The computation of EFI changed with the implementation of VarEPS-Monthly in March 2008. This change had to be reflected in the information stored in the GRIB Header. Therefore, we have 2 versions regarding the content of local definition 19. The layout is the same, and applications do not need to be recompiled, unless they make use of the extra information.

The two definitions follow:

- Definition prior to implementation of VarEPS-Monthly (March 2008)
- Definition after implementation of VarEPS-Monthly

Please, refer to the documentation about Implementation of VarEPS-Monthly for further information.

### Definition prior to March 2008

KSEC1 element | Contents | GRIB octet | Recommended GRIB_API keys | Coded GRIB_API keys | Comments
--- | --- | --- | --- | --- | ---
37 |
    ECMWF local GRIB use definition identifier.
    19 = Extreme forecast index data
| 41 | localDefinitionNumber | localDefinitionNumber |
38 | Class: 1 = operations | 42 | class | marsClass |
39 |
    Type:
     27 = extreme forecast index
     28 = extreme forecast index control
| 43 | type | marsType |
40 | Stream: 1035 = ensemble forecast | 44-45 | stream | marsStream |
41 |
    Version number or experiment identifier.
    (4 ASCII characters, right justified)
| 46-49 | expver | experimentVersionNumber |
42 |
    Zero, for compatibility with Mars labelling
| 50 |  |  |
43 | Ensemble size. | 51 | ensembleSize | ensembleSize |
44 | Power of 10 used to scale climate weight = F, say | 52 | powerOfTenUsedToScaleClimateWeight | powerOfTenUsedToScaleClimateWeight |
45 | Weight*10**F applied to climate month 1, stored as an integer | 53 - 56 | weightAppliedToClimateMonth1 | weightAppliedToClimateMonth1 |
46 | First month used to build climate month 1, YYYYMM | 57-59 | firstMonthUsedToBuildClimateMonth1 | firstMonthUsedToBuildClimateMonth1 |
47 | Last month used to build climate month 1, YYYYMM | 60-62 | lastMonthUsedToBuildClimateMonth1 | lastMonthUsedToBuildClimateMonth1 |
48 | First month used to build climate month 2, YYYYMM | 63-65 | firstMonthUsedToBuildClimateMonth2 | firstMonthUsedToBuildClimateMonth2 |
49 | Last month used to build climate month 2, YYYYMM | 66-68 | lastMonthUsedToBuildClimateMonth2 | lastMonthUsedToBuildClimateMonth2 |
50 | EFI order | 69 | efiOrder | efiOrder |
51 | Set to 0 for this version of EFI(prior to March 2008) | 70 |  |  |
- | Set to zero | 71 - 80 |  |  |

### Definition after March 2008

KSEC1 element | Contents | GRIB octet | Recommended GRIB_API keys | Coded GRIB_API keys | Comments
--- | --- | --- | --- | --- | ---
37 |
    ECMWF local GRIB use definition identifier.
    19 = Extreme forecast index data
| 41 | localDefinitionNumber | localDefinitionNumber |
38 | Class: 1 = operations | 42 | class | marsClass |
39 |
    Type:
     27 = extreme forecast index
     28 = extreme forecast index control
| 43 | type | marsType |
40 | Stream: 1035 = ensemble forecast | 44-45 | stream | marsStream |
41 |
    Version number or experiment identifier.
    (4 ASCII characters, right justified)
| 46-49 | expver | experimentVersionNumber |
42 |
    Zero, for compatibility with Mars labelling
| 50 |  |  |
43 | Ensemble size. | 51 | ensembleSize | ensembleSize |
44 | Version number of the latest experimental Suite(1-255) | 52 |  |  |
45 | Implementation date of the latest model cycle (YYYYMMDDHH) | 53 - 56 |  |  |
46 | Number of re-forecast years in the model climate (Currently set to 18) | 57-59 |  |  |
47 | Length (in number of days) of the climate sampling window centred over the day of the climate run (Currently set to 31) | 60-62 |  |  |
48 | Sample size of the model climate (Currently set to 0 = No climate files prepared for days between two forecast runs) | 63-65 |  |  |
49 | Version of model climate (Currently set to 0 = No climate files prepared for days between two re-forecast runs) | 66-68 |  |  |
50 | Set to 0 for the EFI | 69 |  |  |
51 | Set to 1 for this version of EFI(prior to March 2008) | 70 |  |  |
- | Set to zero | 71-80 |  |  |