Severe Convective Wind Environments

Abstract

Nontornadic thunderstorm winds from long-lived, widespread convective windstorms can have a tremendous impact on human lives and property. To examine environments that support damaging wind producing convection, sounding parameters from Rapid Update Cycle model analyses (at 3-hourly intervals) from 2003 were compared with 7055 reports of damaging winds and 377 081 occurrences of lightning. Groundrelative wind velocity was the most effective at discriminating between damaging and nondamaging wind convective environments. Steep surface-based lapse rates (a traditional damaging wind parameter) generally did not discriminate between damaging and nondamaging wind convective environments. Other parameters, such as convective available potential energy, humidity aloft, and lapse rates aloft were moderately discriminating. This paper presents a composite damaging wind algorithm in which the two most discriminatory parameters were combined, yielding more skill than any individual parameter. Damaging wind environments are then examined further through a selection of cases that highlight common severe wind ingredients and failure modes. A primary result is that, even in seemingly favorable environments, when the winds at the top of the inflow layer were either parallel to the convective line or blowing from warm to cold over a front, damaging winds were less likely. In the former case, it appears that the downdraft winds and the cold pool's gust-front-normal flow are not additive. In the latter case, it appears that convection becomes elevated and does not produce downdrafts that reach the surface. Combining the most discriminatory severe wind parameters with knowledge of these severe wind failure modes may help to improve the situational awareness of forecasters.

Discrimination of Mesoscale Convective System Environments Using Sounding Observations

“…This is an important point, since the effects of the mean wind and its orientation relative to the cold pool are underemphasized aspects of forecasting the strength and structure of quasi-linear MCSs (Evans and Doswell 2001, Corfidi 2003, Parker and Johnson 2004, Kuchera and Parker 2006. Although the MCS motion vector is not an exact analog to the motion of the cold pool, this section examines various properties of the inflowing environment relative to the MCS motion vector to see if these may be used as an indicator of the potential severity of the system and to gain further insight into the propagation characteristics of MCSs.…”

Response of Simulated Squall Lines to Low-Level Cooling

“…Indeed, some examples (e.g., Maddox 1980;Trier and Parsons 1993) reveal that the passage of an elevated MCS may be marked by minimal changes in the surface temperature. Even so, at least a subset of MCSs are known to produce severe winds at night and on the cold side of fronts (e.g., Johns and Hirt 1987;Kuchera and Parker 2006). One possibility is that such systems are still cold pool driven and surface based, despite their comparatively stable boundary layers.…”

Satellite Assessments of Tropopause Dry Intrusions Correlated to Mid-Latitude Storms

“…It is shown that the CAPE and DCAPE over Taizhou at 16:00 LST 18 March 2014 is about 0 and 300 J·kg −1 respectively which means both the convection at low-level and dry intrusion from upper-level are weak. As documented by many studies [23,24], large quantity of energy is needed for the development of severe convective systems. CAPE and DCAPE which are two energy indices are usually used for measuring the energy related to convective systems.…”