is rare that there exists a sufficiently long-term history
of accurate measurements of extreme storm generated winds,
waves, currents and storm surge to estimate the probability
distribution of extremes in the range of rare probabilities
needed for calculation of design loads on offshore or coastal
structures. At a few sites, instrumented platforms or moored
buoys have acquired data over the past twenty years or so,
and satellite altimeters have measured global wave heights
over about a ten year period. However, while such data make
it technically possible to compute extremes directly from
the measurements, the reliability of such estimates must
be questioned at least on the grounds that natural climate
variability on decadal time scales is not properly represented.
Therefore, even in areas with measured data it is still
advisable to generate the long-term database needed to
estimate the climate of extremes through a hindcast approach.
Oceanweather's principals pioneered the development and
application of this approach during their tenure at New
York University in the 1960s and 1970s and extensively refined
and applied this approach to the many new offshore development
projects launched within the past four decades.
the hindcast method as applied to the specification of the
extreme climate consists of the following steps:
historical meteorological data over a period of at least
50 years to identify the most severe storms of
relevant type responsible for extremes;
each storm selected above a threshold of intensity,
numerical hindcast of the time history of the sea state
and currents on a grid of points representing the basin;
of the peak winds, waves, and possibly currents, and their
associated properties, for each storm at each
of the hindcast and calculated
extremes through the process of extremal analysis, which
provides estimates of extremes associated with specified
return periods (return period is the average interval in
years between events equal to or greater than the associated
extremes). Such data are then used by ocean engineers for
the specification of design loads on structures.
hindcast of an individual historical storm consists of two
basic steps. First, the time and space evolution of the
surface marine wind field must be specified as accurately
as possible. This process usually requires the reanalysis
of historical meteorological data by experienced Meteorologists
with the aid of calibrated objective analysis procedures
and/or models. The wind fields are used to drive calibrated
ocean response models (e.g. a spectral wave model, storm
surge model, ocean current model) as the second part of
prototype for modern hindcast studies was the Gulf of Mexico
Ocean Data Gathering Program (ODGP), which began in 1969
and included an extensive measurement program, a wave hindcast
model development and calibration phase, and a hindcast phase,
all culminating in the establishment of reliable extreme
wave heights and wave periods associated with hurricane-generated
sea states in deeper parts of the Gulf of Mexico
continental shelf between the Mississippi Delta and the
Texas/Mexico border (Cardone et al., 1976; Ward et al.,
1979; Haring and Heideman, 1978).
ODGP, hundreds of dedicated hindcast studies have been carried
out at Oceanweather for the offshore and coastal engineering
communities to develop reliable extreme wind, wave, surge
and current design estimates for specific offshore
and coastal structures. Within the past four decades, many basin-wide
hindcast studies have been supported jointly by industry operators.
These so-called Joint Industry Projects (JIP), have also
included the application of the hindcast approach as described
above to the hindcast of several continuous years for the
specification of the operational climate. Major JIPs administered
and/or carried out by Oceanweather within the past four decades
have addressed essentially every global basin. For more on
Oceanweather's historical involvement in JIPs please see MetOcean Studies. Major continuous
hindcasts by Oceanweather include a 60+ year hindcast of
the North Atlantic (AES40, Swail and Cox, 2000) and the
entire globe (GROW, Cox and Swail, 2000).
1976. Cardone, V. J., W. J. Pierson and E. G. Ward. Hindcasting
the directional spectra of hurricane generated waves. J.
Petrol. Technol. 28, 385-394.
Ward, E. G., L. E. Borgman and V. J. Cardone. Statistics
of hurricane Waves in the Gulf of Mexico. OTC 3229. 10th
Annual Offshore Technology Conference, 8-11 May, 1978, Houston,
TX. (also appeared in J.Petrol. Tech., 1979)
Haring, R. E. and J. C. Heideman. Gulf of Mexico rare wave
return periods. OTC 3230, 10th Annual Offshore Technology
Conference, Houston, TX, May 8-11, 1978.
Swail, V.R. and A.T. Cox. On the use of NCEP/NCAR Reanalysis
Surface Marine Wind Fields for a Long Term North Atlantic
Wave Hindcast. J. Atmo. Tech., Vol. 17, No. 4, pp. 532-545
Cox, A.T. and V.R. Swail. A Global Wave Hindcast over the
Period 1958-1997: Validation and Climate Assessment. J.
of Geophys. Res. (Oceans) Vol. 106, No. C2, pp. 2313-2329.