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Service Change Notice 13-25

National Weather Service Headquarters Washington DC

1033 AM EDT Thu Mar 28 2013

 

To:       Subscribers:

          -Family of Services

          -NOAA Weather Wire Service

          -Emergency Managers Weather Information Network

          -NOAAPort

          Other NWS partners and employees

 

From:     Cynthia Abelman

          Chief, Aviation Services Branch

 

Subject:  Format Change for World Area Forecast System (WAFS)

          Upper Air Forecasts Effective November 13, 2013.

 

Effective Wednesday, November 13, 2013, at 1800 Coordinated

Universal Time (UTC), the NWS will cease providing WAFS Global

Gridded Forecasts in the World Meteorological Organization (WMO)

GRIdded Binary 1 (GRIB1) code format. At that time, WAFS Global

Forecasts will only be available in WMO GRIB2 format. 

 

This change is being implemented in accordance with the

International Civil Aviation Organization (ICAO) WAFS Operations

Group seventh meeting. This meeting made GRIB2 WAFS Global

Gridded Forecasts operationally available and conforms to ICAO

Annex 3. All users of WAFS Upper Air Forecasts in GRIB1 format

are urged to migrate to WAFS Upper Air Forecasts in GRIB2 format

at the earliest opportunity.

 

GRIB2 is a binary format developed by the WMO containing gridded

data. GRIB2 was approved for experimental use by the WMO/CBS in

1998 and for operational use in 2000. GRIB2 addressed the GRIB1

problem of tables being full and the format inability to expand

or extend the tables.  GRIB2 introduced a more comprehensive

parameter identification system and expanded use of templates.

 

There are differences in technical encoding between GRIB1 and

GRIB2. There are five major differences, from the meteorological

and operational perspective, between the two formats are:

 

1 GRIB2 is a regular grid with 1.25 X 1.25 degree (~140KM X 140

  KM at the equator) resolution. GRIB1 has the longitudinal

  points on the grid "thinned" as the polar regions are

  approached.

2 GRIB2 bulletins contain data covering the entire globe for each

  level and each parameter in every bulletin. GRIB1 has separate

  bulletins for each "octant" of every level/parameter

  combination.

3 GRIB2 data is compressed using the JPEG2000 standard.

  Appropriate JPEG2000 decompression libraries will be necessary.

4 GRIB2 has a temporal resolution of 3 hours, from T+06 to T+36

  inclusive. GRIB1 has a temporal resolution of 6 hours (T+06

  to T+36 inclusive).

5 GRIB2 has additional levels close to the normal cruise of level

  of airliners.

 

Guidance on the WAFS Global Gridded Forecasts in WMO GRIB2 Format

is available on the WAFS Operations Group Website:

 

http://www.icao.int/safety/meteorology/WAFSOPSG/Pages/GuidanceMaterial.aspx

 

In support of the WAFS, NWS’s World Area Forecast Center

Washington provides global gridded forecasts of upper wind and

temperature data covering Flight Levels FL050-530, tropopause

heights and temperature, and maximum wind (height, speed,

direction). This data is based on output from the Global Forecast

System Numerical Weather Model. The data can be used in flight

planning systems to optimize flights routes or to generate a

range of charts, such and wind and temperature charts, cross

sections, etc.

 

The aforementioned gridded products are produced four times

daily, for T+06 to T+36 hour time steps, and are available in

GRIB2 format on the WAFS Internet File System (WIFS). WIFS is

available to registered users at:

 

http://www.aviationweather.gov/wifs/

 

For technical questions and support in registering a user account

at the WIFS Website or downloading and accessing the GRIB2 data,

contact:

 

Ryan Solomon

Aviation Weather Center

Kansas City, MO 64153

816-584-72048   

ryan.l.Solomon@noaa.gov

 

If you have any questions about this change, or the WAFS Global

Grids data set, please contact:

 

Matt Strahan

Chief, International Operations Branch

Aviation Weather Center/WAFC Washington   

Kansas City, MO 64153

816-584-7204   

matt.strahan@noaa.gov

 

National Technical Implementation Notices are online at:

 

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

 

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