Recent development of the 2013 RAP and HRRR forecast systems has focused on (1) efforts to improve the depiction of the mesoscale environment through refinements to the RAP data assimilation and introduction of 3-km HRRR data assimilation for analysis of storm-scale information and (2) enhancements to RAP and HRRR model physics for improved surface and boundary layer prediction.
In this presentation we will focus on changes to the real-time HRRR configuration for 2013 including the establishment of 3-km data assimilation to incorporate storm-scale information using Gridpoint Statistical Interpolation (GSI) that includes sub-hourly 3-km radar data assimilation during a pre-forecast hour, 3-D variational assimilation of conventional observations and a 3-km non-variational cloud and precipitating hydrometeor analysis using radar reflectivity observations to retrieve rain and snow mixing ratios.
Observed radar reflectivities are used as a proxy for HRRR model latent heating specification that replaces the model microphysics latent heating during four fifteen minute periods of a cycled pre-forecast hour with an emphasis on forcing observed convective structures from higher reflectivity regions. Special attention is given to continuity of convective-scale structures, originating from an accurate storm-scale analysis (initial condition), during much of the free forecast period (several hours).
We will discuss and compare several experiments with and without the use of sub-hourly radar reflectivity observations at the 3-km scale including variations in the retrieval of latent heating rates from the radar reflectivity observations. We will also quantify the impact of the cloud and precipitating hydrometeor analysis. HRRR analysis and forecast improvements, particularly in the first few forecast hours, will be documented with retrospective and real-time verification statistics and case studies from 2012 and 2013.
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