Near Normal Rainfall for August for Antigua, Droughts Continue

11 10 2018

Dale C. S. Destin |

After seeming on track to becoming the driest August on record in Antigua, an 11th hour spurt of rainfall changed the outcome dramatically and happily. The month ended up with near normal rainfall – 102.9 mm (4.05 in). About 70% of the total occurred on August 29 and 30.

Drought Graphic

August is now the wettest month for 2018 – wetter than the past three months, May to July, combined. This has only every happened 5 other times on record dating back to 1928.

The total rainfall for the month – 102.9 mm was a healthy 91% of what normally falls – 113.0 mm (4.45 in). However, was very far from enough, given the severe rainfall deficit we are experiencing.

The last three-month period – June to August, upon which the assessment of the current intensity of the drought is based, was severely dry. In the last three months, only 155.2 mm (6.11 in) of rain fell. This is the fifth driest such period on record and the second driest since 1986.

Cumulatively, June, July and August normally yield 282.4 mm (11.12 in) of rain; however, a massive 45% of it did not fall. This means that we remain in a severe meteorological drought, the worst category on our drought scale.

Severe_to_SevereSo, overall, we remain in a severe drought that is currently at severe intensity. Last month, it was assessed similarly.  Recall that the overall description of the drought is based on the worst intensity achieve 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; however, it got in some water toward the end of August. Notwithstanding, the water levels remains well below extraction level and I am advised by an official of Antigua Public Utilites Authority (APUA) Water Business Unity that the same is true for the other smaller catchments. These are indicative of the fact that the droughts are at severe levels. Nevertheless, the rainfall at the end of August was very useful in tapping up many household cisterns that were or near empty .

Potworks Dam, August 31, 2018, Courtesy Karen Corbin - Humane Society

Potworks Dam, August 31, 2018, Courtesy Karen Corbin – Humane Society.

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, from the water authority. 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, notwithstanding a schedule issued by APUA – the water authority, to provide water to everyone, at least, three times per week.

The eleven-month period – October 2017 to August 2018, the duration of the drought thus far, is deemed severely dry. The total for the last eleven months of 607.1 mm (23.90 in) is the third lowest on record and the lowest since 2001. The period normally gets 1058.2 mm (41.66 in) – a little less than 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 for the next six months – October 2018 to March 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 Oct-Dec 2018

Probabilistic Multi-Model Ensemble Forecast of Rainfall For Oct-Dec 2018

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

Our chance of 2018 being a drier than normal year remains high – 75%, and unchanged from last month. The best forecast for the amount of rainfall for the year is 868 mm (34.2 in) with a 70% chance of the amount ranging between 644 mm (25.4 in) and 1139 mm (44.8 in). Normally, we get 1206.5 mm (47.5 in) annually,

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