Dauphin Island Sea Lab investigating the rapid intensification of Gulf hurricanes
The increase in major hurricanes has lead to researchers to investigating ‘set-up storms’
GREENVILLE, N.C. (WITN) - After devastating hurricane seasons the past several years, researchers are now investigating the affects tropical systems have on the thermal properties of coastal waters. The turbulence tropical cyclones bring to the shallow coastal waters are now suspected of creating a warmer temperature profile from the surface to the sea floor, creating prime conditions for rapid intensification prior to landfall.
Dr. Brian Dzwonkowski of the Dauphin Island Sea Lab and the University of South Alabama and his team are focusing primarily on the set up of Hurricane Michael in 2018. On October 7th, three days before landfall, Michael became a tropical storm. It then went under rapid intensification, reaching category 2 hurricane strength on October 8th and the following day it became a major hurricane. On October 10th, it made landfall as a category 5 hurricane near Mexico Beach, Florida.
This explosive tropical development has not been an isolated incident. Last month Hurricane Laura saw a similar pattern of rapid intensification, blasting Louisiana and Texas as a strong category 4 hurricane. The Dauphin Island Sea Lab team suspects weaker storms preceding these major hurricanes are to blame.
Under normal conditions, the sun’s radiation heats the surface layer of the ocean while leaving a layer of cold water near the surface. This cold water essentially acts as a check to prevent rapid storm intensification by mixing up towards the surface as tropical systems move overhead. The tropical systems struggle to gain energy from the surface water as the cold water from the ocean floor keeps sea surface temperatures from spiking.
However, once a tropical system has mixed the cold layer of water to the surface, this natural hurricane hinderance is removed. The cold water is very difficult to replace and, in many cases, doesn’t return until the winter months. This stacking of hot water on top of warm water creates an energy surplus for any tropical system that follows the first. In 2018, it was Tropical Storm Gordon that lead to this ocean mixing, setting the stage for Hurricane Michael’s explosive development.
Surprisingly, both Hurricane Laura and Hurricane Sally appeared to have similar setups to Hurricane Michael with both storm events being preceded by smaller storms (i.e. Hurricane Hanna and Marco, respectively). This pre-storm setup of the oceanic environment likely contributed to the intensification prior to landfall. Importantly, this pre-landfall intensification was not well predicted by hurricane models or forecasts, which as you can imagine is critical information for evacuation and disaster preparation.
This link between weak and strong storms has been shown to be more prevalent in the Gulf of Mexico. The position of our coast line relative to ocean currents help reduce this effect, however as oceans become warmer, the layer of cold water off our coast will shrink and potentially become less effective at preventing massive short term tropical intensification.
If you would like to read more on the research of the team at the Dauphin Island Sea Lab, you can head here.
Journal Reference: B. Dzwonkowski, J. Coogan, S. Fournier, G. Lockridge, K. Park, T. Lee. Compounding impact of severe weather events fuels marine heatwave in the coastal ocean. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-18339-2
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