This by itself is not such a big deal. However, you will recall that we’ve been mentioning those really big northwesterly swell sets on the port stern quarter? Well, those are crossing these head seas at right angles. The result is a very confused sea-state, with extremely steep occasional peaks.

It is very hard to photograph these waves. Catching them at the right time, through the saloon windows, is a matter of chance (or maybe skill in the case of the good photos). That peak you see above in the background is probably on the order of 15 feet (4.6m).

We’ve been experimenting with different speeds. Running at 9.25 to 9.5 knots – engines turning 1900 RPM – seems to be the best compromise. We’ll go relatively smoothly for a couple of minutes, and then hit one of these crests.

Most of the time when we hit, it looks like this. Not much impact and very little water on deck.

Every few minutes we hit something in the range of 6 to 8 feet (1.8 to 2.4m) just wrong, and then it looks like the photo above. Still not too bad. Without those big swells from the northwest, this would be the extent of it.

But when the northwesterly swell, northeasterly wind wave, and our bow meet in the same space at the same time, the photo is more impressive!

The surprising thing is that speed drops at the most half a knot, and usually less. The main noise we hear is the anchor hitting, rather than the bow itself.

As you probably know, we spent a lot of time modeling various upwind scenarios. Using tank testing and CFD analysis, one can come pretty close to the real world with single sets of waves. But when you have complex crossing situations, as we are in right now, most of the design input comes from experience. There is no accurate way to model what we’ve been going through.

And while we’d rather have it calm, these conditions, which do not often occur (we obviously try to avoid them), provide a wonderful opportunity for us to accumulate data with the array of accelerometers which are tied to the computer. These quantify what we feel as we change speed, wave angle, and even displacement.

The data shown above is for running at an average speed of 9.7 knots through the water. This is what is looks like most of the time.

Here is what he occasional "Big Bang" looks like. Notice the sequence of three large spikes? That is a series of large, closely spaced waves of about 10 feet (3m) in height with a fetch between the crests of at the most 30 feet (9m). They are actually breaking a bit on their crests.

Long after these hours of unpleasantly confused waves have receded from our memory, we’ll be studying this data.

One of the big variables is always the correct speed. Ideally, we want to go just fast enough to push the bow from the first wave into the next crest, before the bow has a chance to drop into the trough. However, with confused sea states, choosing the correct speed is often a question of the lesser of various evils. We have experimented with slowing down to see if we could find the equivalent of heaving to in a sailboat.

This is the data from minimum continuous revs – 1200 RPM – running at 6.5 knots. Vertical accelerations are down, but the stabilizers are not as effective dealing with transverse waves, so the side-to-side and rolling accelerations are up somewhat.

In the end, we find it preferable to maintain a speed around 9.5 knots, with the occasional banging, and get through this patch of water as quickly as possible.

On the other hand, if we felt that slowing down for a period of time would allow this weather to pass, with more favorable conditions some hours (or days) in the future, we might be tempted to heave to and just hang out for a while.

Twelve hours later, and the 22 knots of wind is now down to 14. The seas are dropping off, an there’s more fetch between the crests. However, that northwesterly crossing swell is still with us (and will be until we close with the coast), so motion is somewhat more than we prefer. The barometer is up from 1021mb to 1025 in this short space of time, so we must be approaching the center of the high. Boat speed is up to 10 knots on the GPS.

Dinner last night was lamb stew over pasta. The stew went into the freezer back in early July and now, almost four months later, it tastes really good.

The big news is that for the first time since leaving New Zealand we are using the heater (heat is actually being supplied from the engines rather than the boiler).

Weather wise, it is looking like we’ll have head winds for another day or so, and then the breeze should go more on the beam. If we’re lucky, it may even go behind us the last day pr two. We’re keeping our fingers crossed.

Before leaving Hawaii we discussed with Rick Shema various timing options. Rick’s initial suggestion, based on our wanting to get home, was to leave Sunday. As it turns out, that would have been a good call. The breeze would have been lighter getting away from Oahu, and we’d be 300 miles further down the track, very comfortable in the center of the high that is bringing us head winds right now. We were not quite ready to leave, so we put it off a day. Mistake on our part.

Rick’s second option was to wait until towards the end of the week to leave. The long-range models – GFS and NOGAPs – were both showing the high pushed down and favorable frontal activity. Looking at the MPC fax charts for surface and 500mb this morning indicates Rick’s take on the models was right on. Of course, looking out five days has a lot of inherent risks. But in this case, we would have had a more comfortable and quicker (by a day) passage. On the other hand, as we said earlier, we’re now collecting some valuable data, which we would have otherwise missed.

Another few hours and we’ll be at the halfway point. Just 1250 miles to go as this is being written.