If you are unable to avoid remaining afloat in the Caribbean during hurricane season you need to think through the possible worst-case scenarios and prepare accordingly. Yachtsmen and women who have experienced the full force of a hurricane have reported finding it difficult to even breathe effectively on deck, let alone stand up. Such conditions should not be taken lightly.
Forecasting of tropical storms is now so good that you should be aware of the possibility of a storm at least 2–3 days in advance. Be aware that the transition from ‘tropical wave’ to ‘tropical depression’ to ‘named storm’ to ‘hurricane’ may be very rapid.
Over recent years, the frequency and intensity of hurricanes has increased. Early and late season storms and less predictable storm tracks are further issues. NOAA has now extended the official hurricane season from 1 June until 30 November. Early season storms generally affect the eastern Caribbean and late season storms affect the western Caribbean. However, this is a generalisation and there may always be anomalies.
The boundaries of tropical depressions and hurricanes also continue to expand. Twelve degrees north was, for many years, considered to be a safe latitude. However, more recently, both tropical storms and hurricanes have moved along that latitude. In addition, tropical storms (called ‘extra tropical’) and even hurricanes have affected the east coast of Canada as far north as Nova Scotia. Many scientists see the Caribbean as being in an active part of a long-term cycle with tropical storms and hurricanes becoming more frequent, more intense and following trajectories previously unheard of.
by Denis Webster
Tropical weather systems are born from a large area of rising air along the equator where warm moist air rushes in from the northern and southern hemispheres. This is the area commonly called the doldrums or the Inter Tropical Convergence Zone (ITCZ). It is an area of thunderstorms, rain and no wind. The ITCZ is tracked on a daily basis in many bulletins and can be seen clearly on satellite pictures. It moves south in the dry season (the northern winter) to about approximately 10°S and back north to 10°N in the rainy season (the northern summer).
Air ascending from the ITCZ spreads out at high altitude and then begins to sink over an area of the North Atlantic around 30°N. This causes the semi-permanent feature called the Azores or Bermuda High. Clockwise circulation around this high helps to create the North Atlantic trade wind belt. The strength and direction of the trades varies from season to season and is dependent on the pressure gradient between the Azores High and the ITCZ. Colder, denser air in the northern winter creates a steeper gradient and stronger trade winds. Conversely, in the northern summer, the warmer air around the Azores High is less dense and the pressure gradient with the ITCZ is reduced, resulting in lighter winds. The following pressure gradients are an indication of wind speeds between 10° and 20°N:
The dry season in the tropical North Atlantic is during the northern winter and begins with the formation of the first winter storm over the North American continent. An area of deep, low pressure moves across the continent and heads east into the North Atlantic. Behind this low pressure, cold dense air pushes south, displacing warm air. The dividing line is a cold front. As the low pressure moves east across the Atlantic it will trail a cold front to its south and southwest, out over the warmer water. Cold fronts frequently extend to the Bahamas, part way into the Caribbean basin or, occasionally, all the way to the South American coast. The tracks of low pressure systems slowly migrate south during the dry season. Cold fronts in the Caribbean basin frequently stall, creating a strong pressure gradient and moderate to fresh north-east winds.
As spring arrives in North America, the ground begins to warm. Cold fronts extending into tropical areas become less intense and associated tropical winds become more moderate easterlies or south-easterlies. As the transition continues, troughs frequently establish themselves and remain in position for significant lengths of time. These are influenced by features in the upper atmosphere and may or may not appear as a feature on surface charts. These are frequent features of the Caribbean basin and are characterised by rain showers or thunderstorms.
In late May or early June, particularly off the coastline of Honduras and Belize, in the Gulf of Mexico and off the Florida coast, lows may form in association with upper level features. These may become tropical depressions or even early season hurricanes which move up the US East Coast and into the North Atlantic before dissipating.
The true rainy season arrives with the first appearance of tropical waves. These are travelling low pressure troughs which bring squalls, rain and thunderstorms and can develop into tropical depressions and hurricanes. Tropical waves first appear on charts and in bulletins around the end of May. They begin their march from Africa across the Atlantic in a uniform fashion, usually at a relatively constant speed. Also significant is the northern progression of the ITCZ which moves north from Brazil as far as the eastern Caribbean or Central America. The ITCZ is noted for its days of rain, thunderstorms and gusty winds in squalls.
As the rainy season progresses into October, tropical waves tend to be less frequent and intense, almost disappearing by mid November. In addition, the ITCZ starts to move south below 10°N, with only the occasional foray up into the Caribbean basin. In the western Caribbean, along the Central American coast, rain and thunderstorms often persist into December. Late season hurricanes may develop in the western Caribbean in late October and November, moving inland or up into the Gulf of Mexico.
As precipitation becomes less frequent and the air becomes drier, winds will begin to increase in speed and the wind direction will become more easterly. Typical winds would be easterly at 15 knots.
by Denis Webster
1 North Atlantic hurricanes begin their lives as a tropical wave, although many tropical waves do not develop into hurricanes. During the hurricane season it is a good idea to monitor and track any tropical waves. These usually begin to form from early June and move at various speeds.
2 A tropical wave may be associated with an ‘area of disturbed weather’. When they occur, these areas are reported in tropical weather bulletins. Such an area of disturbed weather may move, dissipate, or develop, depending upon weather conditions. When there is strong vertical wind shear at upper levels, the possibility of storm development decreases because stronger winds at higher altitudes tend to shear the tops of clouds and limit the vertical motion of air. When monitoring tropical waves, the first indication of development will be the inclusion of the word ‘rotation’ in a bulletin description. Circulation of air is not necessarily a concern unless it is associated with other factors. Hurricanes may develop where circulation of air occurs together with abundant moisture and no vertical wind shear. Storm bulletins give assessments of areas where development is expected and contain terms such as ‘wind conditions are favourable for storm development’.
3 When conditions are favourable and observations confirm development, an advisory is issued for a tropical depression. Tropical depressions are the first stage of hurricane development where wind speeds are measured as 33 knots or less. Each tropical depression receives a number (for example TD1) and the location, development and forecast track is reported in bulletins. Some tropical depressions develop very rapidly and they should be monitored very closely.
4 When further development of a tropical depression occurs, wind speeds increase above 34 knots and air rotation becomes evident with a spiraling cloud formation. A central ‘eye’ may be observed. At this stage a tropical storm advisory is issued. Bulletins contain the forecast development and track for the following five days. Tropical storm watches or warnings will be issued for all coastal areas expected to be affected. Storm watches are valid for 36 hours, storm warnings for 24 hours. Your hurricane plans for you and your boat should be in place and executed by this stage.
5 Tropical storms become hurricanes when central wind speeds reach 64 knots. Bulletins and updates are issued at regular intervals and coastal areas will have watches and warnings posted. Hurricane trajectories (tracks) are predicted for a five-day period and include a ‘cone of uncertainty’. Although forecast models and forecaster skills have improved dramatically over the past 15 to 20 years, there are factors which influence the development and track of storms and cannot be accounted for in the models. If you and your vessel are within this ‘cone’, you should be prepared for the worst.
6 Hurricanes can sometimes degenerate back into a tropical wave. This normally occurs if upper level wind shear is too strong. The storm can later re-intensify if the upper level shear abates.
7 Tropical storms and hurricanes are always accompanied by heavy rain and storm surges. Warnings may remain in effect for high water or high waves after the wind speeds have diminished below 64 knots and in areas peripheral to the path of the storm.
by John Franklin (with additional information by Richard Woods)
There are many traditional storm shelters and ‘hurricane holes’ in the Caribbean. However, the increasing number of boats has rendered many of these shelters so overcrowded that finding a safe position becomes impossible. Much of the damage incurred in anchorages is due to the ‘loose cannon’ effect when some boats drag, out of control, often causing other boats to drag or break free from their moorings. In his Cruising Guides, Don Street Jnr has advocated putting to sea to ride out a hurricane rather than being trapped with ‘bareboat bombs’ cannoning around. But this would seem extreme guidance if your own survival is valued more than the survival of your boat. However much your boat has become your life, if a hurricane tracks over you the safest place to be is on the shore.
If you are forced into finding a storm shelter it is important to try to predict where the storm will pass in relation to your planned location and what the likely wind directions will be. This will help you to decide where to anchor and in which directions to lay your anchors.
The following are some of the ‘traditional’ storm shelters. How safe they really are will depend on where the storm centre passes and how crowded they become with other boats.
Grenada: Port Egmont
This is the most protected harbour on the south coat of Grenada. Almost landlocked, it is surrounded by hills on all sides. However, during Hurricane Ivan, which occurred in 2004, the danger came from overcrowding and loose boats.
Many yachtsmen spend the hurricane season on the south coast of Grenada. At the first sign of an approaching tropical storm they sail southwards to Trinidad or Venezuela to be almost certain of escaping the direct path and the worst effects.
St Lucia: Marigot Bay
Marigot Bay is sheltered in all weathers, even in a hurricane, and has been a traditional shelter since the time of Nelson. However, it is now so crowded even in normal circumstances that it is useless as a storm shelter.
Martinique: Le Marin
You would probably be safe if you could pull your boat into the mangroves on the south side but otherwise there are just too many boats in Le Marin for it to be safe in a hurricane.
Martinique: Cohe de Lamentin
Draft in the approach channel is 6ft but otherwise it is described as an excellent hurricane shelter. However, due to the density of boats in Martinique, overcrowding would certainly be a problem.
Guadeloupe: Point a Pitre
There appears to be an excellent storm shelter in the Port du Plaisance de Bas du Fort just inside the harbour entrance. However, in practice overcrowding would be a problem.
Guadeloupe: Riviere Salee
The Riviere Salee has been described as ‘not so much a river as a saltwater mangrove channel’. It is shallow and perfectly sheltered but access is controlled by two bridges at the southern end opening at 0500 Monday to Saturday.
Antigua: English Harbour
This has been a traditional hurricane shelter since the time of Nelson. The safest place is in the mangroves on the north side of Ordnance Bay but overcrowding would certainly be a problem.
Antigua: Jolly Harbour
This is a private resort marina on the west coast of the island. It is not a traditional storm shelter but is very protected.
St Martin
Good shelter may be found tucked up into the mangroves. Again, it is the volume of yachts crowding into any particular anchorage which can cause problems here.
St John: Coral Bay
There are a couple of hurricane holes at the extreme northern end of Coral Bay with good shelter except from the south. Technically this is within the Virgin Islands Coral Reef National Monument and no anchoring is allowed. How this would apply during hurricane conditions is uncertain.
St Thomas: The Lagoon, Benner Bay
Draft is limited to 5ft. It is open to the east so doesn’t provide very good shelter, but it is the best in St Thomas.
Culebra: Ensenada Honda
This is a huge, enclosed harbour with excellent holding but not a lot of protection from the wind. The best location is to the south-west of Cayo Pirata.
Vieques: Ensenada Honda
This is another large, deserted harbour offering complete shelter. The most sheltered location is in the extreme eastern end where it is possible to pull into the mangroves and into the mud.
Vieques: Puerto Ferro
The entrance is shallow (6–7ft) and narrow but once inside it is a small but perfect storm shelter.
Puerto Rico: Bahia de Jobos
On the northern side of Bahia de Jobos are many muddy creeks among the mangroves making it a perfect hurricane shelter. The marina at Fajardo is the largest marina in the Caribbean and has a good reputation for preparing boats effectively against hurricane damage. It is approved of by marine insurers.
Puerto Rico: Salinas
Salinas, just west of Bahia de Jobos, is very sheltered from all directions and offers excellent holding. The best shelter is on the east side among the mangroves.
Dominican Republic: Luperon
Luperon is perhaps the most famous hurricane hole in the Caribbean. It offers all-round protection, shallow water, good holding and mangroves on all sides. In these respects it is a perfect hurricane shelter. However, because of its narrow entrance, the water can become very stagnant and polluted.