An Update on NOAA’s National Water Model and Related Initiatives

Implemented into National Weather Service (NWS) operations just over two years ago, the National Water Model (NWM) provides seamless 24x7 guidance on streamflow conditions and other water budget fields such as soil moisture, snowpack, runoff and evaporation. The system, based on the community Weather Research and Forecasting (WRF)-Hydro software architecture, has been rapidly upgraded via a partnership between the Office of Water Prediction (OWP), the National Center for Atmospheric Research (NCAR) and the National Centers for Environmental Prediction (NCEP). Version 2.0, scheduled for implementation in early 2019, will build on prior capabilities to provide vital hydrologic guidance to NWS River Forecast Centers (RFCs), Weather Forecast Offices (WFOs), NCEP Centers, the Federal Emergency Management Agency (FEMA) and other Federal, private and academic end users. As with prior versions V2.0 is underpinned by a network of 2.7 million vector-type river reaches for river routing, a 1km land surface grid for land surface modeling, and a 250m grid for surface and subsurface routing of runoff. However, departing from previous versions, the new model will feature notable upgrades including use of NWS RFC-based precipitation in a new extended analysis cycle, the addition of Hawaii to the modeling domain, a new medium range ensemble configuration, and improved forcing downscaling and parameter calibration.

One of the other major upgrades initiated in V2.0 centers on improved code modularity. This advance is significant in that it underlies an intensive strategy to establish a broad NWM development community. It is envisioned that the NWM will serve as a common platform for water research and operations. By drawing innovation from across a broad spectrum of interests, the system will support a variety of research and applications beyond its core NWS operational forecasting mission. This community development effort requires both tools to enable collaboration (i.e., code modularity and code management to ensure code accessibility) as well as governance and mechanisms for partnerships (inter-governmental consortiums, partnerships with the private sector and academia, funding calls to enable collaborative work). While it will take time to establish this community, the initial building blocks--such as the IWRSS interagency group and increased code modularity and version control--have already been established.

Beyond community development, NWM V2.0 and subsequent versions will provide the foundation needed to support a variety of additional activities within the NWS and broader hydrologic community. These include a machine learning-based enhancement to better capture the impact of stream regulation, a model extension to simulate combined impact of freshwater and coastal flooding, and an improved shallow groundwater model. Hyper-resolution modeling will support the ability to model flooding in areas of urban coverage or high terrain and NWM-based regional flood inundation mapping efforts will expand to the continental scale to support emergency responders across the Nation.

This presentation will provide an overview of recent and planned NWM upgrades, along with updates on community development and the other hydrologic activity areas discussed above.