Exploring the use of stability fields from a three dimensional objective analysis scheme in the NCAR AutoNowcaster

The National Center for Atmospheric Research (NCAR) AutoNowcaster (ANC) is a short-term convection prediction system that has been running over Texas for the last five years as part of the Forecaster Over The Loop (FOTL) demonstration. The goal of the demonstration is to transfer the ANC system to the National Weather Service (NWS) and integrate the nowcast tools into AWIPS, while showing the benefit of the human interaction with an automated nowcast system. A variety of datasets are incorporated in the forecast logic of the ANC system. and the human interaction with the system is particularly important for identifying mesoscale convergence boundaries. . The meteorologists at the National Weather Service forecast office in Fort Worth, Texas enter in convergence boundaries and provide feedback on the quality of the nowcast products. They also provide valuable insights into the challenges of forecasting convection initiation in their county warning area and have been valuable collaborators as NCAR scientists modify the ANC to improve nowcast performance.

One of the recommendations made by the NWS meteorologists is to substitute the Storm Prediction Center's meso-analysis stability parameters for the RUC stability fields currently used by the ANC. The NWS meteorologist have high praise for the performance of SPC meso-analysis fields and use them very frequently when examining potential for convection initiation. The SPC meso-analysis grids are objective analyses calculated from observations using a short term forecast from the RUC as a first guess. Stability fields are calculated using the objective analysis and virtual soundings extracted from the RUC at model grid points.

This paper will present results from re-running the AutoNowcaster with SPC meso-analysis fields for selected of cases from spring and summer 2010. Qualitative and quantitative comparison of nowcast performance using RUC and SPC meso-analysis stability fields will be presented and discussed.