What We're Watching in the Atlantic as July Starts

A massive dust plume tracked across the Atlantic to the U.S. over the past week-plus, and two additional plumes of dust are moving across the Atlantic basin. These plumes, or the Saharan Air Layer (SAL, typically create sinking air and an increase in vertical wind shear (the change in winds with height), both of which are hostile for tropical cyclone development.

As a result, there hasn't been much tropical development of late. The tropical waves that have formed have done so generally south of the areas of dust as they emerged in the Atlantic from Africa.

Saharan dust plumes are common at this time of year but usually decrease heading into August.

There are signs that some changes are ahead heading into the first week of July, Michael Ventrice Tropics Expert at The Weather Company notes.

The amount of dust will likely wane, and combined with upper-level changes, conditions may become more conducive or favorable for a disturbance to develop into a tropical cyclone in the main development region of the Atlantic, or the area between Africa and the Caribbean Sea, over the next 10 days.

There may also be an opportunity for another system to form closer to the East Coast, although it would likely track northeastward away from the United States, according to Ventrice.

Conditions may then shift back to a less favorable environment for tropical activity in the Atlantic in late July or early August, Ventrice points out.

(MORE: We've Already Seen 6 Unusual Things Happen This Hurricane Season)

What Is Typically Expected In July

Tropical activity is usually still slow in July, but there is a slight uptick and the areas of potential development begin to expand farther east into the Atlantic Ocean, including the main development region.

From 1950-2019, 68 named storms formed in the Atlantic in July, or an average of 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.

An average of one July hurricane develops every two to three years. July 2019 saw one named storm, Hurricane Barry, which made landfall in Louisiana. Two hurricanes formed in July 2018, Beryl and Chris, which was unusual.

Major hurricanes, Category 3 or stronger on the Saffir-Simpson Hurricane Wind Scale, in July are rare. Only five major hurricanes have developed 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 Gulf of Mexico remains somewhat active in July, though the western Caribbean Sea steps down a bit as cold fronts become far less frequent.

Development can also occur from an area north of Hispañola to an area north of the Bahamas. Those storms can either linger off the East Coast and churn up high surf that causes beach erosion and rip currents, curl or recurve harmlessly out into the open Atlantic, or in more rare cases, make landfall along parts of the East Coast.

Only five July hurricanes have made landfall along the East Coast since 1950, none of which reached major hurricane strength.

Recent July Activity

There have been notable July storms, in addition to Hurricane Barry that made landfall along the Gulf Coast in 2019, over the last 15 years.

In 2018, Hurricane Beryl became the second earliest hurricane on record to form in the main development region. Hurricanes forming that far east in early July are unusual.

Hurricane Arthur raked eastern North Carolina with storm surge flooding and strong winds over the Fourth of July holiday in 2014.

Hurricane Alex made landfall in July 2010 in northern Mexico. Its torrential rain flooded the Rio Grande Valley and Monterrey, Mexico.

On July 3, 2008, Tropical Storm Bertha became the earliest named, farthest east named storm in the Atlantic Basin in the satellite era (since 1966). Bertha was also the longest-lived July named storm on record when it lasted 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 very active in July. Five named storms formed that year.

After Hurricane Cindy hit southeastern 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 on record in the Atlantic Basin. It churned in the Caribbean Sea before striking Cancún and Cozumel, Mexico.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.