Assessment of synoptic and microphysical parameters related to lightning in tropical cyclones and storm intensification

The United States was directly impacted by no less than twenty tropical storms or hurricanes between 2004 and 2008. Of these, four achieved category five status at some period during their lifetimes. Although tropical cyclone (TC) track forecasts have improved considerably during the last few years, predicting intensity continues to be a challenge for both meteorologists and computer models. Although a storm's path is influenced greatly by large-scale atmospheric circulations, its strength appears to be dominated by small scale mechanisms within the storm itself.

Most previous research on TC intensity change has employed either numerical modeling or diagnostic approaches using traditional meteorological parameters. Only recently have studies begun to examine electrification as a means for assessing the potential for intensification. Several papers have considered lightning as a proxy for storm intensity, mostly using data from Vaisala's NLDN (National Lightning Detection Network) and LLDN (Long-Range Lightning Detection Network). Some of the research has included satellite-derived microphysical properties as well as infrared and microwave brightness temperatures. Most of this prior research has considered individual storms and has produced conflicting results. Some have found high correlations between lightning frequency and subsequent intensification, while others found no solid relationship between the two. We are seeking to better understand these relations by investigating a large number of storms and a variety of parameters that might influence both lightning and intensity.

We have prepared a dataset describing all storms occurring in the Atlantic Basin since 2004. Our dataset divides each storm into quadrants, with three concentric annuli around the eye. Each of these twelve sectors has been populated with information about TC intensity, lightning activity, humidity, satellite-derived IR and microwave (37 and 85 GHz) brightness temperatures, microphysical information from TRMM, and vertical wind shear. The dataset permits us to examine relationships between the various parameters and TC intensity change.

The proposed paper will describe our dataset and present initial results from it. We will focus on the role of lightning (if any) in predicting future storm intensity. It will describe our preliminary findings about the relations between changes in storm intensity, lightning activity, and the other parameters described above. Since the research is ongoing, future research goals also will be addressed.