An initial assessment of the GOES Microburst Windspeed Potential Index
Kenneth L. Pryor, NOAA/NESDIS, Camp Springs, MD
A suite of products derived from the current generation of Geostationary Operational Environmental Satellite (GOES) (8-P) has been developed and evaluated to assess hazards presented by convective downbursts to aircraft in flight. The MWPI algorithm is intended for implementation in the GOES-R Advanced Baseline Imager (ABI) that has promising capability for providing legacy sounder products with greatly improved temporal and spatial resolution as compared to the existing GOES (8-P) sounders. A GOES sounder-derived wet microburst severity index (WMSI) product to assess the potential magnitude of convective downbursts, incorporating convective available potential energy (CAPE) as well as the vertical theta-e difference (TeD) between the surface and mid-troposphere has been developed and implemented. CAPE has an important role in precipitation formation due to the strong dependence of updraft strength and resultant storm precipitation content on positive buoyant energy. Intended to supplement the use of the GOES WMSI product over the United States Great Plains region, a GOES Hybrid Microburst Index (HMI) product has also evolved. The HMI product infers the presence of a convective boundary layer (CBL) by incorporating the sub-cloud temperature lapse rate as well as the dew point depression difference between the typical level of a convective cloud base and the sub-cloud layer. Thus, the WMSI algorithm is designed to parameterize updraft and downdraft instability within a convective storm, while the HMI algorithm describes the moisture stratification of the sub-cloud layer that may result in further downdraft acceleration due to evaporative cooling, eventually producing strong and potentially damaging winds when the convective downdraft impinges on the earth's surface. Large output values of the microburst index algorithms indicate that the ambient thermodynamic structure of the troposphere fits the prototypical environment for each respective microburst type (i.e. Wet, Hybrid, Dry). Accordingly, a new diagnostic nowcasting product, the Microburst Windspeed Potential Index (MWPI), is derived from merging the WMSI and HMI algorithms and designed to quantify the most relevant factors in convective downburst generation in intermediate thermodynamic environments.
This paper provides an initial assessment of the MWPI algorithm, presents case studies demonstrating effective operational use of the MWPI product, and presents validation results for the 2007 convective season. Although there is not currently an observational requirement for microburst potential for the GOES-R Advanced Baseline Imager (ABI), the ABI does have promising capability to generate a sounding profile with greatly improved temporal and spatial resolution as compared to the existing GOES (8-P) sounders. In light of this capability, the eventual implementation of a sounder-derived microburst potential algorithm is feasible. Considering that seven of the sixteen bands of the ABI are in common with the bands of the heritage sounder, the ABI should effectively produce a sounding profile comparable in quality to the current GOES. The increase in temporal resolution should greatly aid the mesoscale forecaster in the analysis of trends in thermodynamic environments.
Extended Abstract (736K)
Supplementary URL: http://www.orbit.nesdis.noaa.gov/smcd/opdb/kpryor/mburst/mwpi.html
Poster Session 1, Fifth GOES Users' Confererence Poster Session
Wednesday, 23 January 2008, 2:30 PM-4:00 PM, Exhibit Hall B
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