Storm history of Hurricane Ivan

The **storm history of Hurricane Ivan**, the longest tracked tropical cyclone of the 2004 Atlantic hurricane season, lasted from late August through late September. The hurricane developed from a tropical wave that moved off the coast of Africa on August 31. Moving westward from the effects of a ridge, favorable conditions allowed it to develop into Tropical Depression Nine on September 2 in the deep tropical Atlantic Ocean. The cyclone slowly intensified until September 5, when it underwent rapid deepening and reached Category 4 status on the Saffir-Simpson Hurricane Scale; at the time Ivan was the southernmost major hurricane on record.

Ivan quickly weakened because of dry air, but it slowly reorganized itself, passing just south of Grenada as a major hurricane on September 7. The hurricane strengthened into a Category 5 hurricane while in the central Caribbean Sea. Over next the days its intensity changed largely due to eyewall replacement cycles, and Ivan passed just south of Jamaica, the Cayman Islands, and western Cuba with winds at or slightly below Category 5 status. Turning northward and encountering unfavorable conditions, Ivan slowly weakened before making landfall just west of Gulf Shores, Alabama, on September 16 with winds of 120&nbsp;mph (195&nbsp;km/h). The cyclone quickly weakened to tropical depression status as it turned to the northeast, and Ivan transitioned into an extratropical cyclone on September 18.

The remnant low of Ivan turned to the south and southwest, and after crossing Florida on September 21 it began to regain tropical characteristics. It became a tropical depression again on September 22 to the southeast of Louisiana, and Ivan reached winds of 60&nbsp;mph (95&nbsp;km/h) before weakening and moving ashore along southwestern Louisiana as a tropical depression; the circulation of Ivan dissipated after crossing into Texas on September 25. The cyclone broke several intensity records, and its duration was the tenth longest on record for an Atlantic hurricane.

## Formation and intensification
On August 31, a large tropical wave moved off the west coast of Africa. A tropical system along the wave axis contained a low pressure area as well as an impressive outflow pattern, though originally its convection was disorganized and limited. By September 1 a cyclonic circulation with a diameter of 690&nbsp;mile (1115&nbsp;km) was seen on satellite imagery, well to the southeast of the Cape Verde Islands.  As it moved quickly westward, the convection organized and developed into rainbands–bands of showers and thunderstorms that move in a spiral direction towards the center of the storm–and late on September 1 meteorologists began tracking the system using the Dvorak technique. Low amounts of wind shear and favorable outflow allowed strong deep convection to develop and persist near the center, and by 1800&nbsp;UTC on September 2 the system developed into Tropical Depression Nine about 450&nbsp;miles (730&nbsp;km) southwest of Praia, Cape Verde. the Geophysical Fluid Dynamics Laboratory predicted the depression to reach Category 4 status on the Saffir-Simpson Hurricane Scale within three days. Increased northeasterly wind shear shifted the center to the northeastern edge of the deep convection, and despite the shear and its relatively low latitude of 9.7°&nbsp;N, the depression strengthened to attain tropical storm status early on September 3; upon reaching the intensity, the National Hurricane Center classified the system as Tropical Storm *Ivan*. The next day, the deep convection temporarily became disorganized, before reorganizing and developing an eye feature.  Ivan became a hurricane at around 0600&nbsp;UTC on September 5. After reaching hurricane status, Ivan began to rapidly intensify with continued favorable conditions, and in an 18&nbsp;hour period the pressure dropped 39&nbsp;mbar (1.15&nbsp;inHg) as the winds increased by 60&nbsp;mph (95&nbsp;km/h); early on September 6 Ivan reached its first peak intensity of 135&nbsp;mph (215&nbsp;km/h) while about 825&nbsp;miles (1330&nbsp;km) east of the island of Tobago. Shortly after becoming a Category 4 hurricane, the outer convection of the hurricane became ragged. Hurricane Hunters found a Saharan Air Layer in the northern portion of the eye, leaving the eyewall eroded which caused a marked decrease in winds; by late on September 6 Ivan weakened to winds of 105&nbsp;mph (165&nbsp;km/h). Ivan then re-gained major hurricane status as it approached the Lesser Antilles, and at 2130&nbsp;UTC on September 7 the cyclone passed 7&nbsp;miles (11&nbsp;km) south-southwest of the southern tip of Grenada, its closest approach to the island. At the time, the hurricane maintained an eye diameter of 12&nbsp;miles (19&nbsp;km), with the northern portion of the eyewall producing strong winds on the island. and for about 18&nbsp;hours the intensity stayed the same as it paralleled the northern coast of Venezuela offshore. Another period of rapid deepening began late on September 8 as its motion turned to the west-northwest. It is estimated Ivan attained Category 5 status at 0600&nbsp;UTC on September 9, while about 90&nbsp;miles (145&nbsp;km) north of Aruba. As it tracked further away from Jamaica, Ivan again rapidly intensified to Category 5 status, and early on September 12 it reached its peak intensity of 165&nbsp;mph (265&nbsp;km/h) with a pressure of 910&nbsp;mbar (26.87&nbsp;inHg). At 1415&nbsp;UTC on September 12 Ivan passed 25&nbsp;miles (40&nbsp;km) south-southwest of George Town, Cayman Islands, with winds of 150&nbsp;mph (240&nbsp;km/h). After its eyewall became re-established Ivan attained Category 5 status for a third time early on September 13. Shortly thereafter, a trough created a weakness in the ridge to its north, causing the hurricane to turn to the northwest. The combination of the combination of enhanced outflow from the trough and very warm waters allowed Ivan to maintain Category 5 status for 30&nbsp;hours. Early on September 14 the hurricane passed through the Yucatán Channel about 17&nbsp;miles (28&nbsp;km) southwest of Cabo San Antonio, Cuba,

## Gulf of Mexico and Alabama landfall
After entering the southern Gulf of Mexico, Hurricane Ivan weakened to Category 4 status by 0600&nbsp;UTC on September 14. As it slowly turned to the north, southwesterly flow from a large trough over the central United States increased wind shear over the hurricane. By late on September 14 the weakening trend ceased as the eyewall became better defined, and Ivan was expected to restrengthen a little bit over an area of warmer water temperatures. The eye diameter expanded to 60&nbsp;miles (95&nbsp;km/h), though westerly wind shear and dry continued to increase. As Ivan approached the Gulf Coast of the United States, Hurricane Hunters reported erosion of the southern portion of the eyewall, and cooler waters just offshore contributed to further weakening. At around 0650&nbsp;UTC on September 16, Hurricane Ivan made landfall just west of Gulf Shores, Alabama, with winds of 120&nbsp;mph (195&nbsp;km/h). The strongest winds occurred over a narrow area near the southern Alabama and western Florida border. and early on September 17 the cyclone weakened into a tropical depression over northeastern Alabama. Ivan accelerated to the northeast ahead of an approaching cold front, dropping heavy rainfall along its path. Late on September 18, the remnants of Ivan became an extratropical low as it merged with the cold front over the Delmarva Peninsula. The system turned south and southwestward over the next few days. On September 21 the low crossed southern Florida and emerged into the Gulf of Mexico. As it moved across the warm waters of the region the low began to re-acquire tropical characteristics; the low-level circulation became increasingly better defined, and convection redeveloped over the center. It is estimated the low redeveloped into Tropical Depression Ivan late on September 22 while about 175&nbsp;miles (280&nbsp;km) south-southeast of the mouth of the Mississippi River. As an area of deep convection developed over the center, Ivan reached winds of 60&nbsp;mph (95&nbsp;km/h), though the winds decreased as thunderstorm activity diminished. Ivan weakened to a tropical depression at 0000&nbsp;UTC on September 24, and two hours later it moved ashore near Holly Beach, Louisiana. and the circulation dissipated early on September 25. The remnant trough reached the northwestern Gulf of Mexico later that day, producing scatter thunderstorms for a short time, before it diminished.

## Records
Ivan became the southernmost major hurricane on record after reaching Category 3 status on the Saffir-Simpson Hurricane Scale at 10.2°&nbsp;N. Lasting as a tropical cyclone for a total of 450&nbsp;hours, Ivan was the tenth longest tracked Atlantic hurricane on record. After making its first landfall in the United States, the hurricane spawned a total of 117&nbsp;tornadoes,

## Related pages
* Hurricane Ivan
* 2004 Atlantic hurricane season

## References
## Other websites
* NHC Tropical Cyclone Report for Hurricane Ivan
* NHC advisory archives for Hurricane Ivan