This is Part 1 of 3 outlining the hurricanes of the Heartland. This part focuses on the background of hurricanes, as those of us living in the Midwest might not know too much about hurricanes or their forecasting. Part 2 will look at the "Hurricane Hall of Fame" in the United States, while part 3 details the specific storms that made impacts on Nebraska, Iowa, and Missouri.
When you think of Nebraska, Iowa, or Missouri weather, you typically do not think of Hurricanes. Hurricanes and other tropical systems are a problem in the Gulf Coast or East Coast of the United States, or very rarely the West Coast. However, tropical systems have had impacts in parts of the Midwest. How? Well although they are no longer hurricanes they still move ashore as remnant tropical systems which can dump heavy rain, bring gusty wind, or even spawn a few tornadoes.
So in this series of This Week in Weather History, we will look at some of the tropical systems that brought significant impacts to parts of the Midwest.
What Are Hurricanes?
At their most basic form, hurricanes are just areas of low pressure that form over tropical waters. Technically, the meteorological term for a "low-pressure system" we commonly see in the U.S. is an "extratropical cyclone", although low-pressure suffices. The conditions required for hurricane development are:
1.) Warm sea temperatures. Tropical systems thrive on warm ocean waters, it's the fuel. On average, ocean temperatures above 80 degrees are needed for tropical development. This is why tropical systems are more common over the Caribbean/southern Atlantic than the northern Atlantic, as temperatures drop the further north you go.
2.) Colder air aloft. Tropical systems are just areas of rain/thunderstorms, and thunderstorms need colder air aloft to grow and develop.
3.) An urge to spin. This spin is caused by the Coriolis effect, or how the Earth's rotation deflects and spins storms. This is why we commonly see hurricanes form closer to the equator where the Coriolis effect is maximized.
4.) Low wind shear. Wind shear refers to the change in wind with height, either direction or speed. Wind shear is commonly referred to when discussing severe weather, but unlike hurricanes severe storms need strong wind shear. Low wind shear acts to keep the hurricane undisturbed, as higher wind shear can rip storms apart.
The Hazards of Hurricanes
Hurricanes produce a variety of hazards. The most well-known hazard is wind, which causes structural damage. However, there are a bunch of other hazards which sometimes are worse than wind.
The deadliest hazard from hurricanes is storm surge. Storm surge refers to the way hurricanes shove ocean water into the coast, which causes major damage from flooding. Hurricanes also produce very heavy rainfall, which leads to extensive flooding, as exemplified by Hurricane Harvey in 2017. Hurricanes can also spawn tornadoes.
The most dangerous part of the hurricane is the eyewall, where the strongest winds lie. In the center of the hurricane is perhaps its most identifiable feature, the eye, an area of calm weather where the pressure is lower.
Who is in Charge of Hurricane Forecasting?
Forecasting hurricanes has been the responsibility of the National Hurricane Center (NHC) since the 1950s. Every six hours, the NHC gives forecast updates on current or developing tropical systems during hurricane season.
When is Hurricane Season?
Hurricane season lasts in the Atlantic from June 1 to Nov. 30. In the eastern Pacific, Hurricane season begins on May 15 rather than June 1. It is important to note that hurricanes have formed before and after the traditional season ends. Much like tornadoes, hurricane season only denotes the period when hurricanes are most likely to develop.
Hurricane? Typhoon? Cyclone?
Hurricanes have a lot of terminology associated with them depending on where you live in the world. In the Atlantic and eastern Pacific, we refer to them as hurricanes. In the western Pacific, they are known as typhoons. In the Southern Hemisphere, they are referred to as Cyclones.
The Cone of Uncertainty
The NHC forecasts hurricanes using the cone of uncertainty, the track we are all familiar with. The line in the middle is where the eye of the hurricane might track, with the cone referring to the uncertainty of track the further out the storm gets. It does not mean anything about the size or impacts of the storm, just the center track.
The Saffir-Simpson Scale
Much like tornadoes and the Fujita Scale, hurricanes also have a classification system known as the Saffir-Simpson scale named after the meteorologists who founded it. Once the NHC identifies a potential tropical system, it earns an investment title. If that investment begins to intensify, it becomes a Tropical Depression if it has winds less than 35 mph. Once it gets between 35-74 mph, it becomes a Tropical Storm. After going past 74 mph, it becomes a Hurricane.
It is important to note that the Saffir-Simpson scale exclusively refers to wind, it does not take into account storm surge or rainfall.
Why do we name Hurricanes?
Before we named hurricanes like we do today, only significant storms got a post-landfall name. Examples include the "Great September Gale of 1815", the "Great Miami Hurricane of 1926", and the "Labor Day Hurricane of 1935". In the Caribbean, storms were named after the saint's feast day it made landfall on.
Starting in 1950, hurricanes were named after the military code names (alpha, bravo, Charlie, etc.) and soon after exclusively female names. After significant backlash, in 1979 naming responsibility was passed along to the World Meteorological Organization and names were updated for alternating male and female names. Today, there are six lists of names used every year. So, the list of 2023 names was used in 2017. If a named storm becomes significant or deadly, the name is retired and replaced with another name. So for example, Hurricane Idalia is the replacement name for Hurricane Irma, which caused significant damage in Florida in 2017.
So, now that we have the basics of hurricanes, let's jump into some of the most impactful hurricanes to hit the United States from the time of Christopher Columbus to today. That is in part 2.
