Total Lightning Observations of Supercells over North Central Texas

Christopher M Mckinney,Lawence D Carey,Gregory R Patrick

doi:10.55599/ejssm.v4i2.19

Christopher M Mckinney, Lawence D Carey + Show 1 more

Open Access

https://doi.org/10.55599/ejssm.v4i2.19

Copy DOI

Abstract

s part of a collaborative research project between Texas A&M; University and the NOAA/NWS Fort Worth/Dallas Weather Forecast Office, total lightning observations from Vaisala’s Dallas-Fort Worth (DFW) Lightning Detection and Ranging (LDAR II) network have been used to supplement Doppler radar measurements in the diagnosis of thunderstorm updraft strength and analysis of severe weather potential. More specifically, initial observations of severe convection over north-central Texas for three case dates have shown that total lightning flash extent density (FED) and gridded source density peaked prior to, or increased during reported severe weather events. Two lightning holes were observed with one supercell, and numerous FED notches were noted with other cells that likely indicated the updraft region of the thunderstorms. These signatures in the FED corresponded to weak echo regions on the KFWS WSR-88D radar reflectivity data. Additionally, lightning appendages developed for both right- and left- deviant cells prior to shifts in radar-inferred cell track, indicating a possible method for prediction of right or left hand deflections in supercell motion. A cell embedded within a linear MCS also developed a large notch in the FED data on its rear flank that persisted for over 25 min and preceded a severe wind report, indicating another potential forecasting application of total lightning data.

Highlights

Forecasters at the National Weather Service Forecast Office in Fort Worth, TX (WFO FWD) have two sources of lightning information available for their use
The final case presented is from 13 April 2007, when a linear mesoscale convective system (MCS) moved across the Dallas - Fort Worth (DFW) metroplex, including an embedded supercell that crossed northern Tarrant and Dallas Counties
The radar reflectivity cross section through the first lightning hole clearly shows the vaulted shape of a bounded weak echo region (BWER). Both lightning holes were apparent only on one image of either flash extent density (FED) or gridded source density (GSD), they evolved into persistent notches in the lightning data at the same location in the storm as the reflectivity hook echo or updraft notch, similar to the lightning notch described in Demetriades et al (2002)

Summary

Introduction

Forecasters at the National Weather Service Forecast Office in Fort Worth, TX (WFO FWD) have two sources of lightning information available for their use. The network, owned by Vaisala, Inc. of Tucson, AZ provides data on CG strike location, polarity (positive or negative), multiplicity and peak current (e.g., Cummins et al 1998) While this information is of value to forecasters, previous studies have shown that intra-cloud (IC) flash rates can be up to 30 times greater than CG rates (Lang et al 2000). This system, covering a limited geographic area around the DFW metroplex, detects very high frequency (VHF) energy sources which emit radiation in the lightning breakdown process These sources can be compiled to provide information on the three dimensional electrical activity within a cell, comprised of both IC and CG flashes (Rison et al 1999). It is this ability to detect both types of flashes that has led to VHF networks being called “total” lightning networks

Objectives

Results

Discussion

Conclusion