Hurricane Norbert (2008) - Meteorological History

Meteorological History

The origins of Norbert were from a tropical wave that crossed Central America on September 26 and September 27. An area of disturbed weather formed near the Gulf of Tehuantepec on September 28, which at that time was mentioned on the Tropical Weather Outlook (an outlook issued every six hours during hurricane season by the NHC that notes the possibility of tropical cyclogenesis during the next 48 hours). Drifting westward off the coast of Mexico, the system initially consisted of a broad low pressure area and an area of disorganized convection. It slowly organized for several days, and by early on October 4 the system developed enough organized convection to be classified as Tropical Depression Fifteen; at that point, it was located about 230 miles (370 km) south of Acapulco. The depression was located over an area of warm water temperatures and moderate vertical wind shear, and as such was forecast to intensify gradually.

About six hours after forming, the circulation of the depression became exposed from the deep convection, due to the wind shear. At the same time, two tropical cyclone forecast models predicted the tropical cyclone formation of a larger disturbance to the southeast of the depression. One model predicted the new cyclone to absorb the depression, although most other models forecast for the depression to remain the dominant system. By early on October 5, deep convection developed and organized around the center of the depression, and satellite intensity estimates using the Dvorak technique suggested that the system had tropical storm force-winds; as a result, the NHC upgraded the depression to Tropical Storm Norbert, about 245 mi (395 km) south of Zihuatanejo. Norbert slowly intensified, and was upgraded to a hurricane on October 6 as very deep atmospheric convection remained stable despite easterly wind shear.

On October 7, Hurricane Norbert reached Category 2 intensity on the Saffir-Simpson Hurricane Scale while Norbert developed well-defined and closed eyewall as seen in microwave imagery. Overnight on October 8, an eye appeared on infrared satellite, indicating that Norbert was intensifying and the storm was upgraded to a major hurricane respectively. Continuing to rapidly strengthen over warm sea surface temperatures, it reached Category 4 status late on October 8, after intensifying 45 mph (75 km/h) over the previous 24 hours. The storm peak intensity was 135 mph (215 km/h) and a peak pressure of 945 mbar (hPa; 27.91 inHg) while located 350 mi (560 km) south of Cabo San Lucas, Mexico. The peak intensity of Norbert is uncertain as aircraft-based wind speed observations were lower than estimates via Dvorak Technique. However, the cloud pattern became less impressive early on October 9, and was thus downgraded into a Category 3 hurricane, with winds of 125 mph (205 km/h) as it moved. The eye began to erode and as such Norbert underwent an eyewall replacement cycle, where one eye is replaced by another. As a result, when Hurricane Hunters investigated the storm later that day, they found that Norbert had weakened considerably. At that time, it was downgraded into a weak Category 1 hurricane on October 9.

On October 10, Norbert turned towards the north while slowing down as it reached the western edge of a subtropical ridge. In an area of light wind shear, Norbert began to re-intensify as the eyewall replacement cycle completed. The cyclone turned to the north-northeast due to a mid to upper level trough that was moving over the Southwest United States. Norbert managed to restrengthen into a Category 3 hurricane on 0600 UTC October 11, and made landfall as a Category 2 hurricane near Puerto Charley. The next day, Norbert struck southern Sonora at Category 1 intensity. Norbert rapidly dissipated by October 12 while inland over Mexico. Norbert was a Category 2 hurricane at landfall and is currently tied with Hurricane Jimena for the strongest storm to strike the west coast of the Baja California Penisula.