11B.3 Relationships between Sounding-Derived Parameters and Simulated Convective Storm Surface Outflows

Wednesday, 26 January 2011: 4:30 PM
615-617 (Washington State Convention Center)
Cody Kirkpatrick, University of Alabama, Huntsville, AL; and E. W. McCaul Jr.

Anticipating whether or not convective storms will produce strong, damaging winds at the surface remains a challenging forecast problem. In this paper, we explore the relationships between simulated convective storm downdraft and outflow wind speeds and a variety of commonly-used sounding parameters. A set of over 200 unique cloud-resolving numerical simulations is explored, with storms initiated in a variety of environmental regimes. Each storm is tracked and analyzed for 2 h.

Previous results from this parameter space numerical study have shown that convective storm downdraft speeds are relatively difficult to explain in terms of the background environmental conditions. Linear regressions between storm properties and environmental parameters also perform relatively poorly when describing horizontal wind speeds at the lowest model level (126 m AGL), with only 40 percent of the inter-experiment variance explained by the convective available potential energy (CAPE) and the idealized hodograph radius, which is analogous to the amount of deep layer tropospheric wind shear. The amount of variance explained increases to 46 percent when downdraft CAPE is used in lieu of pseudoadiabatic CAPE, which is a better descriptor of updraft behavior. However, using the difference between equivalent potential temperature at the middle levels and the surface, in combination with the hodograph radius, significantly increases the amount of explained variance (70 percent) in 60-120 minute averaged outflow peak wind speeds. The present results offer insight into the environmental conditions that are supportive of strong convective winds at the surface and may be useful to forecasters and researchers in developing algorithms used to predict damaging convective wind gusts.

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