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Technical Implementation Notice 10-44: Amended

National Weather Service Headquarters Washington DC

855 AM EDT Mon Oct 25 2010

 

To:        Subscribers:

           -Family of Services

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network

           -NOAAPORT

           Other NWS Partners...Users and Employees

 

From:      Tim McClung

           Science Plans Branch Chief

           Office of Science and Technology

 

Subject:   Amended: Multi-Grid Hurricane Wave Model Upgrade:

           Rescheduled for November 2, 2010

 

NCEP is postponing this implementation from October 26 to

November 2, 2010, to provide broader customer notification.

 

Effective Tuesday, November 2, 2010, beginning with the 1200

Coordinated Universal Time (UTC) run, the National Centers for

Environmental Prediction (NCEP) will implement a new Hurricane

Wave Model. This multi-grid hurricane wave model will replace the

existing North Atlantic Hurricane (NAH) and North Pacific

Hurricane (NPH) wave models.  The model upgrade will result in a

change of 27 minutes to the product dissemination time and the

generation of new products.  Details of these changes are

outlined below.

 

Model Changes:

 

Instead of two separate models, the hurricane wave model will

now be a single model with multiple two-way nested grids. The new

multi-grid hurricane wave model will use WAVEWATCH-III v3.14, the

same model version as NCEPs Global Multi-Grid Wave Model (the

current NAH and NPH use WAVEWATCH-III v. 2.22). The upgrade to

version 3.14 will result in the following:

 

- Upgraded shallow water physics, which accounts for shallow

  water processes such as wave breaking. Together with the

  increased wave resolution in coastal regions, this change will

  provide a better representation of wave physics in land

  falling hurricanes.

 

- Increasing internal model spectral resolution to 50 components

  in frequency and 36 components in direction. Spectral output

  at the points will continue to be 29 components in frequency

  and 24 components in direction.

 

- Adding a new algorithm to partition the spectral energy into

  wind wave, primary and secondary swells. Spectral parameters

  for these different fields (wave height, peak period and

  direction) will be part of the model output on the new grids

  listed below. These fields will not be added to the existing

  NAH and NPH products.

 

Wind forcing for the global, Alaskan and Pacific Island grids

will be from the Global Forecast System (GFS) winds while all

the other grids will be a blend of the GFS and GFDL hurricane

model winds, as is currently done in the NAH and NPH. The only

exception is the Hawaiian Islands, part of the Pacific Island

grid, which also will have a blend of GFS and GFDL hurricane

model wind forcings.

 

Product Changes

 

As a result of this upgrade, all of the output products from the

new multi-grid hurricane model will be disseminated 27 minutes

later than the current NAH and NPH output products.  Any concerns

with this change in product dissemination time should be directed

to the contact points listed below.

 

The output grids from the multi-grid hurricane wave model will

be as follows:

 

Products with 25x24 spectral resolution:

 

-Current 0.25 degree NAH grids

-Current 0.25 degree NPH grids

 

Products with 50x36 spectral resolution:

 

-New 0.5 degree global domain grid

-New 0.25 degree regional domain for North Atlantic (domain 

 corresponds to current NAH grid)

-New 0.25 degree regional domain for North Pacific (domain

 corresponds to current NPH grid)

-New 10 arc min grid for the North Atlantic regional waters

-New 10 arc min grid for the North Pacific regional waters

-New 10 arc min grid for the Pacific Islands and Hawaii

-New 10x15 arc min grid for the Alaskan waters

-New 4 arc min grid for the US East Coast

-New 4 arc min grid for the US West Coast (including the

 coastal waters of Hawaii )

-New 8x4 arc min grid for the Alaskan coast

 

NCEP will continue to produce the current NAH and NPH output

products, including their respective point output files, until

further notice.  These products will be generated using output

from the new multi-grid hurricane wave model.

 

The new grids will be disseminated via the NCEP server and will

be incorporated into AWIPS on a yet-to-be-determined date. More

details about the NCEP Multi-Grid Hurricane Wave Model are

available at:

 

  http://polar.ncep.noaa.gov/waves/index2.shtml

 

A consistent parallel feed of data will become available on the

NCEP server once the model is running in parallel on the NCEP

Central Computing System, around September 7, 2010.  At this time,

the parallel data will be available at:

 

  http://www.ftp.ncep.noaa.gov/data/nccf/com/wave/para

or

  ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/wave/para

 

Users should ensure their decoders are flexible and are able to

adequately handle changes in content, parameter fields changing

order, changes in the scaling factor component within the Product

Definition Section (PDS) of the GRIB files, and any volume changes

that may occur. These elements may change with future NCEP model

implementations. NCEP will make every attempt to alert users to

these changes prior to any implementation.

 

For questions regarding these model changes, please contact:

 

  Hendrik Tolman

  NCEP/Marine Modeling and Analysis Branch

  Camp Springs , Maryland

  301-763-8000 x 7253

  hendrik.tolman@noaa.gov

 

For questions regarding the dataflow aspects of these data sets,

please contact:

 

  Rebecca Cosgrove

  NCEP/NCO Dataflow Team

  Camp Springs , Maryland 20746

  301-763-8000 x 7198

  ncep.list.pmb-dataflow@noaa.gov

 

NWS National Technical Implementation Notices are online at:

 

  http://www.nws.noaa.gov/os/notif.htm

 

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