1447 Ensemble Generation Approaches in the NCEP CFSv2

Wednesday, 25 January 2017
Malaquias Peña, NOAA/NWS/NCEP/EMC, College Park, MD; and S. Saha, X. Wu, J. Woolen, and D. T. Kleist

This study presents ongoing research on strategies to improve the probabilistic forecast of the CFSv2 in the subseasonal time range. The CFSv2 is a low-resolution (T126L64) coupled model in operations since 2011 with an extensive hindcast dataset, which allows a comprehensive forecast bias correction and an assessment of its a priori skill performance. The CFS operational design generates a 16-member ensemble forecast per day out to 45 days – four of those members are integrated further out to 9 months.  While the long term development of the CFSv3 carries on from a multi-component Unified Global Coupled System (UGCS), we are exploring ways to revamp the coupled CFSv2 in the short term to enhance its forecast skill particularly in the weeks 3 and 4.

Forecast evaluations of the operational CFSv2 show considerable skill to predict the MJO signal beyond 2 weeks. The skill is higher than the uncoupled higher-resolution global ensemble prediction system suggesting that a source of atmospheric predictability may exist in the coupling with the ocean. A study is being started to increase the ensemble size and diversity of the coupled model prediction system to improve its forecast reliability. A first design makes its ensemble initial perturbations consistent with the perturbations in the GSI’s hybrid 4DEnVar; other ensemble generation approaches are being assessed.

- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner