The 2020 Atlantic Hurricane Season in Perspective

NOV. 5, 2020 by CLAY TUCKER and JILL TREPANIER

“It was over in less than two and a half hours,” our neighbor Bob explained about his experience with Hurricane Zeta on October 28, 2020. Bob is a rarity: a permanent resident in the small unincorporated coastal town of Cocodrie, Louisiana. Though the nearest post office in Chauvin, LA services about 2,500 people, only about a dozen people receive mail as far south as Bob does in the state of Louisiana. With high relative sea-level rise in Louisiana, Cocodrie is now reduced to that land adjacent to Louisiana Highway 56, and my family’s property next door to Bob’s house is about five miles from the end of that highway. 

Baton Rouge, Louisiana has been in a record six cones of uncertainty in 2020. The cone of uncertainty is a National Hurricane Center graphic created to show the area where a certain tropical cyclone will likely travel in coming days. The red “cone” gets wider through distance because uncertainty of the models increases through time. Image source: nola.com

Hurricane Zeta was not a record-breaking storm, per se, but the 2020 Atlantic hurricane season has been a record breaker as a whole, including most U.S. landfalling hurricanes (9). Since 1953, hurricanes are named in order alphabetically while skipping letters Q, U, Y, and Z. In the event that there are more hurricanes than letters, naming continues into the Greek alphabet, and 2020 is now only the second time entering the Greek alphabet since hurricane naming began. Also unique to 2020, most of the named storms have happened earlier in the year than usual. For example, Hurricane Laura formed on August 21, 2020, a week earlier than the next earliest ‘L’ storm on record (Hurricane Luis, August 29, 1995). We also experienced a record 5 storms in the Atlantic basin at once!

Bob decided to stay at his coastal residence for Hurricane Zeta, citing that other locals were confident that the cone of uncertainty had shifted east and “it was only going to be a rain event for Cocodrie.” As Category 2 Hurricane Zeta brought 100+ knot winds and even stronger gusts, Bob knew he had made a mistake by staying. Luckily, for most property holders, including Bob, the storm came through quickly, and damage was minimal to most structures. However, on my own drive to our property there are numerous structures with no roof, trailers flipped and turned, and trash everywhere.

Typical damage in Cocodrie, Louisiana after Hurricane Zeta made landfall in the town on October 28, 2020. Minor damage throughout the town includes roof tin missing, personal property scattered from flooding, and windows missing from wind damage. Image source: Clay Tucker.

Louisiana hurricane records this year include strongest landfalling hurricane in any person’s current lifetime (Hurricane Laura); most Louisiana landfalling tropical cyclones (5); and my hometown of Baton Rouge has been in no fewer than 6 cones of uncertainty. And the 2020 Atlantic hurricane season is not even over yet! The official Atlantic hurricane season ends on November 30, but we could certainly see hurricanes in the Atlantic basin until December 31 if the environmental conditions allow.

With that said, no single hurricane nor a single hurricane season can tell us much about hurricane climatology. For those analyses, we must look at the past 170 years of instrumental hurricane records. Luckily, plenty of researchers have done this work for us, and I’d like to outline a few of those accomplishments here. 

  1. Hurricane wind and storm surge intensity: In 2008, scientists analyzed the maximum wind speeds for hurricanes occurring during the period 1981–2006. Hurricane data revealed that, as sea-surface temperatures increased through the end of the 20th century, the sustained winds caused by hurricanes also increased. Other researchindicates a similar pattern: the strongest hurricanes (1851–2010) are becoming stronger, and even computer models show that large city centers like New York City will experience worse storm surge in a warming climate.
Time series plots for Houston, TX accumulated rainfall amounts on the y-axis. Black lines indicate the ordinary least squares regression model and red lines are the models at the 90th percentile. The data here show that hurricanes are becoming more rainy through time. Source: Trepanier and Tucker, 2018.
  • Translation speed: The movement of a hurricane across space is known as its translation speed, and though its effects on hurricane intensity can change based on local conditions, climatologists are quite confident of how it affects landfalling damage. If the storm slows over cooler waters, it will likely cause de-intensification as noted in this study from 2014. However, other research also shows that global translation speed is slowing, noting that a slow-moving storm allows surge to build on the coast and more rain to fall locally. Though nuanced, translation speed along with sea-surface temperature data can be plugged into computer models and used to predict storm damage and protect lives and livelihood.

Even with decades of research, certain hurricane characteristics still allude scientists including changes in hurricane frequencycauses of hurricane rapid intensification, and the effect of size on storm intensity. The 2020 hurricane season may be able to give insight to these questions. As I write this article, yet another storm (Hurricane Eta) is modeled to make landfall near South Florida. Understanding how our current conditions compare to ones in the past will allow us to better prepare for the likely conditions in the future.

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