Meteorological history of Hurricane Katrina
Encyclopedia : M : ME : MET : Meteorological history of Hurricane Katrina
Formation
Tropical Depression Twelve formed over the southeastern Bahamas at 5:00 p.m. EDT (2100 UTC) on August 23, 2005, partially from the remains of Tropical Depression Ten. While normal standards for numbering tropical depressions indicate that the old name/number is retained, satellite data indicates that a second disturbance combined with Tropical Depression Ten to form a new system, which was so designated as Tropical Depression Twelve."[Tropical Depression TWELVE]." National Hurricane Center. August 23, 2005. In a later re-analysis, it was determined that the low-level circulation of Ten had completely detached and dissipated, with only the remnant mid-level circulation moving on and merging with the aforementioned tropical wave. Those conditions did not fulfill the criteria for keeping the same name and identity. Knabb, Richard D.; Rhome, Jamie R. "[Tropical Cyclone Report: Hurricane Katrina]." National Hurricane Center. December 20, 2005.First landfall
The system was upgraded to Tropical Storm Katrina on the morning of August 24. A burst of convection allowed Katrina to become the fourth hurricane of the 2005 season on August 25, only two hours before it made landfall around 6:30 p.m. EST between Hallandale Beach and Aventura, Florida. Katrina had a well-defined eye on doppler radar which remained intact throughout its passage over Florida. The storm weakened over land on August 26 to a tropical storm, and regained strength to hurricane status at 2:00 a.m. EDT, approximately one hour after entering the Gulf of Mexico. Parts of the Florida Keys experienced tropical storm winds throughout August 26, with the Dry Tortugas briefly experiencing hurricane-force winds.
Gulf of Mexico
The initial NHC forecasts predicted that Katrina would begin turning northward after landfall, eventually to hit the Florida Panhandle approximately three to four days in the future. Katrina, however, continued a westerly and west-southwesterly track, which eventually shifted the forecast track westward to New Orleans.
Immediately after the storm entered the Gulf of Mexico, the low wind shear, good upper-level outflow, and the warm sea surface temperatures of the Gulf Loop Current caused Katrina to start intensifying rapidly. On August 27, the storm was upgraded to Category 3 intensity, becoming the third major hurricane of the season. An eyewall replacement cycle disrupted the intensification of maximum winds for about 18 hours, but led to an almost doubling in radius of the storm. A second period of rapid intensification started by 7:00 p.m. CDT on August 28, and by 12:40 a.m. CDT on August 29, Katrina was upgraded to a Category 4 hurricane. It became a Category 5 storm by 7:00 a.m. CDT, twelve hours after the beginning of the second round of rapid intensification, and reached its peak intensity at 1:00 p.m. CDT with maximum sustained winds of 175 mph (280 km/h), gusts of 215 mph (344 km/h) and a central pressure of 26.64 inches or 902 mbar. The minimum pressure made Katrina, at the time, the fourth most intense Atlantic Basin hurricane on record (Hurricanes Rita and Wilma would later surpass Katrina that same year).
By August 29, the storm was large enough that some areas of the Gulf Coast were already experiencing tropical storm-force winds. The center of Katrina was about 200 mi (315 km) away from the mouth of the Mississippi River. Tropical storm-force winds extended 230 statute miles (370 km) away from the center of the storm, and hurricane-force winds extended about 100 miles (165 km) away. Overnight on August 29, and into that morning, Katrina quickly weakened (in terms of maximum sustained winds) as it began to enter another eyewall replacement cycle. The inner eyewall deteriorated before an outer eyewall had fully formed. Slightly-increasing shear and dropping sea surface temperatures also may have played a role in the weakening. In 18 hours, the hurricane's maximum sustained winds decreased from 170 mph (280 km/h) to 125 mph (205 km/h). However, storm surge remained high at landfall because large waves greater than 30 feet in height (up to 55 feet) were generated beforehand when Katrina was at Categories 4 and 5. The waves then combined with the storm surge of the large Category 3 hurricane.
Second and third landfalls
Katrina made its second landfall at 6:10 a.m. CDT on August 29 as a Category 3 hurricane with sustained winds of 125 mph (205 km/h) near Buras-Triumph, Louisiana. At landfall, hurricane-force winds extended outward 120 miles (190 km) from the center and the storm's central pressure was 920 mbar. Because Katrina had just weakened from Category 4 and due to the shape of the coastline, sustained Category 4 winds likely existed on land while the eye was over water. At landfall, hurricane-force winds extended outward 120 miles (190 km) from the center, the storm's pressure was 920 mbar (27.17 inHg), and its forward speed was 15 mph (10 km/h). Making its way up the eastern Louisiana coastline, most communities in Plaquemines, St. Bernard Parish, and Slidell in St. Tammany Parish were severely damaged by storm surge and the strong winds of the eyewall, which also grazed eastern New Orleans.
A few hours later, after weakening slightly, Katrina made its third landfall near the Louisiana/Mississippi border with 120 mph (195 km/h) sustained winds, still at Category 3 intensity. Its minimum pressures at its second and third landfalls were 920 mbar, making Katrina the third strongest hurricane on record to make landfall on the United States.
Because the storm was so large, extremely-damaging eyewall winds and the strong northeastern quadrant of the storm pushed record storm surges onshore, smashing the entire Mississippi Gulf Coast, including towns in Mississippi such as Waveland, Bay St. Louis, Pass Christian, Long Beach, Gulfport, Biloxi, Ocean Springs, Gautier and Pascagoula, and, in Alabama, Bayou La Batre. The storm surges peaked at 34 ft (10.4 m) in Bay St. Louis, Mississippi and at 13 feet (4 m) as far away as Mobile, Alabama (the highest since 1917). Storm surge was particularly high due to the hydrology of the location, the hurricane's extreme size, and the fact that it weakened only shortly before landfall. As Katrina moved inland diagonally over Mississippi, high winds cut a swath of damage that affected almost the entire state.
Demise
Katrina maintained hurricane strength well into Mississippi, but weakened thereafter, losing hurricane strength more than 150 mi (240 km) inland, near Jackson, Mississippi. It was downgraded to a tropical depression near Clarksville, Tennessee and broke in half. One half continued to race northward, affecting the central U.S. along its path, and was last distinguishable in the eastern Great Lakes region on August 31. On August 31, Katrina was absorbed by a frontal boundary and became a powerful extratropical low, causing 50-170 mm (1.97-6.69 in) of rain in 12 hours, as well as gale-force wind gusts from 31 to 61 mph (50 to 98 kp/h) in southeastern Quebec and northern New Brunswick. In the region of Saguenay and Cote-Nord, rain caused breakdowns and failure in roads. The Cote-Nord region was isolated from rest of Quebec for at least 1 week. The other half of Katrina broke off in the eastern part of the Appalachians, primarily leading to a significant tornado outbreak in the area from central Georgia to central Pennsylvania, killing two people and causing millions of dollars in additional damage.At 11:00 p.m. EDT on August 31, the center of the remnant low of what was Katrina had been completely absorbed by a frontal boundary in southeastern Canada, with no discernible circulation."[Tropical Summary Message]." Hydrometeorological Prediction Center. August 31, 2005."[Post-Tropical Storm Katrina Information Statement]." Canadian Hurricane Centre. August 31, 2005.
See also
- redirect
References
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.