HOW HURRICANES ARE FORMED
Tropical cyclones or hurricanes usually form between 9°N and 30°N latitude in the Atlantic Basin comprising the North Atlantic Ocean, Caribbean Sea and the Gulf of Mexico. Many of them start as seedlings coming off the west coast of Africa. They form mostly from June through November, the recognised hurricane season.
Hurricanes need certain conditions to form. Firstly, there must be low air pressure, which would normally come from belts of low pressure within the trade winds system. A disturbance forms in the atmosphere, developing into an area of low atmospheric pressure. Winds begin to move into the centre of the storm seedling from surrounding areas of higher air pressure.
Secondly, warm temperatures are necessary to fuel or power the hurricane. The warm ocean waters of the tropics feed warmth and moisture into the developing storm, providing energy that causes the warm air in the centre to rise faster. Before a hurricane is able to develop, the ocean waters must have a surface temperature of at least 80°F (26.5 Celsius) down to at least 150 feet (50 metres), scientists estimate. This explains the tendency of hurricanes to begin near the equator.
Thirdly, there must be moist ocean air. As a storm system develops, moisture continues to evaporate from the ocean surface. This moisture condenses as it rises high in the atmosphere, creating thunderstorms.
Finally, there must be winds converging or coming together from different directions. Winds swirl around the eye, the calm centre of the hurricane. The eye has a diameter of about twenty miles across and has very few winds or clouds. Surrounding the eye are storm clouds within which the heaviest rains and strongest winds occur. Wind speeds are kept up by the differences in horizontal pressure between the eye and outer regions of the storm.
A hurricane goes through various stages as it develops. 1. It starts as a tropical wave, a west/north westward-moving area of low air pressure. 2. As the warm, moist air over the ocean rises in the low air pressure area, cold air from above replaces it. This produces a tropical disturbance marked by strong winds, heavy rain and thunderclouds. 3. As the air pressure drops and there are sustained winds up to 38 miles per hour, it is called a tropical depression. 4. When the winds have sustained speeds from 39 to 73 miles per hour, it is called a tropical storm (at this point storms are given names). 5. The storm becomes a hurricane when there are sustained winds of over 73 miles per hour. 6. Finally, when a hurricane travels over land or cold water, its energy source (warm water) is gone and the storm weakens and eventually dies. However, the moisture picked up while offshore can produce heavy rains that may cause severe flooding.
THE NORMAL ROUTE OF HURRICANES
Hurricanes leave the west coast of Africa and generally travel in a north-westerly direction. This explains why some Caribbean territories , in particular those in the southern region such as Trinidad, Tobago, Grenada, Guyana, Surinam, Aruba, Bonaire and Curacao are hardly affected by hurricanes.
(Trinidad & Tobago is situated between 10.2° and 11.12° N latitude and 60.3°and 61.56° Wlongitude.) On the other hand, this trajectory means that most of the Caribbean (i.e. those not in the southern region) are exposed to hurricanes. At times the drift of a hurricane is more sharply north-westerly (almost north) and travels over warm waters unhindered by land. It picks up intensity and may end up in North America as a powerful hurricane (category 4 or 5).
DEVIATION FROM THE NORMAL ROUTE
While most hurricanes move in a north-westerly direction, there are times when they move in a more westerly trajectory with little movement to the north. Should this movement persist, the hurricane would pose a threat to the southern Caribbean. Such a trajectory is what caused Hurricane Flora to cause much damage to Tobago in 1963 and Hurricane Ivan to devastate Grenada in 2005. Tropical storm Bret in 1993 slipped between Trinidad and Tobago but kept its westerly direction and hit southern Nicaragua with 45 mph (72 km/h) winds resulting in heavy damage and 184 people being killed . Because of the infrequency of this deviation, territories in the southern Caribbean are often ill-prepared for a hurricane reaching them.
HISTORY OF HURRICANES AFFECTING TRINIDAD & TOBAGO
During the period 1850 to 2000 some twenty-six storms affected Trinidad and Tobago, six of which were hurricanes. In 1933 a tropical storm with an estimated speed of 120km/h struck the south western part of Trinidad in the region of Cedros, causing the deaths of 13 persons and substantial property damage as well. Hurricane Flora struck Tobago on September 30, 1963 with an estimated wind speed of 195km/h causing destruction or damage to about 5750 houses and the deaths of 18 persons in the island. On August 14, 1974 tropical storm Alma made landfall in Trinidad with a wind speed of about 75km/h causing some damage and one death.
Other tropical storms affected the islands albeit to a lesser degree in more recent times. Some of these caused substantial damage due to the accompanying heavy rainfall causing storm surges, flooding and landslides. Arthur and Fran struck in 1990, Bret in 1993, Hurricane Iris in 1995, Hurricane Lenny in 1995 , Hurricane Debby and tropical storm Joyce in 2000. The storm surge caused by Hurricane Lenny in November of 1995 affected almost all the islands of the Eastern Caribbean damaging boats, buildings and infrastructure. In Trinidad the north coast was said to be the worst in 50 years.
Hurricane Debby passed through the Northern Leewards on the morning of the 22nd August 2000. After its passage a feeder band developed over Trinidad and Tobago and flooding resulted in the Barrackpore area.
Ivan reached hurricane strength on September 5, 1,150 miles (1,850 km) to the east of that day, while at 10.6° N latitude, it unexpectedly underwent rapid strengthening, reaching Category 4 intensity by that evening. It was the strongest storm to have ever been known to intensify that far south. Ivan weakened slightly while continuing westward, and struck Grenada on September 7, 2004. The hurricane destroyed 90% of Grenada’s structures and devastated the island’s economy, and was responsible for some 39 deaths in the island. Tobago reported some damage and one death.
ABILITY OF STRUCTURES TO WITHSTAND HURRICANES
The major loss from hurricanes occurs when roofs are damaged or blown off causing substantial damage to the inside of houses and their contents. Many houses in Trinidad and Tobago are simply not adequately protected against hurricane-force winds. Little use is made of protective devices such as hurricane ties or straps. Very few houses are equipped with window shutters. It would appear that many houses are/were not designed or built with hurricanes in mind. The substantial damage to structures in the Caribbean from hurricanes should be a wake-up call to persons in Trinidad and Tobago to pay more attention to the ability of structures to withstand hurricanes.
INSURANCE COVER AGAINST HURRICANE DAMAGE
Most household comprehensive insurance policies cover loss or damage by hurricane and flood caused or occasioned by hurricane. An excess or deductible applies. Commercial fire and special perils policies would also cover the risk provided that hurricane is a named peril. It should be pointed out that if flood is included as a peril but hurricane is not, then flood caused by a hurricane would not be covered. It is important to include both hurricane and flood to ensure that there are no gaps in the cover. A property all risks policy would normally include both perils. The deductible for hurricane and flood under a commercial property policy is usually 2% of the sum insured on each item per location.