(AP) -- Government forecasters are making minor changes to several of the categories in the system for describing hurricane strength.
The Saffir-Simpson Hurricane Wind Scale ranks hurricanes in five categories based on their wind speed.
The National Weather Service says an adjustment is needed to ensure the smooth conversion of units of wind speed measurement for public advisories.
The change broadens the Category 4 wind speed range to 130-156 mph, instead of 131-155 mph. That shifts the Category 3 range to 111-129 mph, instead of 111-130 mph.
Category 5 hurricanes will have top winds of 157 mph or higher, instead of a threshold of 156 mph.
Categories 1 and 2 remain unchanged. No historical storm records will be altered.
The change takes effect May 15.
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affir-Simpson Hurricane Wind Scale: http://www.nhc.noaa.gov/aboutsshws.php