With Potworks Dam about to go totally dry and the vegetation of the Island struggling, there is little doubt that most other droughts are at moderate levels or worse. Happily, the full impacts of the droughts are being masked by the presence of the desalination plants.  According to the Antigua Public Utilities Authority, around 85% of all potable water is coming from the sea via reverse osmosis and is expected to climb to near 90% in days.

The seven-month period – October 2017 to April 2018, the duration of the drought thus far, was seriously dry. The total for the period of 407.92 mm (16.06 in) is the lowest since 2001 and the eighth lowest on record dating back to 1928.

RainfallDeficitGraphic_April2018

Based on the last set of rainfall outlooks, the news is not good for rainfall. Overall, below normal rainfall is most likely for, at least, the next three months – June to August. Additionally, the projected rainfall for 2018 is below normal with a 60% confidence. 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 around 20% or slight.

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 seven-month mark. Will it go another five months? The answer still looks more like to be yes than no.

Keep following us for more on this developing story and all things weather and climate.

 





Drought Eased A Bit For Antigua

2 03 2018

Dale C. S. Destin |

Near normal rainfall for January has eased the drought across Antigua from serious to moderate levels. The island-average rainfall for January was 62.5 mm (2.46 in), 91% of the usual total.

The three-month period – November to January, upon which the assessment of the intensity of the drought is based, had 211.6 mm (8.33 in). It is the second driest such period since 2000 and the 13th driest on record dating back to 1928.

Based on the last set of rainfall outlooks, the news is not good for rainfall. Below to near normal rainfall is expected for the period March to May. Thus, there is every reason to believe that the droughts will worsen or remain the same. There is only a slight chance of them ending over the above mentioned period.

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.

While we can only speak definitively to meteorological droughts, there is little doubt that we are also experiencing agricultural, hydrological and perhaps socioeconomical droughts. These are likely to become more noticeable in the incoming months; however, the full impact will continue to be masked by the presence of desalination plants.

Potworks Dam Feb 13, 2018, Courtesy Karen Corbin - Humane Society

Potworks Dam Feb 13, 2018, Courtesy Karen Corbin – Humane Society

Potworks Dam, the country’s largest catchment with a capacity of around a billion gallons of water, continues to show signs of drying up. Around the middle of February, the water level had fallen to about a quarter or less. It could be totally dry in couple months.

Keep following us for more on this developing story and things weather and climate.





Drought Again For Antigua

27 01 2018

Dale C. S. Destin |

None_to_Serious_DroughtAntigua is back in drought again. There are several types of drought and as of three months ending December 2017, rainfall figures indicate that Antigua has slipped into, at least, a meteorological drought.

The drought started October 2017, when less than 40% of the normal total rainfall fell for the month. It was the second driest October since 2000 and the 13th driest on record dating back to 1928. Normally, October is the wettest month of the year – averaging 161.0 mm (6.34 in); however, this year, only 61.2 mm (2.41 in) fell.

November did not fare any better with respect to rainfall, actually, it was worse. November only got around 32% of its normal rainfall. It was the driest November since 1997 – two decades ago.

Normally, November is the second wettest month of the year, averaging (5.97 in) – only (1.95 in) fell last November. Instead of being the second wettest, it was the second driest month of 2017 and the seventh driest November on record dating back to 1928.

December had near normal rainfall – far from enough to have much of a positive effect on the drought. By the end of the three-month period ending December – the rainfall deficit for the said interval was around 49% or (8.00 in). It is the sixth driest October-December period on record. At this deficit, the meteorological drought is deemed to be at serious levels.

OND_SeasonalRainfall

There is no firm end in sight for the current drought – the chance of it ending over the upcoming three months is moderate, at best. It is more likely to remain the same or get worse.

On average, serious meteorological droughts last around 11 months. The chance of a serious drought ending in a hurry i.e. in less than six months is less than 20%.

Already there are signs of catchment drying up. Potworks Dam, the country’s largest catchment, by far, is well below half. In the past, such a drought would be more impactful socioeconomically; however, with the advent of at least two major desalination plants in the past three years, much of the impacts are being masked.

Potworks Dam Jan 16, 2018, Courtesy Karen Corbin

Potworks Dam Jan 16, 2018, Courtesy Karen Corbin – Humane Society

The last meteorological drought – the worse ever on record, came to an end September 2016. The meteorological drought also degenerated into agricultural, hydrological, socioeconomical and ecological droughts, which were quite costly to the economy of Antigua and Barbuda.

Keep following us for more on this developing story and all things weather and climate.

 





The Worst Drought on Record for Antigua

25 03 2016

Dale C. S. Destin |

Antigua is witnessing the worst drought in recent history, dating back to, at least, 1928. The current drought is now over 32 months in length, similar to the drought of 1964-67. However, to date, the record rainfall deficit of 1143 mm (45 in) caused by the current drought, exceeds that of 1964-67 by 254 mm (10 in) or around 29%.

RainfallDeficitGraphic

While we don’t have observed monthly rainfall totals beyond 1928, we do have annual totals going back to 1871. Based on this record, 2015 is now the driest year in the series. This translates to 2015 rainfall total occurring once per 500 years, on average. Thus, it’s perhaps the most intense drought since the arrival of Christopher Columbus.

Not only the last year has been the driest on record, but so to have the last two years (24 months). Further, the last 32 months – July 2013 to February 2016, is the driest such period on record. We are missing about a year’s worth of rainfall.

Surface water contributes to around 30% of our potable water mix. However, since the drought started, the country has been completely out of surface water twice with an aggregate duration of around 14 months. We were out of surface water April to September 2014 and again from August 2015 to present.

The drought was caused by a number of climate actors not necessarily all acting at the same time. These include mainly an abundance of the dry and dusty Saharan air layer (SAL) from Africa, positive North Atlantic Oscillation (NAO), negative Tropical North Atlantic (TNA) Index and El Nino. It is fairly well established that these phenomena, in the mentioned phases, cause less than normal rainfall across our area with the converse being true.

The drought got kicked off by the SAL along with unpredictably strong vertical wind shear, sinking air and the weakening of the Atlantic Ocean overturning circulation. Happily, this resulted in a failed hurricane season in 2013, but unfortunately it also plunged us into what has become our worst rainfall deficit on record.

Contributing to the persistent drought, the NAO has been predominantly positive over the duration of the drought with only nine of the last 32 months having negative (rain-favoured) values. Meanwhile, the TNA was negative (unfavourable rainfall values) for most of January 2014 to June 2015. In 2015, El Nino developed and reach super (record) strength during the latter half of the year.

Droughts are expensive, and severe droughts are severely expensive. It’s believed that the drought has cost the country hundreds of millions of dollars, directly and indirectly. I will address this matter more in a subsequent blog.

The current drought is anticipated to become the longest on record – a further very unwelcome new record. Initial predictions had the drought easing significantly or ending around mid-year. However, our last set of forecasts has it continuing into the second half of the year.





One of the Worst First-Quarter Rainfall Deficits for Antigua

20 04 2015

Dale C. S. Destin |

Antigua is having its seventh driest start to a year on record. As of the end of March, the average first-quarter (January-March) rainfall total for the island was 90.4 mm (3.56 in). Normally, by now, we would have received 176.0 mm (6.93 in). Thus, there is a relatively huge rainfall deficit of 85.6 mm (3.37 in).

MonthlyRainfallAccumulationforAntigua

This is the second consecutive year that first-quarter rainfall is much lower than normal. However, this year’s first-quarter rainfall is 20% lower than last year’s.

The rainfall for January-March is 49% lower than normal. In other words, we have only received 51% or just a little over half of what we normally get for this period.

Top10DriestFirst-QuartersForAntigua

Only six other first-quarter rainfall totals have been lower; however, none since 2001, and only one since 1983.

All three months of the first-quarter have been quite dry. The wettest of the three months, February, was drier than normal and the other two months were the driest since 2002.

This kind of dryness to the start of the year can only be expected to occur once in every 15 years, on average. In other words, the chance of the first three months of a year having such low rainfall is less than 7%.

At the Airport, the number of wet days (with 1 or more mm) up to the end of March was 15. Usually we would have 27 for the first-quarter.

The sluggish start to rainfall for the year seems due mainly to a positive North Atlantic Oscillation (NAO) or higher than normal surface pressure across the Atlantic Ocean. A positive NOA has a cooling effect on sea surface temperatures (SSTs), which in turn causes unconducive atmospheric conditions for rainfall.

Outlooks for the next six months are not very encouraging. Based on SSTs across the tropical Atlantic and Pacific Oceans, the main drivers of our climate, lower than normal rainfall is likely through the next six months.

We are in the dry season and it does not normally rain a lot; however, relative to this time of the year, this first-quarter deficit is enormous, especially against the backdrop of the current protracted drought and a dismal rainfall outlook for much of the rest of the year.

The last time we had a drier start to the year back in 2001, we were in the midst of a severe drought. The eventually rainfall total for that year was 850.9 mm (33.50 in), much lower than normal and drier than last year.

A dry first-quarter does not always signal a dry year (below normal rainfall year). However, of years with the top 10 driest first-quarters, 6 are dry, 2 are normal, 1 is wet and 2015 is to be decided. We will keep you posted.

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