Using the GFS model grib file that I downloaded on the morning of Nov 1, using RNS to animate sailing down the rhumb line (RL) from Newport to Bermuda, starting from a hypothetical departure time of 1000 on Tuesday Nov 1 --roughly when the NARC departed, and assuming an average SOG of 8 knots, the animated forecast shows that a 1007 mb low is forecast to cross the RL about 320 nm SE of Newport at around 5pm later that day (Tuesday), generating a large region of NE40. Leaving as we hypothetically would have, on the back side of that low, the animation reasonably predicts that we might experience winds increasing above NE30 where we’d be on Wednesday morning and peaking on Wednesday night to the mid to upper-30s –strong but fast reaching conditions. The low was forecast to scoot off to the ENE before we get there. Strong boat? Seasoned crew? Let’s go!
But... the grib also forecasts that it will leave behind 5-6m seas (16-20 ft.), as a region of 6m seas forms over the Gulf Stream (GS) around 0700 on Wednesday, moves slowly SE with us and subsides to under 5m by noon on Thursday. Imagine a forecast for 16-20 ft wind-driven waves from the NE in the region of the GS flowing in the opposite direction. Those would be two-story walls of water parading toward us from the port beam. That mess might take a few days to clear up once the low passed. If the low intensifies or slows down relative to the forecast, then we’d be in even stronger winds and higher seas. In fact the model released on the next day (Nov 2) shows the low to be deeper --1004 mb, moving more more slowly --crossing our RL early Wednesday morning, with stronger winds--in the mid-40s. Let’s wait.
Other sources of weather information saw it coming earlier. On October 31, the NWS Discussion web site advised that a storm would “bomb” off of Hatteras on Tuesday November 1. We all expected the NARC to hold up beyond Nov 1, or come down the coast to the Chesapeake.
But... the grib also forecasts that it will leave behind 5-6m seas (16-20 ft.), as a region of 6m seas forms over the Gulf Stream (GS) around 0700 on Wednesday, moves slowly SE with us and subsides to under 5m by noon on Thursday. Imagine a forecast for 16-20 ft wind-driven waves from the NE in the region of the GS flowing in the opposite direction. Those would be two-story walls of water parading toward us from the port beam. That mess might take a few days to clear up once the low passed. If the low intensifies or slows down relative to the forecast, then we’d be in even stronger winds and higher seas. In fact the model released on the next day (Nov 2) shows the low to be deeper --1004 mb, moving more more slowly --crossing our RL early Wednesday morning, with stronger winds--in the mid-40s. Let’s wait.
Other sources of weather information saw it coming earlier. On October 31, the NWS Discussion web site advised that a storm would “bomb” off of Hatteras on Tuesday November 1. We all expected the NARC to hold up beyond Nov 1, or come down the coast to the Chesapeake.
Here is the GRB model forecast for Nov 5 for wind and wave, as viewed on passageweather.com, issued on Nov 5.
That was the first gale that whacked the NARC fleet. When does the the GFS model first predict the second gale they hit –the one that became Tropical Storm Sean and that caused so much loss? Not until Wednesday morning, November 2, the day after the NARC left!!
- The GFS model grib issued on Tuesday Nov 1 (when the NARC departed Newport) showed a 1013 mb low moving off the coast at Charleston SC on Friday Nov 4. That’s weak. Further, it forecast that low would drift SE then dissipate as a massive 1032 mb high builds along the mid-Atlantic coast east of the Delmarva peninsula. It predicted that by Monday Nov 8, a massive 1028 mb high pressure ridge is set up all the way from Hatteras to Bermuda. The GFS model didn’t yet offer any reason to worry.
- The grib issued on Wednesday, Nov 2 shows the low drifting off of Charleston on Friday morning at 1007 mb, then drifting to the SE and dropping to 1002 mb by midnight. Not good. This low is blocked from moving NE by the massive high pressure ridge running off the Delmarva peninsula. So it will sit out there near our rhumb line over warm water and build nasty seas in its NW quadrant along Cape Hatteras, in the Gulf Stream. (Hear alarm bells ringing.) Already by Nov 2, those of us waiting to depart from the Chesapeake around Nov 7 expected to delay.
- The grib released on Thursday, Nov 3 strengthens it to 1005 mb as it comes off the coast on Friday morning, dropping to 1001 mb by midnight.
- The grib released on Friday, Nov 4 is unchanged, but drops the central pressure to 1000 mb by midnight.
And on and on. Since the NARC had access to weather forecasts from their fleet meteorologists, and since most boats likely could download grib data from satellite or have one of the satellite weather services or pick up their satphone and chat directly with a real meteorologist at a forecasting service, starting already on Wednesday folks must have been thinking about a possible second gale to their south. Depending on when you were where, and how you were doing with the first gale, some boats faced a growing painful decision to endure going SE to Bermuda, or head back to the coast.
On the morning of November 8th, the low was named Tropical Storm Sean. Finally,on November 11th just as the seas were easing off of Hatteras, the gate opened and Heron, Freestyle, the Salty Dogs fleet and the Caribbean 1500 fleet departed Hampton for the islands.
On the morning of November 8th, the low was named Tropical Storm Sean. Finally,on November 11th just as the seas were easing off of Hatteras, the gate opened and Heron, Freestyle, the Salty Dogs fleet and the Caribbean 1500 fleet departed Hampton for the islands.
So to conclude, Baltimore shouldn’t have missed the field goal, and the game should have been settled in overtime. One more post about November and I'll move on. I promise.
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