Thursday, August 18, 2011

Good info on hurricane season and Antigua

Writen for Antigua's Enjoy magazine:

Few things create as much emotion and nervous tension during the summer months as the massive storms we call hurricanes. The word originated from either the ancient Mayan storm god, "Hurakan", or from the Carib word "huracn" meaning god of evil. Either way this word has been scaring people for possibly thousands of years. In recent times science has given us a better understanding of how they form and most importantly how to forecast their strength and track as they come across from Africa. "Hurricane Season" is between June and November with the middle of August to the Middle of September being most active.

A hurricane is a low pressure storm with winds of above 74 mph close to the low pressure center. Hurricanes are classed in categories from 1 to 5 with a cat 1 storm having sustained winds of above 74 mph and a cat 5 having sustained winds of above 155 mph. There are so many variables coming together which scientists are still leaning about that create the necessary conditions for a hurricane to form. All summer long small rain storms make the journey from the West Coast of Africa traveling due west across to the Caribbean.They can give us the occasional rainy day, but for the most part the summer has lovely weather. These "tropical waves" pass through about once a week, and some bring little or no rain at all with just a tiny surge in trade winds. Some have a low enough pressure and strong enough winds and associated rain storms or squalls that they become upgraded to "tropical depressions". Tropical Depressions have winds between 25 and 38 mph. With the right conditions they can strengthen into a "Tropical Storm" and this named system is usually a tighter group of squalls and thunderstorms that are spinning. Tropical Storms must have a sustained wind speed of above 39 mph near the center. Again if conditions are right they can strengthen into a Hurricane. Remember that this would mean there's sustained winds of above 74 mph.


I keep mentioning that ideal conditions are needed and while some are extremely complex, others are not so technical. Almost all of these storms form over the sea, and the sea surface temperature must be above 80 degrees. These warm waters mean there is enough water being evaporated into the atmosphere that thunderstorms are kept alive with the associated energy. Another factor that needed for a storm to form or remain powerful is a light jet stream. Strong jet stream or upper level winds mean the associated wind shear will attack the tops of the thunderstorms breaking them apart. When the jet stream isn't strong and the water temperatures are high, the weather people start paying attention. There are many more variables that need to line up in order for a simple Tropical Wave to develop on its way along the chain towards a hurricane, and because of this the Atlantic only sees about 6 hurricanes a year.


Six sounds bad enough but remember that many hurricanes start and finish in the Atlantic without ever making landfall. Several do make landfall but hurricane force winds usually don't go further than 50 miles from the center which means that if a hurricane goes over Dominica 100 miles to our South it may not give us any hurricane conditions at all. In fact the chances of being hit are so low that records show that in the past 60 years Antigua has had only 6 direct hits. One other thing to remember is that a hurricane is usually averaging about 12mph as it tracks north west in the vicinity of the Caribbean which means that even if it does hit an island the conditions are only felt for a day or less on average. Six days of hurricane conditions in 60 years are not that bad, but you never know which year will be the one when that storm comes your way. The rule of thumb is that during hurricane season you must prepare for the worst and hope for the best. For reports and forecasts from people on the ground here in Antigua visit or search for "antigua weather" on facebook.

marina HDR