Around September 16, the first of a pair of tropical waves entered the Atlantic basin from the east. Unlike its successor, which would become Hurricane Humberto, the leading wave did not generate much thunderstorm activity for much of its journey across the tropical Atlantic. It first attracted notice on September 21, when this activity increased markedly as it approached the Leeward Islands. The system remained too disorganized to consolidate into a tropical cyclone, but it brought significant rainfall across the Caribbean. It first impacted the Leewards on the 23rd, Puerto Rico the next day, and the Dominican Republic on the 25th. After that time, the disturbance slowed down and turned toward the north. Less land interaction and favorable atmospheric conditions allowed it to establish a circulation over the next couple of days. Eventually, the system was designated Tropical Depression Nine a little off the northern coast of east Cuba.
Despite achieving tropical cyclone status, the depression was very still broad and disorganized at first, with mid-level spin displaced from the low-level center. It began to build a dense area of convection near the developing center on the 28th. That afternoon, it was upgraded to Tropical Storm Imelda. Around the same time, the center began to move northward through the Bahamas, bringing tropical storm conditions to some of the islands. Imelda deepened steadily over the next few days and winds increased. By the time it exited the Bahamas on September 29, it was a strong tropical storm. It was upgraded to a hurricane during the morning of September 30.
Imelda did not have the traditional appearance of a hurricane on satellite imagery; some dry air was present near the center and convection did not completely surround it. Nevertheless, it continued strengthening. That day it also took a sharp turn toward the east-northeast. This was due to an approaching trough near the U.S. east coastline and a binary interaction with Hurricane Humberto to Imelda's northeast. As the two cyclones approached each other, the Fujiwhara effect caused them to rotate in a counterclockwise direction around the "center of gravity" between the two. This center of gravity was recurving northeast, so Humberto's eastward progress slowed some, while Imelda was yanked quickly eastward out to sea away from land.
Imelda closed off a circular eyewall and continued to intensify. During the morning of October 1, the cyclone reached its peak intensity as a category 2 hurricane with 100 mph winds and a minimum central pressure of 966 mb. After that time, wind shear increased due to the encroaching trough, but Imelda managed to temporarily maintain its strength due to a favorable trough interaction. This meant it was still near peak intensity when the center of circulation passed within a handful of miles of a direct landfall of Bermuda late on October 1. The center's passage just south of the island brought hurricane-force winds to Bermuda for a few hours, before Imelda sped off to the east.
After that, the storm began to weaken and lose its remaining tropical characteristics. During the morning of October 2, Imelda transitioned to a post-tropical cyclone. Its remnants arced northeastward over the open north Atlantic until they dissipated several days later.
The image above shows Imelda on October 1 at peak intensity. The island of Bermuda is visible at right, directly in the hurricane's path.
Imelda took a sharp turn eastward around September 30, preventing it from affected mainland North America. Nevertheless, the storm brought significant impacts to the Bahamas and Bermuda.
No comments:
Post a Comment