Monday, 24 January 2011: 4:00 PM
602/603 (Washington State Convention Center)
Rapid hurricane intensification has the potential to induce large loss of life. Unfortunately, the physical processes that lead to rapid intensification (RI) intimately depend on small-scale convective events occurring within the eyewall of a hurricane. Thus, a key aspect for recognizing the onset of a RI cycle is to continually observe the evolution of the convective events. To demonstrate this utility, lightning data obtained from the Los Alamos Sferics Array (LASA) for hurricane Rita a major hurricane- will be presented within the following three key topics: 1) The mapping of various lightning types within the hurricane eyewall and the abrupt increase in lightning rate prior and during rapid intensification; 2) the general increase in lightning activity height as demonstrated by a specialized, impulsive intracloud lightning type, during RI; and 3) the evolution, as indicated by lightning, of select convective elements in the eyewall. The last topic is particularly revealing and suggests that the general increase in height of lightning, highlighted in topic two, is an aggregate consequence of numerous short-lived convective events rapidly rotating around the eyewall. The second part of this talk focuses on a high-resolution simulation of the electrification and lightning of Rita during its period of RI. The simulation was carried out on 16000-32000 processors on the DOE machines hosted at ORNL (Jaguar). The model is able to capture the track, intensity evolution and key structural aspects of Rita, such as eye size and eyewall slope. As in the observations, results show individual electrically active convective events rotating along the primary circulation in the eyewall as the storm intensifies. The gross charge structure across the eyewall and those convective events resembles an inverted tripole. The simulated storm experiences an eyewall lightning burst followed by a 10 hPa pressure drop which analysis will be described in more detail during the talk.
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