Audi Hamilton Island Race Week Day One Weather

by Kenn Batt on 22 Aug 2009 For Saturday 22nd August 2009

Nil Warnings current.

Synoptic Discussion

Today can be summed up as a yachtie’s nightmare - light and flicky winds coupled with strong tides. The only consolation will be the sunny and warm conditions and the wonderful scenery.

A weak ridge of high pressure lies over the race area.

Observations

At 0600hr the surface winds at Hamilton Island N’ly at 6kn gusting 7kn, (temp 20C, pressure 1017hPa) indicative of the weak synoptic flow. At Hardy Reef (further offshore) the wind was NNE at 10kn.

Forecast Winds for open water between Hamilton and Lindeman Islands
(Read Discussion below)

1000:MD360 DR(340-030) MS06 SR03-11kn

1200:MD050 DR(010-080) MS07 SR04-12kn

1400:MD040 DR(010-070) MS08 SR05-13kn

1600:MD040 DR(010-070) MS08 SR05-13kn

1800:MD030 DR(340-060) MS07 SR04-12kn

Note 1: First column is mean wind direction in deg Magnetic (MD). It is the
10min average (mean) value at a height of 10m above the water leading up to the hour quoted. The second column is the directional range (DR) of the wind direction in deg Mag. This takes into account the natural oscillation of the wind and is a function of the atmospheric stability, etc. The third column is the mean speed (MS) in knots (kn) and is the average 10min value leading up to the hour quoted at a height of 10m above the water. The last column is the wind speed range (SR) in knots and is the lowest wind speed to highest wind speed in the 10min leading up to forecast hour.

Discussion

Not a good day from a wind versus tide perspective. With the very loose ridge over us, the winds will be light and flicky today. There will be a tendency for the wind direction to draw more left than forecast (330-360deg) in the Whitsunday Passage area and also inside Dent Is. Direction will have a right tendency on the eastern side of the course.

Wind will be lighter in the lee of any landmass e.g. Lindeman Island.

Be extra, extra careful today with the light wind coupled with strong ebb and flood tides.

Natural oscillations today around 20 to 40 deg away from effects of topography, tending around 30 to 60 deg closer to the effects of any land mass.
Weather
Some early fog patches then dry and sunny. Take plenty of sunscreen and warm clothes in case?
Maximum land temperature at Hamilton Island: 25-26 degrees. Sea Temperature: about 23 degrees.

Wind Waves
:
0.2 to 0.5metres, less in lee of land, more when wind wave opposes tidal current.
(Wave heights quoted are Significant wave heights).

Current: A strong ebb this afternoon followed by a strong flood this afternoon. Be extremely careful in channels, etc.
Remember: Tide floods to the south and ebbs to the north in the Whitsundays.
Tide at Shute Harbour: Low of 0.30m at 0550hr and High of 3.10 at 1159hr and Low 0.37m at 1748hr.

Outlook

Sunday: Similar (unfortunately)