Geoscience Reference
In-Depth Information
al, 2004; Kessler and Wilson, 1971; Lakshmanan et al, 2003; Lakshmanan and Smith, 2009;
Lakshmanan et al, 2009; Lenning et al, 1998; Mitchell et al, 1998; Stumpf et al, 1998; Winston,
1998; Witt et al, 1998a, Witt et al, 1998b). The efficacy of the detection depends on the radar
scan strategy and quality of the radar (range, azimuth resolution, cycle time, sensitivity,
elevation angles, number of elevation tilts, etc (Brown et al, 2000; Heinselman et al, 2008;
Lakshmanan et al, 2006; Marshall and Ballantyne, 1975; McLaughlin et al, 2009; Vasiloff,
2001).
2.2 Watches
Watches are based on the concept that the juxtaposition of dynamics, thermodynamics and a
mechanism to create upward motion and/or a mechanism to remove inhibition factors
exists. This is often called the ingredients approach as one looks to see where the various
ingredients come together and that is where severe weather will occur. Historically, this is
based on the original Fawbush and Miller Technique (1953) but it has gone through
significant evolution (Doswell, 1980, 1982, 1985, 2001; Johns and Doswell, 1992; Moller, 2001;
Moninger et al, 1991; Monteverdi et al, 2003; Rasmussen, 2003; Weiss et al 1980).
Fig. 2 shows the morphology of thunderstorms that theoretically develop under different
wind shear and convective available potential energy (CAPE) situations (Brooks et al, 1993;
Brooks et al, 1994; Markowski et al, 1998b; Weisman and Klemp, 1984; Weisman and
Rotunno, 2000). Dynamics is represented by the 0-3 km magnitude of the wind shear. Other
height limits may be used depending on the region and local operational usage. The
atmospheric structure (low level moisture, mid level dry air, strength of inversions, etc) is
important and the thermodynamics is represented by CAPE in this figure. While shear and
CAPE are two basic indices that are often used, many other indices are investigated and
used.
Fig. 2. Thunderstorm type as a function of CAPE and Shear.
