WORLDCATenterprise

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WORLDCATenterprise

WORLDCATenterprise Technical Note
Hawaii Hurricane Model
MD0030 - Issue 1 – November
2003
Proprietary & Confidential
Page 1 of 8
Introduction
The EQECAT Hawaii hurricane model is a probabilistic model designed to estimate
damage and insured losses due to the occurrence of hurricanes in the islands of Hawaii.
The model is used in both the WORLDCATenterprise and USWIND platforms, and it
applies the same methodology used in the U.S. Mainland model. This methodology has
been certified by the Florida Commission on Hurricane Loss Projection Methodology,
and is described in the annual EQECAT submittal to the Florida Commission. This
technical note summarizes the components of the model that are specific to Hawaii.
As with all EQECAT models, the Hawaii hurricane model computes probabilistic losses
and event-by-event results, based on a stochastic database of hypothetical Hawaii
hurricanes. Probabilistic losses include expected annual and exceedance curve results,
reported by ZIP Code, county, state, or at a number of corporate levels.
The eight hurricanes that have affected Hawaii since 1950 can also be modeled as
historical events. These hurricanes, along with their Saffir-Simpson Intensities (SSI) at
landfall or closest approach to the Hawaiian Islands, are listed in Table 1.
Table 1. Historical hurricanes affecting Hawaii since 1950.
Hurricane
Hiki (1950)
Kanoa (1957)
Nina (1957)
Dot (1959)
Fico (1978)
Iwa (1982)
Estelle (1986)
Iniki (1992)
SSI
1
1
1
1
3
2
1
4
In USWIND, user-defined hurricanes can be created by modifying historical hurricanes
or by defining entirely new tracks and then specifying the storm parameter values to be
utilized. This feature is often used to model incoming hurricanes at a variety of potential
landfall locations.
Stochastic Hurricane Database
The stochastic hurricane database for Hawaii has been developed from the data in
‘Northeast and North-central Pacific Basin Best Track Estimates’ by Dr. Chris Landsea
(Reference 1) and NOAA Technical Memorandum ‘A Compilation of Eastern and
Central North Pacific Tropical Cyclone Data’ (Reference 2). This data gives the locations
and wind speeds at six-hour intervals for 642 known tropical cyclones occurring from
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1949 to 1994. Figure 1 is a map of the tracks of all 642 storms in the Landsea reference.
Table 2 summarizes the storm counts by Saffir-Simpson Intensity (SSI).
Figure 1. Tracks of all 642 storms in the Landsea reference.
Table 2. Storm counts by Saffir-Simpson Intensity (SSI), Landsea reference.
SSI
Tropical Storms
1
2
3
4
5
Total
Number of Storms 1949-1994
307
165
46
52
63
9
642
Annual Frequency
6.7
3.6
1.0
1.1
1.4
0.2
14.0
In 46 years of recorded history of tropical cyclones from 1949 to 1994 in the Northeast
and North-central pacific basin, there were 642 storms, with only two making landfall on
the Hawaiian islands with hurricane strength. Of the 642 storms, 335 reached hurricane
strength at some point. The data from these 335 hurricanes were used to develop
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probability distributions, which were then used to simulate stochastic hurricanes by
stratified/importance sampling. The resulting stochastic hurricane database has
approximately 20,000 events, each with a specific annual frequency of occurrence.
All key storm parameters have been derived from data from the central and eastern
Pacific, including radius to maximum winds, forward speed, and decay rate. The
parameterization of forward speed and decay rate is based on storms in the immediate
vicinity of Hawaii; however, due to scarcity of data, the parameterization of radius to
maximum winds includes data from across the central and eastern Pacific. Note that the
techniques used to develop the stochastic set placed greater emphasis on storms occurring
from the late 1960’s onward, when continuous satellite observations were in place.
Hurricane Wind Field Model
The basic methodology for modeling hurricane wind fields is based on NOAA/NWS
Technical Reports (References 3 and 4). The maximum wind speed and over-water wind
field modeling was developed from NOAA/NWS equations (Reference 3), with some
empirical adjustment to the ‘Observed/Gradient Wind Ratio’ in order to generalize the
equations for lower intensity storms. The EQECAT model uses NOAA/NWS methods
(Reference 3) as a starting point for calculating local overland frictional wind speed
reduction, but the specific categories of surface roughness were augmented with
additional information (Reference 5). The surface roughness modifications applied are
based on land use / land cover data at a 200m resolution in Hawaii.
The calculated wind field is a 2-3 sec peak gust wind speed at 10-meter elevation, as this
is the measure that has been found to best correlate with damage. The model calculates
the wind speed at a specific latitude and longitude, assuming that level of detail is
provided as input, i.e. directly or as street address. If the input data is provided at ZIP
Code level, the analysis will take place at the population centroids of the ZIP Codes. If
the input data is provided at county level, it will first be disaggregated to ZIP Code level
using a database of industry values, and then it will be analyzed at the population
centroids of the ZIP Codes.
Vulnerability
EQECAT wind vulnerability functions are based on historically observed damage (in
terms of both claims data and post-hurricane field surveys), experimental research
conducted by Professors Mehta and McDonald at Texas Tech University, and structural
calculations performed by EQECAT engineers.
The claims data analyzed is from two basic sources: (1) claims data from all major storms
during the period 1954-1994 analyzed by Dr. Don Friedman and John Mangano while
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managing the Natural Hazard Research Service (NHRS) effort for The Travelers
Insurance Company; and (2) claims data from Hurricanes Alicia (1983), Elena (1985),
Gloria (1985), Juan (1985), Kate (1985), Hugo (1989), Bob (1991), Andrew (1992), Iniki
(1992), and Opal (1995) provided to EQECAT by insurance companies.
EQECAT teams have conducted post-disaster field surveys for several storms in the past
decade or so, including Hurricanes Andrew (1992), Iniki (1992), Luis (1995), Marilyn
(1995), Opal (1995); Typhoon Paka (1997); and Hurricane Fabian (2003). Some
observations from the post-disaster field survey from Hurricane Iniki are presented in an
EQE summary report ‘Hurricanes Andrew and Iniki’ (Reference 6).
The claims data collected following Hurricane Iniki were analyzed and compared to other
claims data used in the development of the vulnerability functions. For the same
structural type, no significant variation was observed to warrant the creation of separate
vulnerability functions for Hawaii. Building performance in Hawaii has shown
similarities with that of the southeast region of the United States.
The EQECAT software also allows a user to account for the unique characteristics of
individual buildings, e.g., code enforcement, roof-to-wall anchorage, foundation
anchorage, etc. This secondary features option can be used to model specific building
characteristics in Hawaii.
Validations
The meteorology, vulnerability, and actuarial components of the EQECAT Hawaii
hurricane model have been independently developed, verified, and validated. The
meteorology component, completely independent of the other components, calculates
wind speed at each site.
The vulnerability component is entirely independent of all other calculations, e.g.
meteorological, loss, etc. Validation of the vulnerability functions has been performed
independently from other validation tests, e.g. whenever the vulnerability functions have
been validated using claims data from a historical storm, the wind field for that storm has
first been validated independently. If any of the other calculation modules were changed,
no changes would be necessary to the vulnerability functions.
Extensive studies were carried out to test the validity of the EQECAT Hawaii hurricane
model using the 46 years of wind data obtained from Landsea (Reference 1). In order to
validate wind-speed distributions in the model, wind speed data prior to 1970 are
considered less reliable and have been neglected. Since only the wind speed data west of
-120 longitude are relevant to the hurricane model of Hawaii, only those portions of the
entire set have been used for the validation of wind speed and strength. The comparison
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of the strength of storm in terms of the storm maximum wind speed from the model and
the post-1970 data is shown in Figure 2 below.
Figure 2. Distribution of storm maximum wind speed, WSP (post-1970)
The number of storm crossings and the wind speed at the crossing as obtained from
stochastic hurricane database are also compared with the observations. These results
validate the storm path and the wind speed distribution in the EQECAT model, as shown
in Figure 3 below.
Figure 3. Observed and expected count of track crossings
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Figure 4 below provides the modeled peak gust wind speeds for Iniki. Note that the peak
gust wind speed can be observed at different times for different locations.
Figure 4. Modeled peak gust wind speeds for Iniki (1992).
Iniki (1992)
Peak gust wind speed (mph)
140
120
100
60
40
to 156
to 140
to 120
to 80
to 60
Finally, Figure 5 below shows a comparison between actual losses and modeled losses
for Hurricane Iniki on a large insurance portfolio in force as of 1992. The comparison is
by line of business, but the names of the lines are not shown so as not to reveal the
identity of the company.
Figure 5. Loss comparison by line of business
Hurricane Iniki Loss Comparison by LOB
1,000,000
100,000
10,000
Estimated
1,000
Actual
100
10
1
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References
1. Dr. Chris Landsea, Northeast and North-central Pacific Basin Best Track Estimates,
Colorado State University. This data set is now maintained by the National Hurricane
Center and is available at http://www.nhc.noaa.gov/pastall.shtml, under the heading
Past Hurricane Track Files, via a link labeled Eastern North Pacific Tracks File.
2. G. M. Brown and P. W. Leftwich, Jr. (1982), A Compilation of Eastern and Central
North Pacific Tropical Cyclone Data, NOAA Technical Memorandum NWS NHC
16.
3. Schwerdt, R. W., Ho, F. P., and Watkins, R. R. (1979). Meteorological Criteria for
Standard Project Hurricane and Maximum Probable Hurricane Wind Fields, Gulf and
East Coasts of the United States, NOAA Technical Report NWS 23, U.S. Department
of Commerce, National Oceanographic and Atmospheric Administration, National
Weather Service, Washington, DC.
4. Ho, F. P., Su, J. C., Hanevich, K. L., Smith, R. J., and Richards, F. P. (1987).
Hurricane Climatology for the Atlantic and Gulf Coasts of the United States, NOAA
Technical Report NWS 38, U.S. Department of Commerce, National Oceanographic
and Atmospheric Administration, National Weather Service, Washington, DC.
5. Simiu, E. and Scanlan, R. H. (1996). Wind Effects on Structures, John Wiley and
Sons, New York, NY.
6. Hurricanes Andrew and Iniki (1992). EQE Summary Report, available at
http://www.eqe.com/publications/iniki/index.htm.
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