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Improving Forecasts of First Cloud-to-Ground Lightning Flashes Using Relationships Between Reflectivity and in-Cloud Flashes

Title: Improving Forecasts of First Cloud-to-Ground Lightning Flashes Using Relationships Between Reflectivity and in-Cloud Flashes.
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Name(s): Lahr, Andrew D., author
Fuelberg, Henry, professor directing thesis
Misra, Vasubandhu, committee member
Ray, Peter, committee member
Department of Earth, Ocean and Atmospheric Sciences, degree granting department
Florida State University, degree granting institution
Type of Resource: text
Genre: Text
Issuance: monographic
Date Issued: 2014
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource
Language(s): English
Abstract/Description: Studies on the timing of cloud-to-ground (CG) lightning initiation have been conducted for various regions of the United States. There is evidence that in-cloud (IC) flashes often precede CG flashes by 10 or more minutes in the Great Plains. However, this difference in timing seems to decrease in more southern regions. This study analyzes the IC-CG timing issue within ~100 km of Kennedy Space Center, FL. We track 75 discrete single-cell thunderstorms within the KSC domain. Dual-polarimetric radar data overlaid with lightning data are analyzed using the Warning Decision Support System - Integrated Information (WDSS-II) software. Statistics were gathered for three CG initiation scenarios: 1) the first in-cloud flash in the thunderstorm cell, 2) the first 35 dBZ reflectivity at the -10°C altitude, and 3) the first 40 dBZ at -10°C. Verification statistics such as probability of detection (POD) and false alarm ratio (FAR) were computed for each initiation approach. The first in-cloud flash approach produces small lead times (4.8 min) and relatively poor verification statistics, namely a CSI of 75%, a POD of 85%, and an FAR of 15%. The 4.8 min average time between the first IC and CG flashes appears too short to provide useful safety information. The 35 dBZ method provides the greatest lead time (mean of 14.5 min) and compared to the first in-cloud flash method, has a higher CSI (85%) and POD (99%), and a slightly lower FAR (14%). The 40 dBZ method has only marginally better statistics (88% CSI, 97% POD, and 9% FAR), but at the expense of 4 min of average lead time. These results suggest that the 35 dBZ threshold at -10°C is the most operationally applicable for forecasting the first CG flash in Florida.
Identifier: FSU_migr_etd-9023 (IID)
Submitted Note: A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Master of Science.
Degree Awarded: Summer Semester, 2014.
Date of Defense: May 15, 2014.
Keywords: Lightning
Bibliography Note: Includes bibliographical references.
Advisory Committee: Henry Fuelberg, Professor Directing Thesis; Vasubandhu Misra, Committee Member; Peter Ray, Committee Member.
Subject(s): Earth sciences
Oceanography
Atmospheric sciences
Geophysics
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/FSU_migr_etd-9023
Owner Institution: FSU

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Lahr, A. D. (2014). Improving Forecasts of First Cloud-to-Ground Lightning Flashes Using Relationships Between Reflectivity and in-Cloud Flashes. Retrieved from http://purl.flvc.org/fsu/fd/FSU_migr_etd-9023