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Jules Verne Trophy weather
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| by Sylvain Mondon |
| Weather expert ashore, Sylvain Mondon has exercised his science of routing at Météo France since 1993. |
The week's weather round-up - The sixth week at sea
The sixth week began along the northern edge of the zone of high pressure offshore of Argentina. Groupama 3 was still sailing close-hauled to gain ground to the North, as had been the case since rounding Cape Horn. Progress
at that time was steady with an average speed in excess of twenty knots. The wind lifted them slightly as it shifted temporarily
round to the West, even enabling a few bursts of speed at 25 knots, the likes of which hadn't been reached for some time.
However, further North another large obstacle was looming across Groupama 3's course.
Ahead lay a vast transition
zone with conditions alternating between very light winds and small, rather active stormy lows. It was offshore of Rio
that Franck Cammas and his crew entered this extremely tricky zone, where the wind was still predominantly N'ly. The first
low encountered was accompanied by gusts reaching 45/47 knots for 2 hours in heavy seas. After traversing the cold front of
this first system and finding themselves in milder conditions again, Groupama 3 made good headway to the North again at speed
(18/20 knots). The second system encountered on Thursday proved a lot less active and also a lot less organised. As such Franck
Cammas and his crew were forced to constantly adapt to the very changeable wind, both in terms of strength and direction,
though the prevailing wind was a light N'ly. Thanks to a vast amount of tack changes, they managed to extract themselves from
this zone on the evening of Wednesday 10th March.
However, it certainly wasn't the end of the close-hauled sailing
in light winds because immediately after the vast stormy zone, the next obstacle to be negotiated was already in position.
It came in the form of a ridge of high pressure from the Saint Helena High. Before they could claim to traverse it, they first
had to position themselves as best they could with the aim of limiting Groupama 3's exposure to the overly light winds as
much as possible. It's for this reason that Franck Cammas and his crew linked together another series of tack changes on Thursday
11th. This massive amount of effort was rewarded the following night since the ridge of high pressure was finally in the wake
of the giant trimaran which, though still sailing close-hauled throughout the day on Friday 12th, was beginning to accelerate.
The real relief came overnight on Friday, with the first signs of the E'ly tradewinds, which were slowly
shifting round to the SE pumping out 13/ 16 knots of breeze. Conditions became favourable for achieving much greater speeds
than those of previous days. The course towards the equator was covered at high speed with their angle to the wind enabling
them to choose where they would cross the equator. Shortly before crossing the equator (late morning on Sunday) Groupama 3
encountered a few residual squalls (the morning of Sunday 14th) which massively disrupted the tradewinds causing them to become
lighter and hence slowing the giant trimaran's progress to less than 15 knots. As such it was only the start of a section
making headway in fits and starts, which was to last through the whole of Sunday and into the night. However, this is all
part and parcel of the majority of passages through the Doldrums so you simply have to `make do' with what you get. After
making headway at speeds of between 8 and 30 knots for 24 hours, Groupama 3 traversed the fairly inactive Doldrums on Monday
morning as she reached 6 degrees North...
Franck Cammas and his crew were greatly relieved when the NE'ly tradewinds
began to kick in steadily at midday on Monday 15th March, thus enabling them to begin the final sprint to Ushant.
Sylvain Mondon
Meteorological Engineer
Marine weather forecaster
Météo-France
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