Tropical Storm and Hurricane Formation

As the summer approaches, tropical storms become more likely to develop. The most critical factor in hurricane formation is the temperature of the ocean. Once it reaches about 80F, conditions become very favorable for tropical storm development.

Warm ocean waters store copious amounts of energy. As the air moves over the warm water, it becomes very humid. We can easily observe what happens to such air masses during hot summer days. The warm, humid air traveling over land heats up even more. When its temperature increases, it is also getting lighter and is slowly lifted up, sometimes several miles into the sky.

The dew point of that air mass is typically in the 70s and as soon as its temperature drops below its dew point, the cooled water vapor forms rain. It actually is quite a complicated process, but the end result of it is usually heavy rain, often accompanied by thunder. Sometimes the temperature of one of the layers of air above us may be below freezing. Droplets of rain falling through such a cold layer of air may freeze, forming hail.

Summer storms forming over land are usually slow moving, dropping a few inches of rain in one location and leaving a nearby area dry. These storms are very welcome however, because they keep places like Florida green and semitropical in nature.

The other type of a summer storm is not always so welcome, as it sometimes brings more violent weather. Those are the storms that start as a little disturbance somewhere far away, sometimes in the Caribbean Sea, another time near the coast of Africa. As they travel with the prevailing winds, they tend to become stronger and better organized. Some of them become so big and powerful that they are categorized as a hurricane.

There are five categories of hurricanes, depending on their sustained winds. Even the weakest of them, category one, can be dangerous and cause a lot of damage. Category five hurricanes can be extremely deadly, luckily they are quite rare. To reach that strength conditions must be perfect, usually a hurricane can't stay perfectly organized for more than a few hours.

Hurricanes happen every year in the warm Atlantic waters surrounding southeastern United States. In the early part of the hurricane season (June - August) they are usually born in the Carribean, later they originate somewhere near Africa. Those originating in the Carribean Sea don't have much time to develop much strength and become mostly rainmakers, causing floods and mudslides in the mountainous countries of Central America.

Later in the season, every few days, an atmospheric disturbance leaves the western coast of Africa and moves over the Atlantic ocean. The prevailing winds carry it westwards, over the vast ocean, where it gets a chance to collect water vapor from the warm ocean. If the conditions are favorable, the disturbance gets better organized and then its shape, rotation, and wind speed can be observed by weather satellites.

As hurricanes approach the Antilles, the water temperature increases and it's here where the biggest gain in their strength occurs. In most cases their path turns slowly to the north and then northeast, but sometimes their paths are more complicated and difficult to predict.

Although the hurricane season runs from June 1st to November 30th, most hurricanes form in August and September. Some of them make landing on a beach, anywhere from Texas to North Carolina. Once they land, they lose a lot of their punch as they move inland.

They may cause a lot of wind damage, but often the biggest threat to people and infrastructure, is the accompanying flooding. The wind pushes water higher and higher, which, combined with plentiful precipitation, raises water levels in the ocean and in rivers. The longer the storm lingers over an area prone to flooding, the more severe the situation gets.

The National Hurricane Forecast Center, located in Miami, has weather specialists who can predict the path and strength of tropical storms.

In the hurricane season they monitor weather patterns and whenever a depression appears and hurricane formation is imminent, they start issuing advisories every six hours until the storm runs its course.

Public advisories are issued more often when the storm threatens land. Hurricane formation watches and warnings let people pay attention and take action if needed.