10:04 PM Thu 13 Aug 2009 GMT
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'Latest weather chart'
Bureau of Meteorology
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Bit of a mixed bag today as far as wind is concerned. The temperature and lack of rain however will truly have you thinking that you're in 'second heaven'.
Nil Warnings current.
Synoptic Discussion:
A weak high pressure ridge currently lies over the region. A weak trough of low pressure expected to move eastwards through more southern parts this afternoon.
Observations:
At 0630hr surface winds over the Airlie Beach area were out of the WNW averaging around 5-8kn (synoptic wind plus land breeze) and the temperature was around 10-12 deg. At Hamilton Island the wind was NW'ly at 13kn gusting 17kn, (temp 20C, pressure 1017hPa) indicative of the synoptic flow aided by some topographic forcing.
Forecast Winds for middle of Pioneer Bay
(Read Discussion below)
1000:MD200 DR(230-180) MS05 SR02-10kn could be light and variable? Good chance that wind direction is 320-350deg at 10-14kn further offshore
1200:MD040 DR(020-090) MS05 SR02-10kn could be light and variable? Good chance that wind direction is 320-350deg at 10-14kn further offshore
1400:MD040 DR(330-030) MS08 SR04-13kn good chance that it's 2-4kn stronger further offshore and direction 320-340deg?
1600:MD020 DR(320-040) MS10 SR05-16kn good chance that it's 2-4kn stronger further offshore and direction 320-340deg?
1800:MD350 DR(320-030) MS08 SR04-12kn good chance that it's 2-4kn stronger further offshore and direction 320-340deg?
Note 1: First column is mean wind direction in deg Mag (MD). It is the 10min average (mean) value at a height of 10m above the water leading up to the hour quoted. The second cloumn 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
The gradient wind appears to be out of NW at round 20-22kn judging from Hamilton Island observations (allowing for some forcing down the Whitsunday Passage, etc.
This being the case, then the wind direction should hold N-NW at around 10-15kn offshore (closer to the Cones) during today. Closer inshore however, the sea breeze influence is expected to play havoc with the surface winds?
There will probably be a light wind transition zone about 0.5nm across between offshore NW and inshore N-NE'ly? Passage of weak trough may see wind go SW-SE at 8-12kn briefly before trending left?
As you can see there is a great degree of uncertainity today.
Wind lighter in lee of any landmass and briefly stronger and gusty due to convergence around some headlands.
Natural oscillations today around 15 to 25 deg away from effects of topography, tending around 20 to 50 deg closer to the effects of any land mass.
Wind in Whitsunday & Molle Channels should be 2-5 stronger than forecast above and about direction 330-020deg?
Weather
Remaining dry. Take plenty of sunscreen and warm clothes in case?
Maximum land temperature at Airlie Beach: 26 degrees. Sea Temperature: about 22 degrees.
Wind Waves:
0.4 to 1.0metres Less in lee of land, more when wind wave opposes tidal current. (Wave heights quoted are Significant wave heights).
Current: A moderate flood this afternoon. Be very careful particularly in the Channels.
Remember: Tide floods to the south and ebbs to the north in the Whitsundays.
Tide at Shute Harbour: Low of 0.89m at 1043hr and High of 2.95 at 1746hr.
Outlook
Saturday: Dry with W-SW winds 5-8 kn early, shifting E-SE at 8-12 knots during morning.
by Kenn Batt
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Wilsons Promontory, VIC
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