Assessing Hurricane Intensity Changes from Lightning Flashes Using NASA SPoRT’s Geostationary Lightning Mapper Hovmöller and Average Flash Area Products
Over the past 3 years, NASA SPoRT scientists have been studying the size, rate, and energy of lightning flashes located within the inner core of hurricanes and how they relate to hurricane intensity. NASA SPoRT’s Tropical Lead Research Scientist Dr. Patrick Duran previously studied Geostationary Lightning Mapper (GLM) data from Hurricane Dorian (2019) and found the storm went through two very distinctive outbreaks of lightning near its inner eyewall. In Duran’s paper published in Geophysical Research Letters titled “The Evolution of Lightning Flash Density, Flash Size, and Flash Energy During Hurricane Dorian’s (2019) Intensification and Weakening”, his team discovered the first lightning outbreak was associated with rapid intensification of the inner eyewall where large, highly energetic lightning flashes occurred. The second outbreak occurred when the eyewall of a hurricane began to weaken. The rate of lightning flashes increased three-fold during weakening, but the flashes were much smaller in size and less energetic. Hurricanes weaken due to barotropic mixing, eyewall replacement cycles (ERC), or hurricanes interacting with land.
Figure 1. NASA SPoRT GLM Flash Area Hovmöller from 9/27 12Z to 9/28 12Z showing how inner-core lightning within a hurricane correlates to the intensification of Hurricane Ian during an ERC.
This relationship held true for Hurricane Ian as it underwent an ERC between 9/27 19Z to 9/28 11Z. At 19Z 9/27, a double eyewall formed where the outer eyewall slowly started to rob the inner eyewall of moisture and unstable air. This paused the intensity of Hurricane Ian where an outbreak of numerous, smaller flashes occurred was captured by the GLM Hovmöller (Figure 1).
Figure 2. NASA SPoRT GLM Average Flash Area lapse from 9/28 00Z to 9/28 6Z, showing eyewall replacement cycle and the correlation of the energy, location, and size of the lightning flashes courtesy of University of Alabama in Huntsville Atmospheric and Earth Science Department graduate student Kiahna Mollette.
From 9/27 23Z to 9/28 03Z, the inner eyewall completely collapsed as the outer eyewall consolidated as the only eyewall of Hurricane Ian (Figure 2). Shortly after, the new eyewall contracted, causing Hurricane Ian to become highly convective and rapidly intensify between 03Z to 09Z 9/28. Large, highly energetic lightning flashes developed as seen on the GLM Hovmöller during 9/28 03Z to 09Z. This rapid intensification process strengthened Hurricane Ian from a category 3 to a category 4 hurricane by 09Z, clocking 140 mph winds. By 1035Z 9/28, Hurricane Ian reached a high end, category 4 hurricane, producing 155 mph winds.
University of Alabama in Huntsville Atmospheric and Earth Science Department graduate student Kiahna Mollette is currently studying lightning interaction within the tropics with Dr. Patrick Duran and Dr. Christopher Schultz. Mollette is planning to use the GLM Minimum Flash Area Hovmöller and Flash Extent Density outputs produced for Hurricane Ian to further study how the lightning characteristics in the inner eyewall of the hurricane can relate the time progression of hurricane intensity.