Examples of Gust Factor at Water-Land Interface

The CSTAR TC Winds team recently had a conference call reviewing the performance of our experimental tools and methodologies during the 2014 hurricane season. During the discussion of our experiences during Hurricane Arthur, one issue was noted with the performance of the TC Wind Gust methodology at the immediate coast where differing gust factors for the land and marine locations result in some unrepresentative data. The images below demonstrate the issue and a potential work around.

Sustained Winds:

Gust Factors:

over all land=1.50/all water=1.25                  1.50 inland/ 1.375 land near coast/ 1.25 waterGustGustsNew

Note the higher gusts over land in above image on left compared to adjacent water areas in narrow strip of coastal southeast VA. Image at right uses a third gust factor of 1.38 in region of 2-3 grid points (land within 5 to 7.5 km of water). This removes the bias for the most part.  Just experimenting here, exact values of gust factors may vary slightly. Let me know what you think, Thanks, Larry B.

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3 Responses to Examples of Gust Factor at Water-Land Interface

  1. Jonathan Lamb says:

    Larry, that’s an interesting approach to the issue. We encountered something similar when we started using a smart tool that applies the climatology wind gust factors to land and marine. Charleston Harbor is a rather small water body mostly encircled by land along our coast and applying a strictly marine gust factor (1.21) seemed to be giving gust values too low. So I added the option to use a 50/50 average between land and marine gust factors for the Harbor and also Lake Moultrie, an inland lake. It seems to give a better approximation of gusts over these two areas, though admittedly I haven’t had the chance to do a detailed verification of this.

  2. Larry Brown says:

    I’m working on a comparison of some of our ASOS sites, ORF (Norfolk) and NGU (Navy Norfolk) are good test sites near the water that may have a slightly lower gust factor (still a work in progress though).

  3. Pingback: Examining Gust Factors at the Land-Water Interface More Closely | CIMMSE

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