Timothy W. Troutman and Richard Smith, NOAA/NWS, Southern Region Headquarters, Forth Worth, Texas
Mark A. Rose, NOAA/NWS, Weather Forecast Office, Old Hickory, Tennessee
Increased demand, and ability, to place more detailed information in severe weather warnings has led to the need to categorize warning call-to-action (CTA) statements according to the specific situation. This paper will attempt to improve upon previous publications on this topic. The goal of the warning meteorologist is to convey as much information as possible, be as specific as possible, while also being as brief as possible. Individual weather offices are therefore encouraged to develop a set of CTA's which are specific to their local regimes.
This paper attempts to improve on the useful information published by Smith (1999, 2000) and Sharp (2000) by categorizing environment-specific CTA's for tornado, severe thunderstorm, and flood/flash flood warnings. The determination of the environment for severe thunderstorm warning CTA's lies largely in mesoscale features such as the wind profile and WSR-88D reflectivity imagery. For flood/flash flood-producing environments, the meteorologist must understand the atmospheric mechanisms that are creating heavy precipitation, as described by Troutman and Rose (1999).
For a storm expected to produce marginally severe weather, the call-to-action statement "HAIL THE SIZE OF DIMES AND WIND GUSTS UP TO 60 MPH CAN BE EXPECTED" would be much better suited than, say, "THIS IS A VERY DANGEROUS STORM. TAKE COVER NOW. VIOLENT STRAIGHT LINE WINDS AND LARGE HAIL CAN BE EXPECTED." The second example exhibits very poor use of a CTA. The constant abuse of such statements, where the warning far outweighs the threat, may very well contribute to a public that would eventually be loathe to respond to our constantly "crying wolf."
Conversely, a spotter report indicating a large tornado might warrant the more urgent statement "A TORNADO HAS BEEN CONFIRMED! TAKE COVER IN A STURDY BUILDING NOW. MOBILE HOMES AND VEHICLES ARE NOT SAFE," which would be much more effective than saying "RADAR SHOWS STRONG SIGNS THAT A TORNADO IS DEVELOPING. TAKE COVER NOW!" The difference in the two statements is obvious. The call-to-action must reflect the specific threat and urgency of the situation.
If National Weather Service offices adopt such a philosophy in warning composition, the benefits would far outweigh those of the past mentality of using "canned" statements, when inserting the CTA was almost an afterthought. Situation specific CTA's could mean the difference between an overused statement that is ignored by the public and a tailored and specific CTA that catches the ear of the listener.
(Note: This paper can be viewed in its entirety at http://www.srh.noaa.gov/ssd/techmemo/sr215.htm.)