980 Limits Using the EF Scale for Nontornadic Wind Damage

Tuesday, 14 January 2020
Hall B (Boston Convention and Exhibition Center)
Jeffry S. Evans, NOAA/NWS/Weather Forecast Office, Dickinson, TX

One important role the National Weather Service provides is assessing ‘what happened’ after a severe storm strikes a location, in particular an attempt to answer the question ‘how strong were the winds?’. It is one of the more common questions asked after an event, and is an important answer to provide.. With the arrival of the EF-Scale and the mobile, Damage Assessment Toolkit in the past decade, NWS meteorologists have very accessible tools to compare what they are seeing with possible wind strengths. The problem is the EF-Scale is calibrated using a 3-second wind gusts more consistent with a tornado. This limits the utility of the scale for straight-line winds and especially tropical cyclone damage which can place a structure or damage indicator under strong to severe winds over a much longer duration.

This presentation will highlight some real-world examples surveyed by the author, one case being a high-precipitation supercell which produced severe wind damage in Sealy, TX in 2017, and the other an examination of the extreme wind damage well inland associated with hurricane Michael. In both situations, the DAT was used in an attempt to relate the wind damage to possible wind speeds which caused it. However it was clear (especially with hurricane Michael) that the damage was not consistent amongst the damage indicators, highlighting the limits of applying the EF-Scale to non-tornadic winds. While the terminology of ‘damage consistent with an EF-ranked tornado’ might remain valid, the second step to actually estimate wind speeds may be highly suspect until more research is done on wind damage from straight-line winds gusting well beyond a 3 second limit.

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