NOUS41 KWBC 161933 AAC



Technical Implementation Notice 11-58, Amended

National Weather Service Headquarters Washington DC

330 PM EDT Mon Apr 16 2012


TO:      National Weather Service Offices (NWS)

         Federal Aviation Administration Customers (FAA)

         Family of Services Subscribers (FOS)

         Other Customers of NWS Aviation Forecasts


FROM:    Cynthia Abelman

         Chief, Aviation Services Branch


SUBJECT: Amended: Graphical Turbulence Guidance (GTG) Change
         Effective May 1, 2012


NOTE:    The following changes have no impact on NOAA

         Weather Wire Service subscribers


Amended to set the implementation date for Tuesday May 1, 2012. 

Users are cautioned that if a Critical Weather Day (CWD) designation is in effect on May 1, this implementation will be delayed until the conclusion of CWD.  You can monitor the CWD status at the following webpage:


See TIN 11-36, issued July 27, 2011, announcing the intention to replace the Rapid Update Cycle (RUC) model with the Rapid Refresh (RAP) model, and the Public Information Statement issued November 9, 2011, proposing to remove some RUC output products.


Effective May 1, 2012, 1200 Coordinated Universal Time (UTC), the NWS Aviation Weather Center in Kansas City, MO, will update the GTG product in conjunction with the implementation of the RAP model.  This change impacts users as follows:


1. Resolution of the grid spacing will increase from 20KM

     to 13KM. 


2. As a result of increased resolution, the parameter Grid

     ID (PDS OCTET 7), internal to the GRIB file, will change

     to 130. For more information, see



This change will affect the following WMO headers for GTG:


WMO            FLIGHT


-----------    -----

YVW*14 KKCI    FL450

YVW*15 KKCI    FL440

YVW*16 KKCI    FL430

YVW*17 KKCI    FL420

YVW*18 KKCI    FL410

YVW*19 KKCI    FL400

YVW*20 KKCI    FL390

YVW*21 KKCI    FL380

YVW*22 KKCI    FL370

YVW*23 KKCI    FL360

YVW*24 KKCI    FL350

YVW*25 KKCI    FL340

YVW*26 KKCI    FL330

YVW*27 KKCI    FL320

YVW*29 KKCI    FL310

YVW*30 KKCI    FL300

YVW*32 KKCI    FL290

YVW*33 KKCI    FL280

YVW*34 KKCI    FL270

YVW*36 KKCI    FL260

YVW*38 KKCI    FL250

YVW*39 KKCI    FL240

YVW*41 KKCI    FL230

YVW*43 KKCI    FL220

YVW*45 KKCI    FL210

YVW*46 KKCI    FL200

YVW*48 KKCI    FL190

YVW*50 KKCI    FL180

YVW*53 KKCI    170

YVW*55 KKCI    160

YVW*57 KKCI    150

YVW*60 KKCI    140

YVW*62 KKCI    130

YVW*65 KKCI    120

YVW*67 KKCI    110

YVW*70 KKCI    100

ZVW*50 KKCI    Composite


WHERE     *  = A    = 00 HOUR FORECAST

          *  = B    = 01 HOUR FORECAST

          *  = C    = 02 HOUR FORECAST

          *  = D    = 03 HOUR FORECAST

          *  = G    = 06 HOUR FORECAST

          *  = J    = 09 HOUR FORECAST

          *  = M    = 12 HOUR FORECAST


The GTG graphics are computer-generated four-dimensional forecasts of information related to the likelihood of encountering atmospheric turbulence.

The product provides forecasts for the 48 contiguous United States, much of Canada and Mexico, and their respective coastal waters at flight altitudes from 10,000 MSL to FL450 only; it does not provide forecasts from the surface to 10,000 ft.  Users should also be aware that turbulence is a highly dynamic phenomenon and, in case of rapidly changing conditions, the product may not accurately convey a significant hazard.  GTG may be used as a higher-resolution supplement to AIRMETs and SIGMETs, but not as a substitute for the turbulence information they provide. GTG-2 graphics are authorized for use as an unrestricted, supplementary weather product.  The GTG-2 does not have the capability to be amended.  See the definition of primary and supplementary weather products below.


GTG is produced automatically from the 13 KM Weather Research and Forecasting RAP model runs.  GTG produces an Analysis, 1, 2, 3, 6, 9 and 12-hour Turbulence Forecast every hour in GRIB format.  This product also provides a composite field representing the maximum turbulence value between 10,000 and 45,000 feet for each analysis and forecast.


The GTG graphics suite is automatically produced with no human modifications.  Information on the graphics is determined from observational data, pilot weather reports, upper air soundings, satellite soundings, automated aircraft reports, and surface weather reports, all of which are integrated with computer model output.


Early to mid-May, 2012, GTG output in Gridded Binary (GRIB) format will be available through:


- NWS FTP servers at:


- The Family of Services (FOS) High Resolution Data Service and

  Server Access Service


- Satellite Broadcast Network (SBN) NOAAPORT channel


To obtain sample gridded GTG data, contact:


Robert Sallee

Senior Software Engineer - Aviation Weather Center

Kansas City, MO 64153



Questions regarding the new GTG product, contact:


M. Pat Murphy

Warning Coordination Meteorologist

Aviation Weather Center

Kansas City, MO 64153



National Technical Implementation Notices are online at: