11 May That Didn’t Work
That Didn’t Work
Well, that didn’t work. A spectacular failure might be an apt description. After 3 days of laborious effort getting north and east in conditions that ranged from near flat calm to near gales, I’m forced to give all the easting I’ve earned back as I’m blown dead downwind, rolling crazily in steep, dangerous breaking waves and 45 knot winds.
The weather model forecasts had called for SE 15-25 knot winds building gradually over 24 hours. As the front approached and passed over me some 30 hours later, a brief period of 30+ knots and then winds of SExS 25-28 for the following 12 hours. All well and good for getting north. Not easy, but doable.
Expecting the model forecast to get at least one of the either direction, strength, or to timing correct didn’t seem too much ask. I should have known better.
I was finally blown off my intended course last night with winds blowing East at 40-42 knots and gusting close to 50 some 12 hours before the forecast peak winds, Wind waves and swell were over the forecast height of 5 meters, very steep and breaking almost continuously. The secondary and tertiary swell, both running at 45 degrees to the primary swell but in opposing directions, was also large and breaking. To put it mildly, we were in the wrong spot at the wrong time.
If the above all seems rather academic and mundane, let me put some perspective on it. Hold on to your science hats for a bit:
Most would think to increase the force exerted by a 25 knot wind, the wind would have to blow at 3 times that strength, or 75 knots. Not so. The force exerted by the wind increases as the square of the velocity. A wind blowing at 25 knots exerts a force proportional to 25×25 or 525. A wind of 30 knots exerts a force proportional to 30×30 or 900. If you are still with me, you will see that the 5 knot increase from 25 to to 30 very nearly doubles the force. If the wind is blowing 40, the force exerted is proportional to 40×40 or 1600. That is more than three times the force exerted by a 25 knot wind. A relatively small increase in wind, especially at higher velocities, translates into a much larger force. The difference at sea is that the waves generated by a 25 knot winds cannot overwhelm the boat. At 40 knots, they not only can, but statistically will. Overwhelm is a very polite way of saying ‘turn Seaburban upside down’.
To put some perspective on the above bit of science and the model forecast, imagine if you ask the Minister in charge of the Canadian Department of Highways and Transportation how far is it from Vancouver BC to Calgary AB. You would like to go there over a four day weekend and restrict your travel to the trans-Canada highway. The actual distance is something like 800 kilometres or thereabouts. His official answer is ‘Well, it could be 800. Or 2400 kilometres. It’s either one or the other. But I assure, both are correct.’
If the model output misses the mark by a factor of three, it’s not just wrong, it’s a dangerous, glaring error. The difference for mariners is very far removed from academic or trivial. The model output is consistently wrong on all three primary factors (wind strength, direction, timing) and it’s a continual source of aggravation. This time, it has cost us dearly.
Chased most of the way from South Cape north and east by a severe gales and storms south of me and tracking east, gales are now dropping down on me from the north and, most curiously, parking themselves on top of me.
Not that anything or anybody is conspiring against me, but I feel a complex coming on…
Follow my tracks in real-time: