NOUS41 KWBC 081845 AAA
PNSWSH

TECHNICAL IMPLEMENTATION NOTICE 08-40 AMENDED
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
245 PM EDT WED AUG 6 2008

TO:       NATIONAL WEATHER SERVICE /NWS/ OFFICES
          FEDERAL AVIATION ADMINISTRATION USERS
          FAMILY OF SERVICES SUBSCRIBERS
          OTHER USERS OF NWS AVIATION FORECASTS

FROM:     KEVIN L. JOHNSTON
          CHIEF AVIATION SERVICES BRANCH
          NWS OFFICE OF CLIMATE WATER AND WEATHER SERVICES

SUBJECT:  AMENDED DATE: AVIATION WEATHER CENTER /AWC/ GRAPHICAL 
          AIRMET /G-AIRMET/ BECOMES AN OPERATIONAL PRODUCT:
          EFFECTIVE OCTOBER 1 2008

NOTE:     THE FOLLOWING CHANGES HAVE NO IMPACT ON NOAA WEATHER
          WIRE SUBSCRIBERS

AMENDED TO CHANGE THE IMPLEMENTATION DATE TO OCTOBER 1 2008 
CHANGE IN IMPLEMENTATION DATE NEEDED DUE TO TECHNICAL ISSUES.

BEGINNING WEDNESDAY OCTOBER 1 2008 AT 1500 UTC NWS WILL 
BEGIN ISSUING A GRAPHICAL AIRMANS METEOROLOGICAL ADVISORY  
/G-AIRMET/ AS AN OPERATIONAL PRODUCT.

THE G-AIRMET IS A TIME SERIES DEPICTION OF AVIATION WEATHER 
HAZARDS AND ELEMENTS OCCURRING WITH OCCASIONAL OR GREATER 
FREQUENCY THROUGHOUT THE CONTERMINOUS U.S. AND ADJACENT COASTAL 
WATERS IN BUFR-FORMAT. THE AVIATION WEATHER HAZARDS AND ELEMENTS 
DEPICTED ARE:

1.  SURFACE VISIBILITY /IFR VIS/ BELOW THREE /3/ STATUTE
    MILES... INCLUDING THE WEATHER CAUSING THE VISIBILITY
    RESTRICTION.

2.  CLOUD CEILINGS /IFR CIG/ WITH BASES LESS THAN 1000 FEET
    ABOVE GROUND LEVEL /AGL/.

3.  WIDESPREAD MOUNTAIN OBSCURATION /MTN OBSCN/ WHERE VISUAL
    METEOROLOGICAL CONDITIONS /VMC/ CANNOT BE MAINTAINED...
    INCLUDING THE WEATHER CAUSING THE OBSCURATION.

4.  MODERATE TURBULENCE /MOD TURB/...INCLUDING THE TOP AND
    BOTTOM ALTITUDES OF THE TURBULENCE LAYER.

5.  SUSTAINED SURFACE WIND GREATER THAN 30 KNOTS /STG SFC WND/.

6.  NON-CONVECTIVE LOW LEVEL WIND SHEAR POTENTIAL BELOW 2000
    FEET AGL /LLWS/.

7.  MODERATE ICING /MOD ICE/...INCLUDING THE TOP AND BOTTOM
    ALTITUDES OF THE ICING LAYER.  WHEN THE BOTTOM ALTITUDE IS
    GIVEN AS FREEZING LEVEL /FRZLVL/ THE RANGE OF FREEZING LEVEL
    ALTITUDES IS ALSO PROVIDED.

8.  FREEZING LEVEL /FRZLVL/ CONTOURS AT THE SURFACE AND AT
    4000...8000...12000...AND 16000 FEET ABOVE MEAN SEA LEVEL.

9.  MULTIPLE FREEZING LEVELS /M_FZLVL/...INCLUDING THE HEIGHT OF
    THE HIGHEST AND LOWEST FREEZING LEVELS.

THE G-AIRMET WILL BE ISSUED ROUTINELY AT 0255...0855...1455... 
AND 2055 UTC AND AMENDED AS NEEDED BETWEEN ROUTINE ISSUANCES.  
EACH ROUTINE ISSUANCE IS VALID THROUGH 12 HOURS WITH A TIME 
RESOLUTION OF NO MORE THAN THREE HOURS.

THERE ARE THREE BUFR MESSAGES IN THE G-AIRMET:
  -  ONE FOR ITEMS 1 THROUGH 3 /SIERRA/ 
  -  ONE FOR ITEMS 4 THROUGH 6 /TANGO/
  -  ONE FOR ITEMS 7 THROUGH 9 /ZULU/.  

HEADER AND FTP INFORMATION WILL BE PROVIDED IN THE PRODUCT 
DESCRIPTION DOCUMENT BEFORE THE IMPLEMENTATION DATE AT  
/USE LOWER CASE/:

  HTTP://PRODUCTS.WEATHER.GOV/VIEWLIST.PHP

A DETAILED DESCRIPTION OF THE GRAPHICAL AIRMET AND THE BUFR 
ENCODE/DECODE SCHEME IS AVAILABLE AT /USE LOWER CASE/:

  HTTP://AVIATIONWEATHER.GOV/NOTICE/G-AIRMET

REAL-TIME EXAMPLES OF THE GRAPHICAL AIRMET ARE AVAILABLE AT  
/USE LOWER CASE/:

  HTTP://AVIATIONWEATHER.GOV/TESTBED/GFA

FOR ADDITIONAL INFORMATION CONTACT:

  CLINTON E. WALLACE
  CHIEF AVIATION SUPPORT BRANCH
  AVIATION WEATHER CENTER
  KANSAS CITY MISSOURI
  PHONE: 816-584-7248
  E-MAIL: CLINTON.WALLACE@NOAA.GOV

TECHNICAL IMPLEMENTATION NOTICES ARE ONLINE AT /USE LOWER CASE/:

  HTTP://WWW.WEATHER.GOV/OS/NOTIF.HTM

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