Predicting Microbursts in the Northeastern U.S. Using Lightning Flash Rates and Simple Radar Parameters

Stephen M Jessup,Amanda L Burke

doi:10.1155/2018/3639215

Abstract

Convective storms that produce microburst winds are difficult to predict because the strong surface winds arise in a short time period. Previous research suggests that timing and patterns in cloud height, echo top height, vertical integrated liquid (VIL), intracloud (IC) lightning, and cloud-to-ground (CG) lightning may identify and predict microbursts. Eleven quasi-cellular microburst cases and eight non-microburst severe wind cases were identified from New York, Pennsylvania, and New Jersey between 2012 and 2016. Total lightning data (IC + CG) were obtained from Vaisala’s National Lightning Detection Network (NLDN), and radar parameters were obtained from the Thunderstorm Identification Tracking Analysis and Nowcasting (TITAN) software. Values of VIL, echo top height, and cloud height were tracked through time along with total lightning strikes within a 15 km radius of the storm center. These parameters were plotted with respect to their mean and standard deviation for the 45 minutes leading up to event occurrence. Six of eleven cases featured peaks in total and IC lightning within 25 minutes prior to the microburst. These were the only variables among those examined to peak more than half the time for either the microburst cases or the null cases. The results suggest that microbursts behave somewhat differently than severe wind events, particularly in terms of lightning and VIL timing. The results dispute previous research that suggests that microbursts are highly predictable by the behavior of lightning and radar parameters.

Highlights

Microbursts are strong winds exhibiting a divergent damage pattern across an area 4 km wide or less [1]
It appears that orography may play a role in producing microbursts in the Northeastern U.S A twelfth case was located along the northern shore of central Long Island, but its track ran east of the available lightning data. is case was excluded from the analyses
E eight null cases do not show a strong preference for complex topography (Table 2 and triangle points in Figure 2), and they are scattered across New York and Pennsylvania. ey generally occurred earlier in the day than the microbursts (Tables 1 and 2) and produced weaker winds

Summary

Introduction

Microbursts are strong winds exhibiting a divergent damage pattern across an area 4 km wide or less [1]. Prediction of microburst winds is difficult owing to the rapid lifecycle associated with many convective storms. High reflectivities (>50 dBZ) must be above the melting level (−10°C) for the downdraft to be strong enough to create a microburst. A peak, followed by a sharp decrease, in the intracloud (IC) lightning flash rate occurred six minutes before thunderstorm collapse and the subsequent microburst event. Peak values of IC lightning flashes, VIL, echo top heights, and cloud heights about six minutes before the outflow imply a strong updraft in a convective storm [2]. We examine quasi-cellular microbursts and a collection of non-microburst quasi-cellular severe wind events in the Northeast U.S from 2012 to 2016 to determine how well peaks in various radar and lightning parameters perform in predicting microburst occurrence

Data and Methodology

Discussion

Disclosure