Assessing the Skill of Next Day Convection-Allowing WRF Forecasts of Convection Initiating on Outflow Boundaries

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Sunday, 4 January 2015
Robert M. Hepper, Creighton University, Omaha, NE; and T. J. Wagner

Residual outflow boundaries from previous convection often serve as a forcing mechanism for new convective development and can serve to locally enhance severe weather potential. Accurate representation of the location of these boundaries in high-resolution numerical weather prediction guidance is crucial for operational forecasters tasked with making convective forecasts.

This study evaluates next day forecasts from 4 different convection-allowing configurations of the Weather Research and Forecast Model (WRF) in cases in which convection initiated on a residual outflow boundary. Forecasts from the National Severe Storms Laboratory (NSSL) 4 km WRF, the National Center for Environmental Prediction (NCEP) Hires Window 4 km WRF-Advanced Research WRF (ARW) and 4 km WRF-Nonhydrostatic Mesoscale Model (NMM) and the NCEP Experimental 4 km WRF-NMM for SPC are evaluated over 60 such cases from the convective seasons of 2011-2013. Objective verification techniques are employed comparing model 1 hour precipitation forecasts to NCEP Stage IV hourly precipitation analyses. It is expected that results will show that model convective forecasts in these cases are less skillful than cases which do not contain outflow boundaries. Reasons for these deficiencies, including the effects of physics parameterization schemes, will be investigated.