New Standard Aims to Improve Tornado, Severe Wind Estimates

July 10, 2014 · 0 comments

By Jim LaDue, NWS Warning Decision Training Branch

For more than four decades, the go-to for rating tornadoes has been the Fujita Scale, and in the last eight years, the Enhanced Fujita Scale, or EF Scale. Soon, scientists and NWS field teams will have a new and powerful benchmark by which to gauge the extreme winds in tornadoes and other severe wind events.

The American Society of Civil Engineers (ASCE) has approved the EF Scale Stakeholder Group’s proposal to develop a new standard for estimating wind speeds in tornadoes. This standard will allow, for the first time, a rigorous process to improve not only the EF-scale but to adopt new methods to assign wind speed ratings to tornadic and other wind events.

The intent is to standardize methods. According to the ASCE blog, “The content of the standard would include improvements to the existing damage-based EF scale to address known problems and limitations.” ASCE went on to state that the data used for estimating wind speeds would be archived.

The EF Scale Stakeholders Group, composed of meteorologists, wind and structural engineers, a plant biologist, and a hydrologist, held a series of meetings over the past year to discuss methods available to provide wind speed estimations.  The consensus among the group is that many methods exist in addition to that used in the EF Scale today.  These include mobile Doppler radar, tree-fall pattern analysis, structural forensics, and in situ measurements.  The group also discussed ways that the EF Scale could be improved through the correction of current damage indicators and by adding new ones. The outcome of these discussions is available online.

The new standard will be housed under the Structural Engineering Institute (SEI) of the ASCE.  Users of the standard include but are not limited to wind, structural, and forensic engineers, meteorologists, climatologists, forest biologists, risk analysts, emergency managers, building and infrastructure designers, and the media.

Interested parties are encouraged to apply to the committee, selecting Membership Category as either a General member with full voting privileges or as an Associate member with optional voting capabilities. Membership in ASCE is not required to serve on an ASCE Standards Committee.

The online application form to join the committee is available at http://www.asce.org/codes-standards/applicationform/.

The new committee will be chaired by Jim LaDue and cochaired by Marc Levitan of the National Institute of Standards and Technology. For more information or questions about joining the committee, please contact us at james . g . ladue @ noaa . gov and marc . levitan @ nist . gov.