NOUS41 KWBC 131108



Public Information Statement 17-06

National Weather Service Headquarters Washington, DC

708 AM EST Mon Feb 13 2017


To:        Subscribers:

            -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


            Other NWS Partners, Users and Employees


From:       Arun Chawla

            Chief, Marine Modeling & Analysis Branch

           NCEP/Environmental Modeling Center


Subject:  Soliciting Public Comments on the Removal of

          NCEP's hurricane wave (Multi_2) modeling system 

          through March 17, 2017.


The National Centers for Environmental Prediction (NCEP) has

been running a hurricane wave guidance system (Multi_2) since

2008. This system runs after the global deterministic wave model

(Multi_1) and uses the Hurricane Weather Research and

Forecasting (HWRF) winds as input when there is an active storm.

NCEP is proposing to remove the Multi_2 runs from our guidance

suite, replacing its products with higher-quality hurricane wave

data generated by the next coupled hurricane guidance 

system HWRF.


The difference between the two current global wave guidance

systems is that Multi_1 runs using just the GFS forcings, while

Multi_2 runs using a blend of hurricane (HWRF) and GFS forcings.

The hurricane winds are interpolated from the atmospheric

domains to the wave domains. When there is not an active

tropical system, the Multi_2 is forced by the GFS winds, and

therefore the Multi_2 output is identical to the Multi_1 output.


Over the years, the improvements in the resolutions of the

atmospheric models has meant this approach does not provide any

significant advantage over the global wave model (see the link

below comparing the Multi_1 and Multi_2 modeling systems), and

as such Multi_2 is a redundant system. Furthermore, as part of

the HWRF modeling upgrade this year, the WAVEWATCH III model

that forms the core of Multi_1 and Multi_2 will be coupled with

the HWRF model to produce high resolution hurricane driven wave

fields. The wave field from this coupled system (see link)

provides significantly superior wave guidance in hurricane

conditions. Hurricane-driven wave fields will be distributed as

part of the HWRF output data.


The comparison between global wave model (Multi_1), global

hurricane wave model (Multi_2) and high resolution wave

simulations as part of the next coupled hurricane system (HWRF)

can be found here:


Operational Multi_2 data in gridded and text bulletin form are

distributed via the following services and will no longer be

available from the following distribution sources:

the NWS FTP server ( at


where YYYYMMDD is the date.

the NOMADS system at


and on NOAAPORT with the following WMO headers:

E***88 KWBU  for gridded GRIB2 products

AG**4* KWBC  for text bulletins


NWS will evaluate all comments to determine whether to proceed

with this change. If approved, a Service Change Notice will be

issued giving 30 days notice of the implementation date.


Send comments on this proposal to:


   Arun Chawla

   NWS/NCEP Environmental Modeling Center

   College Park, MD


  Rebecca Cosgrove

  NWS/NCEP Central Operations

  College Park, MD


National Public Information Statements are online at: