Easter to See More Hazardous Marine Weather Across Most of the Caribbean

26 03 2016

Dale C. S. Destin |

Fresh to strong gusty winds are causing hazardous seas across most of the Caribbean. This is expected to continue beyond Easter Monday (March 28).

Credit UCAR

Hazardous seas; Credit UCAR

Based on observations from met. offices and weather buoys, the winds were in the range of 15 to 22 knots (17-25 mph) with gusts in excess of 32 knots (37 mph).

In some areas, the winds were much stronger. At the Norman Manley International Airport, Jamaica, peak sustained winds of 26 knots (30 mph) were measured. No doubt parts of that island had gusts in excess of 34 knots (39 mph) – the equivalent to gale force or tropical storm force winds.

Weather report

Weather report from Norman Manley Int’l Airport – Mar 25, 2016, 2 pm local time

Winds were strongest across the Caribbean Sea, south of Jamaica. Today, Buoy 42058 measured winds in the range of 21 to 25 knots (24-29 mph) with gusts reaching 32 knots (37 mph).

Buoy data show the Caribbean Sea, especially south of Jamaica, is basically impassable by boat due to tremendously hazardous seas reaching as high as 4 metres (13 feet). Across the waters Eastern Caribbean, seas are near 2.5 metres (8 feet) and building.

Buoy data for March 25, 2016

Buoy data, seas for Mar 22-26, 2016 GMT/UTC

Buoy Data

Buoy data, wind speed Mar 22-26, 2016 GMT/UTC

The strong winds are in response to the high pressure gradient across the region. Winds blow as a result of differential pressure. The greater this differential is i.e. higher the pressure gradient, the stronger the winds and vice versa.

Surface chart depicting high pressure gradient evident by the closeness of the isobars (black lines)

Surface chart depicting high pressure gradient evident by the closeness and high quantity of the isobars (black lines)

As the winds increase, the friction on the underlying sea surface results in building seas or wind-driven waves. The stronger the winds, the higher the wind-driven waves and vice versa.

A further increase in the pressure gradient is forecast over the next 24 hours. Hence, winds and seas are expected to get higher. Thus, marine conditions are expected to become even more treacherous tomorrow.

Seas could exceed 4.5 metres (15 feet) across the waters between Jamaica and Panama. Meanwhile seas and could exceed 2.7 metres (9 feet) mainly on the Atlantic (east) side of Barbuda, Antigua, Guadeloupe, Dominica and Martinique.

Forecast Seas

Forecast Seas (feet), valid 2 pm (1800 UTC), Sat, March 26, 2016

The winds could increase by another 2 to 5 knots (2-6 mph) with gusts in the upper 20s to lower 40s knots ( upper 20s to upper 40s mph).

Forecast Winds

Forecast Winds (knots), valid around 11 am (1500 UTC) Sat, Mar 26, 2016

Forecast Gusts

Forecast Gusts (knots), valid around 11 am Sat, Mar 26, 2016

Clearly, it goes without saying that mariners should not venture far from port and sea-bathers should be extremely careful. As a matter of fact, sea-bathers should avoid the beaches on the northern and eastern sides of the islands. For Hispaniola and Jamaica, beach-goers should also avoid the waters on the southern side of those islands.

The strong winds could also make some outdoor activities very uncomfortable to perform, if not outright dangerous. This is especially true of work at elevations. Please be guided accordingly.

The winds will start to subside on Sunday. However, seas will not return to safe levels until around Wednesday.

Cuba is the only Island being spared by the strong winds and hazardous seas.

We will keep you updated via our social media platform, which includes twitter, facebook, wordpress, instagram, tumblr, and google+. You are invited to follow for all things weather and climate.

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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.





Needed Showers but Unwelcome Hazardous Seas for Much of the Caribbean

7 03 2016

Dale C. S. Destin |

A cold front is sweeping the Caribbean, bringing much-needed showers but unwelcome strong winds and hazardous seas.

Rainfall

Already, more than an inch of rain has fallen in parts of Cuba and Hispaniola over the past 72 hours. Meanwhile, winds have reached near 20 knots (23 mph) with stronger gusts across Cuba. Seas are near 3 m (10 ft.) and rising, mainly across the northern waters of the Bahamas.

The front is expected to reach Trinidad by around Thursday/Friday, which is very unusual for such a system to go so far south into the Caribbean.

As it moves across the region, showers will spread to the Virgin Islands today; the Leeward Islands late Tuesday/Wednesday; the Windward Islands and Barbados Wednesday/Thursday and Trinidad and Tobago Thursday/Friday.

Most of these islands will likely see rainfall totals in the range of 10-40 mm (0.40-1.60 in). At least minor inland flooding is possible across some islands.

FcastRain

Forecast 5-Day Rainfall Total for the Period March 7-11, 2016

Strong winds and rough seas will reach the various islands within 24 hours after the arrival of the front and continuing for up to 120 hours after the front passes. Thus, by Friday, most of the waters of the Caribbean will be having hazardous seas and will require the requisite warnings for mariners and sea bathers. Seas could peak near 3.5 m (12 ft.) across some areas.

Seas.png

Most areas will see sustained winds in excess of 20 knots (23 mph) with gusts across a few islands reaching gale force strength of near 40 knots (46 mph). Higher elevations can expect higher speeds.

WindGusts.png

With the combination of strong winds, sea swells and wind-driven waves, flooding of low-lying coastal areas due to large breaking waves is possible. Damage to coastlines can also be expected.

The strong winds could also render some routine outdoor activities uncomfortable if not hazardous.

We will continue to follow the progress of this system and keep you posted. Meanwhile, pay attentions forecast coming from your local meteorological office for information specific to you location.





The Latest Round of Seasonal Forecasts for Antigua – Mar to Aug 2016

3 03 2016

Dale C. S. Destin |

Our latest round of seasonal forecasts for Antigua is indicating that the current record longest drought will likely continue into the second half of the year. Both the spring and summer rainfall forecasts are calling for below to near normal rainfall.

SeasonalOutlook_Mar-Aug2016.png

The previous round of forecasts had indicated a high chance of the drought easing to slight levels or ending around the middle of the year. However, the latest round of forecasts is backing away from the optimism of significant showers over the period May-July.

Notwithstanding our forecasts for the upcoming seasons, the prospects for drought busting rainfall is still possible. A number of the global models are forecasting above normal rainfall for the mentioned seasons. However, our downscaled forecasts, which we believe have better skill for our region, are predicting drier than normal weather will persist.

Our drought outlook is also in support of the drought continuing beyond the middle of the year. The periods December 2015-May 2016, October 2015 to June 2016 and September 2015 to August 2016 are projected to see moderate to major rainfall deficits.

Temperatures for the upcoming six months are generally expected to be above normal. Hence, this spring and summer are anticipated to be warmer than normal. This could further exacerbate the scarcity of water.

The next round of forecasts, which will cover April to September 2016, will be available by April 3. Hopefully, we will have better news then. All of our outlooks can be found here








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