Lightning Observations and Tropical Cyclogenesis

Atlantic tropical disturbance cases (2005-10) are used to evaluate the relationships between lightning strikes and the formation of tropical cyclones (tropical cyclogenesis). The lightning data are gathered from the World Wide Lightning Location Network (WWLLN), and the disturbance information is from an assembly of “best track” data, which includes developing and non-developing cases. Overall, the mean number of lightning strikes for developing systems is higher than that of dissipating systems. Results show that there is a significant difference in radial mean lightning density (MLD) in radial intervals in all but two 6hr time intervals in the 48hr period prior to tropical cyclogenesis (genesis) or disturbance dissipation (DD) and that the significance in 5 of 6 time periods is due to higher MLD in the developing cases. Significantly higher MLD 0-150km from disturbance center in dissipating cases may signal DD within eighteen hours. Conversely, significantly higher MLD 100-300km from disturbance center in developing cases may signal genesis within 6hrs, and significantly higher MLD 500-800km from disturbance center in developing cases may be an indicator of genesis within 24-42hrs. Additionally, it is found that increased lightning to the west of the disturbance center favors genesis. The calculation of MLD over the 0-200km annulus reveals more variance for dissipating cases when compared to developing cases across the time period leading to genesis or DD. Through the analysis of lightning strikes in developing and non-developing tropical disturbances, it appears that the use of such data to better predict tropical cyclogenesis is plausible. The geostationary lightning mapper (GLM) that should be available on GOES-R in late 2016 will provide total lightning measurements with higher detection efficiency than the WWLLN. Plans are underway to develop quantitative algorithms to improve tropical cyclone genesis forecasting, where the WWLLN data is being used as a proxy for the GLM.

The presented research was conducted at CSU/CIRA and funded by a NOAA Hollings Scholarship.

Disclaimer: The views, opinions, and findings contained in this article are those of the authors and should not be construed as an official National Oceanic and Atmospheric Administration (NOAA) or U.S. Government position, policy, or decision.