WIND FIELD AND REFLECTIVITY STRUCTURE AND EVOLUTION OF HURRICANE OLIVIA ON 24 SEPTEMBER 1994

Principal Investigator: John F. Gamache
Collaborating scientist(s):

Christopher Samsury/The Weather Channel

Objective: To document the structure of Hurricane Olivia during the NOAA aircraft research mission conducted on 24 September 1994. To document the evolution of the wind field during the 3+ hours of airborne Doppler observations.

Rationale: The two most important forecast parameters for tropical cyclones will be the future positions of the hurricane (track) and how strong will the winds be (intensity). To goal of the airborne mission was to document at 1/2 hour resolution the changes in the tangential, radial and vertical winds, as well as the precipitation structure and intensity, in the core of the storm.

It has been the goal of this experiment since proposed to document the wind field changes in a storm with increasing winds. The case in Hurricane Olivia is the one and only good case of this kind.

Method: Perform the analysis of wind speed and direction for each of the 7 "snapshots" of the inner core wind field. Document the change with time in the wind field. Note the relationship of wind and reflectivity to average shear of wind within the storm core.

Accomplishment: While the wind fields for the 25th of September were done in FY1995, the wind sets for 24 September were completed during FY1996. They were presented at Gamache's 1996 informal research report at AOML.

The analyses show that the overall reflectivity distribution changed little over the 3+ hour period (Figure 1a and 1b). The water under the storm was warm and the mean wind within the core of the storm varied less the 5 m/s with height (Figure 2), and thus there was little disruption by wind shear.

The structure however was apparently conducive to slow deepening. This can be seen in the progression of radius-height averaged analyses of tangential wind shown in Figure 3.

Last modified: 11/13/97