Barometric pressure in the context of "Inch of mercury"

Hurricane Marie is tied as the seventh-most intense Pacific hurricane on record, attaining a barometric pressure of 918 mbar (hPa; 27.11 inHg) in August 2014. The fourteenth named storm, ninth hurricane, and sixth major hurricane of the season, Marie began as a tropical wave that emerged off the west coast of Africa over the Atlantic Ocean on August 10. Some organization of shower and thunderstorm activity initially took place, but dry air soon impinged upon the system and imparted weakening. The wave tracked westward across the Atlantic and Caribbean for several days. On August 19, an area of low pressure consolidated within the wave west of Central America. With favorable atmospheric conditions, convective activity and banding features increased around the system and by August 22, the system acquired enough organization to be classified as Tropical Depression Thirteen-E while situated about 370 mi (595 km) south-southeast of Acapulco, Mexico. Development was initially fast-paced, as the depression acquired tropical storm-force winds within six hours of formation and hurricane-force by August 23. However, due to some vertical wind shear its intensification rate stalled, and for a time it remained a Category 1 hurricane on the Saffir–Simpson hurricane wind scale.

On August 24, Marie developed an eye and rapidly intensified to a Category 5 hurricane with winds of 160 mph (260 km/h). At its peak, the hurricane's gale-force winds spanned an area 575 mi (925 km) across. Marie subsequently underwent an eyewall replacement cycle on August 25 which prompted steady weakening. Over the next several days, Marie progressively degraded to below hurricane strength as it moved into an increasingly hostile environment with cooler waters and a more stable atmosphere. On August 29, after having lost all signs of organized deep convection, Marie degenerated into a remnant low. The large system gradually wound down over the following several days, with winds subsiding below gale-force on August 30. The remnant cyclone eventually lost a well defined center and dissipated on September 2 about 1,200 mi (1,950 km) northeast of Hawaii.

Hurricane Katrina was an extremely powerful and catastrophic tropical cyclone that killed 1,392 people and caused damage estimated at $125 billion, particularly in and around the city of New Orleans, in late August 2005. It is tied with Hurricane Harvey as being the costliest tropical cyclone in the Atlantic basin. Katrina was the twelfth tropical cyclone, the fifth hurricane, the third major hurricane, and the second Category 5 hurricane of the 2005 Atlantic hurricane season. It was also the fourth-most intense Atlantic hurricane to make landfall in the contiguous United States, as measured by barometric pressure.

Katrina formed on August 23, 2005, with the merger of a tropical wave and the remnants of a tropical depression. After briefly strengthening to a tropical storm over south Florida, Katrina entered the Gulf of Mexico on August 26 and rapidly intensified to a Category 5 hurricane before weakening to a Category 3 at its landfall on August 29 near Buras-Triumph, Louisiana.

Hurricane Wilma was the most intense tropical cyclone in the Atlantic basin and the second-most intense tropical cyclone in the Western Hemisphere, both based on barometric pressure, after Hurricane Patricia in 2015. Wilma's rapid intensification led to a 24-hour pressure drop of 97 mbar (2.9 inHg), setting a new basin record. At its peak, Hurricane Wilma's eye contracted to a record minimum diameter of 2.3 mi (3.7 km). In the record-breaking 2005 Atlantic hurricane season, Wilma was the twenty-second storm, thirteenth hurricane, sixth major hurricane, and fourth Category 5 hurricane, and was the second costliest hurricane in Mexican history, behind Hurricane Otis in 2023.

Its origins came from a tropical depression that formed in the Caribbean Sea near Jamaica on October 15, headed westward, and intensified into a tropical storm two days later, which abruptly turned southward and was named Wilma. Continuing to strengthen, Wilma eventually became a hurricane on October 18. Shortly thereafter, explosive intensification occurred, and in only 24 hours, Wilma became a Category 5 hurricane with wind speeds of 185 mph (295 km/h). Wilma's intensity slowly leveled off after becoming a Category 5 hurricane, and winds had decreased to 150 mph (240 km/h) before it reached the Yucatán Peninsula on October 20 and 21. After crossing the Yucatán, Wilma emerged into the Gulf of Mexico as a Category 2 hurricane. As it began accelerating to the northeast, gradual re-intensification occurred, and the hurricane was upgraded to Category 3 status on October 24. Shortly thereafter, Wilma made landfall in Cape Romano, Florida, with winds of 120 mph (190 km/h). As Wilma was crossing Florida, it briefly weakened back to a Category 2 hurricane, but again re-intensified as it reached the Atlantic Ocean. The hurricane intensified into a Category 3 hurricane for the last time, before weakening while accelerating northeastward. By October 26, Wilma transitioned into an extratropical cyclone southeast of Nova Scotia.

Hurricane Florence was a powerful and long-lived tropical cyclone that caused catastrophic damage in the Carolinas in September 2018, primarily as a result of freshwater flooding due to torrential rain. The sixth named storm, third hurricane, and the first major hurricane of the 2018 Atlantic hurricane season, Florence originated from a strong tropical wave that emerged off the west coast of Africa on August 30, 2018. The wave steadily organized, and strengthened into a tropical depression on the next day near Cape Verde. Progressing along a steady west-northwest trajectory, the system gradually strengthened, acquiring tropical storm strength on September 1. An unexpected bout of rapid intensification ensued on September 4–5, culminating with Florence becoming a Category 4 major hurricane on the Saffir–Simpson scale (SSHWS), with estimated maximum sustained winds of 130 mph (215 km/h). Strong wind shear then led to rapid weakening, and Florence weakened to tropical storm strength on September 7. Shifting steering currents led to a westward turn into a more suitable environment; as a result, Florence reintensified to hurricane strength on September 9 and major hurricane status by the following day. Florence reached peak intensity on September 11, with 1-minute winds of 150 mph (240 km/h) and a minimum central pressure of 937 mbar (27.7 inHg). An unexpected eyewall replacement cycle and decreasing oceanic heat content caused a steady weakening trend; however, the storm grew in size at the same time. Early on September 14, Florence made landfall in the United States just south of Wrightsville Beach, North Carolina as a Category 1 hurricane, and weakened further as it slowly moved inland under the influence of weak steering currents. Florence degenerated into a post-tropical cyclone over West Virginia on September 17 and was absorbed by another frontal storm two days later.

Early in the storm's history, the system brought squalls to the Cape Verde islands, resulting in minor landslides and flooding; however, overall effects remained negligible. With the threat of a major impact in the Southeastern and Mid-Atlantic United States becoming evident by September 7, the governors of North Carolina, South Carolina, Virginia, Georgia, and Maryland, and the mayor of Washington, D.C. declared a state of emergency. On September 10 and 11, the states of North Carolina, South Carolina, and Virginia issued mandatory evacuation orders for some of their coastal communities, predicting that emergency personnel would be unable to reach people there once the storm arrived. Though Florence made landfall as a greatly weakened Category 1 hurricane, winds associated with the tropical cyclone were strong enough to uproot trees and power lines, causing extensive power outages across the Carolinas. Furthermore, due to the slow motion of the storm, heavy rain fell throughout the Carolinas for several days. Coupled with a powerful storm surge, the rainfall caused widespread flooding along a long stretch of the North Carolina coast, from New Bern to Wilmington. Inland flooding from Florence inundated cities such as Fayetteville, Smithfield, Lumberton, Durham, and Chapel Hill. Most major roads and highways in the area experienced flooding, with large stretches of I-40, I-95, and US Route 70 remaining impassable for days after the storm's passage. Wilmington was cut off entirely from the rest of the mainland by the flooding. The storm also spawned tornadoes in several places along its path, including an EF2 tornado that killed one person in Virginia. Many places received record-breaking rainfall, with Florence setting maximum rainfall records from a tropical cyclone in both of the Carolinas. Overall, the storm caused $24.23 billion in damage, mostly in the Carolinas, and 54 deaths.

The eye is a region of mostly calm weather at the center of a tropical cyclone. The eye of a storm is a roughly circular area, typically 30–65 kilometers (19–40 miles; 16–35 nautical miles) in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the most severe weather and highest winds of the cyclone occur. The cyclone's lowest barometric pressure occurs in the eye and can be as much as 15 percent lower than the pressure outside the storm.

In strong tropical cyclones, the eye is characterized by light winds and clear skies, surrounded on all sides by a towering, symmetric eyewall. In weaker tropical cyclones, the eye is less well defined and can be covered by the central dense overcast, an area of high, thick clouds that show up brightly on satellite imagery. Weaker or disorganized storms may also feature an eyewall that does not completely encircle the eye or have an eye that features heavy rain. In all storms, however, the eye is where the barometer reading is lowest.

Hurricane Rita is the most intense tropical cyclone on record in the Gulf of Mexico, now tied with Hurricane Milton of 2024, as well as being one of the most intense Atlantic hurricanes on record overall. Part of the record-breaking 2005 Atlantic hurricane season, which included three of the ten most intense Atlantic hurricanes in terms of barometric pressure ever recorded (along with Wilma and Katrina), Rita was the seventeenth named storm, tenth hurricane, fifth major hurricane, and third Category 5 hurricane of the 2005 season. It was also the earliest-forming 17th named storm in the Atlantic until Tropical Storm Rene in 2020. Rita formed near The Bahamas from a tropical wave on September 18, 2005, that originally developed off the coast of West Africa. It moved westward, and after passing through the Florida Straits, Rita entered an environment of abnormally warm waters. Moving west-northwest, it rapidly intensified to reach peak winds of 180 mph (285 km/h), achieving Category 5 status on September 21. However, it weakened to a Category 3 hurricane before making landfall in Johnson's Bayou, Louisiana, between Sabine Pass, Texas and Holly Beach, Louisiana, with winds of 115 mph (185 km/h). Rapidly weakening over land, Rita degenerated into a large low-pressure area over the lower Mississippi Valley by September 26.

In Louisiana, Rita's storm surge inundated low-lying communities along the entire coast, worsening effects caused by Hurricane Katrina less than a month prior, such as topping the hurriedly-repaired Katrina-damaged levees at New Orleans. Parishes in Southwest Louisiana and counties in Southeast Texas where Rita made landfall suffered from severe to catastrophic flooding and wind damage. According to an October 25, 2005, Disaster Center report, 4,526 single-family dwellings were destroyed in Orange and Jefferson counties located in Southeast Texas. Major damage was sustained by 14,256 additional single-family dwellings, and another 26,211 single-family dwellings received minor damage. Mobile homes and apartments also sustained significant damage or total destruction. In all, nine Texas counties and five Louisiana Parishes were declared disaster areas after the storm. Electric service was disrupted in some areas of both Texas and Louisiana for several weeks. Texas reported the most deaths from the hurricane, where 113 deaths were reported, 107 of which were associated with the evacuation of the Houston metropolitan area.