Thanks Judy for asking me to write this. It’s a common question: what is the best wind for snorkelling in Port Phillip Bay? Everyone has a friend who seems to know when the conditions are going to be perfect. How do they do that? While it’s not a perfect science, it’s quite easy to get it right most of the time.
However, it does not mean visibility will necessarily be perfect. I’ll come to that later. To start with, we can learn the rule of thumb about offshore versus onshore winds.
The rule of thumb: offshore versus onshore winds
Wind from sea, let it be
Wind from land, beach is grand
As a general rule, if there is more than a light wind (over 10 knots / 15kph) likely to strike the beach from the sea, then it is going to be choppy. If the land offers protection from the prevailing wind, then it isn’t exposed to chop and the nearshore areas will generally be calm, even if the wind is quite strong.
Wind forecasts
Wind forecasts these days tend to be fairly accurate within 2-3 days. Certainly enough to do some preliminary planning before the weekend. I like the Willy Weather app. It shows the forecast for the next few days as wind strength and direction.
Here are two interpretations, one for the north of the Bay and the other for the south.
Reading wind forecasts for snorkelling in the Northern Bay
In this instance, the winds are strong from the southern quarter on Sunday, which makes snorkelling much of the northern Bay difficult. An easterly wind on the morning of the 26th, however, favours areas around Bayside like Ricketts Point, but by midday, this turns southwest and strengthens. Strong afternoon southerly winds are common in summer due to sea breezes, which occur when the land warms, rises over the Yarra Ranges and sucks air in off the sea.
In summer in the north, it generally pays to swim early. The morning of the 27th January is perfect conditions for much of the northern Bay as the wind is from the north.
Reading wind forecasts for snorkelling in the Southern Bay
Even though wind conditions are strong on 25th, this is perfect for Blairgowrie. We actually swam that morning, even though the wind rose much strong than predicted. It was flat calm. However, by the 27 January, the wind is blowing from the east and northeast, which is parallel to the coast. It would be quite choppy and I would choose to snorkel in the northern bay instead. However, an easterly wind would be terrible for Williamstown area and the west of the bay.
How can we predict visibility
Most beachside visibility is determined by sand sediment which is quite heavy. If wind conditions have been mild for 12-24 hours, much of this is likely to have settled and the shallows will be quite clear.
However, in the north of the Bay, the situation is more complex. The Yarra River plume is an essential part of the Bay’s ecosystemHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More. This carries fine sediment in freshwater layers that float on the top. These lenses of water morph about for days to weeks and move according to the wind and currents. It’s almost impossible to predict exactly where they will go. Therefore, even the most sophisticated scientific models can’t work out visibility for specific points on the map.
As a rule, the closer one is to the Yarra River, the more likely we are to encounter poor visibility. In the southern Bay, the tides are strong and flush out the system daily into Bass Strait, so it tends to be generally better, especially after a high tide.
This is my honest advice.
If wind conditions have been mild for 12-24 hours already, assume it’s going to be reasonable visibility.
If you worry about visibility, you are likely to miss many good snorkels. By contrast, if you follow the rule of thumb for the best wind for snorkelling in Port Phillip Bay, you might have the occasional swim where you can’t see your hand in front of your face. But this is more than made up for by the number of wonderful swims you get to have at other times.
