TECHNICAL INFORMATION SECTION
NDFD Database Contents
Variables
Currently, the NDFD contains data representing the following weather variables. More variables will be added as development of the NDFD progresses. For a complete listing of variables to be included in the NDFD, visit the Development page. NDFD data are available for projections (as described in the table below) at the following UTC times: 0, 3, 6, 9, 12, 15, 18, 21.
| Variables |
No. of Grids |
Projections |
| Max-Temp |
7 |
Every 24 hours, out to 168 hours |
| Min-Temp |
7 |
Every 24 hours, out to 168 hours |
| PoP12 |
14 |
Every 12 hours, out to 168 hours |
Sky Cover |
40 |
Every 3 hours out to 72 hours; every 6 hours out to 168 hours |
| Temperature |
40 |
Every 3 hours out to 72 hours; every 6 hours out to 168 hours |
| Dew Point |
40 |
Every 3 hours out to 72 hours; every 6 hours out to 168 hours |
| Wind Direction |
40 |
Every 3 hours out to 72 hours; every 6 hours out to 168 hours |
| Wind Speed
|
40 |
Every 3 hours out to 72 hours; every 6 hours out to 168 hours |
| Weather |
40 |
Every 3 hours out to 72 hours; every 6 hours out to 168 hours |
| Precipitation Amount |
12
|
Every 6 hours out to 72 hours |
| Snow Amount |
6 |
Every 6 hours out to 36 hours |
| Wave Height |
10 |
Every 12 hours out to 120 hours |
List of Variable Definitions
Grid Resolution
Grids are currently available at 5km spatial resolution.
Temporal resolution of NDFD grids is 3 hours for days 1-3 and 6 hours for days 4-7.
We plan to increase both spatial and temporal resolution over the next few years.
Geographic Coverage
Digital forecast data will be received from all NWS Weather Forecast Offices (WFOs) and will be mosaicked and available for access for the coterminous United States (CONUS), Alaska, Hawaii, and Guam, as well as 16 predefined subsectors covering the CONUS.
How to Access NDFD Data
- Information on general access to data and products on NWS file servers
- Access procedures for files available through NWS anonymous FTP
(including NDFD files)
- NDFD Data Management File Reference
On the FTP server (see #2, above) you will be located in the /SL.us008001 directory. You can then find the subdirectory/file you want by following the following naming convention:
| DIRECTORY NAME |
CONTENTS |
| SL.us008001/ |
Data root - for NWS Telecommunication
Gateway Server (top directory) |
| ST.expr/ |
Status of data as experimental (NDFD data is
expected to be made operational in a
transitional manner). |
| DF.gr2/ |
WMO GRIB files (Edition two) |
| DC.ndfd/ |
Data category: National Digital Forecast
Database |
| AR.aaaaaaaa |
Area of Data: could be CONUS, 1 of 16
CONUS overlapping subsectors, Alaska,
Hawaii, Guam, or Puerto Rico. |
| ds.sssss |
FILE NAME = data subcategory containing
abbreviated NDFD element names. ( The
current file for each element will be kept until
overwritten by a new file for the same element. |
Survey Feedback
User feedback is extremely important in our effort to improve the quality and usefulness of our NDFD data and services. Please take a moment to submit your comments by completing our brief experimental product survey/comment form.
Data Format
Data from the NDFD are provided in GRIB, Edition 2 (WMO 2001). Click here for decoding software. For information on GRIB2, please read "GRIB2 Encoding Details for the NDFD."
Customer Support
For real-time customer support, contact the NWS Telecommunications Gateway at
301-713-0902.
NDFD Technical Workshop Presentations
Approximately 70 individuals from private, public and academic sector organizations and 30 NWS staff members took part in the NDFD Technical Workshop held in Silver Spring, MD on August 13, 2003.
This workshop provided details on the technical aspects of NWS digital forecasts made available via the NDFD. Greg Mandt, Director of the Office of Climate, Water, and Weather Services, provided a historical background of NWS digital forecasting and described how NWS hopes to engage its partners and customers as it continues to enhance the products and services made available via NDFD. A summary is online.
Technical presentations on the NDFD were provided by representatives from the Meteorological Development Laboratory and the Office of the Chief Information Officer. Participants had an opportunity to describe their experiences accessing the NDFD gridded data, and make recommendations for enhancements to the NDFD.
