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Tropical Modeling

The Oceanweather (OWI) team of researchers pioneered the development and application of contemporary techniques for the specification of surface winds and ocean response in tropical cyclones. Those methods have been continuously refined and upgraded for application in basins affected by tropical cyclones. The OWI tropical cyclone model continues to be implemented for use in hindcast studies to derive definitive extreme ocean response (waves, surge, currents) criteria for design of offshore and coastal structures.

Oceanweather developed the Tropical Analyst's WorkStation (TAWS) to reanalyze the temporal evolution of storm parameters. TAWS allows for the description of the radial pressure distribution in the boundary layer using a single or a double exponential analytical formulation which allows the analyst to iterate the Oceanweather Tropical Planetary Boundary Layer (TropPBL) model against available wind and pressure measurements. To learn more about TAWS and our interactive approach see the presentation on Hurricane Harvey (2017) in our Recent Publications.

Tropical modeling is applied in both Oceanweather's development of metocean climatologies and in generating operational forecasts. The ADCIRC community has embraced the methodology and routinely engages Oceanweather for development of reference-level inputs for calibration/validation in detailed storm surge modeling. Wind and pressure fields are routinely developed and licensed for research and commercial applications.

The OWI Tropical Model, first developed as a practical tool in the Ocean Data Gathering Program (ODGP) (Cardone et al., 1976), can provide a fairly complete description of time-space evolution of the surface winds in the boundary layer of a tropical cyclone from the simple model parameters available in historical storms. The model is an application of a theoretical model of the horizontal airflow in the boundary layer of a moving vortex. Numerical integration allows the model to solve the vertically averaged equations of motion that govern a boundary layer subject to horizontal and vertical shear stresses. The equations are resolved in a Cartesian coordinate system whose origin translates at constant velocity, Vf, with the storm center of the pressure field associated with the cyclone. Variations in storm intensity and motion are represented by a series of quasi-steady state solutions.

The original theoretical formulation of the model is given by Chow (1971). A similar model was described in the open literature by Shapiro (1983). The present version of the model is the result of three major upgrades: the first upgrade involved replacement of the empirical scaling law by a similarity boundary layer formulation to link the surface drag, surface wind and the model vertically averaged velocity components (Cardone et al., 1992). The second upgrade (Cardone et al., 1994) added spatial resolution and generalized the pressure field specification. A more complete description of the theoretical development of the upgraded model is given by Thompson and Cardone (1996). Last and most recently, modifications to the model PBL physics allow the introduction a saturation roughness formulation (a capped drag coefficient) consistent with that found by Powell (2007) as part of the Modeling of Relevant Physics of Sedimentation (MORPHOS) project (MORPHOS, 2009).

The model pressure field is described as the sum of an axially symmetric part and a large-scale pressure field of constant gradient. The symmetric part is described in terms of an exponential pressure profile, which has the following parameters:

Po minimum central pressure
dpi pressure deficit associated with up to two radii
Rpi scale radius of exponential pressure profile
Bi profile peakedness parameter

B is an additional scaling parameter whose significance was discussed by Holland (1980). This analytical form is also used to explicitly model the storm pressure field for use in the hydrodynamic model. The model may be prescribed with a single profile (1 dp, B, Rp combination) for storm systems with simple wind profiles. More complex wind profiles such as those which display wind maxima at two radii or those with a shelf-structure to the wind profile are described with a double profile. Cox and Cardone (2007) describe the methodology applied in the analysis of historical tropical cyclones, while Cardone and Cox (2009) discusses the impact of complex wind profiles on the ocean response.

The model is driven from parameters that are derived from data in historical meteorological records and the ambient pressure field. The entire wind field history is computed from knowledge of the variation of those parameters along the storm track by computing solutions, or so-called "snapshots", on the nested grid as often as is necessary to describe different stages of intensity, and then interpolating the entire time history from the snapshots.

As presently formulated, the wind model is free of arbitrary calibration constants, which might link the model to a particular storm type or region. For example, differences in latitude are handled properly in the primitive equation formulation through the Coriolis parameter. The variations in structure between tropical storm types manifest themselves basically in the characteristics of the pressure field of the vortex itself and of the surrounding region. The interaction of a tropical cyclone and its environment can therefore be accounted for by a proper specification of the input parameters. The assignable parameters of the PBL formulation, namely PBL depth and stability, and of the sea surface roughness formulation, are taken from studies performed in the Gulf of Mexico.

The model was validated originally against winds measured in several ODGP storms. It has since been applied to nearly every recent hurricane to affect the United States offshore area, to all major storms to affect the South China Sea since 1945, and to storms affecting many other foreign basins including the Northwest Shelf of Australia, Tasman Sea of New Zealand, Bay of Bengal, Arabian Sea and Caribbean Sea. Many wind comparisons have been published (e.g., Ross and Cardone, 1978; Cardone and Ross, 1979; Forristall et al., 1977; 1978; 1980; Cardone et al., 1992; Cardone and Grant, 1994).

More recent publications on the application of the PBL model in driving the ADCIRC and coupled ADCIRC/SWAN modeling system can be found in Hope et al., 2013 (Hurricane Ike 2008), Dietrich et al., 2011 (Hurricane Gustav 2008), Bacopoulos et al., 2012 (Hurricane Jeanne 2004), and Bunya et al., 2010 (Hurricanes Katrina and Rita 2005). Application in Hurricane Harvey (2017) is presented in Cox et al., 2017.


Bacopoulos, P., W. R. Dally, S. C. Hagen and A. T.Cox. 2012. Observations and Simulation of Winds, Surge, and Currents on Florida's East Coast During Hurricane Jeanne (2004). Coastal Engineering, 60, 84-94.

Bunya, S., J. C. Dietrich, J. J. Westerink, B. A. Ebersole, J. M. Smith, J. H. Atkinson, R. Jensen, D. T. Resio, R. A. Luettich, C. Dawson, V. J. Cardone, A. T. Cox, M. D. Powell, H. J. Westerink, H. J. Roberts. 2010. A High Resolution Coupled Riverine Flow, Tide, Wind, Wind Wave and Storm Surge Model for Southern Louisiana and Mississippi: Part I - Model Development and Validation, Monthly Weather Review, 138, 345-377.

Cardone, V. J., W. J. Pierson and E. G. Ward. 1976. Hindcasting the directional spectra of hurricane generated waves. J. of Petrol. Technol., 28, 385-394.

Cardone, V. J. and D. B. Ross. 1979. State-of-the-art wave prediction methods and data requirements. Ocean Wave Climate ed. M. D. Earle and A. Malahoff. Plenum Publishing Corp., 1979, 61-91.

Cardone, V. J., C. V. Greenwood and J. A. Greenwood. 1992. Unified program for the specification of tropical cyclone boundary layer winds over surfaces of specified roughness. Contract Rep. CERC 92-1, U.S. Army Engrs. Wtrwy. Experiment Station, Vicksburg, Miss.

Cardone, V. J., A. T. Cox, J. A. Greenwood, and E. F. Thompson. 1994. Upgrade of tropical cyclone surface wind field model. Misc. Paper CERC-94-14, U.S. Army Corps of Engineers.

Cardone, V. J. and C. K. Grant. 1994. Southeast Asia meteorological and oceanographic hindcast study (SEAMOS). OSEA 94132. 10th Offshore Southeast Asia Conference, 6-9 December, 1994.

Cardone, V. J., and A. T. Cox. 2009. Tropical cyclone wind field forcing for surge models: critical issues and sensitivities. Natural Hazards: Volume 51, Issue 1 (2009), Page 29.

Chow, S. H., 1971. A study of the wind field in the planetary boundary layer of a moving tropical cyclone. Master of Science Thesis in Meteorology, School of Engineering and Science, New York University, New York, N.Y.

Cox, A. T. and V. J. Cardone. 2007. Specification of Tropical Cyclone Parameters from Aircraft Reconnaissance, 10th International Wind and Wave Workshop, Oahu, Hawaii, November 11-16, 2007.

Cox, A. T., B. T. Callahan, M. Ferguson and M. A. Morrone. 2017. Tropical Cyclone Wind Field Analysis for Ocean Response Modeling: Hurricane Harvey (2017). 1st International Workshop on Waves, Storm Surges and Coastal Hazards Liverpool, UK, 10-15 September 2017.

Dietrich, J. C., J. J. Westerink, A. B. Kennedy, J. M. Smith, R. Jensen, M. Zijlema, L. H. Holthuijsen, C. Dawson, R. A. Luettich, Jr., M. D. Powell, V. J. Cardone, A. T. Cox, G. W. Stone, H. Pourtaheri, M. E. Hope, S. Tanaka, L. G. Westerink, H. J. Westerink, Z. Cobell. 2011. Hurricane Gustav (2008) Waves and Storm Surge: Hindcast, Synoptic Analysis and Validation in Southern Louisiana, Monthly Weather Review, 139, 2488-2522, DOI 10.1175/2011MWR3611.1.

Forristall, G. Z., R. C. Hamilton and V. J. Cardone. 1977. Continental shelf currents in tropical storm Delia: observations and theory. J. of Phys. Oceanog. 7, 532-546.

Forristall, G. Z., E. G. Ward, V. J. Cardone, and L. E. Borgman. 1978. The directional spectra and kinematics of surface waves in Tropical Storm Delia. J. of Phys. Oceanog., 8, 888-909.

Forristall, G. Z., 1980. A two-layer model for hurricane driven currents on an irregular grid. J. Phys. Oceanog., 10, 9, 1417-1438.

Holland, G. J., 1980. An analytical model of the wind and pressure profiles in hurricanes. Mon. Wea. Rev. 1980, 108, 1212-1218.

Hope, M. E., J. J. Westerink, A. B. Kennedy, P. C. Kerr, J. C. Dietrich, C. Dawson, C. J. Bender, J. M. Smith, R. E. Jensen, M. Zijlema, L. H. Holthuijsen, R. A. Luettich Jr., M. D. Powell, V. J. Cardone, A. T. Cox, H. Pourtaheri, H. J. Roberts, J. H. Atkinson, S. Tanaka, H. J. Westerink, and L. G. Westerink. 2013. Hindcast and validation of Hurricane Ike (2008) waves, forerunner, and storm surge, J. of Geophys. Res. Oceans, 118, 4424-4460, doi:10.1002/jgrc.20314.

MORPHOS Report: Oceanweather Tropical Planetary Boundary Layer Model, submitted to U.S. Army Corps of Engineers. 2009.

Powell, M. D., 2007. New findings on hurricane intensity, wind field extent and surface drag behavior. 10th International Workshop on Wave Hindcasting and Forecasting and Coastal Hazard Symposioum. Oahu, Hawaii, 11-16 November, 2007.

Ross, D. B. and V. J. Cardone. 1978. A comparison of parametric and spectral hurricane wave prediction products. Turbulent Fluxes through the Sea Surface, Wave Dynamics, and Prediction, A. Favre and K. Hasselmann, editors, 647-665.

Shapiro, L. J., 1983. The asymmetric boundary layer flow under a translating hurricane. J. of Atmos. Sci. 40, 1984-1998.

Thompson, E. F. and V. J. Cardone. 1996. Practical modeling of hurricane surface wind fields. ASCE J. of Waterway, Port, Coastal and Ocean Engineering. 122, 4, 195-205.


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