All Weather News

What Prompts a Hurricane Warning?

7 Oct 2017, 9:07 am

Simply heading over to the National Hurricane Center website you can find this definition:

Hurricane Warning:  An announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds.

Hurricane Conditions

Right off the bat it gets confusing. What on earth are hurricane conditions?

The definition knows it’s confusing, so in parenthesis is a definition of hurricane conditions. Sustained winds of 74 miles per hour or higher.
But what constitutes a sustained wind?

According to the National Weather Service, a sustained wind is average wind speed 10 meters (33 feet) above the ground over a 1 minute time period.
However, the World Meteorological Organization defines sustained winds as the average speed 10 meters off the ground over a 10 minute time period.

For our warnings, we go with the NWS and the 1 minute criteria.

Timing

Warnings are issued 36 hours in advance of tropical-storm-force winds.
As the definition states, this is simply to help with preparation before conditions hinder anything.

This relatively short time period means that once a warning is issued, the time to act is now!

Tropical Storm Warning

Tropical Storm Warning:  An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are expected somewhere within the specified coastal area within 36 hours. 

At first glance, a tropical storm warning is weirdly close to a hurricane warning. But there is a difference.

Though both warnings are issued 36 hours in advance of tropical-storm-force winds, a tropical storm warning stops there. Meaning the maximum sustained winds are not expected to exceed 73 mph.

This issuance is similar simply due to the fact that the tropical-storm-force winds reach the criteria of wind speeds that hurricane preparedness becomes difficult.

Watch

The simple difference between the watches and warnings issued by the National Hurricane Center is a mere 12 hours.
A watch is issued 48 hours in advance of tropical-storm-force winds.

For WeatherNation — Meteorologist Jeremy LaGoo

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