Friday, June 30, 2017

Where and When the Season's First Atlantic Hurricane Forms

Linda Lam
Published: June 30,2017

The first of any season is something to make note of and the first hurricane of the Atlantic season is no exception.
We've taken a look at where and when the first hurricane of each Atlantic hurricane season developed from 1950-2016, based on data from the National Hurricane Center (NHC), and notice a couple of trends. Many first hurricanes in the Atlantic form close to the U.S., impact land and develop in mid-to-late August.
(MORE: 2017 Atlantic Hurricane Season Forecast | Hurricane Central)
The map below shows where each storm was first designated a hurricane by the NHC.
Each dot represents where each first Atlantic hurricane of the season became a hurricane.
There are a few clusters, including one in the main development region (MDR), off the west coast of Africa into part of the Caribbean. Activity here is usually greatest from August into September.
Two other areas common for development early in the season are closer to the U.S. – in the western Gulf of Mexico and off the Southeast coast.
In June, some of the activity in the Gulf of Mexico and off the Southeast coast comes from decaying cold fronts. In July, cold fronts become much less frequent but thunderstorm complexes rolling off the Southeast coast can linger and lead to tropical cyclone formation.
As hurricane season progresses, tropical waves start coming off the coast of Africa.
(MORE: 10 Most Extreme Hurricane Seasons in the Satellite Era)
Interestingly, a majority of the first hurricanes of the season impacted land, partially due to close formation to land. In 1966, Hurricane Alma become the earliest hurricane to strike the continental U.S. since 1825 when it made landfall in Florida as the equivalent of a Category 2 hurricane on the Saffir-Simpson Hurricane Wind Scale.
Another interesting first hurricane is Agnes (1972), which made landfall in Florida and again in New York and caused extensive flooding, 100 deaths and more than $2 billion in damage.
Hurricane Allen in 1980 was a classic Cape Verde hurricane and reached Category 5 strength, but it weakened some before making landfall near the Texas-Mexico border.
Depiction of when each first Atlantic hurricane of the season became a hurricane.
As the graph above shows, the most common time period for hurricane development is Aug. 16-31, followed by Aug. 1-15. This is not that surprising given that tropical activity typically heats up in the second half of August.
The Atlantic hurricane season officially last June 1-Nov. 30, but tropical cyclones do occur outside of these months. Three of the first hurricanes of the season formed before June 1, including Hurricane Alex in 2016, which formed south of the central Azores; Hurricane Alma in 1970, which developed north of Panama; and, Hurricane Able in 1951, which strengthened into a hurricae off the coast of Florida.
The latest first hurricane of the season during from1950 to 2016 did not occur until Sept. 11 in 2013 (Humberto) and in 2002 (Gustav).
MORE: Atlantic Basin Retired Hurricanes and Tropical Storms (PHOTOS)

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