Potentially Drought-Busting Rainfall This Week

17 04 2016

Dale C. S. Destin |

A trough system could potentially cause drought-busting rainfall across Antigua and the rest of northeast Caribbean during this week. The system could dump up to 150 mm (6.0 in) of rain on the Leeward Islands and the Virgin Islands over the next six days, starting  tonight – Sunday night.

GFS forecast rainfall total for the period 2 pm, April 16 to 2 pm, April 23, 2016

GFS forecast rainfall total for the period 2 pm, April 15 to 2 pm, April 22, 2016

We could get drought-busting rainfall i.e. sufficient rainfall to bring a welcome end to the meteorological and agricultural droughts taking place across Antigua and nearby islands. However, it is unclear as to whether it will be enough to replenish surface catchments and aquifers to end the more serious socioeconomic droughts, which are costing the islands dearly. Nevertheless, the rainfall is likely to put a big dent in this drought also.

Given the potential amount of rainfall that could occur, at least moderate flooding is possible of low-lying and flood-prone areas across the northeast Caribbean, including Antigua and Barbuda. Thus, the requisite watches and warnings may be required for portions of this week.

GFS probability forecast of total rainfall for April 17-23 exceeding 75 mm (3 in)

GFS probability forecast of total rainfall for April 15-22 exceeding 75 mm (3 in)

GFS probability forecast of total rainfall for April 17-23 exceeding 150 mm (6 in)

GFS probability forecast of total rainfall for April 15-22 exceeding 150 mm (6 in)

A number of weather models, including two of the best – the Integrated Forecast System (IFS) and the Global Forecasting System (GFS), are showing very high probabilities of this week being very wet, especially relative to April. However, it is not a 100% certain. Further, the eventual rainfall total is quite uncertain.

Most for the precipitation is likely to be in the form of rain from layer-type clouds as opposed to the showers from convective-type clouds. Notwithstanding, thunderstorms are possible every day from Monday to Friday. The sun could also be hidden by thick clouds for most of the week.

The normal rainfall for April is 85.6 mm (3.37 in). On record dating back to 1928, April 1981 is the wettest with 245.4 mm (9.66 in), and the driest is April 1944 with 5.8 mm (0.23 in). At the V. C. Bird International Airport, the normal rainfall for April 17-22 is 12.7 mm (0.50 in). The wettest was 1992 with 112.0 mm (4.41 in) and the driest of 0.0 mm occurred on at least six occasions since 1961.

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Flying Start to November 2014 Rainfall for Antigua and Barbuda

12 11 2014

By Dale C. S. Destin |

Although we are in the midst of a drought, we have just witnessed one of the wettest starts to November, for many parts of Antigua and Barbuda. The rainfall total for the month got off to a flying start from day 1 with a tropical wave dumping 17.4 mm (0.69”) and it has continued almost unabated up to present. Last weekend, we saw basically a deluge which prompted the issuance of flood watches and warnings. According to radar data, up to 142 mm (5.6”) of rain fell across Antigua and up to 280 mm (11.0”) across Barbuda, as skies opened up in response to a powerful, upper level low pressure system.

Radar Rainfall Totals for Nov 7

Rainfall Totals for Nov 7, 2014

Rainfall Total for Nov 8, 2014

Rainfall Total for Nov 8, 2014

Last weekend’s wet weather was not confined to the northeast Caribbean. Heavy downpours were also experienced further south with in excess of 140 mm (5.5”) measured as far south as St. Lucia, where there were reports of land slides.

72hrs_ending_15Z_Nov10Figures up to November 10 show there has been 113.5 mm (4.47”) of rain at the Met Office located at the V. C. Bird International Airport. This is well above normal for this period and the fifth wettest on record dating back to 1967. It is also the second wettest such period since 1986. On average, the Airport gets 135.1 mm (5.32”) of rainfall during November; thus, the rainfall accumulation for the first 10 days is less than 22 mm away from the average total for the whole month.

Nov1-10_Rain_GraphicIn 48 years, only four other November 1-10 periods, have been wetter: 2011, 1986, 1984 and 1974. The record wettest November 1-10 occurred in 1974, when a staggering 355.3 mm (14.0”) of rain fell.

The wet episode for November has had a quenching impact on the drought. However, it is not over; actually it is far from over. Although the drought has eased to slight levels, another 139.7 mm (5.5”) is needed to end it.

Will we get the needed amount of rainfall to end the drought? It is unclear as the climate is sending mixed signals as to what will happen for the rest of November and the next three months. The spike in rainfall seems to be partially due to warmer than normal North Atlantic sea surface temperatures, which are likely to persist. However, an El Nino is brewing, and if established, could suppress rainfall.

Of course, while these figures are interesting, they don’t tell us where the month will end up overall. On average at the Airport, the rest of November averages 94.6 mm (3.74”) of rainfall. In the past, this period has had as little as 5.6 mm (0.22’’) and as much as 578.3 mm (22.77”).

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