On average, 12 tropical storms — six of which become hurricanes — form over the Atlantic Ocean, Caribbean Sea, or the Gulf of Mexico during the hurricane season, according to the National Weather Service.
In a typical two-year period, the U.S. coastline is struck by an average of three hurricanes, one of which is classified as a major hurricane with winds of 111 mph or greater. The storms can have winds ranging from 74 to over 157 mph that brings destruction from storm surge and torrential rains that have the ability to cause massive flooding.
When such storms approach land, the National Hurricane Center will issue either what is known as a “hurricane watch” or “hurricane warning” for affected communities. So what’s the difference between the two?
When “hurricane conditions” or sustained winds of 74 mph or higher are expected, forecasters will issue what’s known as a hurricane warning.
Hurricane warnings are issued 36 hours in advance of the anticipated onset of tropical-storm-force winds between 39 and 73 mph.
“A warning means that hurricane conditions are expected, whereas a watch means that conditions are possible,” the National Oceanic and Atmospheric Administration’s National Ocean Service (NOS) said.
Since hurricane preparedness activities become difficult once winds reach tropical storm force — which are sustained winds between 39 and 73 mph — hurricane warnings are issued 36 hours in advance of the anticipated onset of those winds to allow for “important” preparation.
“During a hurricane warning, complete storm preparations and immediately leave the threatened area if directed by local officials,” according to the NOS.
Hurricane warnings also can be in effect for other reasons besides wind
“The warning can remain in effect when dangerously high water or a combination of dangerously high water and waves continue, even though winds may be less than hurricane force,” the National Weather Service states.
A hurricane watch means that hurricane conditions — sustained winds of 74 mph or higher — are possible within the specified area. A hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds in an area.
“During a hurricane watch, prepare your home and review your plan for evacuation in case a hurricane or tropical storm warning is issued,” the NOS states. “Listen closely to instructions from local officials.”