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Thread: Weather/Tactics Discussion (Part 1)

  1. #1
    Join Date
    Sep 2007
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    Default Weather/Tactics Discussion (Part 1)

    PART 1: EXITING SF BAY

    Wi-Fi Internet access is available in the vicinity of Corinthian Yacht Club, an invaluable tool for pre-race GAME PLANNING.

    PassageWeather.com gives winds, sea, and pressure forecast charts in vivid color out to 7 days, (remember to subtract 7 hours from UTC for local time.) The Farallon Islands have a webcam which also gives current wind speed (add 7 knts.) and direction. With many weather tools available, and pre-race distractions walking the CYC docks, GAME PLANNING can become overwhelming. The key is keeping it simple, writing in a notebook, and not getting too far ahead.

    Weather forecasts, quite reliable inside 72 hours, begin to degrade in reliability outside 3-5 days. Routing programs and suggested courses from professional services, though helpful in seeing the big picture, can be misleading and take competitors too close to the EPAC High.

    With prop shafts sealed, CYC graciously offers towing to all boats the morning of SHTP start. Smaller boats may chose to sail off the dock. Starts will be on an ebb tide, three hours before slack current at GG bridge (1410), and six hours before max flood (1715). This tide cycle nicely avoids beating into a building flood tide in late afternoon.

    SHTP competitors unfamiliar with the race course from the CYC start as far as Mile Rock/Pt. Bonita, should practice navigating that area. Clearing SF Bay and its obstructions, traffic, wind and tidal zones is not trivial. Equally important, a small separation of boats in the first 10 miles can accordion into hours, even days of advantage at the Finish. Not being clear of land by nightfall can make for a long first night at sea as the afternoon seabreeze dies at sunset near shore, and fades westward into the Gulf of the Farallones by midnight.

    There is significant snow melt runoff this year. This freshwater runoff increases the surface ebb tide, and delays the flood tide. The fastest outgoing (and most favorable) tide will be in the choppiest and muddiest (brown) water, in contrast to flood tide, which is more green/blue ocean water.

    Deeper water will have more favorable ebb current until at least 1430 hours. A depth sounder is a good tactical tool early in the Race. Visually, tide lines can be quite distinct. Race day's ebb tide will have the effect of increasing apparent wind by several knots as boats are set westward.

    Inside SF Bay, the SW-W seabreeze begins to build by 1100., reaching max velocity of 20-25 knots or greater between 1300-1600 hours. The most wind will be just E of the GG Bridge where land narrows the channel and funnels the wind and current.

    Outside SF Bay, the afternoon sea breeze builds a little later and can often seen as a whitecapped windline approaching from the NW. The seabreeze veers from SW to W during the afternoon, favoring boats north of the Bar Channel on the inside of the lift.

    Although June can be the windiest month inside SF Bay, the inboard (N) end of the CYC start line lies in the lee of Belvedere Peninsula, resulting in light and swirling winds in this area. Consider starting near the outboard (southerly) end of the line, which is closer to the building windline funneling in through the Golden Gate, and in more favorable tide.

    Due to the ebb tide, if it is light wind at the start, racers run the risk of being swept across the line early. Be sure to make a pre-start current check at the outboard end inflatable starting buoy. A range transit on the CYC flagpole and clubhouse in the background can be used effectively to tell when one is near or on the start line.

    Just south of the start line, Angel Island is steep-to on its north and western shores. Lighter winds and starboard tack headers are found close aboard Angel Island as the westerly seabreeze lifts up over Angel.

    From the Start, if not laying Angel Island on starboard tack, would suggest sailing closehauled up to Pt. Stuart before tacking to port. This has the benefit of catching the (ebb) tidal race in this vicinity and being set boldly to windward. Again, practice will pay dividends. Especially if practice sails are made during similar tidal cycles to the morning/afternoon of June 19.

    Crossing SF Bay, the wind is likely to make up quickly, catching the unaware with the wrong sail combo. The first jib change/reef, shortly after the start, with the lee rail awash and spectator traffic photographing from close aboard, is not a pleasant prospect. But should be anticipated.

    Outside the GG there is often less wind, more lump, more low clouds and fog, and lower visibility, leaving competitors initially overdressed and underpowered. A friend with a cell phone, stationed on the Marin Headlands or Lands End, can give wind, sea, and visibility reports to competitors before the preparatory signal. Again, no private weather info may be received from shore after racing commences, not even "Honey, its windy out here, I'm freezing, and I can't see you!"

    Commercial shipping, inbound or outbound, will cross the SHTP fleet at some point early in the Race. Although Bar Pilots and the Vessel Traffic Service (VTS) will be aware of the outbound SHTP Fleet, COMMERCIAL SHIPPING HAS RIGHT-OF-WAY AND SHTP RACERS MUST STAY CLEAR. In addition, COLREGS Rule 10 states that "so far as practicable, a vessel shall cross a traffic lane on a heading as nearly as practicable at right angles to the general direction of traffic flow."

    Anticipation is key.

    VHF Channel 14 is used by VTS for all commercial vessel movement within SF Bay. VHF Channel 12 is used by VTS for shipping in the three coastal traffic lanes and within a six mile radius of the "Lightship" (San Francisco Sea Buoy.)

    Updates on ship movements outside SF Bay are given at 15 and 45 minutes after the hour by VTS on VHF 12. What will be heard is commercial vessel name, bearing and range from the San Francisco Sea Buoy, course and speed, and ETA information. AIS also is an invaluable tool near shore. But AIS is visual rather than audible, and likely requires going below into a darkened and bouncing cabin to see what's coming.

    Inbound commercial shipping, after picking up a pilot near the "Lightship" will be coming down the narrow and buoyed Bar Channel at speeds 12-20 knots. Commercial ships passing abreast constricts the Channel further.

    Inbound shipping slows to 12 knots in the vicinity of the Golden Gate Bridge and crosses under the GG Bridge near Center Span. Inbound shipping then generally stays on the City Front (SW) side of the Bay.

    However, Inbound ships sometimes transit the "North Channel" between Alcatraz and Angel Is. if they are very deep draft or headed "Upriver." To see which side of the Bay inbound traffic will use, watch which way the stern is moving as the ship passes under the GG Bridge.

    Outbound Shipping leaves Alcatraz to port, Harding Rock Buoy to Port, and Angel Island to starboard, before turning to port for Center Span of the GG. Outbound shipping in the Bay will be traveling at speeds to 12 knots, before accelerating to full speed once under the GG.

    High speed passenger ferries and chubby Red and White tour boats have sail savvy captains, and will attempt to stay clear of SHTP racers. Tug and Tow are wildcards, often slowing to adjust towlines in SF Bay Approaches. Tugs without tow shepard all transiting tank ships, and these tugs are usually positioned close astern of the ship. Pilot Vessels are orange. Close encounters with slow moving or stationary fishing vessels should be avoided at all costs.

    Suggested reading is USCG's Vessel Traffic Service San Francisco User's Manual, available at http://www.uscg.mil/d11/vtssf/vtssfum.asp

    GAME PLAN recommendation for Exiting SF Bay on Race Day is: In ABSENCE OF SHIPPING, stay in deep water in center Channel for best ebb, and away from bays near the shoreline, where the early flood will be. IN PRESENCE OF SHIPPING, stay out of the Channel and well clear.

    The start will likely be in light airs and wide variations of wind direction/speed near the start line will likely prevail. Don't be early, don't be late. Be prepared for building breeze after 1100.

    And keep jib sheets clear and flaked so as not being caught aback in an unplanned tack thrown at you by the South Tower Demon, and his brother who lives over at the North Tower of the Golden Gate Bridge.
    Last edited by sleddog; 06-05-2010 at 07:21 AM.

  2. #2
    Join Date
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    Another great write up! I've become familiar with the area in the past few months, yet still found several new tidbits of knowledge. Thanks Skip!

  3. #3
    Join Date
    Sep 2007
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    San Mateo
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    This is great stuff Skip. Thanks. Makes me wish I was going.

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