THE ROLE OF LARGE-SCALE FORCING ON THE RAPID INTENSIFICATION OF
HURRICANE EMILY (1987)
Principal Investigator:
John Kaplan
Collaborating scientist(s):
Mark DeMaria (NHC/TPC)
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 tropical cyclone 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 u
pper-level trough may have had on Emily's intensification was undertaken.
Method:
Evaluate the eddy forcing terms in a symmetric 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 fl
ights.
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 azimuthal mean radial (U)
, tangential(V), and vertical wind components were also obtained for both time periods. The differences between the U and V and vertical (not shown) wind components at these two time
periods were computed (Figure) and compared to the changes in storm structure expected based on the balanced vortex model (see Kaplan 1995). Computation of the eddy heat flux terms in the balanced vortex model is currently in
progress and these calculations 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.
Last modified: 8/19/96