Improving Lightning Cessation Guidance Using Polarimetric Radar Data

Abstract

Polarimetric radar data are used to develop lightning cessation guidance for the Cape Canaveral area of central Florida. For this purpose, 80 nonsevere thunderstorm cells in 2012, mostly during the warm season, are analyzed. In-cloud and cloud-to-ground lightning data for the storms are obtained by combining information from the second-generation Lightning Detection and Ranging (LDAR-II) network and the National Lightning Detection Network (NLDN). Storms are tracked using the Warning Decision Support System–Integrated Information (WDSS-II) software, producing time series of radar- and lightning-derived parameters. The 80 storms are split into two categories: 1) 50 isolated storms whose lightning initiation sources are confined to the core or anvil region of the storm and 2) 30 nonisolated cells whose lightning channels are initiated in a nearby active storm and extended to the dissipating study cell. Trends in polarimetric radar parameters at different temperature levels are studied for 40 of the 50 isolated storms to develop cessation guidance. Results based on a completely independent sample of 10 storms reveal that the best-performing cessation algorithm utilizes the presence of graupel and horizontal reflectivity ≥35 dBZ at the −10°C temperature altitude. Lightning is not expected 10 min after both thresholds are no longer met. However, this relationship does not apply to nonisolated cells because a neighboring storm could still be electrically active. Results show that a stratiform cloud region connecting the decaying storm to an active storm might facilitate further channel propagation that might not have occurred otherwise. Thus, the proposed cessation guidelines are not recommended for nonisolated cells.

A simple lightning assimilation technique for improving retrospective WRF simulations

“…For a cloud base temperature less than 208C, the cloud depth must be at least 4 km and the cloud top temperature must be less than 2208C. These criteria were used as reasonable choices to ensure that the subgrid clouds were deep enough to have a mixed-phased layer supportive of lightning [e.g., Mansell et al, 2007;Bruning et al, 2014;Preston and Fuelberg, 2015].…”

Multi-sensor analysis of convective activity in central Italy during the HyMeX SOP 1.1

“…The non-inductive cloud charging mechanism, considered to be the main source of charges involved in lightning flashes within thunderstorms (Saunders, 1993;Latham et al, 2007), is mainly related to the collisions between ice crystals (positively charged) and graupel (typically associated with negative charge in the cloud), suggesting a relation between ice mass and lightning activity. Several studies over the last decade have shown that dual-polarization (DP) radar measurements may exhibit signatures that can be tied to lightning activity (e.g., López and Aubagnac, 1997;Goodman et al, 1989;Rutledge, 1996, 2000;Wiens et al, 2005;Preston and Fuelberg, 2015). López and Aubagnac (1997) showed that the evolution of lightning activity in an Oklahoma supercell thunderstorm that produced copious amounts of hail was related to the changes in the microphysical characteristics of the storm that were inferred from polarimetric radar measurements.…”

Using radar‐derived parameters to forecast lightning cessation for nonisolated storms

“…However, this algorithm failed to safely end advisories for nonisolated storms. The present study extends the work of Preston and Fuelberg [] (hereafter PF15) by examining nonisolated storms with the intent of providing increased understanding that together with future research may provide improved cessation guidance.…”

“…Z H at À10°C is shown along with the WDSS-II storm outline of the cell (white line) and max Z H (52 dBZ) at this time. AfterPreston and Fuelberg [2015].…”