Oceanum New Zealand GFS Wave Forecast

February 2025

Dataset description

The New Zealand wave forecast dataset provides operational wave predictions across New Zealand’s coastal waters and the surrounding Southwest Pacific Ocean (Figure 1). The forecast system comprises a hierarchy of nested domains: a regional 5 km parent grid covering all of New Zealand, with higher-resolution child grids for Auckland (1 km), Eastern Auckland (200 m), Taranaki (1 km), and Port Taranaki (25 m). Wave forecasts are produced using the SWAN (Simulating WAves Nearshore) third-generation spectral wave model, with a 7-day forecast horizon updated every 6 hours (00, 06, 12, 18 UTC).

Wind forcing is provided by NOAA GFS global atmospheric model. Spectral boundary conditions are supplied by the Oceanum Global WW3 wave model forced with GFS winds. Bathymetry is derived from the GEBCO 2021 global bathymetric grid.

The modelling setup employs the ST6 source term parameterisations. Spectra are discretised into 36 directional bins and 32 frequency bins, covering a frequency range from 0.037 to 0.71 Hz with 10% logarithmic increments. The parent grid features a 5 km (0.05 degree) resolution spanning New Zealand’s Exclusive Economic Zone, with progressively finer nested grids for coastal applications.

The dataset provides hourly forecast estimates for key ocean wave parameters (Table 2) including spectral quantities integrated over the full spectrum and for spectral partitions. Partitions are defined from an 8-second split (sea/swell) and from the Watershed method, which identifies one wind-forced partition and up to three swell partitions. Forecasts are archived for 30 days, and frequency-direction wave spectra are available at selected sites across all domains. Nowcast datasets are also available, constructed by retaining the most recent data from each forecast cycle to provide a continuous near-real-time historical record.

Figure 1. Mean significant wave height from the New Zealand hindcast domain (used for forecast validation). The locations of 2D spectra hourly output are shown by the black dots.

Validation

The wave model physics and calibration have been validated against satellite altimeter observations for the corresponding hindcast domain. Validation results are available through the Oceanum Hindcast Satellite Validation App, which provides density scatter plots, quantile comparisons, and statistical metrics for the New Zealand region.

Data description

Table 1. Data description.

Nested domains

Linked Datamesh datasources

New Zealand 5km:

• Oceanum New Zealand GFS wave forecast parameters
• Oceanum New Zealand GFS wave forecast spectra

Auckland 1km:

• Oceanum Auckland 1km GFS wave forecast parameters
• Oceanum Auckland 1km GFS wave forecast spectra

Eastern Auckland 200m:

• Oceanum Eastern Auckland 200m GFS wave forecast parameters
• Oceanum Eastern Auckland 200m GFS wave forecast spectra

Taranaki 1km:

• Oceanum Taranaki GFS wave forecast parameters
• Oceanum Taranaki GFS wave forecast spectra

Port Taranaki 25m:

• Oceanum Port Taranaki GFS wave forecast parameters
• Oceanum Port Taranaki GFS wave forecast spectra

Nowcasts (continuous near-real-time archive):

• Oceanum New Zealand GFS wave nowcast parameters
• Oceanum New Zealand GFS wave nowcast spectra

Gridded output parameters

Integrated wave parameters are stored hourly over the domain at the native model resolution. Table 2 describes the gridded output parameters.

Table 2. Gridded output parameters.

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