|Category 1 hurricane (SSHWS/NWS)|
|Formed||October 31, 2017|
|Dissipated||November 11, 2017|
80 mph (130 km/h) |
|Lowest pressure||972 mbar (hPa); 28.7 inHg|
(Third-costliest tropical cyclone in the Atlantic basin; third-costliest in U.S. history)
|Areas affected||Southeastern United States (especially Alabama, Louisiana)|
|Part of the 2017 Atlantic hurricane season|
Hurricane Klaus was the first hurricane to strike Alabama since Issac in 2012. The fourteenth tropical depression, eleventh named storm, and seventh hurricane of the 2017 Atlantic hurricane season, Klaus developed in the Gulf of Mexico from a long-tracked tropical wave. Designated on November 1, Klaus tracked north-northwestward and steadily intensified into an 80 mph (130 km/h) Category 1 hurricane just before making landfall in Mobile, Alabama on November 3. On November 8, it emerged back over the Gulf of Mexico, strengthening to a tropical storm before making a third and final landfall in Florida on November 9. Klaus quickly tracked across the Southeastern United States, maintaining its strength before emerging into the Atlantic Ocean on November 10. It became extratropical the next day, and dissipated on November 13. Klaus lasted unusually long for a November storm, remaining tropical for 11 days, most of them over land dumping torrential rains.
The third-costliest tropical cyclone on record, approximately $150 billion (2017 USD) in damages were inflicted, primarily from widespread flooding in the Mobile metropolitan area. The storm stalled as it made its way inland, downgrading to a tropical depression while it slowly meandered through Alabama, dropping torrential and unprecedented amounts of rainfall over the state. In a five-day period, many areas received more than 40 inches (1,000 mm) of rain as the system slowly meandered over central Alabama and adjacent waters, causing catastrophic flooding. With peak accumulations of 68.20 in (1732 mm), Klaus was the wettest tropical cyclone on record in the United States. The resulting floods inundated hundreds of thousands of homes and displaced more than 30,000 people.
Seventy-four people died in Alabama alone. Along its entire path, Klaus caused $150 billion (2017 USD) in damage and 77 deaths. Aside from Alabama, areas that saw significant damage were Louisiana, northwestern Florida, and Georgia.
Hurricane Klaus originated from a tropical wave that was first identified by the Jarrell Meteorlogical Center (JMC) off the west coast of Africa on October 17, 2017. Traveling westward, the wave remained weak, barely being notable. By October 22 convection began to increase; however, wind shear in the region prevented this development from continuing. The system entered the Florida Straits several days later, a region with more favorable conditions for cyclonic development. Intermittent convection formed around the wave as it moved west-northwestward before the development maintained itself. On October 31, the system had become sufficiently organized for the JMC to classify it as Tropical Depression Fourteen, with the center of circulation situated roughly 53 mi (85 km) southeast of Key West, Florida.
Deep convection increased further as the depression moved more into the Gulf of Mexico, steered by a ridge over southern Florida, although it remained ragged and displaced from the circulation. A large plume of convection developed over the system on November 1 as outflow improved and wind shear decreased. Later that day, reports from the Hurricane Hunters indicated that the depression intensified into Tropical Storm Klaus about 133 mi (214 km) southwest of Apalachicola, Florida. Lessening shear and unseasonably warm water temperatures around 76 °F (24 °C) allowed the storm to intensify. Although outflow was restricted to the northwest, curved rainbands increased over the eastern half of the system, increasing the extent of tropical storm-force winds. Additionally, a ragged eye became visible on satellite imagery on November 2, and at 18:00 UTC, Klaus intensified into a Category 1 hurricane on the Saffir–Simpson scale.
The hurricane strengthened slightly further to a peak intensity of 80 mph (130 km/h) by 00:00 UTC on November 3. At around 06:30 UTC (2:30 a.m. EDT) that day, Klaus made landfall around Gulf Shores, Alabama, at peak intensity, with a minimum pressure of 972 mbar (hPa; 28.7 inHg). The storm maintained its intensity as it entered Mobile Bay and slowed dramatically to a crawl, making a second landfall in Mobile around 1245 UTC (8:30 a.m. EDT). Within four hours of landfall, the winds dropped below hurricane force as the appearance on radar imagery degraded. For over five days the storm stalled inland, dropping very heavy rainfall and causing widespread flash flooding. Klaus' center drifted back towards the southeast, ultimately re-emerging into the Gulf of Mexico on November 8. Once offshore, Klaus managed to attain a secondary peak of 55 mph (89 km/h), before making its third and final landfall just east of Pensacola, Florida, with winds of 50 mph (85 km/h). The convection diminished while Klaus crossed into Georgia, with the strongest winds near the Atlantic coast. The center elongated as it continued quickly northeastward through the southeastern United States. Klaus emerged into the Atlantic just south of Myrtle Beach, South Carolina late on November 10. Klaus later lost its tropical characteristics on November 11 to the east of North Carolina. Its remnant low continued northeastward towards Atlantic Canada before being absorbed into another extratropical system on November 13.