super computer

Quantitative Precipitation Forecasting

Quantitative precipitation forecasts (QPF) are needed to develop improved hydrological forecasts for flood warning and flood control. At present, QPF skill is often insufficient to provide high-quality hydrologic forecasts. Basic problems contributing to degraded QPF skill include (a) deficiencies in the physical parameterizations of the forecasting models, (b) insufficient model resolution and sub-optimal initial conditions from observations (c) insufficiently advanced data assimilation techniques, to optimally link observations with forecast models, (d) insufficient understanding of the dynamical and physical processes associated with heavy precipitation events for the purpose of model evaluation and improvement and (e) chaotic dynamics, which amplify even the smallest of initial errors.

Approaches to improving QPF have been the focus of NOAA researchers and forecasters for some time. QPF research needs identified several years ago were summarized (Junker et al. 2007) to include:

  • Develop new downscaling and postprocessing techniques
  • Establish new observation systems and techniques (a crosscutting theme discussed in section 3.3)
  • Improve physics parameterizations and initialization of numerical weather prediction models
  • Develop ensemble-based probabilistic quantitative precipitation forecasts (PQPF) techniques
  • Improve the understanding of dynamical and physical processes responsible for rare but heavy and frequent but moderate precipitation events
  • Develop new long-range forecasting techniques

Various activities have been undertaken through the HMT to address these research needs and to provide research results into operations support. These activities include:

  • Establishment of new observational systems and techniques (a crosscutting theme discussed in section 3.3)
  • Numerical Weather Prediction
    • Especially mesoscale ensemble modeling
  • Other QPF Aids
    • Atmospheric River detection and forecasting
    • Reforecasting for statistical postprocessing
    • Subseasonal forecasting
  • QPF verification studies are underway as described in section 4.7, Verification
  • Deployment of workstation upgrades to provide operations support (an activity included under Decision Support Tools in section 4.8)

Major sub-themes in this activity presently include:

  • Numerical Weather Prediction for QPF/PQPF
  • Other QPF Aids
  • COSMIC

NCEP-HPC's HMT efforts are targeted to enhance and extend forecast skill for high-impact weather, especially precipitation. They also play a key role in transition to operations for QPF. For more information, visit the HPC-HMT web site.