Skippers preparing to leave Saint-Malo for the Route du Rhum face an unwelcome complication this week: a rapidly deepening depression named Austen is on course to collide with the start area just as the fleet looks to get away.
Wednesday brings an unstable westerly flow across the start area, with an active trough generating strong gusts as squalls sweep through. It's an unsettled picture, but nothing compared to what follows.
Thursday looks more serious. A disturbed south-westerly flow will build ahead of Austen, which is deepening rapidly over the near Atlantic. At 1200 UTC the depression sits 400 miles west of the Brittany coast, already down to 987hPa.
Overnight Thursday into Friday, Austen keeps intensifying. By the middle of the night it has dropped to 978hPa, parked south of Cornwall, with the wind swinging south to south-westerly and turning stormy over the Brittany headland and the entrance to the Channel. The storm reaches all of Brittany's north coast by the end of the night, bearing the brunt first.
Friday itself stays stormy. South-westerly to westerly winds dominate under Austen's influence, now at 980hPa and centred, by midday, off the south-west coast of England, over the eastern Channel.
A drop from 987hPa to 978hPa in roughly 12 hours marks genuinely rapid intensification, exactly the kind of development race meteorologists watch most closely when a fleet is about to cross open water.
For a fleet gearing up to leave Saint-Malo, this is far from an ideal forecast window. Skippers and router teams will be watching Austen's track closely over the coming days, since even small shifts in her path could reshape the start-day routing calls for both the IMOCA and Ultim fleets.
