NDFD Grids

NDFD data are stored as points on regular grids.  There are 6 grids with each grid derived from points projected from a sphere of radius 6371.2 km.  The CONUS and Northern Hemisphere grids use a Lambert Conformal projection while the Guam, Hawaii, Puerto Rico, and Northern Pacific grids use a Mercator projection.  The Alaska grid is based on a Polar Stereographic projection.  Additional meta-data on NDFD grids are available in three grid definition tables below.

NDFD Horizontal Datum

The NDFD uses the WGS84 geoid.

Grid Locations and Extent

 

CONUS Grid

Image of the CONUS Grid

 

Northern Hemisphere Grid

Image of the Northern Hemisphere Grid

 

Alaska Grid

Image of the Alaska Grid

 

Guam Grid

Image of the Guam Grid

 

Hawaii Grid

Image of the Hawaii Grid

 

Puerto Rico Grid

Image of the Puerto Rico Grid

 

Northern Pacific Grid

Image of the Northern Pacific Grid

 

Oceanic Grid

Image of the Oceanic Grid

 

Micronesia Grid

 

Details of NDFD Grids Found in GRIB2 Meta Data

The NDFD grids, as described in the tables below, are the result of projecting a sphere onto a flat surface. The corner of the grid is found at the point identified in the grid parameters tables as latitude1 and longitude1. Each table lists the number of points in the grid which is the product of the number of points on the parallel and meridian. Grid points are seperated by Dx meters along the x axis (longitude) and Dy meters along the y axis (latitude). The projection type, earth radius, and other grid definition parameters are provided in the tables below. For more information on decoding GRIB2 files, see https://vlab.noaa.gov/web/mdl/ndfd-grib-encoding.

CONUS and Northern Hemisphere Grids

Grid Parameter CONUS 5km CONUS 2.5km Northern Hemisphere
Number of Points 739297 2953665 1509825
Projection Type Lambert Conformal Lambert Conformal Lambert Conformal
Shape of Earth sphere sphere sphere
Earth Radius 6371.2 km 6371.2 km 6371.2 km
Number of Points on the parallel 1073 2145 1473
Number of Points on the Meridian 689 1377 1025
Latitude1 20.191999 20.191999 12.189999
Longitude1 238.445999 238.445999 226.541000
u/v vectors relative to easterly/northerly easterly/northerly easterly/northerly
Dx 5079.406 m 2539.703 m 5079.406 m
Dy 5079.406 m 2539.703 m 5079.406 m
GRIB2 grid, scan mode 64 (0100) 64 (0100) 64 (0100)
Scan i/x direction positive positive positive
Scan j/y direction positive positive positive
Consecutive points in i/x direction i/x direction i/x direction
Adjacent rows scan in same direction same direction same direction
Mesh Latitude 25 25 25
Orientation Longitude 265 265 265
Which Pole is on the Plane north north north
Is Projection Bi-polar no no no
Tangent Latitude1 25 25 25
Tangent Latitude2 25 25 25
Southern Latitude -90 -90 -90
Southern Longitude 0 0 0

Guam, Hawaii, Puerto Rico Grids, Northern Pacific and Oceanic Grids

Grid Parameter Guam Hawaii Puerto Rico N. Pacific Oceanic
Number of Points 37249 72225 75936 1580529 4512981
Projection Type Mercator Mercator Mercator Mercator Mercator
Shape of Earth sphere sphere sphere sphere sphere
Earth Radius 6371.2 km 6371.2 km 6371.2 km 6371.2 km 6371.2 km
Number of Points on the parallel 193 321 339 1473 2517
Number of Points on the Meridian 193 225 224 1073 1793
Latitude1 12.349884 18.072699 16.977485 -25.000000 -30.4192
Longitude1 143.686538 198.474999 291.972167 110.000000 129.906000
u/v vectors relative to easterly/northerly easterly/northerly easterly/northerly easterly/northerly easterly/northerly
Latitude2 16.794399 23.087799 19.544499 60.643999 79.991525
Longitude2 148.280000 206.130999 296.015600 250.871000 10.689223
Dx 2500.0 m 2500.0 m 1250.0 m 10000.0 m 10000.0 m
Dy 2500.0 m 2500.0 m 1250.0 m 10000.0 m 10000.0 m
GRIB2 grid, scan mode 64 (0100) 64 (0100) 64 (0100) 64 (0100) 64 (0100)
Scan i/x direction positive positive positive positive positive
Scan j/y direction positive positive positive positive positive
Consecutive points in i/x direction i/x direction i/x direction i/x direction i/x direction
Adjacent rows scan in same direction same direction same direction same direction same direction
Mesh Latitude 20 20 20 20 20
Orientation Longitude 0 0 0 0 0
Tangent Latitude1 0 0 0 0 0
Tangent Latitude2 0 0 0 0 0
Southern Latitude 0 0 0 0 0
Southern Longitude 0 0 0 0 0

Alaska Grid

Grid Parameter Alaska 6km Alaska 3km
Number of Points 456225 1822145
Projection Type Polar Stereographic Polar Stereographic
Shape of Earth sphere sphere
Earth Radius 6371.2 km 6371.2 km
Number of Points on the parallel 825 1649
Number of Points on the Meridian 553 1105
Latitude1 40.530101 40.530101
Longitude1 181.429000 181.429000
u/v vectors relative to easterly/northerly easterly/northerly
Dx 5953.125 m 2976.5625 m
Dy 5953.125 m 2976.5625 m
GRIB2 grid, scan mode 64 (0100) 64 (0100)
Scan i/x direction positive positive
Scan j/y direction positive positive
Consecutive points in i/x direction i/x direction
Adjacent rows scan in same direction same direction
Mesh Latitude 60 60
Orientation Longitude 210 210
Which Pole is on the Plane north north
Is Projection Bi-polar no no
Tangent Latitude1 90 90
Tangent Latitude2 90 90
Southern Latitude 0 0
Southern Longitude 0 0

Micronesia Grid

Grid Parameter Micronesia        
Number of Points 444507        
Projection Type Mercator        
Shape of Earth sphere        
Earth Radius 6371.2 km        
Number of Points on the parallel 1041        
Number of Points on the Meridian 427        
Latitude1 0.0258958        
Longitude1 129.81        
u/v vectors relative to easterly/northerly        
Latitude2 20.0036        
Longitude2 179.579        
Dx 5000.0 m        
Dy 5000.0 m        
GRIB2 grid, scan mode 64 (0100)        
Scan i/x direction positive        
Scan j/y direction positive        
Consecutive points in i/x direction        
Adjacent rows scan in same direction        
Mesh Latitude 20        
Orientation Longitude 0        
Tangent Latitude1 0        
Tangent Latitude2 0        
Southern Latitude 0        
Southern Longitude 0        

GRIB2 Links

GRIB2 Documentation

  • World Meteorological Organization FM92 GRIB, Edition 2, Code Form and Tables publication
  • GRIB2 Use at NCEP

GRIB2 Decoders

Sources of GRIB2 Files

DeGRIB for NDFD