KS3.1 Development of a New Seamless Prediction System for Very Short Range Storm-Scale Forecasting at DWD

Monday, 28 August 2017: 9:00 AM
Vevey (Swissotel Chicago)
Ulrich Blahak, DWD, Offenbach, Germany; and R. Potthast, K. Wapler, A. Seifert, A. de Lozar, E. Bauernschuberth, C. Welzbacher, R. Osinski, L. Bach, M. Rempel, M. Hoff, and M. Junk

At DWD a new internal project has been set up to develop its future seamless ensemble prediction system for storm-scale forecasting from observation time up to +6 h / +12 h forecasts. The focus is on severe summertime convective events with their associated hazards (heavy precipitation, hail, wind gusts, etc.).

Up to now, for the first 1-2 h this relies mostly on observation-bsaed nowcasting products, whereas convection-allowing ensemble NWP (COSMO-DE-EPS) is only able to reach/outperform the quality of nowcasting at later times. New NWP forecasts are started only every 3 h and after a rather long cut-off time to wait for incoming observational data. 
Moreover, nowcasting and ensemble NWP are treated as two separate and independent methods, and there are few common products available for the forecasters.

The goal of the new project is to narrow down these gaps, on the one hand by enhancements to both nowcasting and NWP separately and on the other hand by mutual information exchange and combination, to further enhance the quality of both. High-resolution observational data (radar, satellite, lightning, GPS-derived moisture, etc.) will be exploited. We consider in particular:

  • Nowcasting ensembles, ensembles of "objects", also informed by uncertainties from NWP
  • Life cycle in nowcasting, informed by radar, lightning and satellite data and by informations from ensemble-NWP
  • Rapid Update Cycle (RUC) ensemble NWP: 1-km-scale, LETKF, hourly update, ~40 members, advanced model physics (2-moment microphysics including hail, 3D-turbulence)
  • LETKF assimilation in ensemble NWP in observation space of:
    • 3D-radar-data (native observations as well as nowcast "objects")
    • Meteosat SEVIRI IR and VIS satellite data
    • Lightning flash densities using the Lightning Potential Index as a forward operator
  • New products combining nowcasting and NWP ensemble information in a probabilistic way for our forecasters

This project has been started in early 2017 and the presentation will give an overview on the plans 
and present results of first case studies.

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