21st Conf. on Severe Local Storms and 19th Conf. on Weather Analysis and Forecasting/15th Conf. on Numerical Weather Prediction

Tuesday, 13 August 2002
An Assessment of 3-and 6-h RUC CAPE forecasts
Barry Schwartz, NOAA/ERL/FSL, Boulder, CO; and S. Benjamin
Forecasted soundings produced by Numerical Weather Prediction (NWP) models are commonly used by forecasters to assess the potential for convection. Diagnostic quantities such as Convective Available Potential Energy (CAPE) and Convective Inhibition (CIN) are the most commonly derived quantities that are routinely examined by sever weather forecasters. The Rapid Update Cycle (RUC) running operationally at the National Centers for Environmental Prediction (NCEP) is unique among the suite of NWP models available to forecasters in that it provides short term forecasts (1-12 h) updated every hour. In spring of 2002, a new 20-km version of the RUC will replace the operational 40-km version running at NCEP. In addition to higher horiozontal resolution, the 20-km RUC features improvements to land-surface, convective parameterizations, and soil type fields that should result in improved surface temperature and humidity forecasts that are critical to accurately depicting CAPE and CIN. In this paper, we present a verification of 3-h (6-h) CAPE and CIN forecasts from 0900 (0600) and 2100 (1800) UTC against radiosonde observations for the spring and summer of 2002 from the new 20-km version of the RUC. CAPE and CIN forecasts are derived different ways to demonstrate the volatility of these quantities to the method used to derive them.

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