WIND FIELD AND REFLECTIVITY STRUCTURE AND EVOLUTION OF HURRICANE OLIVIA
ON 24 SEPTEMBER 1994
D. Marks, Jr.
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 are the future positions of the hurricane (track)
and future strength of the winds (intensity). The 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 (appropriately called the Eyewall
Evolution Experiment) since first proposed to document the wind field changes
in a storm with increasing winds. Up until then, the intensification
of a hurricane had not been observed by airborne Doppler as well as it
was in Hurricane Olivia was on 24 September 1994.
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.
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 little more
than 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: 02/05/00