July is the second month of Atlantic hurricane season. It is often quiet in the Atlantic (some years have no activity at all in the month), but tends to be slightly more active than June. According to NOAA, 118 tropical storms and 55 hurricanes have formed in the month of July since reliable records began in 1851.  25 hurricanes have made landfall in the United States in the month of July, most recently Category 2 Hurricane Arthur in early July 2014, which made landfall in the Outer Banks of North Carolina. On average, July has a tropical storm form about 7 out of 10 years and a hurricane form about 3 out of 10 years.  In rare cases, a major hurricane occurs.

Where do storms form in July?

Atlantic storms in July occur throughout the basin. However, they most commonly form in the Gulf of Mexico, along the Gulf Stream, or near the Lesser Antilles. In most seasons, the far eastern Atlantic does not see much activity in July due to Saharan Air Layer (SAL) outbreaks, which typically arrests development.  There are some exceptions, such as Bertha in 2008, which formed near Cape Verde and eventually strengthened into a category 3 hurricane. There are indications that the Atlantic Main Development Region (MDR) may not be quiet this July – the National Hurricane Center (NHC) has highlighted the potential for slow development of a tropical wave in the eastern Atlantic. Development in the eastern Atlantic in July is uncommon, but far from unprecedented. Perhaps the most destructive Atlantic hurricane in the month of July was Hurricane Dennis in July 2005, a strong category 4 hurricane which made landfall near Pensacola, Florida. Dennis caused 88 fatalities and over $3 billion in damage.

How strong are Atlantic storms in July?

July in the Atlantic has had extremes – ranging from no tropical storms at all to a category 5 hurricane. Last season (in addition to 2009 and 2012), no named storms formed in the month of July at all. On the opposite extreme, in 2005, Hurricane Emily strengthened into a category 5 hurricane on July 16, becoming the only category 5 hurricane on record for the month of July in the Atlantic. Dennis and Emily were extremely rare events, however. 46.7% (55 of 118) Atlantic named storms in the month of July have acquired hurricane strength.

This July, I am predicting one or two named storms will form in the Atlantic, with the possibility of one hurricane. Models predict that conditions will be more favorable than usual in the Atlantic MDR for the month, and this region will have to be watched all month. I will be back for a post tomorrow on the tropical wave in the eastern Atlantic, which has potential to develop over the next week or so. In their 8:00 p.m. EDT Tropical Weather Outlook, NHC gave this system a 10 percent chance of development within 48 hours and a 40 percent chance within five days.