# Initial state perturbations for ensemble forecasting (OpenIFS-OpenEPS)

**URL:** <https://forum.ecmwf.int/t/initial-state-perturbations-for-ensemble-forecasting-openifs-openeps/14474>\
**Category:** OpenIFS Data Hub\
**Tags:** openifs-48r1\
**Created:** [4 December 2025 13:46 UTC](https://forum.ecmwf.int/t/initial-state-perturbations-for-ensemble-forecasting-openifs-openeps/14474 "2025-12-04T13:46:30Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Sandor\_Istvan\_Maho](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/s/7c8e57/32.png) [@Sandor\_Istvan\_Maho](https://forum.ecmwf.int/u/Sandor_Istvan_Maho)\
**Post date:** [4 December 2025 13:46 UTC](https://forum.ecmwf.int/t/initial-state-perturbations-for-ensemble-forecasting-openifs-openeps/14474/1 "2025-12-04T13:46:32Z")

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Hello,

Recently there have been discussion in the joint University of Helsinki - ECMWF meetings that I will investigate the effect of initial state uncertainty in our ensemble simulations.

I would like to ask if you could provide me perturbed initial data (based on ERA5) for 50 members at TL639 resolution for the date of 2001-10-28 18 UTC? I am planning to run a 10-day forecast with OpenEPS with SPPT&perturbed initial states, only perturbed initial states and only SPPT and draw important conclusions.

Best regards,

Sandor

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**Author:** ![Marcus\_Koehler](https://forum.ecmwf.int/user_avatar/forum.ecmwf.int/marcus_koehler/32/1000_2.png) [@Marcus\_Koehler](https://forum.ecmwf.int/u/Marcus_Koehler)\
**Post date:** [8 December 2025 11:12 UTC](https://forum.ecmwf.int/t/initial-state-perturbations-for-ensemble-forecasting-openifs-openeps/14474/2 "2025-12-08T11:12:28Z")

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Hello Sandor,

Thank you for your post. Indeed, the Data Hub does not support the creation of ensemble initial data, and we have no immediate plans to include this.  
On a case-by-case basis we can however consider this as a bespoke request. As we have already spoken about this earlier, I will open an [OpenIFS Support query](https://openifs.ecmwf.int/support) for you and we can then continue the discussion there.

Regards,

Marcus