Such watches are known as “PDS” watches. PDS tornado (TOR) watches are issued when the forecaster has high confidence that multiple strong (F2-F3 on the Fujita Scale) or violent tornadoes (F4-F5 on the Fujita Scale) will occur in the watch area, while PDS severe thunderstorm (SEV) watches are issued when there is a threat of a high end “derecho” (e.g. Johns and Hirt 1987, Coniglio et al. 2004) ...
