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Earth from Orbit: Atlantic Hurricane Season Hits Its Peak

September 16, 2021

Sept. 10 marked the peak of the Atlantic hurricane season, which officially runs from June 1 through Nov. 30. Climatologists determined this peak date by recording the total number of named storms in the Atlantic basin over the last 100 hurricane seasons and taking an average of when the most storms occur. Around 75% of Atlantic seasons since the beginning of the satellite era in 1966 have had at least one named storm on September 10 and about 50% of seasons have had at least one active hurricane on that date. Historically, September has seen more Category 5 hurricanes than any other month, with 21 storms reaching that level on the Saffir-Simpson Hurricane Wind Scale.

Tropical activity tends to peak around this time because of warmer Atlantic Ocean temperatures and weaker wind shear. As summer progresses, the water temperature in the tropics rises, thanks to sunny days, warmer air temperatures, and more moisture in the atmosphere. Warmer ocean temperatures drive greater storm activity. Wind shear, a change in wind speed or direction with height, is stronger in the spring and weakens through June and July. By late August, wind shear reaches a minimum. Wind shear can help prevent the development of tropical storms and hurricanes. 

The 2021 Atlantic hurricane season has been an active one, with 14 named storms to date, including six hurricanes and three major hurricanes (Category 3, 4 or 5). An average Atlantic hurricane season sees eight named storms and three hurricanes by mid-September. Only four other years since satellite observations began in 1966 had 14 or more named storms by September 12: 2005, 2011, 2012, and 2020.

Throughout hurricane season, NOAA satellites have remained vigilant, monitoring the ocean and atmospheric conditions that lead to the development of tropical storms and hurricanes. Once a storm forms, the satellites provide critical data—such as location, movement, and intensity—to track the storms. NOAA satellites have monitored several recent storms. 

Tropical Storm Larry formed on Sept. 1 in the far eastern Atlantic Ocean about 175 miles south of the Cabo Verde Islands. Larry quickly strengthened into a major Category 3 hurricane on Sept. 3 and remained a strong Category 3 storm for several days. Hurricane Larry made landfall on Sept. 11 in Newfoundland with maximum sustained winds of 80 mph, a Category 1 hurricane. 

Tropical Storm Mindy formed on Sept. 8 in the northeast Gulf of Mexico and made landfall at St. Vincent Island, Florida less than five hours later. 

Tropical Storm Nicholas developed in the southwestern Gulf of Mexico on Sept. 12, strengthened into a hurricane on Sept. 13, and made landfall on Sept. 14 along the Texas coastline on eastern part of the Matagorda Peninsula as a Category 1 hurricane. Nicholas moved slowly toward the Houston metropolitan area, bringing heavy rainfall and tropical storm force winds.

Just because we’ve passed the peak of Atlantic hurricane season, it doesn’t mean hurricanes are no longer a threat. Dangerous storms can happen anytime during hurricane season. Also, the Atlantic typically experiences a secondary peak in mid-October, mainly for the Caribbean Sea and the Gulf of Mexico region. As water temperatures in the Atlantic Ocean start to cool and wind shear increases, the majority of tropical activity shifts back into the Caribbean Sea and Gulf of Mexico, where water temperatures are usually still very warm. 

As the Atlantic hurricane season continues, NOAA satellites remain our watchful eyes in the sky, providing critical information for hurricane forecasting, tracking, and intensity estimation.