As the remnants of Hurricane Ian begin to fade, it brings questions of what’s to come for the rest of hurricane season. Though not the first hurricane of the year, with Hurricane Fiona bringing “significant damage to Atlantic Canada after ravaging Puerto Rico and the Dominican Republic”, Hurricane Ian is far from the last. The National Hurricane Center, which maintains “a continuous watch on tropical cyclones and areas of disturbed weather within the North Atlantic and eastern North Pacific basins”, currently has its eye on the tropics, where two systems have the potential to become the next tropical storm. The first system is a tropical wave that’s “located several hundred miles east of the Caribbean Sea” and “is traveling west between 15 and 20 mph”. The second system is “an elongated area of low pressure located a few hundred miles south-southwest of the Cabo Verde Islands” that has a higher chance to become a tropical storm.
But what is a tropical storm, and how does it differ from a hurricane?
First, “an area of low atmospheric pressure” forms and is known as a tropical depression, which is the precursor to a tropical storm. A tropical depression is defined by a maximum sustained wind speed of 38 mph (33 knots) or less. Only a 1 mph difference separates a tropical depression from a tropical storm; as soon as the tropical depression’s wind speed rises to 39 mph, it becomes a tropical storm. It is from here that a hurricane can easily form. Philip Klotzbach, a hurricane researcher at Colorado State University, says that there are two main factors that help determine hurricane season: wind and water temperature. Hurricanes need warm water to thrive and “surface water temperatures about 80 degrees Fahrenheit are prime hurricane fuel”.
Klotzbach explains that the less wind there is, the better that is for the hurricane: “The [wind shear] is the change in wind direction and speed with height in the atmosphere. Too much shear tears apart hurricanes”.
As a tropical storm’s winds pick up and grow, they become a hurricane—defined by winds of “74 mph (64 knots) or higher”. They easily shift to major hurricane status once their winds reach a sustained “111 mph (96 knots) or higher”.
For now, the National Hurricane Center is keeping a close eye on the two evolving cyclones.
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