In this course you can learn about the mechanics of global weather, the foundations of ocean meteorology, predictive modeling and how sailors receive data via satellite and use high-performance navigation software. This course looks at oceanic meteorology and climatology through the lens of the sport of sailing. You will gain a basic knowledge of meteorology needed by sailors to take part in a regatta such as the Barcelona World Race, the only double-handed, round the world regatta with no stops. You will learn about the strategies employed during a round the world regatta and how these are put to use on board the latest ocean racing yachts.
Video 5.1.1 From Barcelona to the Gibraltar Strait
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En provenance du cours de Universitat de Barcelona
Strategies for winning. Meteorology in a round the world regatta
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À partir de la leçon
Climatology and meteorology in the Barcelona World Race: From the Mediterranean Sea to the Indian Ocean
We begin now by going over the Barcelona World Race round the world route.
In Module 5 you will learn about general and specific strategies for sailing from Barcelona to the Indian Ocean.
Rencontrer les enseignants
Tomàs Molina
[MUSIC]
This subject will talk about getting out of Barcelona,
down the Mediterranean into the Straits of Gibraltar.
It's very important to understand that the Mediterranean is a land locked
body of water, meaning it has no real, direct contact with the sea.
There are only two direct contacts.
One is the Strait of Gibraltar, Pillars of Hercules, very narrow, not very deep.
And there's another one that's even worse, which is the Strait of Suez.
All this is part of the Mediterranean, a few rivers coming into it,
the Rhone is the main one, the Po, with the water coming from the Alps.
But it's not enough to correct all the evaporation that's going on.
As you see, here we've got north of Africa is all pretty hot, especially in summer,
lot of [INAUDIBLE] evaporation going on making the Mediterranean a very salty sea.
And the ocean, the ocean which is out here tries to correct that, we'll talk about it
later on but we'll see it has some major implications from currents.
The other thing is important to realize is that it's land-locked,
and weather gets a lot more complicated once land gets involved.
In the middle of the ocean,
weather forecasting is a lot easier than being close to the shore.
Okay, so the race starts from Barcelona.
Right here in Spain, Catalonia.
Protected by the Pyrenees, big mountain ridge over here.
And protected by the whole of Spain.
You could see here on the map, that's any green surface here in Galicia,
France, but once we get into Spain, it gets drier and drier as we go east, and
we're protected from the Atlantic weather.
[INAUDIBLE] first part of the course.
We go from Barcelona to the Straits of Gibraltar, it's the only way out.
And you can see that the course will change quite often.
Here, here, here, Cabo de Gata, and then on to Gibraltar.
A few islands in the way, which could become an obstacle or
they could be an opportunity, and always the choice here, are we going for
the winds offshore, the gradient winds, thinking that there's no lands,
or do we go for local effects, the sea breezes during the day?
As the land heats up, it gives a sea-breeze onto
the coast that only extends ten maybe fifteen miles.
Land breezes in the night, even smaller distance.
As the land cools down,
the air starts gliding down, katabatic winds they call it.
But normally you have to be right into the beach to get that.
Okay, and then eventually we end up here in the Alboran Sea.
Here it becomes different in that the Straight of Gibraltar
is massive Venturi effect, right?
Any easterly wind gets strongly accelerated,
any westerly wind gets strongly accelerated.
Inside the strait, northerly or
southerly winds are extremely, extremely rare if not impossible.
It always gets channeled by the strait and accelerated.
This is a site here from Gibraltar Strait.
Gibraltar itself is over here.
We then go down, well, down west to the coast,
you can see these mountain ranges over here.
The Spanish mainlands.
If I go back a little bit, Gibraltar over there.
Go over to the other side, we'll end up in Morocco.
And as you see, on the Moroccan side, it's all pretty mountainous as well.
And that is what is causing this channeling effect, this Venturi effect.
Always more winds in Gibraltar or just on the other side of it, where the wind
blows out of it and then sort of funnels out basically, like a big fan.
It's like the thing you use to light your chimney back at home.
So this is Gibraltar Strait seen from the top, and
the arrows you see here are currents, and the color is intensity.
Red is more intense, right?
As I've said before, it's very complicated, the currents in Gibraltar.
In general, as the water evaporates in the Mediterranean,
that water has to be resupplied.
It comes from the ocean.
So on the surface, there's a general east-going current,
coming from the ocean, going to the Mediterranean.
Below that, the boats can't use that, there's a current going from
east to west, as the water in the Mediterranean is saltier, heavier, and
therefore flowing out more or less by gravity.
The old Phoenicians used to use that.
They used to drop kind of cells down in the water very deep with stones, and
they would let them self be dragged out by the currents deep down towards the ocean.
As you will see for some of the competitors it's really hard to deal with
this current, if you get there the wrong time with no wind.
Here's just a little animation, if you see how the current intensifies.
Current intensifies with the actual moon movements like normal tides.
And you can see here that, as the tide goes up and down, those currents, although they
stay in a general west to east direction, they get more intense and less intense.
The other thing that complicates is that there are veins of currents.
Sometimes it's good to get really close in to Gibraltar, really close into the coast.
Sometimes you have to be in the middle.
Sometimes you have to be in a Moroccan Coast.
It's a big head cruncher for the navigators on board, the skippers.
So here the boats have just left Barcelona.
At the moment they can go anywhere they like, but all have to come back together
here to go through the narrow exit, Gibraltar Straits.
Straight line, there's no need to go and look for wind at the beach,
right, which is good because it's a bit of a detour.
As we go forward, we can see there's a little bit of driving going on here and
a little bit of hesitation on what to do with Ibiza by the green boat over here.
First I thought we were going to go to the east of it,
then we realized it was a bad plan.
They came back, and as you see here,
the leading boats have picked up a little bit of wind and they go over Valencia.
And these boats went light for a little while.
So here they've already lost a part, few miles, right,
which could be very expensive for here later on.
I think any competitor leaving Barcelona
is not concerned about being the first boat out of Gibraltar.
What is most important is to not get left behind.
Be in touch with the leaders.
It is the Mediterranean.
Weather forecasting in Mediterranean is complicated at best.
Got all this land mass here, local breezes, currents and
all that sort of stuff, anything could happen.
People will be relieved once they get out of here, out in the open ocean, and
they have more control over their destiny.
The beginning part is the most complicated.
All right, so let's go forward.
Here you can see that the options have been limited.
They all have to make the right-hand turn.
We're going to Gibraltar.
So as you go here to there you lose 10 degrees.
Here there's another 20 degrees that goes right.
So the option to go offshore is quite limited here as you keep on going right.
Once we get into the Mar Del Alboran, the Alboran Sea, which is down south here
between Morocco and Spain, we'll see that the options open a little bit.
So here you can see, we've got a what the Spanish call "Poniente", right,
which means this breeze from the West.
The Sun goes down, poniente.
It's been accelerated here through the strait.
All right, and here people will try to find something different
on one of the coasts.
If you go in the middle, you're in the middle of the current going that way and
the breeze will be pretty much dead west meaning full beat.
If you go to the sides, as it funnels out, maybe on Spanish
coast you can find a breeze that is further left, more towards the southwest.
Make longer port takes, short starboard takes,
and the other way around on the Moroccan coast.
It's a decision navigators have to make now.
As you can see here,
it clearly seems to be paying off on the Moroccan side of life.
I'll zoom in a bit more.
As those boats have found more breeze, they managed to get ahead
of those boats and they're the first ones to reach Gibraltar.
If they manage to get through there first,
they're in good shape.
So there we go.
Boats that took the northern part of the Alboran Sea have lost massively.
The boats that have entered the Moroccan coast have done very well, and
first boat is now entering into the straits.
As we've seen before, the strong currents here in the straits.
So it's all a matter of timing now.
You can't control when you get there,
and when you get there the currents that are there is what you get.
It all depends on the moon phase,
if the tide has reinforced the currents or if you're getting there at select tide and
it's easy to get through, so there's a bit of luck involved.
The only thing you can do beforehand is try to be one of the first boats to get
here, so no one can get away.
So here we see these boats go through fairly easily, no problem.
As we go further down,
we can see that here it really got complicated for these boats.
These boats, the breeze went right,
there was not enough wind to go to sail fast enough to beat the current.
Sometimes you can actually sail in the water but
you're sailing through the water at let's say three knots in very light airs,
and if that water at the same time is moving the other way at three and
half knots, although you're moving through the water, the whole body of water you
are in is moving further away from distance than you can make up for it, and
then it actually pays off to put the anchor.
Almost impossible to put the anchor in Gibraltar, because it's 100, 200,
300 meters deep.
So you see some boats here actually going backwards.
Let's see.
Try to show you again.
You can see here the black boat actually going backwards.
It's struggling really.
And there finally they get out.
So what I spoke about before, you're not so concerned about being the first boat
out, you're very concerned about not losing touch with the leaders.
Some of the boats here have already lost touch with the leaders, and for
them it's going to be a very long race around the world.
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