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these days. And routing optimization programs using customized boat performance polars do the math and guide our strategic decisions. Navigators just push the buttons and enjoy the ride. Right? Maybe not. There's a new weather map and an updated forecast every six hours, and you can't afford to miss even one update if conditions are changing. The GFS wind forecast A fast boat can ride a tropical depression for a thousand miles, is available at 5:00, 11:00, staying to the northwest of the center of the low for stronger 17:00 and 23:00 UTC. For wind at a better angle. a second opinion, the European global weather model, ECMWF, comes in at 7:00 and 19:00 UTC. For a third opinion there's NAVGEM, the Navy model, available at 6:00, 12:00, 18:00 and 24:00. The Navy also has a wave model, WW3, at 5:00, 11:00, 17:00 and 23:00. In coastal waters, the relatively new HRRR, "High Resolution Rapid Refresh," is updated every hour with thermal sea breeze effects included. And don't forget the new NDFD GRIB files, which show the GFS model as interpreted by human meteorologists. It's the GFS computer model passed through a human reality filter. Find the updates an hour after the unmodified GFS at 6:00, 12:00, 18:00 and 24:00. Sometimes you want the forecaster's version; sometimes you want the raw computer output because it might show a slight wind bend or other artifact in the model that the forecaster has smoothed out. So a navigator who is doing their job really needs to look at both. Plus recalibrating all the forecasts when the observed "ground truth" is not the same as the forecast baseline. Ocean current observations are also available for download. Fortunately for the navigator, the RTOFS model is only updated once a day, and the OSCAR current chart every five days. This is why the navigator never sleeps. Especially these days, with virtually round-theclock updates to feed into the routing software and inform the race strategy. This is also why I could
MAX EBB
ne would think that ocean race navigation has become much easier in the last couple of decades. GPS and instant position finding is the least of it. We have inexpensive satphone data links for email, and GRIB files for weather and wind charts with amazingly reliable forecasts. Even broadband connections are affordable for medium-size boats
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Latitude 38
• May, 2020
barely keep my eyes open when I turned on the laptop in the middle of the night. I had been sleeping with this computer as my pillow for the last couple of days. Fighting back the fatigue, I downloaded the 0400 PDT update and ran another routing optimization. We had jibed onto port to take the boat way south of rhumbline, hoping to latch onto a tropical low that was moving west at 16 knots. I was navigating a fast boat, fast enough to match the speed of the weather system, staying just north and west of the low for stronger wind at a better angle. It was risky — if we fell back behind the center of the low, the wind would be lighter and lifted, and we would be out of the race. But now we were back on starboard jibe, with a good wind angle, and moving up rapidly in the standings after taking a big hit during the port-tack detour to the south. The forecast update confirmed the motion of the low pressure system, the routing software agreed with my strategy, and I gave the watch on deck a new course to steer. I wanted to sail a little on the hot side of max downwind VMG. Actually, I almost never give a helmsman a compass course to steer. Much better to have them sail VMG upwind or downwind, or tell them to maximize boat speed on a hot reach. But this crew needs a compass course, so that would have to do till the next correction. Despite my fatigue, I could not resist checking the latest race standings: We had moved up to second place, pulling ahead of a huge fleet of boats! But one other boat had jibed south just a few hours before I had made the same move. Now they were a little farther south, closer to the center of the tropical low, on starboard tack and going faster in more wind. I attempted to go back to sleep, but then decided I had better check the NDFD forecaster-mediated version of the weather map, available in less than an hour at 0500 local time. The human forecasters might know just a little bit more about the likely track of the tropical depression than the computer model. I could not leave any stone unturned if we were going to have any chance of passing the lead boat. My alarm was set, but it was hard to sleep knowing that I only had 40 minutes to the next download. How did that other boat know to jibe south hours before I did? And how did I ever let this computer simulation of an ocean race take over my entire life? I typed "open chat
