Autumn is the high point of the hurricane season, also known as the Cape Verdean season, after the islands on which the so-called “hurricane highway” is being built. Here are seven facts about this great – and sometimes deadly – weather phenomenon.
1. The Hurricane Highway begins near the African coast.
The Hurricane Highway begins on the Cape Verde Islands off the northwest coast of Africa. Thunderstorms intended to become hurricanes often create a tropical depression near the islands that slowly organizes and intensifies over the following week as the system moves towards the Caribbean. These storms take a long time to band together, but they also have to travel a great deal of distance without losing their power to reach the east coast as a hurricane. Some storms can thrive with little wind shear, abundant warm water, and moist air, while others starve and disperse when encountering cooler water and strong winds, or when taking in dry, dusty air from the Sahara.
2. The Hurricane Highway emerges from an eastern jet stream.
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3. The largest hurricanes start with the smallest storms on the Hurricane Highway.
Hurricanes, cyclones, typhoons – these are all names for the same force of nature as Hurricane Andrew, which hit the east coast in 1992. Cyclones like Andrew don’t just form out of the air. All tropical cyclones require a relatively small “core” of thunderstorms to develop. When the air and water temperatures are right, these thunderstorm groups sometimes turn into a violent low pressure system that can cause great damage. We see many of these seedling thunderstorms over the ocean each year, but only a small number of them turn into hurricanes.
4. Hurricanes form in different places in different months.
Where a tropical storm or hurricane begins its journey across the ocean depends on what time of year it forms. Storms that form at the beginning of the season usually begin with thunderstorms or cold fronts that stop very close to land over the water. Almost all storms that form in the Atlantic in June come to life within a few hundred miles of land. However, when we reach the peak of the hurricane season, they continue to form in the ocean – all the way to the coast of Africa.
5. Fall is the height of the hurricane season on the hurricane highway.
The Atlantic hurricane season runs from June 1st to November 30th. Storms are most common during this six-month period of the year, but can sometimes form sooner or later. However, the period between mid-August and mid-October is typically the climatological peak of the season. This is because as the seawater warms, the atmosphere becomes conducive to violent storms and increases the risk of hurricanes and tropical storms.
6. Cape Verdean hurricanes can easily land in the record books.
Tropical waves migrating west from the African coast in the middle of summer are the culprits for some of the worst hurricanes we have seen in the United States. For example, on August 8, 2005, a small tropical wave appeared off the coast of Africa that soon became Tropical Depression 10. That Depression would fall apart a few days later, but its remains continued to move towards the United States and evolved into a new tropical Depression over the Bahamas on August 23rd. This new tropical depression became Hurricane Katrina, the costliest hurricane to ever hit the United States.
It’s a similar story for many – but not all – of the major hurricanes in recent history. Hurricanes Andrew, Dennis, Ivan, Isabel and Ike were all Cape Verde-type storms that came to life thousands of kilometers from where they would ultimately wreak havoc.
7. In other places, strong hurricanes can still form in autumn.
While the Far Eastern part of the Atlantic Ocean is a hotbed of activity at this time of year, this isn’t the only place to watch if you live near the coast. Storms that form near the land can quickly turn into disaster. Hurricane Sandy formed south of Jamaica and hit New Jersey within a few days in 2012. A tropical depression that developed east of Florida on September 18, 2005, exploded just three days later with 180 mph winds in Hurricane Rita – the most intense storm ever recorded in the Gulf of Mexico.
Meteorologists are currently forecasting an above-average hurricane season in 2020. It might be worth preparing for it: NOAA is suggesting collecting some key catastrophe supplies, getting insurance, and finding the safest hill.