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SgBFish
14-02-2008, 04:30 PM
How does a tide change affect the strength of the wind? An old bloke was telling me that when a tide change occurs that brings the wind against the tide the breeze will tend to increase.

That would mean in Moreton Bay when the tide starts to flood into the bay against a SE wind the breeze would tend to increase.

Is there any truth to this?

Scott

cuzzamundi
14-02-2008, 05:50 PM
I've found that in certain exposed places i've fished land based, the onshore wind will increase as the tide comes in, then start to drop off once it ebbs. I'm not sure about the above theory, as i can't see how an increasing wind would be spurred on by an opposite tidal direction. Be interested to hear if anyone can offer an explanation, as im not willing to disparage what he's saying, despite having no reason to see how myself.

cuzza

seatime
14-02-2008, 06:42 PM
Need an oceanographer to explain the effects properly.
As cuzza has noted a large body of water moving (like a tidal flow) will create it's own wind - if the tide moves in a direction similar to the existing wind it increases wind strength to a degree, dependant on the tidal range. Temperature also has a role to play.
When looking at a place like Moreton Bay, which creates it's own kind of micro climate, temperature differences come in play again. e.g the water in the shallow bay has warmed faster than the deeper water outside the bay. Depending on the time of year and temp variances, wind direction and tidal range, winds can and do increase after a tide change.
I'd really appreciate an expert giving a concise explanation.

Vindicator
14-02-2008, 07:03 PM
I don't know whether it was the tide or not but something changed last sunday when we got out wide and turned it to utter sh!t. Maybe it was the tide, not sure but it turned quickly.

Cheers
Kezza

Horse
14-02-2008, 07:25 PM
Tidal infuences can change atmospheric pressures but the big thing to note is that if the tidal run is into the breeze then add the speed of the current to the actual wind speed to guage the effect. Wind against tide also slows the surface and can make waves stand up more

FNQCairns
14-02-2008, 07:32 PM
I don't think tide has any real bearing on the wind but the wind certainly has a bearing on the tide....that is the waves and wave form that exists at differing tidal stages but thats pretty obvious I guess.

I have seen 30kn really back up a dam like Blowering or Talbingo etc, amazing the tidal effect that can have on the downwind end. So would expect that to also hold true for tidal estuary etc but how much in the open ocean??

cheers fnq

seatime
14-02-2008, 07:49 PM
The basis for the positioning of the wind farms in Europe & UK (7m tides) is the wind sheer created by the large tidal ranges.

Oh Gee
14-02-2008, 08:42 PM
I dont think the tides do have an effect but it is quite possable the things that create the tides may have. The sun and the moon. If i think back to my skool daze thay tried to teach me that the atomsphere is a liquid, just not as dense as water. Ergo, some air movements would be tidal. But then again I have be knowen to be wong.

g

sandbankmagnet
14-02-2008, 08:57 PM
Errr OK G.

Your science teachers were wrong. There's 3 states of matter. Solid, Liquid and Gas.

I think your English teacher was wrong too.

cbs
14-02-2008, 09:58 PM
Let me first say that I have been a racing sailor for 25 years.

I am not aware of any direct change in absolute wind strength as a result of tide change. It is of course possible to experience a change in apparrent wind strength (and direction) as a result of being on a boat in a moving tide. This is much the same effect as the breeze one feels when sticking your head out of a moving vehicle on a still day.

If there was a significant effect, then I am sure that I would know about it rather than always worrying about being "in phase" with wind shifts and worrying about where the next shift will come from. as part of the game we play.

The only effect I could think of is it may be possible for a very large sandbank or other exposed bottom during a low tide to create a local breeze in much the same manner as a sea breeze forms from heating of the land. I would think that such an effect could be found in certain local areas at certain ideal conditions. It would need to be a very large bank to generate anything more than a slight vesper of breeze. This would not however be a direct result of the movement of water however, only a secondary effect.

Martijnf
14-02-2008, 10:19 PM
I think your English teacher was wrong too

lol..ouch

Anyway wouldn't it simply have something to do with temperature as stated before?

We get that here in Holland in the evening quite a lot (I live near the coast) where when the temperature between sea and land levels out, the wind drops.
During the day when it's very hot on land and cold(er) out at sea, it creates a movement in the air.

Not an expert here either though.

webby
15-02-2008, 10:08 AM
Tides have very little effect on winds, its really the opposite that winds do effect tides.
Any wind against tides has its effects of increasing surface chop.
The same applies to mid to strong winds with the tides will also create surface chop especially in the bay where winds are funnelled between the big island and land.
As land cools slower then water, you get the land breezes early morning, which can depending on strength effect and quiten down offshore winds.
This usually disappates when both surface water and land are equal temp, which allows the offshore winds to increase, the reason the N/E and E pick up late morning.
The two winds that generate the worst conditions in the bay would be S/E and N/E.
Mid to Strong S/W also have their effects on flood tides especialy the mid to eastern sides of the bay.
The reason a lot get caught out when fishing the sheltered inside of Moreton, and heading back across the bay to be met with a strong N/E chop.
You also quite often get S/e blowing in the bottom of the bay, and E blowing in the mid to top of bay as the wind change of a arvo.
regards

SgBFish
15-02-2008, 07:37 PM
Webby I you have made a typo.
The land cools faster and heats faster than the surrounding ocean. In winter the cooler land than water generates higher air pressures over the land and lower pressure over the water hence we get W from the land out to see as the air moves from higher pressure to lower. As the land heats up and equalises in temp the breeze drop to nothing and if the land heats up enough it generates lower pressure over land air pressure and the E or NE sea breeze funnels in. The hotter the day the greater the differential.
The worst winds in the bay depend on where you are and where you are going. Heading home from Moreton into 25Knots of W is not something I want to do too often.
You are dead right on the NE in the bay. It fills in from the land hence people heading home from Moreton at the end of a typical summer’s day will experience stronger NE the further they head W into the bay. And yes wind against tide will stand up waves.
I just see so often from my place at Margate that when SE conditions prevail and tide starts to come in the wind more than often increase.
Scott

seatime
15-02-2008, 08:45 PM
Tides have very little effect on winds, its really the opposite that winds do effect tides.
Any wind against tides has its effects of increasing surface chop.
The same applies to mid to strong winds with the tides will also create surface chop especially in the bay where winds are funnelled between the big island and land.
As land cools slower then water, you get the land breezes early morning, which can depending on strength effect and quiten down offshore winds.
This usually disappates when both surface water and land are equal temp, which allows the offshore winds to increase, the reason the N/E and E pick up late morning.
The two winds that generate the worst conditions in the bay would be S/E and N/E.
Mid to Strong S/W also have their effects on flood tides especialy the mid to eastern sides of the bay.
The reason a lot get caught out when fishing the sheltered inside of Moreton, and heading back across the bay to be met with a strong N/E chop.
You also quite often get S/e blowing in the bottom of the bay, and E blowing in the mid to top of bay as the wind change of a arvo.
regards

Webby, I'm a bit confused about your explanation in the part I highlighted.

If the land cools slower than the water, how does this create land breezes (a breeze from land to the sea or offshore). Isn't a land breeze created when the water cools slower than the land, such as in winter?
If the land was warmer than the water wouldn't that create a sea breeze (onshore)- a breeze from the sea to the land?
If surface water and land are equal temperature, how does this allow offshore winds (land breezes) to increase, as temperature differences between the land and sea are the mechanism for local breezes (sea breeze/land breeze)?

cheers

edit: had dinner between starting reply and finishing.

webby
15-02-2008, 09:05 PM
My mistake in typing to fast you are right the the land does cool slower then the sea.
regards