EFP: 2003 Spring Experiment Summary

Working Hypotheses

  1. Numerical modelers can learn to incorporate more operational relevance in their research efforts if they work closely with forecasters in an experimental forecasting exercise.
  2. Operational forecasters can make more skillful interpretations of numerical model output if they work with numerical modelers in an experimental forecasting exercise.

Specific Objectives

  1. Overarching objective: To investigate emerging applications for short-range ensemble forecasts (SREFs) and deterministic high resolution predictions in the context of severe convection forecasting.
  2. Specific research interests: (a) to compare the utility of experimental high-resolution (convection-allowing) WRF-model forecasts with that of operational mesoscale models in forecasts of convective initiation and evolution, and (b) to explore the implementation and use of human-generated perturbations in formulating a spectrum of initial conditions for mesoscale ensemble forecasts.
  3. Specific operational interests: (a) to explore the ability of SREF systems to provide unique and meaningful guidance in operational severe weather forecasting, and (b) to examine the utility of new high resolution models to predict convective initiation and evolution, as it relates to improving lead-time for convective watches.

Preliminary Results

  1. Numerous diagnostic algorithms were developed to provide a wide variety of potentially useful analysis fields from SREF output.
  2. Experimental forecasting exercises revealed that SREF guidance had a measurable positive impact on predictive skill in experimental Day 2 convective outlook products.
  3. The use of human-generated perturbations showed promise in ensemble forecasting; forecasts associated with this method of ensemble generation outperformed the operational SREF in episodes with moderate-to-high probability of severe weather occurrence, but not in cases of low probability.
  4. Convection-allowing numerical forecasts for the 0–12 h time frame were found to be inferior to coarser-resolution operational forecasts, but they were judged to be severely handicapped by a small integration domain and very coarse initial conditions.


  1. Many SREF diagnostic algorithms were tested, refined, and implemented in SPC operations; they now play a major role in the preparation of convective outlooks for the 1-3 day time frame.

Related Publications

  • Bright, D. R., S. J. Weiss, J. J. Levit, and D. J. Stensrud, 2003: The utility of short-range ensemble forecasts in real-time prediction of severe convective weather at the Storm Prediction Center. Preprints, 10th Conference on Mesoscale Processes, Portland, OR, Amer. Meteor. Soc., CD-ROM, 2.8.
  • Bright, D. R. and P. Nutter, 2004: On the challenges of identifying the “best” ensemble member in operational forecasting. Preprints, 16th Conference on Numerical Weather Prediction, Seattle, WA, Amer. Meteor. Soc., CD-ROM, J11.3.
  • Bright, D. R., M. S. Wandishin, S. J. Weiss, J. J. Levit, J. S. Kain, and D. J. Stensrud, 2004: Evaluation of short-range ensemble forecasts during the 2003 SPC/NSSL Spring Program. Preprints, 22nd Conf. on Severe Local Storms, Hyannis, MA, Amer. Meteor. Soc., CD-ROM, P15.5.
  • Homar, V., D. J. Stensrud, J. J. Levit, and D. R. Bright, 2006: Value of human-generated perturbations in short-range ensemble forecasts of severe weather. Wea. Forecasting, 21, 347–363.
  • Kain, J. S., S. J. Weiss, D. R. Bright, M. E. Baldwin, M. Dahmer, and J. J. Levit, 2004: Subjective verification of deterministic models during the 2003 SPC/NSSL Spring Program. Preprints, 20th Conference on Weather Analysis and Forecasting/16th Conference on Numerical Weather Prediction, Seattle, WA, Amer. Meteor. Soc., CD-ROM, 9.3.