27th Conference on Hurricanes and Tropical Meteorology


An Overview of the Stages of Genesis of Tropical Storm Gert


Krystal M. Valde, University of Miami/CIMAS and NOAA/AOML Hurricane Research Division, Miami, FL; and M. L. Black and R. F. Rogers

During July 2005, NOAA's Hurricane Research Division, in collaboration with NASA, began the first phase of the Intensity Forecasting Experiment (IFEX). In this phase, NOAA WP-3D aircraft coordinated flights with the NASA ER-2 to collect observations during the entire life cycle of a tropical cyclone, in hope that these observations will help scientist to better understand the processes that are involved in tropical cyclone genesis, intensity change, motion, and rainfall. Observations from numerous candidate storms were collected. This study, however, will mainly focus on the genesis stages of Tropical Storm Gert from 22 July 2005 to 24 July 2005. Tropical Storm Gert first began as a tropical wave with an area of deep convection over the western Caribbean on Thursday 21 July 2005. With vigorous convection, moderate shear, and an indication of an anticyclone aloft and banding features, this disturbance became a potential candidate for the genesis study. On 22 July, the area of interest's mesoscale convection began to look better organized, resulting in the first research flight into the storm. Dropsonde data from this flight indicated that the disturbance was still an open wave with 35kt winds at 700mb in the northeastern area of the wave and 25kt at the surface in the southeastern portion. A follow-up day flight was scheduled on 23 July, in which the tropical wave, based on satellite imagery, seem to have formed a broad center of circulation located in the Central Bay of Campeche. Associated with the circulation was a burst of convection on the eastern edge of the circulation, as well as scattered convection on the west and north side of the center. The dropsonde data from this flight measured northwesterly winds near the coast of Mexico, confirming a center of circulation was located there. As a result of this data, the tropical wave was declared T.D. #7. That same day, a coordinated night flight mission with the WP-3D and ER-2 collected data to the north of the circulation, where an area of deep convection was forming. As a result, the data indicated a possibility of a new center forming to the north, near the area of deep convection and T.D. #7 was upgraded to Tropical Storm Gert. A final flight on 24 July took place, in which the area of deep convection from the previous night decreased, leaving scattered convection to east and north of the storm. Data from the plane showed numerous wind shifts and the possibility of multiple centers suggested from flight level wind data. Dropsonde observations also showed the displacement of the primary vortex from the surface to 700mb and 850mb. Tropical Storm Gert finally made landfall on the evening of 24 July near Tampico, Mexico with maximum sustained winds of ~45mph. Using dropsonde data, flight-level data, and radar observations collected from these flights this study will closely examine the structural changes within the core of Tropical Storm Gert as it transitioned from a wave to a tropical storm.

Session 14B, Tropical Cyclogenesis IV
Thursday, 27 April 2006, 3:30 PM-5:30 PM, Regency Grand Ballroom

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