9:39 PM Fri 19 Aug 2011 GMT
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'Forecast for 4pm today Audi Hamilton Island Race Week 2011 day 1'
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Audi Hamilton Island Race Week forecast for day one - Warnings: Nil Warnings current at time of issue. Synoptic Discussion: A large high pressure system with a central pressure of 1034 hPa situated east of Tasmania, is moving eastward into the southern Tasman Sea and is expected to strengthen during the next few days.
A complex low [1014 hPa central pressure] situated off the northern NSW coast is expected to move northwards during the weekend.
Observations: At 0600hr the surface wind at Hamilton Island was 160 deg at 06kn, gusting 07kn (temp 17C, pressure 1019hPa) indicative of the synoptic wind. At Hardy Reef (further offshore at 19.7S 149.2E) the wind was SSE at 7kn.
Forecast Winds for Surprise Rock (Read Discussion below):
1000:MeanDir:150d DirRange:170-130d MeanSp:10kn Gust:13kn
1300:MeanDir:140d DirRange:160-120d MeanSp:11kn Gust:14kn
1600:MeanDir:130d DirRange:150-110d MeanSp:12kn Gust:15kn
1900:MeanDir:120d DirRange:140-100d MeanSp:12kn Gust:15kn
Note: Winds could be light and variable for a time this morning before a weak sea breeze develops?
Key: MeanDir: Mean wind direction Degrees True, DirRange: Wind direction range Deg T , MeanSp: mean wind speed in Knots, Gust: Maximum wind speed possible in the 10secs leading up to the hour in Knots.
Discussion: Some model disagreement today.
Most models are happy with SE'ly winds trending left over the area as the gradient wind is expected to increase to around 15kn (as I'm forecasting above).
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Forecast Audi Hamilton Island Race Week day 1 -
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One model however (see Forecast chart for 4pm above) would like to see a weak bubble high develop over the area during the afternoon.
If this occurs then you should see some weak sea breeze activity via a glass-out or a light and variable situation later this morning or afternoon?
Wind may be a little stronger at times than above in Dent Passage/Fitzallen Passage due to funnelling?
Wind may also be channeled/funnelled and hence stronger between islands and out of some bays. Wind may be lighter and more variable in the lee of any land mass.
Natural oscillations: around 15 to 20 deg away from the effects of the land.
Weather: Dry and sunny. Maximum land temperature at Hamilton Island: 23 degrees.
Wind Waves: 0.5 to 1.4metres, less in lee of land, more in open water and when wind wave opposes tidal current.
(Wave heights quoted are Significant wave heights).
Current: A moderate flood this morning and early afternoon followed by a moderate ebb later this afternoon/evening. 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 1.14m at 0822hr, High 2.44m at 1506hr and Low 1.62m at 2117hr
Sea Temperature: about 22 degrees.
Outlook Sunday: Dry and sunny. SE 14-18kn (ave)
Audi Hamilton Island Race Week
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by Kenn Batt
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Double Is Pt, QLD
