Wednesday, October 22, 2014

Tropical Storm Hanna (2014)

Storm Active: October 21-22, 27

On October 17, Tropical Storm Trudy formed in the eastern Pacific basin. The next day, it made landfall in Mexico and quickly dissipated over the mountainous terrain. On October 19, a low pressure system began to form over the Bay of Campeche from the remnants of Trudy. Producing scattered shower activity throughout the southwestern Gulf of Mexico, the system slowly meandered to the east-northeast and moved farther over water over the next few days. During the day of October 21, the low deepened significantly and gained definition, though the associated convection did not yet meet the criteria of a tropical cyclone. That night, however, a small but persistent area of thunderstorm activity developed near the center of circulation, and the system was designated Tropical Depression Nine.

Despite being over warm water, the system faced unfavorable atmospheric conditions, including shear out of the west and interaction with a frontal boundary to its northeast. This front caused heavy rain across the northern Yucatan through Cuba and the neighboring islands, but this moisture was not associated with Nine. On October 22, the system turned east-southeast towards the Mexican coast. Failing to strengthen, the system made landfall that evening as a weak tropical depression, and was downgraded to a remnant low just a few hours afterward.

On October 24, the system emerged over water on the eastern side of the Yucatan peninsula and began to drift generally east-southeast. Though atmospheric conditions were unfavorable, the low maintained its identity for the next few days, and concentrated thunderstorm activity reappeared during the day of October 26. By this time, the system had changed tack and was drifting westward toward the coast of Honduras. On the morning of October 27, despite the fact that a portion of the circulation was interacting with land, the low was producing gale force winds and had acquired an organized convective structure. It was therefore upgraded to Tropical Storm Hanna.

A few hours later, the center moved inland over northeastern Nicaragua. Hanna quickly lost definition and was downgraded to a tropical depression that evening. It then degenerated into a remnant low as it moved west-southwestward over the mountainous terrain of Central America. Despite this, heavy rains continued over portions of northern Nicaragua and southern Honduras, bringing 3-5 inches to many areas. On October 28, the low moved northwestward and emerged into the Gulf of Honduras, but it once again made landfall in Belize early on the 29th, eliminating any chance of redevelopment. Tropical moisture associated with Hanna eventually made it as far as the southwestern United States.



The above image shows Hanna on October 27, a few hours after regeneration into a tropical cyclone.



Despite mostly favorable conditions, Hanna did not significantly intensify during its lifetime due to land interaction.

Sources: http://upload.wikimedia.org/wikipedia/commons/0/01/Hanna_Oct_27_2014_1600Z.jpg, http://upload.wikimedia.org/wikipedia/commons/6/63/Hanna_2014_track.png