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Minor tweaks to the Saffir-Simpson Hurricane Wind Scale go into effect this year

Posted at 7:11 AM, Apr 02, 2012
and last updated 2012-04-02 07:14:04-04

RICHMOND, Va. (WTVR) - A slight change to the Saffir-Simpson Hurricane Wind Scale (SSHWS) thresholds for the different categories goes into effect May 15, 2012. This is a minor, technical change because of the conversion between reporting wind speeds in knots versus miles per hour (which is mainly used in the United States for the general public). When the National Hurricane Center (NHC) in Miami, Florida issues any tropical advisory products, they convert intensities measured in knots to miles per hour and kilometers per hour, which are wind speeds to which most people can relate. Next, they round whatever that measurement is up or down to the closest 5-mph or 5-km/h increment. The change in thresholds only applies to major hurricane categories (three through five), and it's just a tick up of one mile per hour. The National Hurricane Center says, "This change follows a public comment period conducted in 2011."  Here are the updated categories and wind speed thresholds:

Minor Modification of Saffir-Simpson Hurricane Wind Scale Thresholds Effective May 15, 2012

Despite this one mile per hour change, the NHC says, "Since intensities are assigned using 5-kt increments, neither storms in the historical record nor any future storms will have their SSHWS category changed as a result of this modification to the scale."

You can click here to read the official statement on why this minor change is happening from the National Hurricane Center.

In case you're curious, here's the comparison of the old to new thresholds from the NHC:

The SSHWS will change as follows:


Category 3: 111-130 mph (96-113 kt, 178-209 km/h)
Category 4: 131-155 mph (114-135 kt, 210-249 km/h)
Category 5: 156 mph or higher (136 kt or higher, 250 km/h or


Category 3: 111-129 mph (96-112 kt, 178-208 km/h)
Category 4: 130-156 mph (113-136 kt, 209-251 km/h)
Category 5: 157 mph or higher (137 kt or higher, 252 km/h or

There will be no change to the wind speeds currently assigned to
Categories 1 and 2.

Learn more about the Saffir-Simpson Hurricane Wind Scale by clicking here.

You can prepare for this year's tropical season by stocking up on readiness supplies during the Hurricane Sales Tax Holiday in Virginia May 25 to 31.

Meteorologist Carrie Rose
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