Tropical Storm Earl: The Evolution of a Hurricane
August 30, 2010
On August 24th, Tropical Depression Seven reached sustained winds of 40 mph, prompting the National Hurricane Center to designate it a tropical storm. Thus, Earl became the fifth named storm of the 2010 Atlantic hurricane season. Out in the Pacific, the weakening Frank is the third hurricane of their season.
Hurricanes begin as tropical disturbances over the ocean in areas where moist air is rising and cooling. The cooling effect forms tiny water droplets which eventually combine to make clouds. Under normal conditions, the clouds reach a saturation point, causing thunderstorms which release the water.
In a case like Earl’s, the heat energy and moisture rising into the atmosphere are so intense that multiple Cumulonimbus clouds form faster than storms can release the water. As the warm air continues to rise and cool, winds slowly begin to swirl around the low pressure near the surface of the ocean. When swirling winds become observable, a tropical disturbance is upgraded to a tropical depression.
Tropical Storm Earl is a classic case of the evolution of a hurricane. As the storm began its trek across the Atlantic, it continued to pick up moisture and wind speed. When a tropical depression reaches sustained winds of 39 mph or more, as Earl did a few days ago, the storm is designated a tropical storm.
Earl’s wind speeds have remained steady at 45 mph for the last day or so, keeping him at the Tropical Storm designation. But if he follows a typical progression of gathering strength over the warm Caribbean waters, Earl could become a category 1 hurricane with sustained winds of at least 74 mph.
When a storm reaches hurricane status, meteorologists can identify what’s known as the “eye” of the storm. This is the area where the low pressure is concentrated. The smaller eye, the greater he wind speed. Earl’s eye is still relatively large. But if the storm system tightens up there will be a noticeably smaller eye with higher wind speeds.
The life of a hurricane can range anywhere between three and fourteen days. Earl is in his third day as of this writing, but it’s still too early to tell what will happen. If he turns north before reaching Bermuda, Earl will probably fall apart with little consequence. But if the storm tracks more to the west, it still has the potential to impact the southern U.S. coast.
