wsws wpwp dw wpwp wsws NARR ONLY Variations in x (size parameter)

Size Parameter Fit x can also be estimated by applying a nonlinear least squares fit to the 34, 50, and 64 kt Best-Track wind radii.

Cross Section Analysis

Wave Model: General The 2G spectral wave model WISWAVE, developed by D. Resio (1977) for the U.S. Army Corps of Engineers (USACE), is used in this study. WISWAVE has been shown to capture hurricane events quite well and is considered a good tool for assessing rapidly changing conditions associated with frontal passages in the GOM. Previous studies (e.g., Tracy and Cialone 2003) have shown that WISWAVE provides consistent results when compared with the more advanced/complex 3G WAM and WAVEWATCH III models.

Tunable Features (Wave Model) – Resolution Spatial Temporal Directional Spectral – Drag Coefficient

Wave Model: Physics – predicts directional spectra as well as integrated wave properties such as significant wave height, peak wave period, vector mean wave direction, and sea and swell components as a function of atmosphere wind input. – Wave growth is based on the Phillips and Miles mechanism (1957) – Weak non-linear wave-wave interaction, linear refraction, shoaling and dissipation are included in the source function on the right.

Original definition resulted from work by the oceanographer Walter Monk during World War II. [ [ Intended to mathematically express the height estimated by a "trained observer". It is commonly used as a measure of the height of ocean waves. Significant wave height Average wave height (trough to crest) of the one-third largest waves

The period corresponding to the frequency band with the maximum value of spectral density in the nondirectional wave spectrum. It is the reciprocal of the peak frequency. Dominant or peak wave period, DPD 8.3 s 4.4 s 2.6 s

X fit vs X climo

Directional Resolution Tuning The directional resolution of the wave model was increased from 16 to 36 direction bins to better represent the wave field generated by a wind field with strong curvature.

Surface Drag

Drag Coefficient Tuning The drag coefficient was capped at wind speeds exceeding 20m/s and 25m/s and the output was compared with the original drag coefficient parameterization.

Wind Speed Statistics(post tuning) U 10 NRMSEU 10 Bias Buoy Station #

Wave Statistics (significant wave height) SWH NRMSESWH Bias Buoy Station #

Wave Statistics (dominant wave period) T d NRMSET d Bias Buoy Station #

Summary/Status/Questions Apply to a subset of GOM TC’s Is the NARR sufficient for tropical storms? Quadrant-dependent drag coefficient? Wind speed/drag coefficient cap MC Ensembles Powell (2003)