Eastern Region technical attachment (National Weather Service (U.S.)) ; no. 1998-09

"Vertically integrated liquid (VIL) as an indicator of thunderstorm severity has been studied by researchers since the early 1970s (Greene and Clark 1972). With the arrival of the WSR-88D radar, VIL became operationally available at offices with warning responsibility as a tool for gauging the potential severity of thunderstorms. VIL density has also been shown to be useful in efforts to identify thunderstorms that have a high potential for producing severe hail (Troutman and Rose 1997, Amburn and Wolf 1997). However, for severe hail producing thunderstorms, a threshold VIL density was shown to be more consistent from season to season, and day to day than a threshold VIL (Amburn and Wolf 1997). A threshold VIL density that could be used operationally at NWSFO Charleston WV was desired. However, previous studies done in different geographical areas have shown some variation in specific threshold grid-based VIL density values, with positive but differing amounts of success. With this in mind, a local study of VIL density was undertaken at the National Weather Service Forecast Office (NWSFO) Charleston WV, using data from the KRLX WSR-88D located in Ruthdale, 6 miles south of Charleston"--Introduction.

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