Audi Hamilton Island Race Week Day 4 Weather

9:29 PM Tue 25 Aug 2009 GMT

'10pm-Prognosis-Wednesday 26th August 2009 - Audi Hamilton Island Race Week' Bureau of Meteorology

Audi Hamilton Island Race Week Day 4 Weather Forecast

Issued by Kenn Batt at 0700hr for Wednesday 26th August 2009

Nil Warnings current.

Synoptic Discussion :

More of the same unfortunately though the chance of a better sea breeze structure has increased compared to last few days. The only saving grace being the beautiful environment and sailing friends.

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

4am.-Wed-26th-August 2009 - Audi Hamilton Island Race Week - Bureau of Meteorology

Observations :

At 0600hr the surface wind at Hamilton Island was WSW at 5kn gusting 7kn, (temp 21C, pressure 1016hPa) indicative of the land breeze. At Hardy Reef (further offshore at 19.7S 149.2E) the wind was NNE at 8kn indicative of weak synoptic flow.

Forecast Winds for open water 4nm East of Surprise Rock (i.e. east of Hamilton Island) (Read Discussion below)

1000:MD020 DR(340-050) MS05 SR01-09kn chance glass-out?
1200:MD030 DR(350-060) MS05 SR01-11kn chance glass-out?
1400:MD050 DR(360-080) MS07 SR02-12kn
1600:MD050 DR(360-080) MS08 SR03-13kn
1800:MD050 DR(350-080) MS06 SR02-12kn

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

Model guidance this morning is at last showing some fair agreement between the different models. The trend today is to the right as the sea breeze kicks in a little more than compared to the last few days?

Like Tuesday, it won't be a good day from a wind vs tide perspective.

With the very loose ridge axis still over you, the winds will be light and flicky to start with today. There will be an overall tendency for the wind direction to draw right (onshore) due to a slightly stronger sea breeze component.

The sea breeze potential is expected to be greatest within 0.5 to 1nm of the eastern side of Whitsunday Island and within a 1nm or so of the mainland due to greater land/sea temperature difference.

There is the good chance that the wind in the Whitsunday Passage holds 340-360deg at 6-11kn during the morning/afternoon. The direction is expected to trend more right closer to the mainland coast.

Wind will be lighter and very flicky close in the lee of any landmass e.g. Whitsunday Island, etc.

Be extra, extra careful today with the lightish winds coupled with the strong flood tide.

Natural oscillations today around 40 to 60 deg!

NB: Heavy showers and thunderstorms can create very gusty and erratic winds over short time scales.

Weather
Mostly fine with just the slight chance of an afternoon shower or thunderstorm. Take plenty of sunscreen and warm clothes in case?
Maximum land temperature at Hamilton Island: 25-26 degrees. Sea Temperature: about 23-24 degrees.

Wind Waves :
0.0 to 0.4metres, less in lee of land, more when wind wave opposes tidal current.(Wave heights quoted are Significant wave heights).

Current : A strong flood for much of the day. 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 0.90m at 0848hr and High of 2.80 at 1550hr and Low 1.38m at 2230hr.

Outlook

Thursday to Saturday: SE-NE 8-14kn (ave)

by Kenn Batt