P72 High resolution WRF-ARW ensemble experiment for a challenging winter precipitation forecast event over the Delmarva

Dumais Jr, Robert, Huaqing Cai, John Raby, Jeff Passner and Brian Reen, U.S. Army Research Laboratory

This study uses the WRF-ARW, centered near the DC metro, to produce a 28 member ensemble of 6-h forecasts for a challenging 2016 winter precipitation forecast across the Delmarva. Although observed accumulated precipitation amounts were not significant, forecasts leading up to the event were highly varied in terms of forecasts for localized precipitation amounts, precipitation type, low level thermodynamic fields, and evolution of the developing offshore low pressure. The model applies three nests (9, 3, and 1 km) and 57 vertical levels. The main forecast period of interest is 09 Feb 12-18 UTC. Leading up to this day, several successive forecast cycles of global models (in addition to mesoscale and ensemble modeling systems) produced by the various operational centers offered an inconsistent and wide array of near-surface temperature and precipitation solutions for the forecast region. This research employs the use of an ensemble composed of members using different physics, diffusion, and lateral boundary condition/external forcing options (and with multiple nests) in order to examine forecast variability across a short nowcast (0-6 h) window.