Hurricane Ike - Meteorological History

Meteorological History

Hurricane Ike can be traced to a westerly wave leaving western Sudan on August 19, which moved westward through Nigeria and Mali and reached the coastal country of Senegal on August 28. Moving into the Atlantic Ocean, the wave slowly intensified over subsequent days while moving generally toward the west-northwest. On September 1, the wave developed a sufficient amount of convection and was designated Tropical Depression Nine. The depression had developed a large amount of convection as well as cyclonically curved bands. Satellite estimates were already indicating that the depression was a tropical storm; the National Hurricane Center did not classify it as such, however, because the convection was newly formed. The depression continued to intensify as it became better organized, and at 5:00 pm EDT (21:00 UTC), it was upgraded to Tropical Storm Ike. Ike was located in an environment that was supportive of intensification, and the forecast showed Ike becoming a hurricane within 36 hours of its upgrade.

During the overnight hours of September 1, Ike stopped intensifying, as a part of the eastern band began to erode as northerly wind shear began to impact the system. By late morning on September 2, Ike began to intensify again as shear relaxed a little on the system. Throughout the day, deep convection developed around the center of Ike indicating that the storm was still strengthening. Ike also quickened its movement to 18 mph (29 km/h) due to a strengthening mid-level high located to the north-northeast of Ike. Again intensification stopped during the overnight hours as the structure of Ike remained mostly unchanged.

Ike remained at the same intensity and structure through the early morning hours of September 3. However, by the late morning, Ike began to intensify again. Microwave satellites depicted an eye beginning to form and Ike strengthened just below hurricane status. The eye continued to become better defined and by mid-afternoon Ike was upgraded to a hurricane. Ike was in an area that lacked vertical wind shear and intensification was likely. Due to the lack of wind shear, Ike began to undergo explosive intensification and was upgraded to a major hurricane with winds of 115 mph (185 km/h) only three hours after being upgraded to a hurricane. During the three hour span, it is estimated that the pressure dropped 24 mbar (0.71 inHg). Ike continued to intensify and was further upgraded to a Category 4 hurricane on the Saffir-Simpson Hurricane Scale three hours later with winds of 135 mph (215 km/h) and an estimated pressure of 948 mbar (27.99 inHg). These were satellite estimates, not actual measurements (as it was still too far from land for reconnaissance aircraft to reach).

By the early morning hours on September 4, Ike had reached its peak intensity of 145 mph (230 km/h) with an estimated pressure of 935 mbar (27.61 inHg), making it the most intense storm of the season.

Ike was now forecast to weaken as the upper-level high to the north of the system continued to strengthen resulting in stronger northerly wind shear affecting Ike. The explosive intensification lasted roughly 24 hours as Ike intensified from a tropical storm to a Category 4 hurricane with a pressure drop of 61 mbar (1.80 inHg). By the late morning, Ike began to weaken as the cloud tops around the eye began to warm. Models were forecasting Ike to encounter strong wind shear and slowly weaken but maintain major hurricane status. This trend of the clouds warming continued through the afternoon and Ike continued to weaken slowly. By mid-afternoon, Ike was barely a Category 4 hurricane with winds of 135 mph (215 km/h). Ike began to show signs of intensification once more during the late night hours. The eye became more clear and better defined and the clouds around the eye began to deepen and become colder.

The show of possible strengthening did not last long, however, and by the morning of September 5, northerly wind shear began to erode the northern part of the system, and the cloud tops around the eye began to warm once more. The structure of the eye became less prominent as microwave satellite imagery showed that the inner structure of Ike was not deteriorating or beginning to undergo an eyewall replacement cycle. A later pass made by the satellite found that the northern eye wall had eroded and most of the convection was in the southern semicircle of the storm. This indicated that Ike was continuing to weaken as it remained in a hostile environment. Ike slowly weakened to a low-end Category Three by the afternoon hours. A ridge to the north of Ike continued to push the storm towards the southwest, into an area more favorable for intensification.

Ike maintained its intensity throughout the night as its eye briefly reappeared around 8 pm EDT, leading the NHC to forecast a slow strengthening trend. Overnight, Ike reformed a 24 nmi (48 km) wide eye, however, it was cloud covered. However, during the late morning hours on September 6, wind shear weakened Ike to a Category Two hurricane. This weakening was short lived and Ike began to undergo another round of rapid intensification, though not as significant as the first. Ike's eye began to clear out again and the system became better organized and based on an Air Force Reconnaissance Aircraft measurement, Ike had intensified into a Category Four six hours after being downgraded to a Category Two. During the afternoon and overnight, Ike had winds sustained at 135 mph (217 km/h) as it approached and passed over the Turks and Caicos Islands by the early morning hours of September 7.

Ike made landfall as a Category 4 hurricane in Holguín Province, Cuba on the evening of September 7, near Cabo Lucrecia on the northern coast. It passed across the central provinces of Holguín, Las Tunas, and Camagüey, emerging south of Cuba on September 8. It made landfall a second time as a Category 1 hurricane in Pinar del Río before entering the Gulf in the afternoon of September 9.

During the night of September 10, Ike exhibited a rapid drop in central pressure, falling from 963 mbar (28.44 inHg) to 944 mbar (27.88 inHg) as it passed over the Loop Current in the Gulf of Mexico. This drop was not reflected by wind speed, however, which only increased to 100 mph (160 km/h) from 85 mph (140 km/h). Multiple wind maxima were noted by the National Hurricane Center, indicating the structure was absorbing and distributing energy over a large area, rather than concentrating it near the center. The pressure was significantly lower than normal for a low-end Category 2 hurricane, as 944 mbar (27.88 inHg) is more typical of a strong Category 3 or a Category 4 hurricane.

Over the next two days, Ike maintained a steady course towards Galveston and Houston. It increased only slightly in intensity to 110 mph (175 km/h) – the high end of Category 2 – but exhibited an unusually large wind field. This caused a projected storm surge of a Category 4 height though the windspeeds were that of a Category 2. As it approached the Texas coast, the inner structure and eyewall became more organized.

Ike made U.S. landfall at Galveston, Texas, on September 13 at 2:10 am CDT (0710 UTC), as a high Category 2 hurricane with winds of 110 mph (175 km/h) and a central pressure of 950 mbar (28.05 inHg). The 2:00 am NHC advisory cited tropical storm and hurricane force winds extending 275 miles (443 km) and 120 miles (190 km), respectively, from the center. Around 3:00 am CDT (0800 UTC), it passed over San Leon, Texas and made its final landfall near Baytown, Texas around 4:00 am CDT (0900 UTC).

On September 13, Ike began a slow turn north, then northeast. After losing strength to tropical-storm force winds near Palestine, Texas around 1 pm, it passed 100 miles (160 km) to the east of Dallas and west of Little Rock, Arkansas. Maintaining tropical storm-force winds as it moved inland, it tracked across Arkansas on the night of September 13 and also produced tornadoes across the state. It brought heavy rainfall all along its path, but moved more quickly the farther north it went as it slowly lost tropical characteristics.

Early on September 14, Tropical Storm Ike merged with a large cold front moving from west to east over the central U.S. and became extratropical. This deep low pressure continued toward the north-east spreading heavy rains and damaging winds with hurricane-force gusts across a large portion of the Midwest. It moved into Canada that night, giving strong winds and heavy rain across Southern Ontario and most of Quebec, before exiting into the Atlantic at the latitude of the Labrador Sea, early on the 16th.