Forecast Waves in Pegasus Bay 

The plot below shows the forecast wave heights and directions for the next week.
The forecasts come from the NOAA global wave forecasting model Multi WaveWatch3 (MWW3) for a node at 173° E 43.5° S which is in Pegasus Bay,
21 km E of Waimairi Beach and 17.5 kn NE off the entrance to Lyttelton Harbour, as shown here.

Of particular interest are waves from the directions
between ENE and ESE (67.5 and 112.5°N)
because these waves generate IG waves at Sumner Head,
as presented here.