Observation-based 0-6 hr Probabilistic Forecasts

This paper describes an observation-based system to produce 0-6hr nowcasts of convection on the synoptic scale. The NCWF forecasts combine traditional radar extrapolation techniques with the use of RUC data to capture storm growth and large-scale storm trends. The use of the RUC environmental data and its effects on the NCWF probabilities are examined. The radar data are used to identify a set of cases based on the organization of the convection and its stage of evolution. For each case, synoptic pattern characteristics, proximity soundings, dominant forcing mechanisms, and thermodynamic properties are evaluated. The current NCWF forecasts are evaluated to find systematic strengths and weaknesses. The utility of each RUC predictor field used for determining the NCWF convection likelihood is assessed. These results lend insight into characteristics of convection not well resolved by the NCWF algorithm and indicate model parameter thresholds that may need modified. One of the goals of this work is to combine observation based nowcasts with NWP-based probabilities to create a 0-6 hr forecast.