Meridien Marinas Airlie Beach Race Week Weather Day 4 -The Trade Winds

9:15 PM Mon 17 Aug 2009 GMT

'4am Tuesday 18th August 2009' Bureau of Meteorology

A Strong Wind Warning is current.

Synoptic Discussion:

Ah the return of the Good Old Trade Winds. Some of you will be rejoicing today?

A ridge of high pressure currently resides over the race area. This ridge is expected to be strengthened later today with the arrival of a S-SE surge.

Observations:

At 0630hr surface winds over the Airlie Beach area were out of the SW averaging around 3-6kn (land breeze) and the temperature was around 12 deg. At Hamilton Island the wind was S'ly at 7kn gusting 9n, (temp 20C, pressure 1020hPa) indicative of the synoptic flow.

Forecast Winds for Middle of Pioneer Bay (Read Discussion below)

1000:MD140 DR(120-160) MS14 SR10-20kn may be 150-160deg?

1200:MD130 DR(110-150) MS16 SR12-22kn

1400:MD120 DR(110-140) MS16 SR12-23kn

1600:MD120 DR(110-140) MS17 SR13-25kn

1800:MD130 DR(110-160) MS18 SR15-30kn

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.

Forecast 10pm Tuesday 18th August 2009 - Bureau of Meteorology

Discussion

The BIG questions today are:

1. When will the surge arrive? Most of the models are predicting that the 25-30kn (ave) winds will arrive later this evening.

2. How strong will the pre-surge SE'ly be?

3. How far left will the pre-surge wind direction go?

Hopefully they have been answered extremely well in the wind forecast above?

Nevertheless extreme vigilence is required today as that surge may come a little earlier? As such wind speeds will average 20-25kn.

Wind will be lighter close in the lee of any landmass and stronger between islands (in channels due to acceleration) and around some headlands, in the form of 'bullets'.

Wind direction is expected to be 10-30 degrees more left and 3-5 knots stronger than forecast above in the Passage and Channel at times.

Natural oscillations today around 15 to 20 deg away from effects of topography, tending around 30 to 50 deg closer to the effects of any land mass.

Weather

Mostly dry and partly cloudy. Take plenty of sunscreen and very warm, waterproof clothes today.

Maximum land temperature at Airlie Beach: 25 degrees. Sea Temperature: about 22 degrees. Much cooler on the water though!

Wind Waves:

0.5 to 1.8metres, less in lee of land, more when wind wave opposes tidal current.
(Wave heights quoted are significant wave heights).

Current: A strong ebb this morning, followed by a very strong flood later this afternoon. Be very careful particularly in the Passage, Channel, etc.

Remember: Tide floods to the south and ebbs to the north in the Whitsundays.

Tide at Shute Harbour: High of 2.74 at 0857hr , Low of 0.12m at 1445hr and High of 4.06 at 2128hr.

Outlook

Wednesday: Possible showers with S-SE at 18-25kn, slowly easing during the afternoon.

by Kenn Batt