North Sails Weather forecast - Audi Hamilton Is RW

'Day 6 - Audi Hamilton Island Race Week 2008' Bureau of Meteorology

Courtesy of North Sails Australia, this Weather Forecast was issued by Kenn Batt at 0630hr for Friday 29th August 2008, for 2008 Audi Hamilton Island Race Week.

Yesterday:

So much for the mostly sunny bit, low cloud hung around pretty much for the whole day. With a maximum temperature of 22deg it would still have been nice at Whitehaven? For the IRC guys who raced yesterday, the wind between 1000 to 1300hr was 160-140deg at 10-12knots. The weather station at the Airport reported the wind going to max left of 110-120deg after 1500hr at a speed of 14-16kn.

Synoptic Discussion:

The high over south-east Australia will move southeast and reach the New Zealand area by the weekend. A ridge will persist along the tropical east coast during this period with moderate to fresh SE winds. The inland trough will continue to move slowly westwards and break off from the coastal section which should drift eastward as it weakens further. This coastal trough and associated weak low is currently preventing the ridge from really strengthening along the Qld coast.

Day 6 - Audi Hamilton Island Race Week 2008 - Bureau of Meteorology

Observations:

At 0600hr, the surface wind at Hamilton Island Airport was from SSE (160degT) at 12kt, gusting 16kt (temp 18C pressure 1019hPa) indicative of the general synoptic flow, although it does suffer from the effects of topographic forcing at times. At Creal Reef, further off the coast and to SE of Hamilton Island, the wind was a E'ly at 16kn (indicative of true surface wind). Hardy Reef (offshore to NE) was reporting a wind from 131deg at 16-17kn.

Forecast Discussion:

Forecast confidence level: Above average.
A ridge of high pressure will hang in over the race area, but has been prevented from building so far because of the trough and low further south near Brisbane. As such the surface winds for racing today will be pretty much like yesterday. There is chance however, that as the trough drifts eastwards, the ridge could push up and allow the winds to freshen more than forecast? A moderate sea breeze component will be evident and this will see the wind direction close to the mainland pulling about 20-30deg more left than forecast for further offshore.

Natural wind oscillations today around 15 to 25 deg away from effects of topography, tending 25 to 60 deg closer to the effects of any land mass.
Expect wind speed to be 3-5kn stronger in channels/passages due to localized funneling and direction quite flicky.

Forecast Winds for Hamilton Island Area in open water

1000:MD150 DR(170-130) MS13 SR08-17kn
1200:MD140 DR(160-120) MS14 SR09-19kn
1400:MD130 DR(150-110) MS13 SR08-18kn
1600:MD120 DR(140-100) MS15 SR11-20kn
1800:MD120 DR(140-100) MS16 SR12-21kn

Key: First column is mean wind direction in deg Mag (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.

Other Possibilities:

50% chance that direction trends 10-20deg further left than forecast above?
40% chance that wind speed will be 2-5 knots stronger than forecast above later this afternoon?
20% chance that direction flicks right by 20-30deg later this afternoon?

Weather

Cloudy at times with chance of a shower. Take plenty of sunscreen and warm clothing.

Maximum land temperature at Hamilton Island: 22 degrees
Sea Temperature: 19-20 degrees

Wind Waves:0.5 to 1.2 metre. Less near land, more when wind wave opposes tidal stream. (Wave heights quoted are Significant wave heights).

Current:A good ebb tide this afternoon. Care in the channels particularly.

Tidefloods to the south and ebbs to the north in the Whitsundays.

Tide (Shute Harbour): High of 2.85m at 0939hr Low of 0.18m at 1525hr and High of 3.93m at 2200hr

Outlook

Saturday: Chance of showers. SE/E winds 14-19 knots (ave)

by Kenn Batt

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