THE ROLE OF LARGE-SCALE FORCING ON THE RAPID INTENSIFICATION OF
HURRICANE EMILY (1987)
Principal Investigator:
John Kaplan
Collaborating
scientist(s):
Mark DeMaria (NHC)
Objective:
Use data collected during NOAA P-3 research flights to
examine the role that an upper-level trough may have played in the
rapid intensification of Hurricane Emily (1987).
Rationale:
Past research suggests that the interaction between
upper-level troughs and tropical cyclones is related to TC
intensification. Early on 25 September, Emily (1987) intensified rapidly
and unexpectedly while an upper-level trough was situated a few hundred
kilometers northwest of the storm center. Since NOAA P-3 aircraft had
collected data in Emily's large-scale environment twice during the 24 h
immediately preceding this rapid intensification, a quantitative
evaluation of the role that the upper-level trough may have had on
Emily's intensification was undertaken.
Method:
Evaluate the terms in the balanced vortex model, and compare
the changes in kinematic structure expected due to the forcing
from these terms to the observed structural changes in Emily using data
collected during NOAA P-3 research flights.
Accomplishment:
The angular momentum flux terms in the balanced vortex
model were evaluated and radius height (R-P) plots of these
quantities were obtained for each of the two time periods for which
NOAA P-3 data were collected. (R-P) plots of the radial (U), tangential
(V), and vertical (W) wind components were also obtained for both time
periods. The differences between the wind components at these two time
periods were computed (Figure) and compared to the
changes in
storm structure expected based on the balanced vortex theory. These results
were part of a presentation made at the 21st Conference on Hurricanes
and Tropical Meteorology. Work also began on evaluating the remaining
terms in the balanced vortex model and the results of this research will
be reported on in the future.
Key reference:
Kaplan, J., 1995: An examination of the role of
large-scale forcing on the rapid intensification of Hurricane
Emily (1987). Preprints, 21st Conf. on Hurricanes and Tropical
Meteorology, Miami, FL, Amer. Meteor. Soc., 332-334.
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