Wednesday, June 28, 2017

Atlantic Hurricane Season: What to Expect in July

Jonathan Belles, Chris Dolce and Jonathan Erdman
Published: June 27,2017

The Atlantic hurricane season in July typically brings a slight uptick in tropical storms and hurricanes in the western Atlantic Ocean and Gulf of Mexico.
(MORE: Hurricane Central)
Development areas of tropical cyclones also begin to expand east into the Atlantic Ocean in July and the frequency of tropical storms and hurricanes increases.
Despite that, June and July combined typically account for only 14 percent of the Atlantic hurricane season's named storms, paling in comparison to the volume of named storms in the core months of August through October.
(MORE: 10 Hurricane Myths Debunked)
Tropical storm (red) and hurricane (white) frequency by month in the Atlantic Basin.
From 1950-2016, 63 named storms formed in July, averaging about one named storm in July each year. Incidentally, the Atlantic season's first named storm will have formed by the second week of July in a typical season.
Of those named storms from 1950-2016, 27 strengthened to hurricanes, for an average of one July hurricane every two to three years.
Major hurricanes, Category 3 or stronger on the Saffir-Simpson Hurricane Wind Scale, in July are rare. Only five major hurricanes have flared during the hurricane season's second month since 1950.

A Subtle Shift East

July is a month of transition. Formation areas spread east to include more of the Atlantic Ocean to the east of the Lesser Antilles.
"The tropical waves coming off western Africa every two to four days are a little better defined than in June," says Dr. Rick Knabb, former director of the National Hurricane Center and hurricane expert at The Weather Channel. "That's one reason why we start to look farther east for development in July."
Typical origin and tracks of July tropical cyclones in the Atlantic Basin.
The primary season for long-track tropical cyclones from the eastern Atlantic, known as Cape Verde storms, is in August and September.
(MORE: Why Cape Verde Matters in Hurricane Season)
The Gulf of Mexico remains somewhat active in July, though the western Caribbean Sea steps down a bit as cold fronts become far less frequent going into the summer months.
June tropical storms and late season cold fronts can also cool waters in the Gulf of Mexico and Caribbean.
Development can also occur from north of Hispañola to north of the Bahamas from thunderstorm complexes that roll off the Southeast coast. Those storms can either linger off the East Coast, churning up high surf leading to beach erosion and rip currents, curl or recurve harmlessly out into the open Atlantic, or in more rare cases, landfall along parts of the East Coast.
Including 2014's Hurricane Arthur, only five July hurricanes have made landfall along the East Coast since 1950, none reaching Category 3 strength.
These are all averages. Not every July follows this perfect script.

Recent July Activity

Although 2016 did not have any tropical storms in July, this lack of activity was somewhat of an abnormality recently. Only three other seasons in the past 10 years – 2007, 2009, and 2012 – failed to produce a named storm in July.
On the contrary, 2017 has already generated three tropical storms with Arlene in April and Bret and Cindy in June.
The only other year during the satellite era to have three or more tropical storms through the end of June was 2012, which had four tropical storms between May and June before going quiet in July. The 2012 Atlantic hurricane season ended up being one of the most active hurricane seasons with 19 tropical storms, including Hurricane Sandy.
Named storm origin points in July.
The last 10 years has featured quite a few notable July storms.
Over the Fourth of July holiday in 2014, Hurricane Arthur raked eastern North Carolina and the Outer Banks with storm surge flooding and strong winds.
Hurricane Alex made landfall in July 2010 in northern Mexico, wringing out torrential, flooding rain in the Rio Grande Valley and Monterrey, Mexico. In 2011, we had three named storms form in the Atlantic basin during July.
The transition to formation areas in the central and eastern Atlantic mentioned earlier was illustrated in one of the most extreme examples in 2008.
On July 3, 2008, Tropical Storm Bertha became the farthest east named storm to form in the Atlantic Basin so early in the season in the satellite era. Bertha became the earliest-in-season hurricane farthest east in the Atlantic (at about 50W longitude) and the longest-lived July named storm on record, lasting 17 days in the open waters of the Atlantic Ocean.
Also in July 2008, Category 2 Hurricane Dolly made landfall in southern Texas.
The record-smashing 2005 hurricane season was active in July.
After the landfall of Hurricane Cindy in southeast Louisiana, Hurricane Dennis was, at the time, the strongest July Atlantic Basin hurricane on record. It made landfall in the Florida Panhandle.
Just six days after Dennis made landfall, Hurricane Emily became the only Category 5 July hurricane of record in the Atlantic Basin, churning in the Caribbean Sea before striking Cancun and Cozumel, Mexico. Five named storms formed in July 2005.
Before 2005 there were plenty of Julys without a named storm. Three consecutive Julys (1999-2001) were devoid of even a single named storm.

MORE: Hurricanes From Space

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