2009 Audi Hamilton Island Race Week Weather Forecast - Friday

9:26 PM Thu 27 Aug 2009 GMT

'10pm prognosis Friday 28th August' Bureau of Meteorology

2009 Audi Hamilton Island Race Week Weather Forecast

Issued by Kenn Batt at 0630hr for Friday 28th August 2009

Nil Warnings current.

Synoptic Discussion :

Like yesterday the sea breeze component is expected to re-enforce the light to moderate E-NE synoptic flow today.

A weak ridge of high pressure still lies over the race area. A weak E-NE pressure gradient persists.

Observations :

At 0600hr the surface wind at Hamilton Island was NE at 5kn (temp 21C, pressure 1017hPa. At Hardy Reef (further offshore at 19.7S 149.2E) the wind was E at 5kn 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:MD120 DR(080-140) MS05 SR01-09kn slight chance glass-out?
1200:MD090 DR(060-130) MS08 SR04-12kn
1400:MD080 DR(040-120) MS13 SR09-17kn chance of right trend?
1600:MD070 DR(040-120) MS12 SR07-15kn chance of right trend?
1800:MD070 DR(030-120) MS11 SR06-14kn chance of right trend?

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.

4am Friday August 28th - Bureau of Meteorology

Discussion

Like yesterday some of the better computer models are again hinting at moderate pressure this afternoon? The wind direction is expected to crank up from the SE and then slowly trend left as the sea breeze component cuts in. There is a chance however, that the direction may crank right during the afternoon 090 to 130deg. Be especially vigilant today!

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

The wind flow in the Whitsunday Passage is expected to be more variable compared to that at the more eastern forecast point above. The wind speed is expected to be 2-3kn stronger close to the mainland coast compared to offshore due to stronger sea breeze.

Wind will be lighter and very flicky close in the lee of any landmass e.g. Whitsunday Island, etc. Speed acceleration can be expected between islands.

Be extra careful this afternoon with the lightish winds coupled with a strong flood tide.

Natural wind oscillations around 20 to 35 deg in unperturbed flow!

Weather
Some early low cloud 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 23-24 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 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: High of 2.08m at 0545hr, Low of 1.01m at 1132hr and High of 3.01m at 1835hr.

Outlook

Saturday: SE-NE 5-12kn (ave)

by Kenn Batt