ABSTRACT

This bulletin, prepared by Dr. Y. Y. Chao, Mr. L. D. Burroughs, and Dr. H. L. Tolman of the Ocean Modeling Branch (OMB), Environmental Modeling Center (EMC), National Centers for Environmental Prediction (NCEP), describes automated wave guidance for Western North Atlantic and adjacent waters in alphanumeric, AFOS, facsimile, and Gridded Binary (GRIB) formats. This guidance has been implemented internally on the new IBM computer and is scheduled for operational implementation after the IBM is moved to Bowie, Maryland sometime in the late Fall 1999.

The East Coast and Gulf of Mexico (ECGM) regional wave model will be replaced with the Western North Atlantic (WNA) regional wave model. The WNA is based on the NOAA WAVEWATCH-III (NWW3) which is described in detail in Technical Procedures Bulletin (TPB) 453 (Chen, Burroughs, and Tolman 1999) and Tolman (1999a, b, and c). The NWW3 provides the boundary conditions to the WNA. More specifically, the WNA accounts for wave dispersion within discrete spectral bins by adding in diffusion terms to the propagation equation (Booij and Holthuijsen 1987); it uses the Chalikov and Belevich (1993) formulation for wave generation and the Tolman and Chalikov (1996) formulation for wave dissipation; it employs a third order finite differencing method with a Total Variance Diminishing limiter to solve wave propagation; its computer code has been optimized to utilize the Massively Parallel Processing (MPP) structure of the new IBM R/S 6000 SP computer; it uses a larger domain (98.25oW - 29.75oW by 0.25oS - 50.25oN instead of 98oW. - 65oW by 15oN - 45oN) and a higher directional resolution (24 directions to replace 12).

Various graphics and text products for the WNA are available at http://polar.wwb.noaa.gov/waves/products.html.

The following wind and wave parameters are available in GRIB format at the web site above, on Family of Services (FOS), and on AWIPS as GRIB bulletins: Hs, Dm, Tm, peak wave period and direction, wind sea peak period and direction, wind speed and direction, and u- and v-wind components. Note, however, that significant wind sea height, significant swell height, and mean swell period and direction are no longer provided. The peak period and direction replaces the swell period and direction for a large part of the domain. The AWIPS GRIB products should become available in AWIPS a part of software Build 5.0.

The current set of AFOS and facsimile products will remain until there is no longer a need for them. The data used to produce them will come from the WNA. The AFOS and facsimile products already in existence have been converted to be used on AWIPS.

Spectral text bulletins for the WNA are available at the web site above. These files are in ASCII and are available by anonymous ftp from the directory ftp://polar.wwb.noaa.gov/pub/waves/. These bulletins will be implemented on AWIPS as soon as headers can be derived for them.

The wave guidance will be generated twice daily based on the 0000 and 1200 UTC cycles of the Aviation (AVN) run of the Global Spectral Atmospheric Model.



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