Current Atlas for San Francisco

[Liquorice]

6 of us are sailing San Francisco bay in late March.
We've got 2 x J-80's chartered with J World in Jack London Square.

This is for all those sailors who are based in San Francisco:
I've got tide tables on my iPad but what about a current atlas?
Should I be concerned about current? - I suspect yes!
Can someone point me in the direction, either on line or book with current predictions that I can use for planning purposes?
These J-80's don't have motors and I'd like to be able to get back to the bar every evening!!!
sam :-)
(...and if anyone has suggestions for day sails out of Jack London Square that would be welcome too!!!(we're serious sailors so we don't mind long days!)

[GeorgeB]

If you have a Palm Pilot, there is an app called “tide tool” that shows the current velocities at various spots on the Bay. Local tide books (like the one named “Tide Tool” – no relation to the app) have charts in the back showing general current velocities and directions in one hour increments from max food or max ebb at the gate. The downside is they are averages and do not take into consideration the runoff from the Sierras which can skew the data a lot. The tides on the Bay are amazingly complex and it can take years to master them. There are software licenses like “Go Flow” that provide some really accurate predictions.

My boat is across from Jack London (in Alameda). What are your dates that you will be down here? Perhaps we’ll see each other out on the Bay. Unfortunately, the lack of an engine and the desire to do happy hour at Heinhold’s is going to limit where you will be able to sail. Jack London is 2 ˝ NM down the Estuary from the Bay. The prevailing winds blow straight down it from the Bay so expect to do 50+ tacks to get out as the Estuary is only about a thousand feet wide for most of its length. The good news is that it is dredged so you can get to within a couple of feet of the breakwall before you need to tack. Down here, March may not have the best or consistent winds as it usually is too early in the season for our normal wind pattern. In normal winters, you can easily add a knot to any ebb current and expect the ebb to start sooner and end later than the prediction.

[SlowButSteady]

I used to sail out of Alameda Marina (a couple more miles up the Oakland-Alameda Estuary from JL Square), so I've had some experience with the wind and currents you're likely to encounter. Most of the little tide books you can get at marine stores, bait shops, et cetera, will have current info and time off-sets toward the back. Also, you can use "Mr. Tides" on a Mac, but I don't know if there is an iPad version. The tidal flow in the Estuary can be a bit frustrating on a calm day, particularly along the stretch from JLS to Middle Harbor. However, since the afternoon winds almost always blow from SF Bay proper into the Estuary it would have to be a heck of an ebb to keep you from getting back to JLS. Having said that, I did get caught by a HUGE ebb one evening as I was trying to get back from Gashouse Cove to Alameda (I sat almost stationary off Pier 39, fighting the ebb, for what seemed like hours). By the time I got back into the Estuary the wind had died, but tide had finally started to turn and I more or less drifted back to Alameda Marina.

As for day trips from JLS, South Beach Marina or Central Basin are both easy daysails. Pier 39 and SF Aquatic Park are also well within range. Tiburon, Angel Island, or Sausalito will take a bit longer, but fine if you're game for a long day. The great advantage you have is that the Estuary is usually downwind from the Central Bay, so your return trip should be a nice run. Just watch out for them big ol' container ships.