it was apparent that the weather pattern in the Pacific was unusual this year. The classic (normal) route from Victoria to Maui is usually to sail parallel to the western US coastline at ~100 NM to 200 NM offshore to about
San Francisco, turn right around the southern end of the Pacific high and catch the trade winds all the way to Hawaii; basically one long spinnaker run. This year, however, several of the earlier routes predicted by Expedition - who has now been renamed by us Hal 9000 Mk II - showed String Theory taking a much more northerly route to Hawaii. Some route options were almost completely above the rhumb line (the rhumb line is the shortest route between two points on a curved surface) between Victoria and Hawaii and others crossed back and forth over it. Some of the northerly routes would require the use of white sails to beat upwind almost the entire way. Based upon historical knowledge of past Vic-Maui races, such routes are very rare but as race day grew closer, it was
apparent that the option of taking such a route was a real possibility for this year's race.
The phenomenon that was causing the unusual weather patterns in the Pacific was the presence of two (and actually sometimes three) smaller high pressure systems over the north Pacific instead of one very large one. The normal (classic) route is the way it is because the one large high pressure system over the northern Pacific establishes the latitude of the trade winds AND creates a dead wind zone over the rhumb line. But with two smaller high pressure systems over the northern Pacific, their predicted location was such that the southern high pressure system would push the trade winds further south than usual this year and the presence of a second, more northerly high pressure system, would create a path between the two high pressure areas that happened to be more-or-less in line with the rhumb line (i.e. there is a path between the southern high pressure system and the northern high pressure system).
In the weeks leading up to race day, Hal predicted several "optimal" route options for String Theory as the daily weather forecasts changed. And while Hal may have determined that one of the optimal route options for String
Theory was to take the path between the two high pressure systems - particularly given that to take the classic route this year would require traveling much further south than usual - Hal couldn't be expected to know that the two high pressure systems are unusual and that there was a strong possibility that they could either a) collapse into each other and form the "normal" single large high pressure system or b) shift over-top of you.
If the two high pressure systems were to collapse into the single large system while you're trying take the path between them, you'd be caught in the middle of the newly formed large high pressure system; likely for days,
with no wind at all. If they shifted over-top of you, you could find yourself either in the middle of a high pressure system or in the no go zone between the two high pressure systems. And even if the two high pressure
systems don't collapse or shift, the winds generated at the edge of a high pressure system are relatively weak and String Theory is not very competitive in light air; particularly when compared to some of our competitor's boats which are smaller, lighter, or both. But at some point during a passage between the two high pressure systems, String Theory would likely be facing a stretch of light winds; possible for days.
By race day, Hal was still sometimes predicting that a path between the multiple high pressure systems would be an option for an optimal route. So the choices facing Team String Theory once we were out of the Juan de Fuca
Strait were 1) do we take the more conservative, but much longer, classic route which would takes us south of both high pressure systems, or 2) do we take our chances and try to follow the narrow path between the two high
pressure systems which, while riskier, is shorter. Because of how dependent on the weather forecast this decision was, this was a decision that Gunnar planned on making in real time once out of the Juan de Fuca Strait and on our way south.
Of course, since you're all probably watching our progress on Yellow Brick Road, you know that we chose to take our chances and take the path between two high pressure systems. In fact most of the fleet appears to have chosen to do the same thing with various degrees of success. What's not so obvious from watching our path on Yellowbrick, though, is why we're one of the more northerly of the boats taking this path. It really comes down to Hal's recommendations, which, as mentioned previously, are updated at least twice a day using our actual boat position, the latest weather information, and Gunnar's experience and intuition.
Because high pressure systems in the northern hemisphere always turn clockwise, the winds where the two high pressure systems meet will be going in opposite directions and therefore will be extremely variable, quite confusing, and generally not very strong (i.e. there is a no-go occlusion zone in the middle). It is not a place you want to be if you're trying to win a race in a sailboat. So really, the path between the two high pressure systems is actually two different paths. One path is to skirt the southern edge of the most northerly high pressure system, the second is to skirt the northern edge of the southerly high pressure system. The advantages of the more southerly path is several: 1) for the specific characteristics of String Theory (types of sails on board, hull design, etc.) it is the route that Hal has consistently predicted will be an optimal route for String Theory, 2) it is the shorter of the two possible paths and therefore you minimize the time you spend traveling between two potentially collapsing or shifting high pressure systems, and 3) it puts us in a good position (more specifically a good wind angle) for the sail into Lahaina. The downside of skirting the northern edge of the southerly high is that
String Theory would be beating into the wind - a slower and rougher ride - rather than on a spinnaker run if the route that skirted the southern edge of the northerly high were to be the one taken.
And to complicate things just a little bit further, Hal's predictions are time sensitive. The end result of all of this is if we don't travel as far as Hal predicts we should for a given course or we don't track the course as well as Hal needs us to, we could find ourselves arriving at a way point that no longer has the wind speeds or wind direction we need to realize the benefits of the optimized route chosen by Hal. We could also find ourselves losing more ground than predicted against our competitors who are better able to take advantage of light winds generated at the edges of the high pressure systems. Hence the title of this blog entry, Threading the Needle.
As this blog entry is written, we're now about halfway through our traverse between the heart of the two high pressure systems, and as predicted, the wind conditions to get here (i.e. skirting the northern edge of the
southerly high) were very light. As you've no doubt seen on Yellowbrick, our progress was very slow and it was an extremely painful ~24 hours on String Theory. Mike had been practicing his noose knots and slyly looking towards the top of the mast. If our attempt fails we're not sure that Hal will make it out alive...We know from the most recent 17:00 roll call results that we've lost ground to almost all of our competitors. However, Hal is still
predicting that if we continue to believe in his predictions and we continue to sail the most optimized path we can, given the latest weather forecasts, stronger winds are in our future when we start to pass through the two systems. Gunnar hopes that because of our choice to follow a path that took us closer to the no-go zone between the two highs as compared to the rest of the fleet, we'll see the stronger winds a bit before the rest of the fleet to the south of us and thus the (relatively) short term pain we've just experienced in the stretch of light winds will pay off in the long run. Because we only receive updates twice per day about the location of the other race boats, by watching the progress of the boats on Yellowbrick you'll probably know before we do if our gamble has paid off.
Signed: Boats Are Never As Noisy As Busily Racing Each Active Day