4.1 What Defines a Severe Thunderstorm? Perceptions from a Cross Section of Residents of the Lower Rio Grande Valley in South Texas 

Tuesday, 9 January 2018: 8:30 AM
Ballroom F (ACC) (Austin, Texas)
Barry S. Goldsmith, NOAA/NWSFO, Brownsville, TX; and K. Sherman-Morris, J. J. Schroeder, and M. M. Torres

The Lower Rio Grande Valley of south Texas sees an average of 23.2 severe thunderstorm events per year, based on the official NWS severe storm database from 1996 to 2016. The frequency of severe weather is lower in the Rio Grande Valley than in other portions of Texas; for example, north Texas and extreme southern Oklahoma received an average of 842.8 events per year during the same period. Normalized for population, the number of events in north Texas is approximately three times greater than in the Rio Grande Valley. The authors hypothesized that the dearth of events in the Rio Grande Valley influences a population’s perception of the meaning of the term severe thunderstorm.

Responses heard during subjective, informal discussions about the definition of a severe thunderstorm with members of the Rio Grande Valley community almost never matched the official NWS definition. Members included residents and public safety partners at events ranging from town-hall style meetings to storm spotter training classes. The most common answers were “a lot of lightning” and “very heavy rain”, followed by winds of varying speed and damage levels, and hail of varying size and intensity. Based on this apparent discrepancy between official warning criteria and the perception of a “severe” weather event by a cross-section of the Rio Grande Valley community, a semi-structured interview survey was created and administered to quantify the meaning of the information received when an NWS Severe Thunderstorm Warning was issued.

Initial results from the survey will be presented. The authors hope to gain better insight into how people in a region with a relatively low number of severe thunderstorm events and warnings react to the warning message, especially if the survey outcomes match the hypothesis – that frequent lightning and very heavy rain define individuals’ perception of what is “severe.” If these are the outcomes, other questions can be addressed for future discussion and research, including: If a warning is in effect and frequent lightning and very heavy rain occur, was the population served appropriately – even if the event does not reach NWS criteria? If this is the perception of “severe”, are there other methods to provide frequent lightning and very heavy rain information for a heightened level of readiness? How much at risk are neighborhoods, individuals, or businesses to wind and hail hazards that fall below official NWS warning criteria, and are there other methods to better communicate the risk?

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