The NextGen 4-D Data Cube for aviation guidance will require a continuous stream of fresh observations, and even more importantly, procedures for merging these observations into a best estimate of the state of the atmosphere. Assimilation of an increasing number of observations at a high frequency (at least hourly) is essential for nowcasting and for high-frequency refreshing of numerical weather prediction (NWP) models. Perhaps the most important component of the current weather guidance gridded data for 2-12h over the United States is provided by the hourly updated Rapid Update Cycle (RUC) from NOAA. High-frequency NWP updating will become much more critical in the NextGen era than currently.

In this presentation, we describe the following changes we foresee for high-frequency NWP guidance within the NextGen era.

Hourly updated NWP is headed toward larger domains and higher-resolution, especially over critical areas for aviation activities:

·Rapid Refresh – 2009 – Larger domain, over North America with hourly updating, 2.6x larger than current RUC domain. Will use WRF model and NOAA GSI data assimilation but with RUC-specific enhancements (e.g., ceiling/visibility assimilation, radar assimilation, cloud microphysics)

Further proposed plans beyond Rapid Refresh

·Enhanced Rapid Refresh – 2012 – cover North Pacific and North Atlantic with hourly updating using latest aircraft and satellite observations.

·Global Rapid Refresh (GRR) – 2016 – cover full globe with hourly update cycle

·High-Resolution Rapid Refresh (HRRR) – 2012 – hourly updated, radar-assimilating, convection-resolving (2-3km)

Use of hourly-updated probabilistic forecasts using ensembles including deterministic members.

·Very Short-Range Ensemble Forecasts (VSREF)

·Requirement for hourly updating will continue into probabilistic forecasts.