Waves
Localised waves - from local winds – short wavelength, choppy, confused
Distant waves – groundswell - generated from distant storms, long wavelength, groomed lines
Plus combination of both
Beyond the bay 2014
Weather effects on the Sea • Increasing Southwesterly, fixed fetch • Initially light to moderate winds • Note wave heights
Beyond the bay 2014
2014 Ocean Racing Club of Victoria Inc. 1 Fetch and Wind Strength
• Increasing 30 then 40 knots • South Westerly example 30 -40 knots
Beyond the bay 2014
2014 Ocean Racing Club of Victoria Inc. 2 Tides – Rule of Twelfths • Chart depth = Lowest Astronomical Tide, the lowest possible theoretical tide http://en.wikipedia.org/wiki/Rule_of_twelfths
Beyond the bay 2014
Tide vs stream flows (Heads) • Slack water and high/low tide vary by 3hr. It is stream flows you want to look at for transiting the heads.
http://www.bom.gov.au/oceanography/tides/MAPS/vic.shtml
Beyond the bay 2014
2014 Ocean Racing Club of Victoria Inc. 3 Stream predictions • Exiting heads aim for slack water • Entering heads aim for Flood or slack water • Avoid Ebb, especially in a southerly and/or SW swell • BOM tide forecast is not adjusted for daylight savings
Beyond the bay 2014
Currents
• Sometimes a major impact, it pays to check • See Integrated Marine Observing System • http://oceancurrent.imos.org.au/
Beyond the bay 2014
2014 Ocean Racing Club of Victoria Inc. 4 Warning signs • Barometer dropping/rising fast You must observe and log data • Look at that strange cloud over while at sea – every 2hrs at least there !! • Lightning and thunder • Sudden unexplained drop in wind or sudden increase in wind • You “sense” something not quite right, your instinct is talking to you – trust it
Beyond the bay 2014
What to do ? • Ideally head to somewhere safe • But don’t head into the bad weather o Face wind, low is to the left o Which is typically a Port tack • Prepare the boat (early) o Smaller headsail (first) o Reef main (next) or go Trysail o Storm boards in o Secure loose items o Eat and drink while calmer o Have minimal people on deck, clipped on
Beyond the bay 2014
2014 Ocean Racing Club of Victoria Inc. 5