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Hurricane Watches & Warnings

Isle of Palms Fire Chief Ann Graham, at left, and Isle of Palms police officer Thomas Molino...
Isle of Palms Fire Chief Ann Graham, at left, and Isle of Palms police officer Thomas Molino III raise a tropical storm warning flag over the Isle of Palms Connector shortly after Charleston County, S.C., went under a tropical storm warning due to Hurricane Florence Thursday, Sept. 13, 2018, in Isle of Palms, S.C. (AP Photo/Mic Smith)(Mic Smith | AP)
Updated: Jun. 7, 2021 at 5:58 AM CDT
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The National Hurricane Center issues alerts that relate specifically to tropical storms and hurricanes. It’s important to know what each alert means.

The alerts start with watches and are a signal to start preparing for severe tropical weather.

Tropical Storm Watch - Tropical storm conditions (sustained winds of 39 to 73 mph) are possible within the specified area within 48 hours.

Hurricane Watch - Hurricane conditions (sustained winds of 74 mph or greater) are possible within your area. Because it may not be safe to prepare for a hurricane once winds reach tropical storm force, The NHC issues hurricane watches 48 hours before it anticipates tropical storm-force winds.

Storm Surge Watch - There is a possibility of life-threatening inundation from rising water moving inland from the shoreline somewhere within the specified area, generally within 48 hours.

As the tropical system approaches land, forecasters will upgrade to warnings. When a tropical weather warning has been issued you need to activate your hurricane plan and get together your survival supplies or evacuate.

Tropical Storm Warning - Tropical storm conditions (sustained winds of 39 to 73 mph) are expected within your area within 36 hours.

Hurricane Warning - Hurricane conditions (sustained winds of 74 mph or greater) are expected somewhere within the specified area. NHC issues a hurricane warning 36 hours in advance of tropical storm-force winds to give you time to complete your preparations. All preparations should be complete. Evacuate immediately if so ordered.

Storm Surge Warning - There is a danger of life-threatening inundation from rising water moving inland from the shoreline somewhere within the specified area, generally within 36 hours. If you are under a storm surge warning, check for evacuation orders from your local officials.

Extreme Wind Warning - Extreme sustained winds of a major hurricane (115 mph or greater), usually associated with the eyewall, are expected to begin within an hour. Take immediate shelter in the interior portion of a well-built structure.

Whenever a tropical depression, tropical storm, or hurricane has formed in the Atlantic, the NOAA National Hurricane Center (NHC) issues tropical cyclone updates.(Source: NOAA National Hurricane Center)

Whenever a tropical cyclone (a tropical depression, tropical storm, or hurricane) or a subtropical storm has formed in the Atlantic, the NOAA National Hurricane Center (NHC) issues tropical cyclone updates at least every 6 hours at 5 am, 11 am, 5 pm, and 11 pm EDT.

When coastal tropical storm or hurricane watches or warnings are in effect, the NHC issues Tropical Cyclone Public advisories every 3 hours.

What do the red flags with black squares in the middle represent?

These flags are usually seen during the hurricane season, flying from places such as U.S. Coast Guard stations, and some marinas. The flags date back to the days before radio storm warnings when such flags were the only way to warn those aboard ships of storms. With the advent of radio, and the internet many of these types of flags are no longer in use.

One of the square flags warns mariners that a storm warning has been posted. A storm warning means winds between 48-63 knots (55-73 mph) are likely within 24 hours.

Two flags mean a hurricane warning is in effect for winds equal or greater than 64 knots (74 mph) are likely within 24 hours.

These flags are usually seen during the hurricane season, flying from places such as U.S. Coast...
These flags are usually seen during the hurricane season, flying from places such as U.S. Coast Guard stations, and some marinas. With the advent of radio, and the internet many of these types of flags are no longer in use.(Source: NOAA)

Pennants are also used to indicate additional marine advisories. One pennant indicates a small-craft advisory which alerts mariners that weather, potentially dangerous to small craft, is either occurring or is forecast. Dangerous conditions include rough seas and winds of 18-33 knots (28-32 mph). When two pennants are hoisted, one below the other, a gale warning is in effect and is issued when winds blow between 34 and 47 knots (39-54 mph).

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Background Picture: Hurricane flags flap in the wind as Hurricane Irene approaches Saturday, Aug. 27, 2011 in Monteo, N.C. . (AP Photo/John Bazemore)

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