Hurricane Laura & the Wind Speed Dilemma: ‘Looking at sustained winds, one would conclude that Laura was only a weak category two hurricane’
Thursday, August 27, 2020
Hurricane Laura and the Wind Speed Dilemma
Last night, Hurricane Laura made landfall on the southwestern coast of Louisiana, bring heavy rain (6-8 inches), strong winds (gusting to 132 mph at one location), and a coastal storm surge (roughly 10 feet at the most vulnerable locations).
The NWS Lake Charles radar image at midnight central time showed a well defined eye as the storm was making landfall.
Now the dilemma and interesting part. Based on reconnaissance aircraft and other information, the National Weather Service’s National Hurricane Center had estimated that Laura was a Category Four hurricane just prior to landfall, and according to the official Saffir-Simpson scale, that means the sustained surface (10-m) winds, averaged over a few minutes, were between 130 and 156 mph (see below). Not gusts, sustained winds.
Saffir-Simpson Hurricane Categories
But here is the issue. What were the maximum sustained winds that occurred last night as Laura made landfall? Looking at all available stations, the highest sustained wind was 98 mph at Lake Charles Airport. The map below shows the sustained winds at 1 AM, when the storm was just moving inland (wind barbs show sustained winds, with gusts in red). The blue arrow indicates Lake Charles Airport.
Looking at the sustained winds, one would conclude that Laura was only a weak category two hurricane (96-110 mph).
And then there are gusts. Gusts are not used as part of the Saffir-Simpson hurricane scale, but, let’s face it, gusts are very important. The big damage in most storms are done by the gusts.
Below are the maximum gusts of Laura. Two locations are extreme: Calcasieu Pass on the coast and Lake Charles, a few miles to the north (127 and 132 mph gusts, respectively)