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It seemed a good idea at the time! Perfect plan foiled as blocking weather pattern fades August 5, 2000 Since the start of the Quebec to St Malo race on July 30, sailors have had to deal with a blocked summer weather pattern. Jet stream and mid level winds aligned to trap surface features in place, in particular a blocked high west of Portugal and a mid-Atlantic low pressure cell east of Newfoundland. Strategic sailing Yesterday fleet leader Groupama, skippered by Frank Cammas, relied on the brilliance of Belgian navigator Marcel Van Triest to risk a more northerly route, beating into gentle easterlies rotating off the top of a weak low pressure cell mid-Atlantic. It appears they planned to sail north of that low, through a warm front and into westerly winds rotating around the top of a blocked high pressure cell, centred to the west of Portugal. The plan seemed water-tight. The blocking situation had been building for days and there appeared to be no end in sight. Once Groupama sailed into the westerly winds associated with the high, it was clear sailing, downwind, towards Brittany and St Malo. August 4, 0000GMT:The horseshoe-shaped cloud band, incorporating a warm and cold front, is a good sign that the jet stream is traveling a convoluted path. It would make sense to sail over the top of this mess, as Groupama tried to do. Image courtesy of Intellicast. This jet stream map for August 4 0000GMT, shows the strange path of winds aloft. It is easy to see how a low pressure cell east of Newfoundland and a high west of Portugal can remain in their positions with the jet stream corralling them from above. Image courtesy of the Aviation Weather Center. Extreme risk Meanwhile, Biscuits La Trinitaine, skippered by Marc Guillemot with routing advice from Pierre Lasnier of Meteomer, dove south - a seemingly extreme and ludicrous gamble. Sure, they would be sailing with eased sheets, as winds around the low turned north then north west. Tail winds would give them better speed, but if the low remained stationary, getting through its stalled frontal cloud band would prove a problem and any ground gained would be lost. Once through the trough of low pressure, another problem could have reared its head: The high west of Portugal stood between those yachts which took the southern route and St Malo. There would be no point sailing through the high because there's no wind in the centre of such a system. Yachts would have to sail around the high, which translates into more distance and time. What happened? Someone had good advice, because that blocking situation has deteriorated within 24 hours, and the subtropical High is filling in strongly behind a band of low pressure along the US eastern seaboard. The result? Biscuits la Trinitaine gained from downwind sailing early on, and never had to pay the penalty of navigating through a stalled frontal cloud band. Smart stuff! Keep an eye on the competitors at the Quebec to St Malo official web site August 5, 1800GMT: Where's the blocking situation here? Looks like Groupama has been tricked, while Biscuits la Trinitaine made huge gains. Image courtesy of the Aviation Weather Center. August 5 0000 GMT: The convoluted jet stream is fading fast and now North Atlantic weather systems will resume their march eastwards. The sub-tropical high east of Bermuda looks like it is filling in, and could bring westerly winds right across the Atlantic. Image courtesy of Intellicast. More great reading:
Useful sailing sites: www.transat2000.com - The official home page for the Quebec to St Malo trans-Atlantic race. www.kenwoodcup.com - the official home page of the biennial Kenwood Cup competition in Hawaii. www.sail-online.com - news and information with a French flair. www.sailingworld.com - news from the publishers of Cruising World and Sailing World magazines. © weather-wise.com 2000 |