NCEP USE OF THE EXTENDED GRIB PDS SECTION
FOR DESCRIBING ENSEMBLE OUTPUT
EXTENSION OF PDS SECTION FOR ENSEMBLE PRODUCTS 


Octet 
Description 

41 
Identifies application1 = Ensemble 

42 
Type1 = Unperturbed control forecast


43 
Identification numberIf Byte 42 = 1, byte 43 will = 1 or 2:
If Byte 42 = 2 or 3, byte 43 will = 1,2,3,4 or 5: 

44  Product Identifier 1 = Full field (individual forecast) / Unweighted mean (cluster/ens) 2 = Weighted mean (of raw forecasts) 3 = Full field (individual forecast of bias correction) : the values are modified by considered bias 4 = Weighted mean ( of bias corrected forecasts) 5 = Weights: statistically decided weights for each ensemble member 6 = Climate percentile: percentile values from climate distribution 7 = daily climate mean: from 40year NCEP/NCAR reanalysis 8 = daily climate standard deviation from daily mean: from 40year NCEP/NCAR reanalysis 11 = Standard deviation with respect to ensemble mean 12 = Standard deviation with respect to ensemble mean, normalized 21 = maximum value of all members 22 = minimum value of all members 23 = The ensemble forecast value for X% probability (X is given in byte 45  integer value 0  100) 24 = The ensemble mode forecast (mode = 3*medium  2*mean) 

45 
Spatial Smoothing of Product or Probability (if byte 44 = 23)(number of highest total wavenumber included)255 = Original resolution retained 

Octet 46 and above are used only if needed 

Probability Section 

46 
Probability product definition:If octet 9=191 or 192, defines variable in terms of octet 9 table (see below for more details) 

47 
Probability type1 = Probability of event below lower limit


4851  Probability lower limit (unit as in octet 9; floating point number)  
5255  Probability upper limit (unit as in octet 9; floating point number)  
5660  Reserved  
Octet 61 and above are used only if octet 42=4 or 5 

Clustering Section 

61 
Ensemble size (number of members, including controls)  
62  Cluster size (number of members)  
63  Number of clusters  
64  Clustering Method
1 = AC 

6567  Northern latitude of clustering domain (in thousandths of degree)  
6870  Southern latitude of clustering domain (in thousandths of degree)  
7173  Eastern longitude of clustering domain (in thousandths of degree)  
7476  Western longitude of clustering domain (in thousandths of degree)  
7786  Cluster Membership (If octet 42=4) Indicates in binary (on/off) format, which members of
the 