National Weather Service revises storm warning practices

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Due to the experience of Hurricane Sandy, the National Weather Service is changing the way it handles post-tropical cyclones, which are closed areas of low pressure that were once designated tropical cyclones but no longer qualify.

The first of these changes gives the NWS the option to continue issuing formal advisories on post-tropical cyclones when they pose a significant threat to life and property and when a transfer of responsibility to another office would result in an unacceptable discontinuity in service.

The second change gives the NWS the option to keep hurricane and tropical storm watches and warnings in place for those systems.

Beginning June 1, the start of the Atlantic hurricane season, the following new watch/warning definitions will go into effect:

• Hurricane/Typhoon Warning: An announcement that sustained winds of 64 knots (74 mph or 119 km/hr) or higher are expected somewhere within the specified area in association with a tropical, subtropical or post-tropical cyclone. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds (24 hours for the Western North Pacific). 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.

• Hurricane Watch: An announcement that sustained winds of 64 knots (74 mph or 119 km/hr) or higher are possible within the specified area in association with a tropical, subtropical or post-tropical cyclone. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical storm force winds.

• Tropical Storm Warning: An announcement that sustained winds of 34 to 63 knots (39 to 73 mph or 63 to 118 km/hr) are expected somewhere within the specified area within 36 hours (24 hours for the Western North Pacific) in association with a tropical, subtropical or post-tropical cyclone.

• Tropical Storm Watch: An announcement that sustained winds of 34 to 63 knots (39 to 73 mph or 63 to 118 km/hr) are possible within the specified area within 48 hours in association with a tropical, subtropical or post-tropical cyclone.

Click here for the full notice.

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