Notes on Ellesmere Wave Forecasts 

The time series of wave height, period and direction come from the NOAA WaveWatch 3 multigrid (NWW3) model. There is information about the model here. The data were extracted for the node off Lake Ellesmere at 172.5 E 44 S.

The table below shows the statistics of the waves that occurred from 1-Feb-2005 to 31-Jul-2011.

At the top is a row of percentages with corresponding heights. These are the green dashed lines on the forecast. They are called percentage exceedance values. For 1% of the time, waves exceed 3.38 m in height. Conversely, for 99% of the time, waves are less than 3.38 m in height.

For 50% of the time, the waves are under 1.13 m in height. This means that if the forecast wave height is at or below the lowest green dashed line, the sea will be slight relative to the conditions that normally occur at this site. But if the forecast wave height is above this line, the sea will be rough, and if it is above the top dashed line, it will be extremely rough.

The body of the table shows the statistics of the direction of the waves. For 50% of the time (first column), the predominant wave direction is S to SSW, with more than 60% of waves coming from this half quadrant. These waves have come from storms in the Southern Ocean. The remaining waves come mainly from the ESE. These waves have propagated around Banks Peninsula from northeasterly storms. As the wave heights increase, the S to SSW sector becomes more dominant, and the largest waves are predominantly from this sector (96%).

Distribution (%) of the direction of waves over various heights.
Direction Top 50%
Hs > 1.13 m
Top 10%
Hs > 2.06 m
Top 5%
Hs > 2.50 m
Top 1%
Hs > 3.38 m
N 0.0% 0.0% 0.0% 0.0%
NNE 0.0% 0.0% 0.0% 0.0%
NE 0.1% 0.0% 0.0% 0.0%
ENE 4.5% 1.3% 0.0% 0.0%
E 6.4% 1.7% 1.7% 0.0%
ESE 10.7% 5.5% 2.5% 4.2%
SE 7.3% 5.5% 4.2% 0.0%
SSE 8.7% 6.3% 8.4% 20.8%
S 37.2% 47.3% 48.7% 58.3%
SSW 24.9% 32.5% 34.5% 16.7%
SW 0.2% 0.0% 0.0% 0.0%
WSW 0.0% 0.0% 0.0% 0.0%
W 0.0% 0.0% 0.0% 0.0%
WNW 0.0% 0.0% 0.0% 0.0%
NW 0.0% 0.0% 0.0% 0.0%
NNW 0.0% 0.0% 0.0% 0.0%