The Nearshore Wave Prediction System (NWPS) is currently being developed at
NCEP's Environmental Modeling Center (EMC) and a number of participating
Weather Forecast Offices (WFOs), in particular WFO Miami, WFO Eureka and
Southern Region HQ. NWPS is designed to provide on-demand, high-resolution
nearshore wave model guidance to coastal NWS forecasters throughout the
United States. It is being tested to run centrally on NCEP's operational
supercomputer, triggered in real time by forecast wind grids prepared
and submitted by the individual WFOs.
Click to enlarge
NWPS is driven by forecaster-developed wind grids produced in AWIPS 2,
and offshore wave boundary conditions from the operational
WAVEWATCH III model. The nested nearshore wave model used is
Wave-current interaction is included using surface current fields from the
Real-Time Ocean Forecast System (RTOFS-Global).
The influence of tides and storm surge is accounted for by using output
from the Extratropical Surge and Tide Operational Forecast System
(ESTOFS, extratropical conditions),
or the probabilistic model P-SURGE
(tropical conditions). The computational grids have a nominal resolution of 1.8 km,
with further nesting down to 500 m or less in high-impact areas. NWPS produces
fields of integral wave parameters, wave spectra and individually tracked wave
systems (Gerling-Hanson plots). These, together with real-time and 30-day retrospective
validation graphics can be viewed in the model validation interface below.
Below are the combined monthly validation statistics at all coastal data buoys in
the NWS Southern and Eastern Regions respectively, computed as a 30-day, moving-window
retrospective. For real-time validation, as well as buoy-specific
validation statistics, please see the model validation viewer above.
Southern Region Validation Statistics Click to enlarge
Eastern Region Validation Statistics Click to enlarge
Southern Region Statistics History Click to enlarge
Eastern Region Statistics History Click to enlarge
Follow the system development on our Wiki Page
Van der Westhuysen, A. J., R. Padilla-Hernandez, P. Santos, A. Gibbs, D. Gaer,
T. Nicolini, S. Tjaden, E. M. Devaliere and H. L. Tolman. Development and validation
of the Nearshore Wave Prediction System. Proc. 93rd AMS Annual Meeting,
Am. Meteor. Soc., Austin, 2013. Available here
Gibbs, A., P. Santos, A. J. van der Westhuysen and R. Padilla-Hernandez.
NWS Southern Region Numerical Optimization and Sensitivity Evaluation in Non-Stationary
SWAN Simulations. Proc. 92nd AMS Annual Meeting, Am. Meteor. Soc.,
New Orleans, 2012. Available here
Settelmaier, J. B., A. Gibbs, P. Santos, T. Freeman, D. Gaer. Simulating
Waves Nearshore (SWAN) Modeling Efforts at the National Weather Service
(NWS) Southern Region (SR) Coastal Weather Forecast Offices (WFOs).
Proc. 91st AMS Annual Meeting, Am. Meteor. Soc., Seattle, 2011.
Unstructured mesh implementation
SWAN and WW3's unstructured grid functionality is currently being
incorporated into NWPS. With flexible unstructured grids, computational
time can be optimized by concentrating computational grid points only in
those nearshore regions where it is required to adequately resolve physical
processes at small spatial scales. This is demonstrated below for WFO Key
Unstructured mesh over WFO Key West domain. Click to enlarge
Forecast guidance produced using NWPS (with SWAN wave model). Click to animate
Zoom of unstructured mesh over Key West. Click to enlarge
Forecast guidance over zoomed-in domain. Click to animate.
Inclusion of time-dependent P-Surge water levels
during hurricane events
Tropical cyclone events are characterized by a high uncertainty in the
atmospheric forcing. As a result, a probabilistic approach is followed by
NWS's National Hurricane Center (NHC) to produce cyclone-related coastal
surge forecasts during tropical cyclone events using the P-Surge system,
based on the highly-efficient Sea, Lake, and Overland Surges from Hurricanes
(SLOSH) model. One type of output from P-Surge is the composite surge level
fields associated with a given exceedance level (e.g. 10-50%). Since these
exceedance fields represent a single water level surface, they can be
applied in a single deterministic NWPS run at a given exceedance level.
Since the P-Surge fields include inundation of overland regions, it enables
the computation of overland waves in flooded areas in NWPS, as shown below
for WFO New Orleans during Hurricane Isaac (2012).
Total water depth from P-Surge surge levels (20% exceeedance) and
ESTOFS tides. Click to animate
Forecast guidance produced using NWPS (SWAN). Click to animate