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.

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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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A Slow Start to October’s Rainfall for Antigua

20 10 2014

Dale C. S. Destin |

Rainfall continues to be a very scarce commodity in Antigua and Barbuda. Like most of the rest of the months for the past year, the rainfall for October has been quite discouraging, thus far. The first half of October has seen a significant rainfall deficit across much of Antigua according to preliminary statistics at the Antigua and Barbuda Met Service Climate Section.

Figures up to October 16 show there has been 36.0 mm of rain at the Met Office located at the V. C. Bird International Airport. This is only 50% of the October average of 71.8 mm, just about the amount that should have fallen by this point.

Rainfall_OctoberThis makes this first half of October the 16th driest at the Airport based on available records dating back to 1967. Three of the last four first half of October has seen worse rainfall deficits. However, the overall trend is positive although not significant.

Many persons were hoping that Hurricane Gonzalo would have put a dent in the drought; however, this was just not to be. The system produced only 1-5 inches across Antigua and 4-6 inches across Barbuda; however the higher totals were isolated and away from the most of the islands catchments.

The low rainfall figures appear to be due largely to sinking air associated with the Madden-Julian Oscillation in our part of the world for much of the first 16 days of October.

Of course, while these figures are interesting, they don’t tell us where the month will end up overall. A few days of wet weather, which looks unlikely at the moment, could drastically alter the statistics. So we’ll have to wait for the full-month figures before making any judgements. September had a much worse start and was able to limp into the near normal range in the end. It should be noted the rainfall for the second half of October is trending downward, although not significantly.

The outlook for the month called for near normal rainfall; thus we shall see what happens at the end of the month.

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Antigua’s Water Crisis

4 03 2014

By Dale C. S. Destin |

Antigua is on the verge of running out of water. According to the Antigua Public Utilities Authority (APUA), the water authority, the island is experiencing a water crisis stemming from the current drought, which dates back to late summer 2013. The water authority has indicated that there was only one month’s supply of surface water remaining as of February 21 and most of the limited water flowing through the country’s taps is from the desalination of seawater.

2013 Rainfall vs NormalThis news came as a thief in the night for most residents. At the beginning of the crisis in January, after days of dry taps and silence, APUA eventually issued a statement blaming a downed water plant and being out of water treatment chemicals which they said would be rectified in days. Then, after more silence and the problem unresolved, they then announced that the country was almost out of water due to the drought. However, the rainfall numbers for 2013 don’t support the dire circumstances being painted by the water authority. Whereas the rainfall for 2013 was not typical, with the dry season wetter than the wet season, the aggregate at the end of the year was near normal.  The actual figure was 46.20 inches for 2013 as compared to the normal of 47.37 inches for a given year.

Digging deeper into the numbers, seven months of 2013 had above normal rainfall, two had near normal rainfall and only three months had below normal rainfall – February, July and October (click image for larger view). Six months had over four inches of rainfall and four months had over five inches, one more than normal in each case. If near normal rainfall is now the threshold for plunging Antigua into a water crisis, then it means that about seven out of every 10 years, this predicament can be anticipated. This could result in major socio-economic problem for Antigua as the success of a country is closely linked to adequate freshwater supplies.

There is no gainsaying that there is a drought. However, it has been slight to moderate for much of the time, apart from a very brief period over July to September when there was a serious rainfall deficit, due almost exclusively to a very dry July.

The logical question then is, “why is Antigua running out of water?” The rainfall for 2013 is more than enough to serve the country’s needs. The 46.20 inches of rainfall is the equivalent of 72.2 billion gallons of water falling on Antigua during 2013. Why has APUA failed to capture enough of this water for storage for the dry season? Why is it that nearly all of it was allowed to runoff into the sea? If Antigua is a “drought prone” country, why haven’t there been strategies and institutions put in place to effectively mitigate and adapt to this hazard? Where is the national drought plan? Better can and should be done.








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