Code table 1.4, 4.3 and 4.6: Adding new entries to better describe type of forecasting

[sebvi]

Initial request

In the context of several, related developments, ECMWF is requesting new entries in several code table to support the new products.

For data which have the only purpose to demonstrate the data layout, for example as demo data for new templates proposed in a WMO Fast-track, we request a new entry for identifying sample data in code table 1.4. In the same table, EWCMWF is also requesting a specific entry to clearly label Machine learning based products.

Different forecast products with forecast skills on different forecast horizons are combined and weighted to produce a seamless composite forecast product. In this context, ECMWF is requesting a new entry "blended forecasts" in code table 4.3.

Finally, ECMWF is proposing to extend code table 4.6 with new entries to facilitate the identification of the different type of peturbations to produce perturbed forecasts.

Amendment details

ADD to code table 1.4 Type of data Code	Description
9	Experimental data (see Note)
10	ML based forecast (see Note)

Note: 9 – Data for demonstrational purposes only; 10 – forecast from Machine Learning (ML) model.

ADD to code table 4.3 Type of generating process Code	Description
22	Blended forecast (see note)

Note: Combination of different forecast products to produce a smooth, continuous forecast by applying weights to each individual prediction system which depend on the lead time and forecast skill (e.g. seamless prediction using nowcasting to short-range to medium-range).

ADD to code table 4.6 Type of ensemble forecast Code	Description
5	Unperturbed forecast
6	Perturbed forecast
7	Initial conditions perturbations (see Note)
8	Model physics perturbations (see Note)
9	Initial conditions + model physics perturbations (see Note)

Note: 7 – Ensemble members are initialised from different initial conditions; 8 – model physics are perturbed e.g., with methods like SPPT, SPP, SKEB, etc.; 9 – combination of 7and 8.

Comments

No response

Requestor(s)

Sebastien Villaume (ECMWF) Robert Osinski (ECMWF)

Stakeholder(s)

ECMWF

Publication(s)

Manual on Codes (WMO-No. 306), Volume I.2, GRIB code table 1.4 (update) Manual on Codes (WMO-No. 306), Volume I.2, GRIB code table 4.3 (update) Manual on Codes (WMO-No. 306), Volume I.2, GRIB code table 4.6 (update)

Expected impact of change

LOW

Collaborators

No response

References

No response

Validation

No response

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference.14.May.2024 notes: Sebastien introduced the proposal; @sebvi change sample data to experimental data;

[sebvi]

proposal updated to use "experimental data". Branch created and updated

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference.24and26.June.2024 notes: branch is ready for validation;