"The first rule of hurricane coverage is that every broadcast must begin with palm trees bending in the wind."
Figure 1: Palm Trees blown by Hurricane Jimena (2009). Photo: REUTERS
Hurricane Matthew was the strongest hurricane in the 2016 Atlantic season with sustained maximum winds reaching 140 kt on 06Z October 1st. It will be one of the most memorable storms for some years because of the panic that it caused along the Southeast United States. This panic was warranted because of the strength of Hurricane Matthew and the storm still did considerable damage, but it could have been much worse. Fortunately Matthew underwent an eyewall replacement cycle shown in Figure 2. The formation of a secondary eyewall caused a weakening of the maximum winds but expansion of the overall wind field. Matthew also began to encounter significant southwesterly vertical wind shear as it crossed the Bahamas which caused asymmetries to develope and the overall vortex to weaken. Southwesterly shear also meant thata majority of the convective rainbands were orientated offshore on the eastern side. This asymmetry can be seen at later times using lightning in Figure 3.
Figure 2: (Left) Microwave and (Right) visible satellite imagery of Hurricane Matthew (2016) at 16Z October 6th
Hurricane Matthew had a considerable amount of lightning during its intensification period. Past studies have shown that lightning could be used as a forecast tool for intensification. The animation below shows the progression of lightning binned azimuthally every 20 km in addition to plots of the density of lightning around the storm center. Hurricane center fixes from the National Hurricane Center (NHC) Best Track Dataset were linearly interpolated to hourly to create these figures. It is very interesting to see that lightning was annular roughly 6 hours prior to peak intensification at 00Z October 1st. Lightning which is often used as a proxy for moist convection can also be used to identify the location of the strongest convection in the rainbands.
From 12Z September 28th to 00Z October 20th: Eyewall (0-50km) Flashes Recorded : 3551 Inner Core (0-100km) Flashes Recorded : 4889 Rainband (100-500km) Flashes Recorded : 183432
Figure 3: Animation of the lightning from the World Wide Lightning Location Network (WWLLN) in Hurricane Matthew as it intensified and moved along the coast of Florida. The red lines indicate the 100km and 400km radii with the red dot being the storm center. WWLLN data provided by CIRA.
Figure 4: Track and intensity from the NHC Best Track Dataset for all 2016 Atlantic Hurricanes.