Hurricane Size Matters: Why A Storm's Wind Field Is Just As Important As Its Category

Yahoo

6 hours ago

A hurricane's category is one of the most well-known metrics to describe how dangerous a storm is, but that single number only tells part of the story. Another key bit of information about a storm is how big it is.
We're specifically talking about how large the storm's wind circulation extends, meaning how far from the storm's center tropical-storm- and hurricane-force winds extend.
And the size of a storm is more impactful than just the number of people and the size of the region that experiences damaging winds.
Storm Surge
A perfect starting place to highlight the importance of a hurricane's size is with Hurricane Charley (2004) and Hurricane Ian (2022).
The two storms were near twins in many ways: same landfall location (near Cayo Costa, Florida, a barrier island about 23 miles west-northwest of downtown Fort Myers), same maximum windspeed, nearly identical minimum pressure and even similar time of day.
And yet, the storms had significantly different impacts to Florida, partially due to the storms' different sizes.
(MORE: Hurricane Ian Vs. Charley: Similar Landfalls, Different Storms)
Charlie was much smaller than Ian, which limited the storm surge to 7 feet or less in a small part of southwest Florida's coast.
But Ian's larger wind field helped produce much higher storm surge in parts of the southwest Florida coast near and to the south and east of its landfall. For example, surge inundation along the river in downtown Fort Myers obliterated the previous high water record and was more than double the peak surge from Charley.
But why did that happen?
A larger storm blowing over a greater area of the ocean will generate the highest storm surge, if all other factors are equal.
Other notable examples of devastating storm surge driven by a storm's size include:
-Hurricane Ike (2008): Ike was a Category 2 hurricane at landfall but generated a 15- to 20-foot storm surge that wiped out most structures on Texas's Bolivar Peninsula.
-Hurricane Katrina (2005): Katrina had weakened to a Category 3 at landfall but produced a record U.S. storm surge of 28 feet along the Mississippi Coast.
-'Superstorm' Sandy (2012): Sandy had tropical-storm-force winds 1,000 miles wide — the largest Atlantic tropical cyclone on record since at least 1988 — before it produced record storm surge along parts of the New Jersey, New York and Connecticut coasts.
What About Smaller Storms?
Just like a large storm isn't necessarily an indicator of maximum wind speed, a hurricane having strong winds doesn't mean it's large.
Hurricane Andrew in 1992 only had tropical-storm-force winds extending up to 90 miles from its center when it made its Category 5 landfall in South Florida.
Smaller storms like these can produce intense swaths of wind damage close to their center.
They can also rapidly develop more often thanks to the large amount of vorticity and angular momentum being transferred into the center of the storm. But they can also be more fragile and susceptible to hostile conditions such as wind shear and dry air.
Many smaller, more intense hurricanes eventually become somewhat larger by simply replacing their eyewall with a more expansive outer eyewall, making its wind field more expansive.
This was recently seen with Hurricane Erin, which underwent an eyewall replacement cycle after explosively intensifying into a Category 5 hurricane.
Sara Tonks is a content meteorologist with weather.com and has a bachelor's and a master's degree from Georgia Tech in Earth and Atmospheric Sciences along with a master's degree from Unity Environmental University in Marine Science.