Or you could just watch the 6.00 weather forecasts.

What an absolute crock of smoking dog s**t.....
" and on the bays wind will from the east at 25-30 kilometers per hour"
w.t.f.?? whats wrong with knots? and don't tell me knots per our either.

Even the BOM have many forecasts with wind predictions in Km/h. If you on land, who gives a toss how windy it is? If your going on the bay, then the forecast is important and you will know what a knot is, and what that means in real life.
ie am I going to get smashed or go for the screecher.

rant over.
Good thread anyway.
and by the way, I'd waste $20 for an ebay toy that told me the windstrength.
Who cares if you risk looking like a knob using it, if it gives you a bit of a better guess, go for it.

crustysailor said...
Even the BOM have many forecasts with wind predictions in Km/h.

Perhaps that would be because we actually have the metric system in this country?

But seriously, you'll find that all land based forecasts are in km/hr. All open ocean forecasts for seafaring types are in knots. That's just the way it is...

... my recommendation would be if you want the most accurate forecast for the Australian Continent follow BOM.GOV.AU. They have spent plenty of our tax money to get it right most of the time. Then compare that to the forecasts on Seabreeze. It seems that combo is pretty reliable. Unless you are talking about freak locations like Gerroa where local weather patterns play a big factor.

My method is:

- if I'm at the beach and it's on I rig up and go out.
- if on the beach I can hear a definite wind noise in my ears (not between my ears) I go out with light wind gear.
- white caps and I rig smaller
- sand blasting and I rig smallest

If I'm at work or at home:
- read the BOM forecast for the bay.
- look at the marine simulation covering the area (to get an indication of the time of day things are going to happen.
- have my gear in the car all the time
- watch the observations for Fawkner Beacon and Moorabbin airport (Fawkner usually read a tad high for my beach so Moorabbin airport confirms what I hope is happening.
- if both crack 12-13 knots I'm off.
- I check the BOM radar as a safety check to make sure there are no deadly storms around.
- If I am away down the coast I will check the BOM stations on either side of where I am.

If I'm at Sandy Pt and there no wind on the bay but wind in the trees I will drive to Shallow Inlet and have a look, checking windmills on the way. If not I go surfing.

But the terrain affects the wind coming into my sail just as it affects anemometer readings, that's my point. The grunt part is only a couple of meters above the water. Good wind at 10m up is useless to me when I'm stuck in a shorebreak or a big set of waves. If it's 12-13 kts on the water, I'm screwed, 15 kts gives me a fighting chance. That's the distinction I'm using it for.
Where did I say that a hand-held anemometer is a flawless device that will make the wind blow steady and true on all quarters at precisely the speed measured ?
At the end of the day, wind is part of an emergent system, and subject to all sorts of vagaries and changes throughout the day. We all know that.
BOM forecasts typically cover about 300km of coastline each, which is a rough stab at best for any given beach.
Wind in bushfire zones in bushfire season is not really representative of we are dealing with either, so I'm not sure how pertinent that experience might be to this discussion.

Ian K said...

KenHo said...




10 metre heights are more useful for kites than for us pole-dancers.

Have to disagree, 10 metres is just as useful for both, 20 metres would be even better for both lots, less terrain effects, but the BOMs worldwide set 10 metres as the standard as a practical compromise.

I spent decades trying to measure wind for bushfire experts, On one expedition I shimmied up and down a 30 metre tower 3 times a day trying to get a temperamental anemometer to put out sensible numbers. No, on second thoughts, it was a thermometer, never mind. No matter how many anemometers you put up a pole the top one will always be the one to misbehave. I've concluded wind in the real world is next to impossible to measure. But if you must put a number to it. Give me the sail size you were using or the number recorded by a specified BOM anemometer. Anything else is rubbish.

Water turbulence affects wind fetch badly. The rising and falling peaks and troughs mess up the flow big time. Contrast that to say, Sandy Point where there is an open fetch with wind coming of a solid sand-bank. Ther eis no disturbance to the flow there, and the wind can really get itself organised. The results prove that.
Get stuck in the trough of a big set of waves and there is no wind. You can feel the dramatic difference as you rise up onto the crest of a swell. You get the same compression effect as a dune or hill gives. So a steady 12kts at 10m up feels like 6 in the trough and 16-17 on the crest.
Places like Elliott Hds where you get a ton of tall wind chop right in the river mouth, especially on a wind against tide, suffer a lot. It an be a solid 30kt howler, and there will be dead spots that nearly kill you.
It's not always a sunny well-mixed day and I'm not really a flat water, large gear sailor either.
Sure, those conditions are easy to call, and I'm not saying that me or anyone else can never estimate wind right.
It's more that some conditions can be difficult to gauge accurately, and then it's nice to have an objective measure to help.

All weather systems are emergent. That is, while there it is possible to define the set of rules that make it function, there is such a high level of complexity that you have to run the system to see what will actually happen.
More than 3 days out and it becomes chaotic.
Which is why 7 day forecasts are rarely if ever on the money.

Ian K said...

Ken. Why would there be good wind at 10 metres but none at the surface? The ratio varies a bit but surely not not by that much on a sunny well-mixed day over the same patch of water. What do the kiters say, they can sample both heights very easily?

Not sure that wind qualifies as an emergent system type of behaviour, it's bad but not that bad, that's more global economy sort of unpredicability.