Meteorology / Forecast Data FTP / NCEP NAM

Note that the NCEP models are run at much higher spatial resolution than what is archived on the ARL server. If calculations using the higher resolution date are desired, then the original GRIB encoded files must be obtained from the NCEP server and converted to the HYSPLIT compatible format.

The procedure under this FTP menu tab accesses the NCEP anonymous FTP server and transfers the NAM (North America Mesoscale) forecast GRIB files on the 40 km AWIPS 212 grid (15 Mb per file) or the 12 km AWIPS 218 grid tiles (2 Mb per file). NAM forecast data consist of one forecast time (every 3 h) per file. The GRIB files are then converted on the same horizontal grid to a HYSPLIT compatible file which requires 3.5 Mb (212 grid) or 1 Mb (218 grid) per time period.

The menu is used to select the forecast initialization time (cycle), the duration of the forecast, the output directory, and file name. "Save GRIB files" option is checked, the downloaded files are saved rather than deleted after each forecast hour is processed. The downloaded GRIB data can be reprocessed through the "NAM forecast" menu tab. Note that only the forecast files from the previous 24-h are available from the NCEP server If archive data are required, the file can be created manually be processing only the initialization times and +3 hour forecasts with every 6-h initialization cycle.



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