NOUS41 KWBC 071542 AAC



Technical Implementation Notice 11-58 Amended

National Weather Service Headquarters Washington DC

1042 AM EST Wed Mar 7 2012


To       NWS Offices

         Federal Aviation Administration

         Family Of Services Subscribers

         Other Users of NWS Aviation Forecasts


From     Cynthia Abelmann

         Chief, Aviation Services Branch


Subject: Amended Graphical Turbulence Guidance To Be Updated

         Effective March 20, 2012


The following changes have no impact on NOAA Weather Wire Service Subscribers

The previous amendment to this change notice contained an erroneous date. The correct date for this change is March 20, 2012 to coincide with the National Centers for Environmental Prediction (NCEP) replacement of the Rapid Update Cycle (RUC) model with the Rapid Refresh (RAP) model. See TIN 11-53 for details on this change. Graphical Turbulence Guidance is based on the RUC, and will be based on the RAP effective March 20, 2012. 

Effective March 20, 2012, 1200 Coordinated Universal Time (UTC), the NWS Aviation Weather Center (AWC) in Kansas City, Missouri, will update The Graphical Turbulence Guidance (GTG) product in conjunction with the implementation of the Rapid Refresh (RAP) model.  The following changes with potential impact to end users of this product include:

Resolution of the grid spacing will increase from 20KM to 13KM.  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

Additional forecast hours valid at 04, 05, 07, 08, 10 and 11 hours

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

          *  = E    = 04 HOUR FORECAST

          *  = F    = 05 HOUR FORECAST

          *  = G    = 06 HOUR FORECAST

          *  = H    = 07 HOUR FORECAST

          *  = I    = 08 HOUR FORECAST

          *  = J    = 09 HOUR FORECAST

          *  = K    = 10 HOUR FORECAST

          *  = L    = 11 HOUR FORECAST

          *  = M    = 12 HOUR FORECAST


The GTG graphics are computer-generated 4-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 Rapid Refresh (RAP) model runs. GTG produces an Analysis, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12-hour Turbulence Forecast every hour in GRIB format. This product also provides a composite field representing the maximum turbulence value between 10 and 45 thousand 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.


On January 24, 2012, GTG output in Gridded Binary (GRIB) format will be available through


1. NWS FTP servers at:


2. The Family Of Services (FOS) High Resolution Data Service and Server Access Service


3. 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



For 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: