By Talbot Wilson
Newport RI, June 18, 2014— Tacticians, navigators and skippers in the Newport Bermuda Race have choices to make in deciding the fastest route to Bermuda. The straight — rhumb line— course is the shortest distance between two points, but it may not be the fastest. Two choices could determine victory or defeat. Will the wind or the Gulf Stream current be more important? The choice must be made before the race starts Friday.
For more than forty years Frank Bohlen has studied ocean and near-shore currents. Since 2002 he has prepared detailed analyses of the ocean between Newport and Bermuda in the months prior to this race. In his recent online tutorials on the race website, he has described Gulf Stream development using images from NOAA and other sources, found at Gulf Stream Tutorials.
How will the Gulf Stream current flow? Dr. Bohlen commented on the Gulf Stream choices this week. “The Gulf Stream in the vicinity of the straight line Newport to Bermuda route (the rhumb line) has been dominated by a deep meander. The meander has remained nearly stationary and deepened causing the direction of the flows in the main body of the Stream to rotate clockwise to a nearly northwest to southeast flow essentially paralleling the rhumb line for a distance of about 180 nautical miles.“
“The few shots of surface sea water temperatures that have been obtained recently suggest that the meander is the process of “pinching off” favoring formation of a cold core ring south of the main body of the Stream, increasing the development of the warm core feature north of the Stream near the edge of the continental shelf and redirecting the main body Gulf Stream flows to a southwest-northeast course crossing the rhumb line approximately 240 nm from Newport.”
“If this remains unchanged, the Gulf Stream will have little direct influence on optimum course selection. At the moment the warm feature north of the Stream favors a near rhumb line course from Newport to south of 39o N with a slight bias to the west to accommodate some amount of easterly set through the main body of the Stream. The Stream near the rhumb line is approximately 60nm in width with flows proceeding south to north east of the rhumb line.”
“To the south, the westerly edge of the cold core ring presently centered to the east of the rhumb line is in close contact with the rhumb line. This favors a direct course to Bermuda. The ring is expected to drift slowly (2-3 nm/day) to the west so that some additional course alteration to the west may be necessary to take full advantage of the ring currents. The combination of these Gulf Stream current features favor a course west of the rhumb line, with exact details dependent of boat characteristics and wind speeds and directions.”
Which way will the wind blow? When considering how long-term wind shifts, happening over three or four days, will determine their course to an island 635nm away, a racer’s mantra is ‘sail fast to the new wind’. Ken Campbell of Commander’s Weather shared his insights on wind with the Bermuda Race Organizing Committee as of Tuesday morning, four days before the start.
“For 2014 there are similarities to the 2002 race.” Campbell wrote. That year, a strong Gulf Stream meander ran into the face of a similar strong wind, creating very rough seas.
“Strong southwest winds are expected late Sunday night and Monday which will cause very rough conditions on the Gulf Stream. This should primarily affect the smaller yachts. The larger yachts will probably be in the strong SW winds, 20-30+ kts, for a shorter period of time and should be generally out of or getting out the Gulf Stream by then. It will be a very active weather pattern for late June”
“For the start day, sunshine and light north winds Friday morning will glass off [decline] in late morning and then fill in with a light south-southwest sea breeze during the afternoon.”
There are two low pressure systems coming, Campbell noted. Looking at the lows from Tuesday morning, he predicts the first should reach the coast Saturday morning and then move out to sea and pass south of much of the fleet. Winds should become east to northeast. The strongest winds should be late Saturday and Saturday evening, when 15-30kt wind is possible for the larger yachts in the fleet. The very northern tip of the Gulf Stream will be rough, but the southeast meander will be perpendicular to the wind, so not that rough.
Sunday should be the transition day from the northeast to east winds to strong southwest winds. The second low pressure system should move off the New Jersey coast Monday morning. Strong southwest winds should spread from west to east and southwest to northeast across the fleet. Southwest winds 20-30+ kts on Monday could impact the smaller half of the fleet the most. If they are still in the Gulf Stream,it will be a rough ride for the smaller yachts. Southwest winds should back and diminish for the approach into Bermuda for the smaller yachts on Tuesday and Wednesday,” Campbell concluded.
Skippers make their choices. With a current that favors west of the rhumb line and weather coming from the west, tacticians, navigators and skippers look at their choices. The race to Bermuda is in four parts— Newport to the Gulf Stream, the path through the stream, the exit from the stream to about 50-70nm from Bermuda and the final approach through the often fickle ’happy valley’ to the Bermuda finish.
This discussion was based on the current and wind observations and a forecast on Tuesday, June 17. All could change by the time the racers make their final commitment. Which way will winners go? Follow them starting Friday afternoon on Pantaenius Race Tracking to see if your choice is a winner or not.