Forecast Winds for Sea East of Hamilton Island

by Kenn Batt, sponsored by North Sails on 27 Aug 2005 Weather Forecast for 2005 Hahn Premium Race Week brought to you by North Sails

“North Sails proudly assisting the Premium Tropical Regatta”

For Saturday 27th August 2005 Issued at 0530hr

Synoptic Discussion:

A slow moving 1037hPa high pressure system over Victoria extends a firm ridge over the region. Fresh to strong SE Trade winds are expected again today and will persist into early next week. A Strong Wind Warning is current for area.

Observations at 0530hr:

On the radar there were some precipitation echoes to the north of the Whitsundays. Moving approx. from SE to NW at around 25kt.
Surface wind at Hamilton Island was 130deg magnetic at 26kt, gusting 29kt (funneling effects). At Hardy Reef (19:44.04S/149:10.85E)it was 130deg mag at 22kt.

Forecast Winds for Open Sea Area East of Hamilton Island

0900:130/24 gust 32 kt
1000:130/24 gust 32kt
1200:130/26 gust 35kt
1400: 120/26 gust 36kt
1600: 130/26 gust 35kt
Direction should be 5-10 degrees more right (veered) and speed around 3 knots stronger at times due to general funneling of winds through Dent, Molle and Whitsunday Passages.

NB: Any shower activity can produce squally (gusts up to 40kt) and erratic (temporary directional change of up to 50 degrees from mean flow) winds.

Natural wind oscillations today around 10 to 15 deg away from effects of topography, tending around 20 to 60 deg closer to the effects of any land mass. Wind speed can be stronger due to effects of channeling between islands, etc and lighter in lee of headlands, etc. Alternate bands of maximum and minimum wind speed, some 5-15 mins apart, normally characterize trade wind flow.

NOTE 1: Wind directions MAGNETIC, first speed is 10 min average and last speed is
maximum one minute gust during the 10min period leading up to the forecast hour. All at a height of 10m.
NOTE 2: The trend in both wind direction and speed is the most important aspect of any marine forecast. Forecast values will differ from observed values from time to time for a number of reasons including yacht’s position within race area, compass calibration, instrument calibration, land mass in the flow, etc

Forecast confidence level: 90%, based on state of art forecast models and grey matter.
Other Possibilities
70% chance that mean wind speed including gusts could be 2 knots stronger than forecast above, particularly this afternoon.

Weather

Partly cloudy with the chance (60%) of a shower or two(with a marked reduction in visibility). Take plenty of sunscreen, warm clothes and wet weather gear.
Maximum land temperature at Hamilton Is: 21 degrees. Sea Temp: 21 degrees

Wind Waves: 1.0 to 2.5 metre. Less near land. Note that wind opposing tide can create higher than forecast wave heights Swell: SE around 2m in open water. (Wave heights quoted are Significant wave heights). Current: A very strong tidal influence. Tide floods to the south and ebbs to the north in the Whitsundays generally, marked localised variations occur. Consult chart and 100 Magic Miles for further information.

Outlook
Sunday: Chance shower . SE winds 20/25, reaching 25/30 knots at times.
Monday: Chance shower. SE winds 20/25.
Tuesday: Chance shower. SE/E winds 20/25, easing 15/20 knots during afternoon.
Wednesday: Mostly dry. SE/E winds 14/18 knots.
Thursday: Dry. SE/E winds 14/18knots.

Tides for Shute Harbour

Sat 27 Sun 28 Mon 29 Tue 30 Wed 31 Thu 1 Fri 2
Time Ht Time Ht Time Ht Time Ht Time Ht Time Ht Time Ht
0528 2.12 0115 1.05 0209 0.83 0249 0.69 0322 0.65 0351 0.67 0415 0.71
1124 0.90 0655 2.20 0754 2.35 0837 2.47 0911 2.54 0939 2.57 1004 2.59
1824 3.06 1237 0.83 1334 0.72 1417 0.63 1452 0.57 1520 0.54 1546 0.53
1926 3.26 2013 3.40 2051 3.48 2124 3.50 2152 3.49 2219 3.45

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