Hurricane season: How does a hurricane form and its risks

Hurricanes are one of the most powerful weather events on our planet. We want to dig a little deeper and understand how these powerful and destructive forces of nature form. What other threats can they bring in addition to the wind?

Hurricanes are one of the most powerful weather events on our planet. We want to dig a little deeper and understand how these powerful and destructive forces of nature form. What other threats can they bring in addition to the wind?

Hurricanes usually have their origins in the warm waters of tropical oceans. They typically start as a disorganized cluster of thunderstorms sparked from a passing tropical wave or a front. Thunderstorms will tap into the moisture-providing warm water and intensify. Stronger storms, in turn, result in instability that leads to more thunderstorm activity.

As the feedback process continues, the thunderstorm cluster will intensify, become better defined, and likely be labeled a “tropical disturbance.” When identifying tropical disturbances, meteorologists look for organized storm activity that maintains its structure for at least 24 hours.

If atmospheric conditions remain favorable, the tropical disturbance will continue to strengthen. Once wind speeds reach 30 mph, the system becomes a tropical depression. At this point, the infamous spin in the lower levels of the storm is usually present.

If its maximum sustained winds reach at least 39 mph and up to 73 mph, it is called a tropical storm. The storm has a better-defined cyclonic pattern in this stage, with the winds and storms closer to its center. When storms are named, it is because they have reached tropical storm status. Storms are named by the National Hurricane Center in Miami, Florida.

The named storm becomes a hurricane if it continues to strengthen. Categories are given based on the maximum sustained wind speed of the storm using the Saffir-Simpson scale shown below.

Since hurricanes are categorized based solely on wind speed, many believe higher-categorized storms are the most threatening. Although this is true in general terms, it is important to remember that every storm is different, and the dangers can change depending on the trajectory, time of impact, and speed. No storm is the same. A storm’s threats often go well beyond the wind.

Hurricanes and tropical storms produce rain bands that spiral outward from the center of the storm. Sometimes, turbulence and rotating air in the rainbands can favor tornado-producing storms. While tornadoes embedded within hurricanes are usually weak and short-lived, they are challenging to predict and cause extensive damage.

Tornadoes are most frequent in the leading right quadrant of the storm, where conditions are often most favorable for rotating air.

When dealing with a landfalling hurricane (or one coming close to the shore), beaches are a natural buffer between the ocean and inland communities, ecosystems, and natural resources. However, these important environments can suffer extreme and catastrophic changes in response to winds, waves, and storm surge during a hurricane.

Seawater will inevitably begin to eat away at loose sand, soils, or rocks, putting at-risk infrastructure adjacent to the coast. As a result, beaches are stripped of their sand, and asphalt along road cracks, and homes could lose their foundations.

A paper published in the Journal of Geophysical Research Letters studied the erosion impact Hurricane Maria had on 75 beaches across Puerto Rico in 2017. The results found at Maria caused erosion of 9 to 15 meters along its path, up to 120 feet at beaches. That's roughly the length of an Olympic-sized swimming pool!

When a cyclone makes landfall, seawater can push several miles inland, worsening erosion and flooding communities adjacent to the coast, sometimes several dozen feet deep. Storm surge is the abnormal rise in water generated by a storm above the forecast astronomical tide.

If the cyclone is exceptionally expansive or powerful, storm surge can often go far beyond the coast. For example, Hurricane Ike carried a storm surge more than 28 miles inland from the coast of Texas and Louisiana. As mentioned before, no storm can be treated alike—how far or high storm surge can get will depend on the terrain, coastline, and storm trajectory.

Excessive rain can affect cities well away from the coast. There are times when a storm can slow down and its rains fall over a region intensively, causing flooding and catastrophic impacts. A hurricane’s remnants also cause big flooding risks. In 2021, although Hurricane Ida made landfall in Louisiana, its remnants traveled over the Mississippi and Ohio valleys and ultimately flooded parts of the Northeast. Specifically, New York City was affected by flash flooding that caused deaths and disrupted regional transit.