Hurricane Kenneth (2005) - Meteorological History

Meteorological History

The origins of Kenneth are believed to have been from a tropical wave that crossed Central America into the eastern North Pacific Ocean on September 9. The system tracked westward within the Intertropical Convergence Zone — a belt of thunderstorm activity across the eastern Pacific Ocean — and on September 13 its associated thunderstorm activity began showing signs of organization. Despite being located only 625 miles (1010 km) east-southeast of the larger Tropical Depression Ten, the National Hurricane Center remarked the potential for further development of the system; as the depression was further west and moving faster than the system, little interference from Jova was anticipated. The system organized further, and at 1800 UTC on September 14 the National Hurricane Center began classifying it as Tropical Depression Eleven about 900 miles (1450 km) west-southwest of Cabo San Lucas, Mexico. The depression maintained a general westward track throughout its entire duration, due to the subtropical ridge to its north.

Initially, the depression was forecast to reach maximum strength as a tropical storm before weakening, and only the Geophysical Fluid Dynamics Laboratory's hurricane model predicted it to attain hurricane status. However, low amounts of wind shear and warm sea surface temperatures favored further intensification. After being previously removed from the primary thunderstorm activity, the circulation became situated beneath a persistent area of deep convection. It is estimated the cyclone intensified into Tropical Storm Kenneth early on September 15. The storm quickly developed banding features—spiral rain showers of convection—as its convection formed into a central area of deep convection. These were all signs for further development, and Kenneth attained hurricane status early on September 16. By September 17, the hurricane had finished an eyewall replacement cycle, meaning its original eye was replaced by a larger, better defined eye. As a result, it quickly intensified and attained major hurricane status. With a 23 mile (37 km) wide eye surrounded by very cold cloud tops, Kenneth strengthened to reach peak sustained winds of 135 mph (215 km/h), a Category 4 hurricane on the Saffir-Simpson scale, on September 18 about 1725 miles (2790 km) east of the Big Island of Hawaii.

After maintaining peak strength for about 18 hours, Kenneth began a sharp weakening trend due to unfavorable north-northeasterly wind shear; this was caused by the anticyclone over Hurricane Jova, which eroded the eyewall of Hurricane Kenneth. While weakening, the hurricane turned to a southwest drift, due to a weakness in steering currents. By September 20, its deepest convection was confined to the southern half of the hurricane, and later in the day Kenneth weakened to tropical storm status. Reduced moisture in the atmosphere weakened the system further, and by September 21 its circulation was exposed to the east-northeast of the convection. Kenneth began a steady west-northwest track due to a weak ridge to its north. Operationally the storm was predicted to continue weakening and dissipate within four days. However, deep convection re-developed near the center as the outflow became better defined, and Kenneth remained a moderate tropical storm for several days. On September 24, the motion became nearly stationary as steering currents again weakened. Vertical shear sharply declined, allowing the convection to become more symmetrical and for an eye feature to develop. On September 25, Kenneth again attained hurricane status while located about 1085 miles (1745 km) east-southeast of the Big Island of Hawaii.

Hurricane Kenneth maintained minimal hurricane status for about 30 hours as it drifted southwestward, during which it entered the area of responsibility of the Central Pacific Hurricane Center. Increasing shear weakened Kenneth to tropical storm status on September 26, and it began a steady northwest track under the influence of low- to mid-level steering flow. By September 27, most of its convection had dissipated, excluding a small area of thunderstorms to the southeast of the center. Convection intermittently reformed near the center, though the combination of wind shear and cooler water temperatures prevented restrengthening. On September 29, an intensifying upper-level trough over the Hawaiian Islands weakened Kenneth to tropical depression status. Thunderstorms failed to reform, and on September 30 it degenerated into a tropical wave about 40 miles (65 km) east of the Big Island of Hawaii. A remnant swirl of clouds later moved onshore of the Big Island.