CAPS Storm-Scale Ensemble Forecasting System for the NOAA HWT 2012 Spring Experiment: Impact of IC/LBC Perturbations

Since 2007, CAPS provides storm-scale ensemble forecasting (SSEF) products to the annual HWT Spring Experiment. The 2012 NOAA HWT Spring Experiment runs from May 07 to June 08, 2012. The 2012 CAPS SSEF consists of 28 multi-model multi-physics ensemble members using four NWP modeling systems (23 WRF-ARW, 1 WRF-NMM, 1 ARPS, and 3 COAMPS members). New in 2012 is the simulated GOES satellite IR channel brightness temperatures computed using CRTM and other two RTMs, with probabilities and ensemble means of these simulated synthetic GOES-R infrared imagery generated in realtime as part of upgraded real-time post-processing package in supporting the GOES-R Proving Ground Project. The WRF newly added stochastic kinetic-energy backscatter (SKEB) perturbation option is also applied to a small group of members to allow evaluation of its impact to the SSEF performance at convection-permitting grid resolution. Post-season evaluation of the SSEF QPF data reveals the ARW control member has widely outperformed all perturbed members in QPF skill scores, a surprise departure from previous years. It is attributed to the NAM upgrade in late 2011 from WRF-NMM to NMMB, which served as background and LBCs for the ARW control member, and the unchanged SREF system, which were used to drive all perturbed SSEF members. Case reruns were performed using different IC/LBC perturbation extraction methods to examine their impact to the SSEF QPF skill, and will be presented at the Conference.