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Assessing Lightning Threat using Vaisala VHF Total Lightning Mapping Network Data . Gregory Patrick NOAA/NWS Weather Forecast Office Fort Worth/Dallas TX. Southern Thunder Workshop Cocoa Beach, FL July 28, 2009. Outline. Motivation Background Information

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assessing lightning threat using vaisala vhf total lightning mapping network data

Assessing Lightning Threat using Vaisala VHF Total Lightning Mapping Network Data

Gregory Patrick

NOAA/NWS

Weather Forecast Office

Fort Worth/Dallas TX

Southern Thunder Workshop

Cocoa Beach, FL

July 28, 2009

slide2

Outline

  • Motivation
  • Background Information
  • Network and Data Overview
  • Recent Examples of Flash Extent Density
  • Conclusions
  • Ideas for Future Research
slide3

Motivation

  • Informal assessments past several years suggest that lightning activity > 40 km from active convection is common and poses a public safety hazard
  • Realization that Total Lightning data could be more fully utilized in product issuances that convey CG threat
slide4

Background

  • Value of Total Lightning mapping data has been proven as an aid for severe thunderstorm detection and analysis
  • Not as many studies on lightning threat posed by CG flashes well-removed from highest radar reflectivity
slide5

Network and Data Overview

DFW LDAR II network

  • Range approx 150 km
  • Data file (netCDF) arrives at WFO Fort Worth every 2 min
  • Flash Extent Density (FED) is most commonly used product at WFO FWD
  • FED units are Flashes km-2 min-1

DFW

North

data from network sensors

LDAR II Data Flow

FWD AWIPS D2D Wkstn

(ave latency ~ 2 min)

Data from Network Sensors

Processing andComms – Tucson

(netCDF file)

SRH FileServer

LS1 ServerFWD AWIPS

slide7

Examples

  • 24 Apr 2008 Extensive Lightning in Anvil Region
  • 06 Nov 2006 Widespread Lightning north of active convective region (trailing stratiform region of MCS)
slide8

Composite Reflectivity

Imminent

CG threat?

Cluster of Severe

Thunderstorms

Moving East

slide9

Flash Extent Density

24 Apr 2008

Cluster of Severe

Thunderstorms

slide11

Examples

  • 24 Apr 2008 Extensive Lightning in Anvil Region
  • 06 Nov 2006 Widespread Lightning north of active convective region
slide12

0.5 deg Reflectivity Movie

07 UTC – 08 UTC 06 Nov 2006

What is the CG lightning threat across Denton and

Collin Counties?

slide13

Flash Extent Density Movie

07 UTC – 08 UTC 06 Nov 2006

What is the CG lightning threat across Denton and

Collin Counties?

slide14

NLDN Cloud-to-ground flashes

07 UTC – 08 UTC 06 Nov 2006

Denton – 8 CGs

Collin - 10 CGs

slide15

Conclusions

  • Real-time Total Lightning data has significant value in addition to its use in severe weather operations
  • Mapping in-cloud flash data in real time helps forecasters visualize threat areas outside convective core regions
  • A combination of NLDN, total lightning, and radar reflectivity is needed to properly assess CG lightning threat in many situations
slide16

Ideas for Future Research

Why do some long-distance anvil and stratiform region cloud lightning flashes produce isolated CG lightning flashes and others do not?

FED + NLDN at 2352 UTC 17 April 2008

95 km

slide17

Ideas for Future Research

FED - 17 April 2008 at 2348z

Why are isolated cloud lightning flashes initiating in forward anvil regions and how often do they occur?

Detached cloud flash in anvil

region

Supercell

slide18

Questions?

gregory.patrick@noaa.gov

slide19

Network and Data Overview

DFW LDAR II network

  • Lightning discharge process emits VHF radiation pulses
  • VHF pulses (~ 62 MHz) and Time of Arrival technique used to reconstruct individual cloud and CG flashes in 3D
  • Range approx 150 km
  • Data file (netCDF) arrives at WFO Fort Worth every 2 min
  • Flash Extent Density (FED) is concise integration of data

DFW

North

slide20
Flash Extent Density is the number of lightning flashes that pass through a specific grid box area during a specific time interval (2 min)

Computed after all lightning sources are grouped together into flashes

FED units are Flashes km-2 min-1

Flash Extent Density