This bulletin, prepared by Dr. H. S. Chen, Mr. L. D. Burroughs, and H. L. Tolman of the Ocean Modeling Branch (OMB), Environmental Modeling Center (EMC), National Centers for Environmental Prediction (NCEP), describes automated global ocean wave guidance provided in graphic, alphanumeric, and GRIB formats. This guidance was implemented operational use in 1999.

The NOAA/WAM will be replaced with the NOAA WAVEWATCH III (NWW3). The NWW3 is a third generation model, but differs in many respects from the NOAA/WAM: it accounts for wave dispersion within a discrete spectral bin by adding diffusion terms to the propagation equation (Booij and Holthuijsen 1987); it uses the Chalikov and Belevich (1993) formulation fori wave generation and the Tolman and Chalikov (1996) formulation for wave dissipation; it employs a third order finite difference method by utilizing a split-mode scheme with a Total Variance Diminishing limiter to solve wave propagation; its computer code has been optimized to fully utilize the MPP structure of the new IBM R/S 6000 SP; it uses a higher spatial resolution (1.25o x 1.00o lon./lat. grid instead of 2.5o x 2.5o), a slightly larger domain in north-south extension (78oN - 78oS rather than 77.5oN - 67.5 oS), and a higher directional resolution (24 directions in place of 12).

The bulletins and graphics of the new guidance follow the same formats shown in TPB No. 426 (Chen, 1995), except for the following differences :

  1. The full NWW3 resolution and domain are used for AWIPS, while the NOAA/WAM resolution and domain are used for AFOS and facsimile products.
  2. 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 NWW3. The AWIPS GRIB products should become available in AWIPS as a part of software Build 4.2.
  3. The following wind and wave parameters are available in GRIB format at the web site above, on Family of Services (FOS), and AWIPS: Hs, Dm, Tm, peak wave period and direction, wind sea peak wave 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 overall peak period and direction replaces the swell period and direction for a large part of the domain.
  4. Spectral text bulletins for the NWW3 are available at http://polar.wwb.noaa.gov/waves. These files are in ASCII and are available by anonymous ftp from the directory ftp://polar.wwb.noaa.gov/pub/waves/date.cycle, where date represents the date in yyyymmdd format and cycle represents the run cycle identifier (t00z or t12z, respectively). These bulletins will be implemented on AWIPS as soon as headers can be derived for them. The ocean wave guidance will continue to be generated twice daily out to 72 hours based on the 0000 and 1200 UTC cycles of the Aviation (AVN) run of the Global Spectral Atmospheric Model, but using data supplied by the (NWW3).

    Technical Procedures Bulletin No. 426 is now operationally obsolete.


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