Brief Summary of History of the Research into the Problem

"Despite the ubiquity and abundance of P. semispinosus, only two previous studies have assessed habitat use, with both showing a generalized habitat use. [brief summary of these studies]." (Lambert and Adler, p. 70)

"In previous studies, California supercell tornadoes have been documented with the more typical right-moving cyclonically rotating storms (e.g., Monteverdi and Quadros 1994; Braun and Monteverdi 1991) although nonsupercell tornadoes are probably the most common in the state (Blier and Batten 1994). Although radar signatures have been documented for California storms (see, e.g., Carbone 1983; Monteverdi and Johnson 1996), the hooks seen thus far were cyclonic.

There are published cases of both anticyclonic tornadoes and anticyclonic supercells in the refereed literature. Fujita (1977) provided the first documentation of anticyclonic tornadoes but did not postulate a relation of the tornadoes to the storm-scale rotation. Fujita and Grandoso (1968) first hypothesized that leftward-propagating, anticyclonic thunderstorms occur as part of storm splitting. This was verified in modeling studies by Wilhelmson and Klemp (1978) and Weisman and Klemp (1982), who showed that storms propagating to the left of the hodograph rotate anticyclonically. However, no case study of an anticyclonic tornado in association with an anticyclonic supercell has yet appeared in the reviewed literature." (Monteverdi, J.P., W. Blier, G. Stumpf, W. Pi, and K. Anderson, 2001: First WSR-88D Documentation of an Anticyclonic Supercell with Anticyclonic Tornadoes: The Sunnyvale–Los Altos, California, Tornadoes of 4 May 1998. Mon. Wea. Rev., 129, 2805–2814.)

"California tornadic thunderstorms and their counterparts in other parts of the world in similar climatological environments (e.g., Hanstrum et al. 1998) have only recently been subjected to systematic documentation. Indeed, preconceived notions persist that tornadic storms either are not a forecasting problem in California or are “freak” events (see Monteverdi and Quadros 1994)." (Monteverdi, J.P., C.A. Doswell, and G.S. Lipari, 2003: Shear Parameter Thresholds for Forecasting Tornadic Thunderstorms in Northern and Central California. Wea. Forecasting, 18, 357–370.)