French multihull circuit kicks off its 2001 season with a tactical course around the Azores Islands

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Franck Cammas' Open 60 trimaran Groupama is a favourite in this year's Challenge Mondial-Assistance after winning last year's Quebec to St Malo race and placing third in the solo trans-Atlantic. This new boat will have technology and reliability on its side, but the 28 year old skipper will have to remain weather-wise if he hopes to play his race well.

A Synoptic challenge

The French multihill fleet kicks off their Atlantic
racing season with a tactical ocean course

May 9, 2001

The French offshore multihull season starts with a real corker come May 12, as nine Open 60 trimarans run the gauntlet of East Atlantic weather.

Called the Challenge Mondial Assistance, this new ocean racing course leaves Cherbourg on the north coast of Brittany, rounds the Azores Islands and returns to Tarragona, on the east coast of Spain by way of the Straits of Gibraltar and the Med.

All up this race involves 2700 miles of tricky forecasting, and careful synoptic analysis. Considering just how closely matched many of these terrific tris are, it will be little surprise to see the winner decided in the final fickle miles of the Mediterranean.

Not so typical

Typically the French multihull circuit kicks off its summer Atlantic sailing season with a 'grand-prix' event, an around-the-buoys regatta close to shore, where tactics revolve around boat handling. On this ocean passage, weather will dictate the tactics and all the skippers agree: This course will be a real beauty!

Never a dull moment

At first glance, the initial two legs of the Challenge Mondial Assistance appear straight forward. We can expect high pressure over the Azores driving surface winds in a clockwise direction around its perimetre. Trimarans leaving Cherbourg can expect a close reach on their passage to and from San Miguel.

Keep an eye on Marc Guillemot's La Trinitaine - Team Ethyphar in this year's Challenge Mondial Assistance. Last year Marc and his boat placed second in the solo trans-Atlantic and the Quebec to St Malo.

Too simple

But this is all a little too simple.

For starters, spring in the East Atlantic is a turbulent time

Frontal systems push through this corner of the ocean - some of them quite nasty. Let us not forget the brutal clobbering delivered to the monohull fleet in last June’s solo trans-Atlantic race.

With a typical frontal system, in which warm and cold fronts push deep into the south from low pressure cells east of Newfoundland, sailors coming from the English Channel could expect winds to veer into the south-west quadrant with the arrival of a warm front and veer quickly to the north-west as the cold front moves through.

In a situation where vigorous westerly flow is happening, these frontal systems could move through the eastern Atlantic every three days, giving skippers a wet and windy bash all the way to the Azores, and a wild downhill slide to the Straits of Gibralter.

Viva la difference

Is this year different?

Spring 2001 is offering the French multihull fleet an unusual challenge.

Jet streams influence the path of storms and this year the jet flowing over eastern Canada and the western Atlantic has tended to swing well north of Great Britain, while another jet stream - or storm track - runs right over the Mediterranean.

As a result of this jet stream signature, an elongated high pressure cell has become the dominant feature over the Azores, with a ridge of high pressure reaching to the north-east as far as Iceland and Norway and bathing the Scottish moors in brilliant sunshine.

To the south of this high, low pressure has repeatedly formed, driving warm and moist air into the Mediterranean and southern Europe, while winds circulating around the high drive cold dry air into eastern Europe. Stormy weather is the result.

France recorded its wettest and coldest April for many decades.

According to Ken Campbell, weather router for Yves Bourgnon and his yacht Bayer-France, this scenario is likely to persist into May, and if it continues past May 12, skippers will have to gibe downwind out of the English Channel to the Azores.

"The position and strength of the Azores High is going to be the key thing for the first half of the race," says Campbell. "Skippers will need to get into best package of breeze not over 25 knots."

Beware the wind shadow

With the Azores high typically centred over the Azores - thus the name given to it - winds around these islands tend to be light. Add to this a wind-shadowing effect from tall volcanic peaks, and skippers must remain vigilant that they don’t get caught without a breeze by sailing too close the leeward side of these islands. Considering the speeds these Open 60 trimarans are capable of in even light airs, nobody want to get stuck in a calm.

If Ken Campbell’s long-range forecast is right, and the elongated Azores High remains, skippers can expect a broad reach from the Azores to Cadiz on the south coast of Spain before navigating through light and fickle airs towards the Straits of Gibralter.

"From Cape St Vincent to Cadiz winds can be light," notes Campbell.

"The time of day and what the sea breeze is doing will influence any decision making.

"This is not a long stretch, about four to eight hours, but as we saw last year in the Quebec to St Malo, how you maneuver past the coastline is extremely important. If you get stuck in a hole fleet sails around you."

Wind funnel

The straits of Gibralter are well known - and tend to funnel winds from the west or east, depending on what the weather is doing. With wind against tide, boat breaking conditions can result. It can be hairy. Timing is crucial, but really, at the end of the day, there is little a skipper can do to avoid a blast of east wind, except sail the boat in a masterly fashion.

Fortunately, the effect of these straits is limited to 25 miles either side of The Rock.

Homeward bound

The Mediterranean will be the deciding ground for this competitive fleet of trimarans

Campbell notes that the primary role for routers along this stretch is to keep in contact with the boat and prevent the sailors from falling into no-man’s land - the zone of less wind or, heaven forbid, no wind.

"We will stay inshore or offshore depending on the state of the sea breeze," he says.

Campbell notes that Bourgnon's Bayer is an older and heavier boat. That didn't stop this skilled team from smashing the 24 hour distance record for Open 60 trimarans during last year's Quebec to St Malo, but the reality remains that light airs will be trying for everyone involved.

"Were as fast as anybody in 15-25 knots, says Campbell, "but we're at a distinct disadvantage in light airs."

"The places where we will have problems is in light winds around the Azores and either side of Gibralter. Here, routing skills come to the fore.

"We can’t be losing ground in light conditions. We have to remain with everyone else."

A look at the weather

Atlantic jet streams
May 5, 1800gmt

This chart shows one jet stream flowing from east of Cape Cod and Nova Scotia to the west and north of Scotland. This stream has been the dominant storm track for the month of April.

Another jet stream flows from the east Atlantic over north Africa into the Mediterranean. Between these two streams lies high pressure, roughly centred over the Azores - the first 'mark' in the Challenge Mondial Assistance. This same high pressure cell extends a ridge to the north east, sometimes covering Scandinavia.

If this jet stream pattern remains past the May 12 start, expect the unusual high pressure 'footprint' to remain. If the northern jet moves south, forcing the ridge of high pressure away from northern Europe, expect the 'standard' synoptic situation to resume - and that includes the movement of frontal systems through the race course.

East Atlantic
Cloud and pressure composite
May 5, 00gmt

You can clearly see high pressure west of Spain ridging to the north-east over Scotland. The moors are bathed in sunshine while a cold funnel of wind is blowing from the north-east onto western Europe.

A 983mb low west of Iceland will be shunted to the north, steered by the jet stream as pictures above, which in turn is influenced by the powerful high (1028mb) over the Azores. Meanwhile, on the other side of the high in the Mediterranean, low pressure is forming bringing changeable winds underneath its region of developing cloud.

If this unusual synoptic situation remains for the Challenge Mondial Assistance, skippers will be reaching out of the English Channel with the wind at their backs before entering a large zone of light airs directly underneath the high.

Hot links for the east Atlantic:

The UK's met office offers terrific weather images and information, starting with this animated satellite image of the eastern Atlantic and Europe, updated every six hours.

Check out winds in more detail with isobars included, in this cloud and pressure composite image.

For an animated look at how winds behave, complete with colour-coded isobars, view this three-day animated pressure forecast.

View the east Atlantic in infra-red from the UK's met office.

Surface pressure for the eastern North Atlantic compliments of Ocean Weather.

Quickscat satellite derived winds for the east Atlantic:
Waters west of Great Britain including the English Channel and Bay of Biscay,
Waters from the Azores to Gibralter,
Waters of the northern Med and southern Med (detail here is poor).

24 hour forecast for Wind and direction in both the north and south Atlantic, thanks to the ocean modelling branch of NOAA. (forecasts use the AVN model). Also: 48 hour forecast, 72 hour forecast, 96 hour forecast.

Wind analysis from the University of Wisconsin showing surface, upper and jet stream - or water vapor - winds. As well, there are charts showing wind shear and upper level divergence. For the arm-chair sailor, the low-mid level infra-red winds tell an awful lot about the sea state where the boats are. Colour-coded arrows report wind strengths and direction at different levels. Remember: Friction at the surface slows the wind down a bit, so it will never be as strong at wave height as it shows on the 900hPa chart.

The University of Nottingham offers geo-stationary satellite information showing the east Atlantic and Europe/Africa.

The Aviation Weather Centre offers these terrific flight level charts SIGWX) which show the position of jet streams over much of the globe (mostly Northern Hemisphere). Because upper level winds, like the jet stream, steer our weather systems, knowing where these winds are and how they are behaving helps us to understand whether systems are moving east to west quickly or whether they will stalling because of a kink in the pipe-line.