As the Atlantic hurricane season enters its busiest period, monitoring extends far beyond the Gulf of Mexico and the Caribbean Sea.
Some of the systems that later become major concerns first emerge off Africa and then track west across the Atlantic. When a disturbance starts that far from land, it can take quite a while to approach the United States.
Storms that develop much closer to shore, though, can leave far less time to get ready, according to WUSF.
Here's what to know
Florida State University meteorologist Dr. Robert Hart explained that African tropical waves typically move west at about 15 mph.
At that speed, a wave steadily crossing the Atlantic would take around 12 to 14 days to reach the United States coast.
That broader area of concern becomes especially important in August and September, when stronger tropical waves are more likely to originate over Africa and enter the Atlantic basin.
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By the time a system reaches the Lesser Antilles, the remaining trip to the continental United States takes about five to six days, WUSF reported.
A storm that develops in the Gulf of Mexico may reach the U.S. or eastern Mexico in as little as one to three days.
In general, systems that form farther east give residents and forecasters more lead time, although extra time does not automatically mean a storm is more dangerous.
More background
How far a storm has to travel is only one part of the hurricane risk picture.
Its point of origin and whether it strengthens into a hurricane also affect the odds that it will eventually hit the United States.
A hurricane forming over the tropical Atlantic near the Cabo Verde Islands has less than a 10% chance of later striking the continental United States.
One reason is that stronger storms in the open Atlantic are more likely to curve north and remain over water.
That chance rises to roughly 30% to 40% when a system reaches hurricane strength in the Caribbean, making those storms a more pressing concern for coastal communities in the Lower 48.
These tropical waves are important even when they never become named storms.
WUSF noted that they carry moisture westward from Africa across the Atlantic, and that the Caribbean would be desert-like without them.
What can be done?
Warning time varies widely from one tropical threat to another.
A wave leaving Africa may be watched for many days, while a Gulf system can force action on a much shorter timeline.
Waiting until a storm is nearby can leave little time to gather supplies, review evacuation routes, charge devices, or protect a home from heavy rain and strong winds.
A faraway disturbance is not automatically likely to hit the United States.
A storm's track, strength, and location all shape the risk, which is why forecasts continue to change as systems develop.
Storm tracking reflects both where a system is and how quickly conditions can shift from a distant Atlantic watch to a short-notice coastal threat.
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