Drought Deepens…Relief Uncertain

9 07 2020

Dale Destin|

The paltry rainfall for the last three months for Antigua, has caused the meteorological drought to plunge from moderate to severe levels. The rainfall for April-June (AMJ) amounted to only 82.6 mm (3.25 in). This is the sixth driest AMJ on record, dating back to 1928. Further, the rainfall for AMJ represents only meagre 32 percent of the normal total of 274.6 mm (10.81 in). 

Potworks Dam in the background, going on three months, without a drop of its billion-gallon-water capacity. (“Normal” corrected for units Jul 14, 2020)

Other droughts have also tumbled with the meteotological drought, which is considered the mother of them all. These others are at moderate or worse intensity.

The rainfall for June was below normal for the third month in a row. The rainfall of 45.7 mm (1.80 in) was only 66 percent of the normal total for the month of 69.3 mm (2.73 in).

Although drier than normal, it was wetter than the last two Junes combined and more than the last two months combined. This is an indication of just how dry those months were.

Recall that we had very happy first-quarter rainfall. The first three months of the year was wetter than normal. However, since then, things have gone south. Rainfall for the year, thus far, for the dry season – Jan to June, stands at below normal.

The dry season rainfall of 320 mm (12.6 in) amounts to just 74 percent of the normal total of 434.3 mm (17.1 in). It is the driest three-month period since June-August 2018.

The woefully low rainfall since March looks to be mainly due to higher than normal pressure at the lower levels of the atmosphere. This unusual arrangement of pressure resulted in, more often than usual, sinking air, which inhibited warm rising air needed for cloud formation and rainfall.  A record amount of Saharan Dust during June would have also played a huge role in stifling rainfall.

Low level pessure anomaly across the Caribbean Basin and parts of the North Atlantic – April 1 to June 30, 2020. Higher that usual low level pressure inhibits the water cycle and hence, rainfall.
High-level Omega anomaly across the Caribbean Basin and parts of the North Atlantic – April 1 to June 30, 2020. Positive values indicate sinking motion, which is bad for rainfall.

Relief from the drought weather is becoming uncertain. The forecast for July-September (JAS) is for a 45 percent chance of above normal rainfall. This means that rainfall required to bring us out of drought is unlikely.

Looking beyond JAS, my latest forecast calls for less than 40 percent chance of above normal rainfall for the rest of the year, the wet season – July to December. This means that near or below normal rainfall is more likely than drought busting rainfall.  

Considering the whole year, 2020 will most likely be drier than usual. My latest projection is for a 50 percent chance of below normal rainfall, 30 percent chance of the usual rainfall and 20 percent chance of the year getting more than usual rainfall.

How dry it is projected to be? At this time, Antigua’s most likely rainfall for 2020 is 1026 mm (40.4 mm) with a 70 percent confidence that it will fall in the range of 760 to 1349 mm (30 to 53 in). Normally, the island gets 1207 mm (47.5 in).

Projected rainfall for Antigua in inches. There is a 20% chance of it being above normal (A 20%), 30% chance of it being near normal (N 30%) and 50% chance of it being below normal (B 50%). Background pic courtesy Karen Corbin of the Humane Society.

The parched weather was not restricted to Antigua and Barbuda. Much of the rest of the region have been suffering the same fate. There are a few exceptions, most notably is Cuba.

May was a record dry month for Anguilla and St. Thomas. Parts of the Dominican Republic and Belize saw record low rainfall for April. Severe or worse droughts are being experienced in many islands, including Aruba, Barbados, Martinique and St. Lucia.

Rainfall anomaly across the Caribbean Basin – January 7 to July 4, 2020 based on CPC CMORPH

Large scale atmospheric and ocean conditions continue to trend in the direction that would usually cause relief across the Caribbean Basin, including Antigua and Barbuda. However, models continue to not be very enthusiastic about forecasting significant rainfall for much of the region.

The favourable conditions for rainfall for our area are: warmer than usual tropical North Atlantic and cooling of the central to eastern equatorial Pacific i.e. a developing La Nina. Once these two things happen together, we invariably get good rainfall. However, what we can’t predict beyond a week, could negate the positive conditions – Saharan Dust, the x-factor. If it does not let up, it will suppress rainfall and wipe out any optimism in the forecasts for drought-stopping rain.

From all that have been examined, the drought is unlikely to end for the foreseeable future and if it were to, it would only be temporary. This is not to say that we won’t see more rainfall in the second half of the year than the first. We will; however, it is unlikely to end the drought.

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2 responses

9 07 2020
kernacjohn

This is very bad news for an already dry country. It seems we may get some rain relief as I’ve noticed the approach of another Tropical wave that may move towards the north of the islands. But I’m no meteorologist. I just follow them since Hurricane Maria. Hope something good happens in this unpredictable year.

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9 07 2020
Dale C. S. Destin - 268Weather

Yes, there will be rain but what the article speaks to is the quantity required to put a dent or end the drought. The amount required is uncertain, if not unlikely for the foreseeable future. There will be further monthly updates to see how things are evolving. So, the news could be different the next time around. Thanks for your feedback!

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