by Kenn Batt
2011 Meridien Marinas Airlie Beach Race Week day four forecast: Nil Warnings current. Synoptic Discussion: A ridge of high pressure lies over the race area.
Forecast 2011 Merdien Marinas Airlie Beach Race Week Day 4
Observations: At 0600hr Hamilton Island was reporting the following conditions:
Wind 170deg at 13kn gusting to 16kn, Temp 18C, Pressure 1019hPa). Light SW land breezes were observed at coastal mainland places. Some weak shower cells were observed well offshore.
Forecast Winds for Middle of Pioneer Bay (Read Discussion below).
1000:MD140 DR(160-120) MS06 SR02-09kn, could be light and variable or glassout?
1200:MD120 DR(140-100) MS08 SR04-11kn, could be light and variable or glassout?
1400:MD110 DR(130-090) MS08 SR05-12kn, could be 080-040deg?
1600:MD090 DR(110-070) MS10 SR06-14kn, could be 060-040deg?
1800:MD090 DR(110-070) MS10 SR06-14kn, could be 060-040deg?
Whitsunday Passage and Molle Channel: Wind speeds maybe two to three knots stronger at times than those above particularly around some headlands and in more constrained locations. Wind direction could be 10-30deg more left than above at times.
Further offshore: 130-110deg at 8-12kn (ave)
Key to wind forecast: First column is forecast 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: A ridge of high pressure currently lies over the Qld coast. Forecast gradient wind is expected to be 090deg at around 15kn.
This gradient should keep a SE’ly into the area which is expected to trend left during the afternoon. It appears that we are now entering a lighter wind phase?
The big questions today are (hopefully answered in forecast above??):
1. How far left will the surface direction get?
2. How quickly will the direction turn left?
3. How strong will the winds be?
4. Will the wind drop out this morning and a light sea breeze develop?
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 wind oscillations today around 15 to 20 deg away from effects of topography, tending 30 to 50 deg closer to the effects of any land mass and in lighter wind regimes.
Other possibilities: 65% chance that wind drops out this morning and a 5-12kn E-NE sea breeze develops late morning/early afternoon??
Weather: Remaining fine. Some cloud and isolated weak shower activity further seawards.
Maximum land temperature at Airlie Beach: about 23 degrees.
Wind Waves: 0.4 to 1.0metres, less in lee of land, more when wind wave opposes tidal current and further offshore depending on fetch.
(Wave heights quoted are significant wave heights).
Tide at Shute Harbour: Low of 0.74m at 0600hr, High of 2.70m at 1203hr and Low of 0.81m at 1744hr.
Tidal Stream: Slack stream around start times becoming a good ebb during this afternoon. Be very careful particularly in the passages, channels, close to islands, etc.
Remember: Tide floods to the south and ebbs to the north in the Whitsundays.
Sea Temperature: 20-21 degrees.
Outlook: Wednesday: Similar to above. Thursday: Glassout to weak seabreeze??
Meridien Marinas Airlie Beach Race Week website