Evolution of Eyewall Convective Events as Indicated by Intracloud and Cloud-to-Ground Lightning Activity during the Rapid Intensification of Hurricanes Rita and Katrina

Abstract

Lightning data (cloud-to-ground plus intracloud) obtained from the Los Alamos Sferic Array (LASA) for 2005's Hurricanes Rita and Katrina were analyzed to provide a first insight into the three-dimensional electrical activity of rapidly intensifying hurricanes. This information is crucial for modelers aiming at better forecasting hurricane intensity, because it is inherently related to key structural aspects of the storm often misrepresented in numerical models. Analysis of the intracloud narrow bipolar events (NBEs) for Rita revealed a general increase in discharge heights during the period of rapid intensification. The results also showed that for the case of Rita, NBEs were useful in tracking and mapping the evolution of individual strong convective elements embedded in the eyewall during rapid intensification. Those results are particularly revealing, and suggest that the general increase in height of the intracloud lightning is an aggregate consequence of numerous short-lived convective events rotating rapidly around the eyewall of Rita. A similar rise in discharge heights during periods of intensification was also observed for Katrina. However, the NBE lightning data show that for Katrina, the eyewall convection persisted for several hours at a fixed location instead of rotating cyclonically along the eyewall. This highlights the idea that NBE lightning data can also be used to identify different convective regimes attributed to possibly different internal or external forcing mechanism(s).

Tropical Cyclone Lightning and Rapid Intensity Change

“…These capabilities would require the ability to relate lightning activity to variables that are predicted in the model such as updraft speed, supercooled water, and cloud ice. Several groups are currently developing these capabilities (e.g., McCaul et al 2009;Fierro et al 2011), which have the potential to provide information on tropical cyclones and their environments that is not normally available from other sources. The very episodic behavior of lightning activity described in this and other studies suggests that the relationships between lightning and other physical variables are very nonlinear, so the assimilation of this new data source is a challenging problem.…”

“…The threedimensional charge distribution can also be measured from LMAs, which allows the source height of the lightning to be estimated. Fierro et al (2011) used LASA data to investigate the lightning activity in Hurricanes Rita and Katrina from the 2005 hurricane season while the cyclones were in the Gulf of Mexico. Results showed that the total lightning information was useful for monitoring the convective evolution of those storms.…”

“…Unfortunately, the range of the LMAs is limited to a few hundred kilometers, so these systems are not well suited for statistical studies with large samples. A special class of IC lightning called narrow bipolar events (NBE) can be detected at longer ranges because of their characteristic large amplitudes (Fierro et al 2011), but still cannot provide basinwide coverage.…”

A lightning climatology of the South-West Indian Ocean

“…More than 9 of these depressions reach the stage of moderate tropical storms (TSs), of which half become TCs (Caroff et al, 2008). As highlighted by more and more studies, tropical cyclones exhibit specific lightning activity (Black and Hallet, 1999;Squires and Businger, 2008;Price et al, 2009;Abarca et al, 2010;Fierro et al, 2011;DeMaria et al, 2012, among others). Here, we focus on the impact of the tropical storms on the lightning climatology of the SWIO, and we try to quantify the proportion of lightning associated with TSs and TCs.…”

Interaction of Atmospheric Plasma Vortices

“…Broadband noise was detected in the observation of thunderstorm activity by a microsatellite ''Chibis-M'' with the help of a radio frequency analyzer that indicates the clustering of the cloud system (see http://press.cosmos.ru/ nauchnye-rezultaty-raboty-mikrosputnika-chibis-m). The lightning flash rates can be considered as an indicator of the hurricane genesis (LEARY AND RITCHIE 2009;PRICE et al 2009;FIERRO et al 2011). …”