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Thread: Weather/Tactics Discussion (Part 2)

  1. #1
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    Default Weather/Tactics Discussion (Part 2)

    PART 2 CROSSING the GULF of the FARALLONES

    With the Golden Gate astern, a line between Pt. Bonita on the N side of the Channel and Mile Rock to the S marks the entrance to the Gulf of the Farallones. Both Bonita and Mile Rock have washing machine conditions close aboard, with square waves caused by tidal rips in their vicinity. They are best left at a distance of .25 mi or more on Race Day.

    However, .25 mi distance off from Bonita or Mile Rocks puts one very close to East and West Bound Traffic Lanes. And navigators must be alert for possible oncoming shipping and stay clear of whichever lane(s) is/are being transited.

    The Gulf of the Farallones begins with a shoal expanse of coastal water westward to the horse-shoe shaped San Francisco Bar. The San Francisco Bar Channel (Main Ship Channel) bisects the Bar and is dredged to a control depth of 55 feet. The Bar Channel is 2000 feet wide, and marked by eight buoys, (4 red, 4 green.)

    On the horseshoe shaped Bar, outside the Shipping Channel, the water depth is 20 to 30 feet less: about 25-35 feet over the North Bar, and 35 feet over the South Bar. This is shoal water indeed, and during Winter, Spring, and Fall, the SF Bar can break heavily and dangerously. Luckily for SHTP racers, the Bar rarely breaks during June-August, and can be transited with caution at any point outside the Shipping Channel, as long as the latent swell is 10 feet or less.

    Unless there is zero commercial traffic in the vicinity, SHTP racers really should stay out of the Main Ship Channel as far as the " Lightship." (The Lightship is no longer a lightship, but a large red/white navigational buoy marked "SF" where the pilot vessels hang out.

    Commercial shipping slows to steerage in the vicinity of the Lightship to briefly embark or disembark their pilots, using the NW, SW, or S designated traffic lanes as their approach or departure.

    Experienced local racers take advantage of an ebb tide by staying in the deepest water on the edges of the Channel, just outside the Channel buoys.

    If all goes well, the SHTP fleet should be in the vicinity of the Lightship, perhaps several miles south, at about 1500 hours.

    West of the Lightship, the heave of the ocean swell begins to be felt. It is 26 miles, 240 degrees m from the GG Bridge to the vicinity of the SE Farallon Island

    In most SHTP races, the Farallones are left to starboard at an approximate distance of 5-7 miles This is because an approximate course to Point A on the SE lobe of the EPAC High is around 225m.

    For practical purposes, until the building WNW afternoon seabreeze fills and one can steer a consistent 225m, the SE Farallon should be considered the “windward mark.” This is a better proposition than leaving SF Bay, turning left at Lands End, setting the self steering, and languishing in lighter airs near Pt. Montara overnight.

    Fog and low clouds predominate in the Gulf of the Farallones in June. The SE Farallon may not even be sighted. Bird and sealife in the area is plentiful. In the '08 SHTP a sealion came aboard FERAL for a visit, and Tom had to discourage the pinniped and defend his ship by snapping a foulie jacket.

    In the Gulf of the Farallones, ocean swells are topped with short steep wind chop any time the wind gets above 16-18 knots. If all goes well, the majority of the SHTP fleet should be south of the Farallones by dark, on starboard tack, with sheets beginning to be eased on a close reach., as they head for Pt. A, 450 miles, and 3-4 days to the SW.

    But not quite so fast. 25% of races from SF to Hawaii experience a "Southerly Surge" or reversal of the predominant NW wind in near shore waters. A "Southerly Surge" is a weather phenomenon that begins in Southern California, usually at the end of a heat wave, and migrates up the California Coast at a speed of 15-20 knots. It is characterized by stratus, low clouds, fog, and light winds from the SW through SE.

    Southerly Surges are very visible on satellite photos before the start. They are also characterized by rapid reversal of wind direction, from NW to S at coastal and near shore weather buoys.

    Southerly Surges were experienced at the starts of the '06 and '08 SHTP, making for light airs, even drifting as the fleet crossed the Gulf of the Farallones and beyond.

    The problem with a Southerly Surge event is Hawaii is dead to windward. Port tack takes you in the direction of Alaska, and starboard towards Mexico. Some racers in Southerly Surges have passed Pt. Reyes close aboard. Others have seen the lights of Half Moon Bay.

    The influence of a Southerly Surge can be felt for several hundred miles, as far west as 124-125 W, where a transition to the normal NW gradient wind from the NW is made.

    What to do if a Southerly Surge is occuring or in the forecast?

    First, know that your race will be slowed by 1-2 days at the outset, and shipping extra water before leaving the dock may be a prudent call.

    Second, put on your light air thinking cap, toilet paper telltales, and hand steer as much as you can. Because most autopilots and windvanes will not respond well to the light and variable winds of a Southerly Surge.

    Lastly, get West as fast as possible, because a Southerly Surge will eventually dissipate, usually beginning from the north and extending to the south. Boats positioned to the north and west usually will get the new wind first.

    GAME PLAN for crossing the Gulf of the Farallones: When leaving the Golden Gate, consider the SE Farallon Island the windward mark until such time as a course of 225m can be made. If the forecast is for NW winds 10-20, or 15-25, initially be on the north side of the Main Shipping Channel to meet this wind first. Be alert for shipping in the Gulf of the Farallones. If a Southerly Surge event is occuring, all bets are off and timing is going to be delayed.
    Last edited by sleddog; 05-24-2010 at 08:01 AM.

  2. #2
    Join Date
    Sep 2007
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    Hi Skip,
    Much more complex than what I *should* have done in 08 which was to follow you. Andy Hall told me I should do that and I didn't listen. :-)

    Thanks for taking the time to do this for all of us. It's a fitting tribute to Wildflower. You and she will be sorely missed in Hanalei Bay!

    John
    Dream Chaser

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