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Better wind estimates when hurricanes hit those high buildings

Study shows how wind changes with height

Tall buildings are at risk for higher winds aloft during hurricanes. Research is improving wind estimates in analyzing hurricane landfalls.
Tall buildings are at risk for higher winds aloft during hurricanes. Research is improving wind estimates in analyzing hurricane landfalls.

Hi-rise buildings took a hard hit in South Florida after Hurricane Wilma in 2005 blew out windows dozens of stories up leaving giant shards of glass on the street below.

Although Wilma made landfall in Cape Romano, Florida on October 24th, 2005 with winds of 120 mph, it crossed Florida, weakening only slightly to a Category 2 hurricane, before reintensifying over the Atlantic Ocean.

NOAA scientists at the Hurricane Research Division in Miami are studying how the winds closest to the surface change during the landfall.

Wind speeds are stronger the higher up you go because objects on land cause wind to be weaker at the surface than above due to friction.

In hurricanes, the strongest wind occurs where friction is no longer important, near the top of a region we call the boundary layer.

Model of the HBL for Hurricane Irene. The dark blue line represents the height of the pre-existing HBL from over the open ocean. The magenta curve represents the growth of the boundary layer response to the surface roughness  at the coast.
Model of the HBL for Hurricane Irene. The dark blue line represents the height of the pre-existing HBL from over the open ocean. The magenta curve represents the growth of the boundary layer response to the surface roughness at the coast. (.,)

Some people live close to the surface, but others live in high-rise buildings that extend hundreds of meters above the surface.

To better predict and lessen wind damage along the coast, it is necessary to understand how the wind changes with height above the surface to where the wind is strongest.

Using data collected by the NOAA P-3 hurricane hunter aircraft, Doppler radar, and two University of Oklahoma mobile Doppler weather radars, scientists confirmed previous understanding on how the wind changes with height just above the surface.

Friction from land reduces the wind speed in the area within about 1000 m of the surface, but does not affect the wind above that.

The bands of rain and thunderstorms that rotate around the hurricane away from the core, will focus very strong winds at the edges of the bands due to the boundary dropping very low to the surface.

This knowledge will help provide more reliable wind estimates of surface wind speed in future storms when actual data is not available.


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