Most boaters residing on the Gulf and Atlantic coasts are aware of hurricanes and the destruction potential of these topical cyclones. Hurican is the Caribbean God of evil and the unpredictable, devastating nature of hurricanes belays its name sake. Sailors have historically understood the threat of hurricanes and knowledge of the tropical cyclones is vital for marine safety. Not much can be done to manage the path of a hurricane, but sailors often have the ability to stay clear of the storms. Knowledge of the weather is essential to preserving marine safety.
Formation of Tropical Cyclones - An existing weather disturbance, warm water, moisture in the atmosphere, atmospheric instability, light winds aloft and the proper starting point are needed to form a tropical cyclone in the North Atlantic. 75% of tropical cyclones develop from the weather disturbances caused by the tropical easterly waves originating form the coast of Africa. Once maximum sustained winds exceed 63 knots or 118 kilometer per mile, tropical cyclones are classified as hurricanes. September has the highest average number of named topical storms at 3.6 each year.
Tropical Disturbances - These organized convection systems ranging from 100 to 300 miles in diameter originate in the topics or subtopics. They present a non-frontal migratory appearance and last for more than 24 hours.
Tropical Depressions - These weather systems present a closed surface circulation pattern and have maximum sustained surface wind speeds of less than 33 knots.
Tropical Storms - These tropical cyclones have a maximum sustained surface wind speed ranging
from 34 to 63 knots.
Subtropical Cyclones - These are low pressure systems that originate over subtropical waters and have a cold core. They do however display some features of tropical cyclone cloud structures. In the right conditions, these storms can evolve into tropical cyclones.
Hurricane Categories Storm intensity is classified with the Saffir-Simpson Hurricane Scale (SSHS) according the strength of the hurricane winds. A Category 1 hurricane has the lowest wind speeds and a Category 5 is the strongest. The seriousness of these categories is however qualified, a lower category hurricane can cause much more damage due to flooding or its approach to the coast compared to a higher category storm. Tropical storms can even cause major damage to property and life from coastal flooding.
SSHS Hurricane Definitions and Effects:
- Winds of 64 to 82 knots. Damage is limited to unanchored structures, trees, and coastal flooding. An example storm is Hurricane Earl for 1998
- Winds of 83 to 95 knots. Damage to roofs, doors and windows. Unanchored structures like mobile homes suffer considerable damage. Flooding damages coastal structures like piers and boats may break their moorings. An example storm is Huricane Georges of 1998
- Winds of 96 to 113 knots. There is some structural damage to small buildings and mobile homes are destroyed. Coastal flooding destroys smaller building and damages larger structures from floating debris. Flooding extends inward from the shoreline. An example storm is Hurricane Fran of 1996 and Katrina of 2005
- Winds of 114 to 135 knots. There is extensive damage to smaller residential structures with some structural failure of roofs. Beaches suffer extensive erosion and flooding extends well inland from the coast. An example storm is Hurricane Andrew of 1992
- Winds are over 135 knots. Many residential and commercial building suffer complete roof failures. Some smaller building are completely destroyed or blown over. Evacuation of residential areas may be a problem. An example storm is Hurricane Camille of 1969
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