Why Some Tropical Weather Systems Take Weeks to Hit the U.S.

Forecasters have been monitoring the development of Erin for several days already. Yet, its potential impacts on the U.S. are still days away. Why does it take so long for some of these features to make it to American soil after coming to life? Here is an inside look at how forecasters determine the anticipated speed of any particular tropical weather maker.

Why Tropical Weather Systems Can Take Up to Two Weeks to Reach the U.S.

It can take days or weeks for a tropical storm or hurricane to reach the U.S. The features that start as tropical waves coming off the coast of Africa naturally take the longest, simply due to the length of the journey across the Atlantic. For instance, some features can take over 10 days to make the trek from Africa to the waters near the U.S.

The steering winds in place at the time of the journey largely influence how long it takes to cross the basin. This is why forecasters pay close attention to what is happening thousands of miles away to determine the projected track of a feature.

Going back to 1989, Hurricane Hugo took two weeks to find its way to the U.S. after forming off the coast of western Africa. Hugo became a tropical depression on September 10, a common time for storms to ignite in the eastern Atlantic. The featured moved on a west-northwest path through the Atlantic in the weeks ahead. It took nearly two weeks for Hugo to hit South Carolina, coming ashore as a massive Category 4 storm on September 22.

More recently, Hurricane Florence also took almost two weeks to move from its starting point near Africa to its eventual landfall location in eastern North Carolina. Both Hugo and Florence came in right about average, taking 12 or more days to hit the U.S. coastline after forming in the waters off of western Africa.

Storms That Form Closer to Home Can Strike Quickly

In contrast, storms that ignite close to home in the Gulf may only take a few days to reach the U.S. coastline as a result of the proximity. This was demonstrated in 2018 when Hurricane Michael caused catastrophic damage just a few days after forming off the coast of the Yucatan Peninsula in Mexico.

Michael started as a tropical depression in the northwestern Caribbean in the early morning hours of October 7. Based on historical averages, it takes about 2 to 4 days for a storm that forms in this part of the basin to reach the U.S.

Falling within that range, Michael made landfall at Mexico Beach, Florida, roughly three and a half days later. The monster Category 5 storm was packing maximum sustained winds of 160 mph when it moved ashore.

The time it takes for a storm to reach land is significant, as it affects how much lead time people in the path have to prepare. Michael formed and strengthened so quickly that residents did not have as much time to prepare and evacuate.

Knowing the average time that a storm may take to reach your area will help you to plan accordingly. We will continue to monitor the tropics and provide updates heading into the heart of the Atlantic hurricane season.

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