by Kenn Batt
Telcoinabox Airlie Beach Race Week - Day 4 forecast: Nil Warnings current at time of writing for this area.
Synoptic Discussion: A high currently centred over NSW and moving slowly east, is extending a weakening ridge along the Queensland coast.
At 0600hr Hamilton Island was reporting the following conditions:
Wind 150deg at 19kn (ave) gusting to 22kn, Temp 17C, Pressure 1022hPa).
Forecast Winds for Middle of Pioneer Bay (Read Discussion below):
1000:MD140 DR(170-130) MS16 SR10-21kn
1200:MD125 DR(145-105) MS14 SR08-20kn
1400:MD120 DR(140-100) MS12 SR06-18kn
1600:MD100 DR(120-080) MS12 SR06-17kn
1800:MD090 DR(110-070) MS12 SR06-17kn
Note: Direction trending 10-30deg more left than forecast above closer to Pioneer Bay coast after about 1100hr.
Whitsunday Passage and Molle Channel: Wind speeds 2 to 5kn stronger in places at times than those above especially this morning, before easing during mid-late afternoon. Localised patchy winds possible early afternoon. Winds could be gusty and erratic around some headlands and in more constrained locations.
Note: 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: Today will be a little complex to say the least. A line separating a stronger pressure gradient to the north from a weaker gradient to the south is expected to lie over the Whitsunday area. How quickly north this line moves will determine the strength of the winds today? My achy joints are saying that you should see a light-moderate W-SW land breeze inshore early this morning, being replaced quickly by a moderate, a little fresh at times, synoptic SE’er during the morning. The direction is then expected to trend left (or into the east) and ease??? during the afternoon. The wind could become quite patchy in places? A late morning 'glassout' to a sea breeze is possible in Pioneer Bay?
Forecast chart for 1600hr today - Telcoinaback Airlie Beach Race Week 2012
Other possibilities: 55% chance that wind speeds stay in the 12-16kn (ave) range from 150-120deg for your racing today, especially offshore and in Whitsundays?
40% chance that there is a 'glassout’ in Pioneer Bay later this morning followed by an E-NE sea breeze at 8-12kn (ave)?
Note: Wind will be lighter in the lee of any landmass and stronger and more gusty between islands (in channels and passages) and around some headlands.
Natural oscillations today around 15 to 25 deg away from effects of topography, tending 30 to 50 deg closer to the effects of any land mass (including islands and headlands).
Weather: Cool at first. Slight chance of an early light shower. A fine and mostly sunny day. Maximum land temperature at Airlie Beach: about 22 degrees.
Wind Waves: 0.8 to 2.0 metres. Less in lee of land, more when wind wave opposes tidal current and further offshore.
(Wave heights quoted are significant wave heights).
Tide at Shute Harbour: High of 2.51m at 0841hr, Low of 0.56m at 1429hr and High of 3.48m at 2106hr.
Tidal Stream: A good ebb this morning and early afternoon, becoming slack before a strong flood later this afternoon/evening. Be very careful particularly in passages, channels, close to islands, etc.
Remember: Tidal currents generally flood to the south and ebb to the north in the Whitsundays (with a multitude of local effects and eddies. So be prepared!).
Sea Temperature: about 19-20 degrees.
Wednesday: Mostly sunny. SE at 8 to 14 kn (ave), tending E-NE during the late morning/afternoon. Could be a morning 'glassout' to a 8-12kn (ave) E-NE afternoon seabreeze.
Airlie Beach Race Week website