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 waters surrounding Alaska alphanumeric 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 Gulf of Alaska (GAK; a second generation) regional wave model will be replaced with the Alaska Waters (AKW; a third generation) regional wave model. The AKW 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 AKW. Morespecifically, the AKW accounts for wave dispersion within discrete spectral bins by adding in diffusion termsto 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; itemploys a third order finite differencing method with a Total VarianceDiminishing limiter to solve wave propagation; its computer code has been optimized to utilize theMassively Parallel Processing (MPP) structure of the new IBM R/S 6000 SP computer; it uses a higherspatial resolution (0.50o x 0.25o rather than 30 n mi x 30 n mi), a larger domain (160oE - 124oW by 45oN -75oN instead of 155oW. - 132oW by 53oN - 61oN), a higher frequency resolution (25 frequencies in place of20), and a higher directional resolution (24 directions to replace 12).

Various graphics and text products for the AKW 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 ofServices (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 ofthe domain.

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

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

Technical Procedures Bulletin No. 427 is now operationally obsolete.



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