IPET Report 3 Vol VIII

Pre- and Post-Landfall Parameter Variation
The parameterization concerns exclusively the hurricane characteristics at landfall. One
possibility, which has often been used in hurricane hazard analysis, is to assume straight paths
and constant values of ΔP , R max, V and B prior to landfall; see for example Russell (1971),
Batts et al. (1980), Georgiou et al. (1983), Neumann (1991), and Vickery and Twisdale (1995a).
A more refined approach is used for the hurricane path and the pre-landfall variability of these
parameters, as described in the following sections.
Pre-Landfall Parameter Variation. All tropical storms (not just hurricanes) after 1890 in
the HURDAT record that made landfall within latitudes 85W and 95W are used to estimate the
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mean hurricane path for landfall angles θ around −60 , −30
, 0, 30 , 60 . Results are shown in
Figure 13, where the dots represent average locations at 12 hour intervals relative to the time of
landfall. These paths are used in all the hurricane analyses.
°N relative
to landfall
position
6
4
2
0
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6
teta=(-75°,-45°) (-45°,-15°) (-15°,15°) (15°,45°) (45°,75°)
4
-2 -4 -6 -8 -10
°W relative to landfall position
Figure 13. Mean Hurricane Path Depending on Landfall Angle θ
2
0
Post-landfall Conditions. After landfall, several hurricane parameters undergo significant
changes. For example, the pressure deficit ΔP decreases in an approximately exponential way
and the radius of maximum winds R max tends to increase. The only change that may have
significant effect on surges and waves is the temporal decay of ΔP .
Volume VIII Engineering and Operational Risk and Reliability Analysis VIII-31
This is a preliminary report subject to revision; it does not contain final conclusions of the United States Army Corps of Engineers.
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