NOAA’s National Weather Service NDFD Dissemination Services Allan Darling Office of the CIO, Telecommunication Operations Center National Digital Forecast Database Technical Workshop August 13, 2003

NDFD Technical Workshop 2003 NDFD Dissemination Services What will we cover? Where to find NDFD product files Information about the servers where the data is stored How files are named How files are constructed How product headings are formed What a “super heading” is Where to go for more information

NDFD Technical Workshop 2003 NDFD Dissemination Services Where to find NDFD product files – Files are available via: ftp://tgftp.nws.noaa.gov ftp://ptgftp.nws.noaa.gov (Access to ptgftp.nws.noaa.gov is limited to SAS customers - see for more information about Server Access Services.

NDFD Technical Workshop 2003 NDFD Dissemination Services About the servers – All servers are classed a operational systems with 24x7 support and monitoring tgftp.nws.noaa.gov – Cluster of five public anonymous FTP servers weather.noaa.gov – Cluster of five public HTTP servers ptgftp.nws.noaa.gov – Cluster of two restricted access anonymous FTP servers

NDFD Technical Workshop 2003 NDFD Dissemination Services Where to find NDFD product files – On each server, NDFD data is found under the path: /SL.us008001/ST.expr/DF.gr2/DC.ndfd/... The path indicates that the data is on the public NWSTG FTP server, is experimental, is encoded in WMO GRIB Edition 2 format, and is all related to the NDFD data category. See for more information about the directory and file naming standards used on the NWSTG FTP and HTTP Servershttp://

NDFD Technical Workshop 2003 NDFD Dissemination Services How files are named – Following the data format and category directories, the last directory and the file name specify: the geographic area ( /AR.aaaaaaaa ) the data subcategory ( /ds.sssss ) A list of all the NDFD Sectors (geographic areas) and the data subcategories is available at This spreadsheet also defines the NDFD sectors by Lat/Lon and grid points

NDFD Technical Workshop 2003 NDFD Dissemination Services How files are named – The file ftp://tgftp.nws.noaa.gov/SL.us008001/ST.expr /DF.gr2/DC.ndfd/AR.midatlan/ds.maxt.bin contains the daytime maximum temperature for the Mid-Atlantic sector.

NDFD Technical Workshop 2003 NDFD Dissemination Services How files are constructed – Files are comprised of: A flag field separator block (option 2) A super heading One or more GRIB products each comprised of A flag field separator block (option 2) A WMO Heading A GRIB product

NDFD Technical Workshop 2003 NDFD Dissemination Services How files are constructed – A flag field separator block (option 2) is a file delimiter that provides the length of the product that follows it. The format is: ****nnnnnnnnnn****lf Where nnnnnnnnnn is the length of the product following the seperator, in bytes and lf is an ASCII line feed. See for more details.

NDFD Technical Workshop 2003 NDFD Dissemination Services How files are constructed – **** **** YGCZ99 KWBN **** **** YGCB00 KWBN GRIB **** **** YGCC00 KWBN GRIB **** **** YGCI00 KWBN GRIB

NDFD Technical Workshop 2003 NDFD Dissemination Services How product headings are formed – Generic WMO Heading: T 1 T 2 A 1 A 2 ii CCCC Generic NDFD Heading: YT 2 A 1 A 2 ii KWBN T 2 specified the data type (data subcategory) A 1 specifies the geographic designator (NDFD sector) A 2 and ii together specify the NDFD reference time (not represented in the directory or file names)

NDFD Technical Workshop 2003 NDFD Dissemination Services How product headings are formed – Generic NDFD Heading: YT 2 A 1 A 2 ii KWBN The possible values for T 2, A 1, A 2, and ii and their meanings are specified on the NDFD WMO Heading Reference page at

NDFD Technical Workshop 2003 NDFD Dissemination Services A = SKY COVER B = WIND DIRECTION C = WIND SPEED D = PROBABILITY OF PRECIPITATION (12 HOURS) E = SURFACE TEMPERATURE F = DEWPOINT TEMPERATURE G = DAYTIME MAXIMUM TEMPERATURE H = NIGHTTIME MINIMUM TEMPERATURE I = QUANTITATIVE PRECIPITATION J = WEATHER K = WAVE HEIGHT S = SNOWFALL AMOUNT U = FREE AIR WIND DIRECTION V = FREE AIR WIND SPEED How product headings are formed – T 2 – data type

NDFD Technical Workshop 2003 NDFD Dissemination Services **** **** YGCZ99 KWBN **** **** YGCB00 KWBN GRIB **** **** YGCC00 KWBN GRIB **** **** YGCI00 KWBN GRIB YGCB00 KWBN Y -NDFD Product G – Daytime Maximum Temperature C – Mid-Atlantic Sector B – Day 1 00 – Hour 0 Decoding a product heading -

NDFD Technical Workshop 2003 NDFD Dissemination Services What is a “super heading”? In order to aggregate all of the forecast periods for one data subcategory and one sector, the “super heading” was developed. The super heading specifies the data subcategory in T 2 and the geographic sector in A 1. A 2 and ii are fixed as “Z99”: NDFD Super Heading: YT 2 A 1 Z99 KWBN

NDFD Technical Workshop 2003 NDFD Dissemination Services **** **** YGCZ99 KWBN **** **** YGCB00 KWBN GRIB **** **** YGCC00 KWBN GRIB **** **** YGCI00 KWBN GRIB YGCZ99 KWBN Y -NDFD Product G – Daytime Maximum Temperature C – Mid-Atlantic Sector Z99 – Super Heading The super heading contains one or more instances of a flag field separator, WMO heading and GRIB product. What is a “super heading”?

NDFD Technical Workshop 2003 NDFD Dissemination Services **** **** YGCZ99 KWBN **** **** YGCB00 KWBN GRIB **** **** YGCC00 KWBN GRIB **** **** YGCI00 KWBN GRIB **** **** YGCZ99 KWBN is the length, in bytes, of the super heading and all the following groups of flag field separators, WMO headings, and GRIB products. Super heading flag field separator -

NDFD Technical Workshop 2003 NDFD Dissemination Services **** **** YGCZ99 KWBN **** **** YGCB00 KWBN GRIB **** **** YGCC00 KWBN GRIB **** **** YGCI00 KWBN GRIB **** **** YGCB00 KWBN GRIB is the length, in bytes, of the single heading and GRIB product. “Regular” flag field separator -

NDFD Technical Workshop 2003 NDFD Dissemination Services For more dissemination information – NWSTG Data Management NDFD Reference Directory and File Naming Standards – Family of Services Main Page – Gateway File Standards and Content Structures –