1. Richard Dewey RVYC / UVic Swiftsure.org Web Site  Race Info  Currents During Race rdewey@uvic.ca

2. Tidal Heights and Currents Tidal currents “flood” in from the ocean on a rising tide and “ebb” out to the ocean on a falling tide.

3. Surface Slope Drives Tidal Currents Currents flow down-hill, from higher to lower water. Racers needn’t worry too much about tidal height, except when anchoring or rock hopping. Local current patterns are determined by the channels, straits, and sounds in response to these ocean and basin “sieches”. Mean flows in June: surface water exiting Salish Sea (¼-½ knot), some of this is in the tidal current table values. Weak ( ≈ ¼ knot) in 2015

4. Deep vs Shallow Tidal Currents Deep water has more inertia, will ride “up-hill” to stop,  reversals are lagged/delayed. Shallow and boundary layer flows have more friction (turbulence), can be slower & will stop and reverse sooner. Lateral convergence or vertical shoaling can result in accelerated flows.

5. Points of Sail in a Current Although the speed of the current is low compared to the wind (hopefully), a few knots of current over time will make a difference. Avoid currents on the windward quarter. Heading into a tide, try to keep the tide under the leeward bow, (lee-bow). A current under the lee side always better than on the windward side: apparent wind and lift.

6. Tidal Current Station Tidal Height Station

7. Reading Tidal Height Tables PDT=PST+1 Victoria (CHS)

8. Tidal Height: May 23 – 25, 2015

9. Tidal Current Station Tidal Height Station

10. Reading Tidal Current Tables PDT=PST+1 Race Passage 1 knot = ~0.5m/s + flood - ebb

11. Tidal Currents: May 23 – 25, 2015

12. Foreman, et al, 2004

23. Tidal Currents: May 23 – 25, 2015

24. Good Luck! At Swiftsure.org  Race Info  Currents During Race (please save PDF files, don’t print ) Richard Dewey rdewey@uvic.ca