Warning Impact Statements
Many of the National Weather Service's Weather Forecast Offices—primarily those located within the Central and Southern Region Headquarters—use a multi-tier impact-based warning (IBW) system of impact statements to notify the public and emergency management officials of the severity of specific severe weather phenomena. The impact statement system—initially used only for tornado and severe thunderstorm warnings—was first employed by the WFOs in Wichita and Topeka, Kansas, and Springfield, St. Louis and Kansas City/Pleasant Hill, Missouri beginning with the 2012 Spring severe weather season, eventually expanded to include 33 additional National Weather Service Weather Forecast Offices within the Central Region Headquarters in 2013, and then to eight additional offices within the Eastern, Southern and Western Regions in the spring of 2014.
Under this system, the warning product will include text denoting the specific hazard (i.e., 60 mph wind gusts and quarter size hail) and applicable sourcing (either via indication from Doppler weather radar, or visual confirmation from storm spotters or other emergency management officials) and the level of impact to life and/or property. In order of increasing risk by warning type, these statements—which may be modified at the discretion of the regional forecast office—are:
Tornado Warning | ||
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Tornado impact attribute | Impact statement(s) (in sentence order, where applicable) | |
Landspout / weak tornado |
(For landspouts and weak tornadoes, alternative impact statements may be utilized at the discretion of the Weather Forecast Office; all other statements are standard nationwide.) | |
"Base" (default) |
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Considerable (may accompany wording for a PDS Tornado Warning or a Tornado Emergency) |
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Catastrophic (accompanies wording for a PDS Tornado Warning or a Tornado Emergency) |
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Severe Thunderstorm Warning | ||
Thunderstorm attribute | Impact statement(s) (in sentence order, where applicable) | |
Wind (60 mph) |
(This alternate damage impact statement should include both aforementioned statements.) | |
Wind (70 mph) |
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Wind (80 mph) |
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Wind (90 mph) |
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Wind (100 mph+) |
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Hail (up to 1.25") |
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Hail (1.50" to 2.50") |
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Hail (2.75"+) |
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