Atlantic hurricane

An Atlantic hurricane is a type of tropical cyclone that forms in the Atlantic Ocean primarily between June and November. These storms are powerful systems with continuously rotating winds around a low-pressure center. They bring stormy weather over a wide area, not just near the center of the storm.

These storms begin as organized groups of clouds and thunderstorms over warm tropical or subtropical waters. They develop a closed circulation at low levels, which helps them grow into stronger systems.

Tropical storms are defined by having maximum sustained winds of at least 39 mph, while hurricanes need winds of 75 mph or more. Until the mid-1900s, storms were named randomly. In 1953, the practice began of using predetermined lists of names for storms. If a hurricane causes a lot of damage or loss of life, its name is retired from the list. On average, each season brings about 14 named storms, with 7 becoming hurricanes and 3 becoming major hurricanes of Category 3 or higher. In April 2004, Catarina was the first hurricane ever recorded in the South Atlantic Ocean.

Description

An Atlantic hurricane is a type of tropical cyclone that forms in the Atlantic Ocean. These storms happen mostly between June and November. They spin around a low pressure center, creating bad weather over a wide area, not just in the calm center called the eye. Hurricanes are groups of clouds and storms that start over warm waters and have a special kind of wind pattern. They are different from tornadoes, which are another kind of spinning storm. Hurricanes form over areas of low pressure.

In the North Atlantic and the Eastern Pacific, we call these storms "hurricanes," but in the Western Pacific near Asia, they are called "typhoons." The general word "cyclone" is used in other parts of the world. A tropical storm has winds of at least 39 mph, while a hurricane needs winds of 75 mph or more. The United States National Hurricane Center watches for these storms in the North Atlantic and gives out important updates. It is one of the special weather centers for tropical storms, as decided by the World Meteorological Organization.

Steering factors

Tropical cyclones are guided by the air flowing around them from the ground up to about eight miles high. Neil Frank, who used to lead the National Hurricane Center in the United States, compared this to a leaf moving in a stream or a brick sliding through a river of air. The way air moves around high-pressure and low-pressure areas changes where hurricanes go.

In warm parts of the world far from the poles, storms usually move west with a bit of a turn toward the north. This happens because of a high-pressure system stretching east to west. South of this high-pressure area, winds blow from east to west. If this high-pressure system weakens, a storm might turn north and then curve back toward the northeast. North of the high-pressure area, winds blow from west to east, pushing storms further east.

Intensity

Tropical cyclones, also known as hurricanes, can be grouped by how strong they are. We figure out their strength by looking at either their fastest winds or their lowest pressure. Some of the strongest hurricanes ever recorded include Hurricane Allen, Hurricane Melissa, Hurricane Opal, Hurricane Wilma, and Hurricane Gilbert. These storms had very low pressure and very fast winds.

Many of these powerful hurricanes stayed strong even when they reached land. The 1935 Labor Day hurricane was the strongest when it hit land, and Hurricane Melissa was the second strongest. Others, like Hurricane Gilbert, stayed very powerful when they made landfall too.

Climatology

See also: Tropical cyclogenesis

Climatology helps us understand the usual patterns of an average hurricane season and can help predict future storms. Most Atlantic hurricanes start from tropical waves in warm waters far north of the equator near the Intertropical Convergence Zone. The Coriolis force is usually too weak to start the storm's spin near the equator. Hurricanes often form in the Gulf of Mexico, the Caribbean Sea, the tropical Atlantic Ocean, and sometimes near the Cape Verde Islands, creating Cape Verde hurricanes. Storms can also grow stronger over the Gulf Stream off the U.S. coast when water temperatures are warm enough.

Most Atlantic hurricanes form between August and November, when conditions are just right. About 97 percent of these storms appear between June 1 and November 30, which is the official hurricane season. On average, there are 14 named storms each season, with 7 becoming hurricanes and 3 becoming major hurricanes (Category 3 or stronger). The busiest time is usually around mid-September.

The official hurricane season starts on June 1 and ends on November 30, but sometimes storms can form outside these dates. Since records began, there have been storms in every month of the year, though they are rare outside the season. The National Hurricane Center (NHC) watches for these storms and gives warnings to keep people safe.

Seasonal variation

Most North Atlantic tropical cyclones form between August 1 and November 30, when disturbances are most common. About 97 percent of tropical cyclones in the North Atlantic develop between June 1 and November 30, marking the modern hurricane season. On average, 14 named storms happen each season, with 7 becoming hurricanes and 3 becoming major hurricanes (Category 3 or stronger). Activity peaks around mid-September.

Though the season starts on June 1, the official end was once October 31 but is now November 30. Still, storms sometimes form outside these dates. Since September 2021, 88 storms have formed outside the season, with the latest being Tropical Storm Ana in May 2021. The earliest storm on record was in January 1938, and the latest major hurricane was in December 2005.

June

June starts the hurricane season, but activity is usually low, with about one storm every two years. Early-season storms often form in the Gulf of Mexico or off the U.S. East Coast.

Since 1851, 81 June storms have formed. Two major hurricanes occurred in June, including Hurricane Audrey in 1957. The farthest-east storm in June was Tropical Storm Bret in 2023.

July

July sees very little activity, with about one storm each year. Storms usually form in the eastern Caribbean, the Gulf of Mexico, near the Bahamas, or off the U.S. East Coast.

Since 1851, 105 July storms have formed. Ten became major hurricanes, including Hurricane Emily in 2005 and Hurricane Beryl in 2024, both reaching Category 5. The longest-lasting July storm was Hurricane Bertha in 2008, lasting 17 days.

August

August has more storms than July because wind conditions improve. About 2.8 storms form each August. By August 30, there are usually four named storms, including one hurricane, and the first intense hurricane forms by September 4.

September

September is the peak month for hurricanes, with about three storms each year. By September 24, there are usually seven named storms, including four hurricanes, and two major hurricanes. Few of these intense storms hit land.

October

October has fewer storms than September because wind conditions change. About 1.8 storms form each October. By October 21, there are usually nine named storms with five hurricanes. A third major hurricane often forms after September 28. Storms in October more often form in the Caribbean and Gulf of Mexico.

November

November usually has only one storm every other year, and major hurricanes are rare. Strong November hurricanes include the Cuba hurricane of 1932, Hurricane Lenny of 1999, and Hurricane Kate of 1985. Hurricane Eta became a major hurricane in November 2020, as did Hurricane Iota the same month.

Off-season

Further information: Off-season storms

Though the season runs from June 1 to November 30, storms can form any month. Since 1870, 32 off-season storms have formed, with 18 in May. Nine formed in December, three in April, and one each in January, February, and March. The most off-season storms were in 1887, with four. January has had two Category 1 hurricanes: one in 1938 and Hurricane Alex in 2016. No major hurricanes occur off-season.

Monitoring

The United States National Hurricane Center (NHC) watches tropical weather in the North Atlantic and issues reports and warnings. It is one of the Regional Specialized Meteorological Centers for tropical cyclones, as set by the World Meteorological Organization.

Extremes

See also: List of Atlantic hurricane records

Hurricane Katrina was one of the most expensive and deadly hurricanes in U.S. history.

Hurricane Harvey also caused a lot of damage and flooding in Texas.

The year with the most tropical storms was the 2020 Atlantic hurricane season, with 30 storms. The 2005 Atlantic hurricane season had the most powerful hurricanes, with 7 major hurricanes.

The weakest season since 1946 was the 1983 Atlantic hurricane season, with only four tropical storms. The 1914 Atlantic hurricane season was the weakest ever recorded, with just one storm.

Hurricane Wilma was the strongest hurricane ever recorded in the Atlantic, with very low pressure.

Hurricane Sandy was the biggest hurricane, with very wide winds.

The 1899 San Ciriaco hurricane lasted the longest, for over 27 days.

Hurricane Ivan created the most tornadoes of any hurricane on record.

The Great Hurricane of 1780 was the deadliest hurricane in history.

The Galveston Hurricane of 1900 was the deadliest to hit the U.S. mainland.

Hurricane Katrina and Hurricane Harvey were the most damaging, causing a lot of money in losses.

Trends

See also: Atlantic hurricane reanalysis

Paleoclimatology and historical trends

Studies show that big hurricanes hitting the Gulf Coast change over many hundreds or even thousands of years. There were times long ago when many big hurricanes hit the area, and other times when fewer did. Scientists think this pattern is linked to the position of a big area of high pressure in the Atlantic Ocean called the Azores High. When this high pressure area moves, it changes where hurricanes travel.

In recent centuries, hurricanes seem to be hitting areas farther north more often. This shift may be connected to changes in Earth’s climate.

Climate change

Since 1979, big hurricanes in the Atlantic Ocean have become stronger. Scientists believe this is linked to changes in Earth’s climate. While the total number of hurricanes each year hasn’t clearly gone up, the ones that form are often more powerful.

Impact

Hurricanes are causing more damage today because more people and buildings are near the coast. Some of the costliest hurricanes ever have happened in recent years. Even though we now have better tools to track storms, it’s clear that the strongest hurricanes are becoming more common.

Names

In the past, storms were given names in different ways. By the mid-1900s, storms were only given female names. In 1979, they started using both male and female names. In 1953, storms began using names from a set list. If a storm causes a lot of damage, its name might be retired so it isn’t used again. Each season, about 14 named storms happen in the North Atlantic, with 7 becoming hurricanes and 3 becoming major hurricanes.