Sailing on Shilshole Bay

Shilshole Bay is the area of Puget Sound to the west of Meadow Point and to the east of the shipping lanes. This guide will hopefully provide persons new to this venue with some of the generally well accepted local knowledge. It is important to point out that opinions vary and this is only one opinion. My hope is that this will spur others to discuss and document their opinions so the newbie racers and the out of town sailors will have a base from which to build. First some facts and then some conjecture about the local conditions.

Important Facts

Water Depth	From 200 to 700 ft.
Water Temp	From 45 to 55 F (in June it is about 52F)
Air Temp	From 52 to 65 in June

Big Picture

The weather systems generally move in from the northern Pacific Ocean from a west - northwest direction. The rare exception is the "pineapple express" that comes ashore from the southwest. After coming ashore on the Washington coast, these systems attempt to pass over the Olympic Mountain range (approx 6,000 to 8,000 ft above sea level). Due to some kind of atmospheric force the systems are prevented from passing over the Olympic Range and are forced to take a path around either the northern or southern boundary of the range. This situation creates some of the rainiest places in the US in the coastal areas to the west of the Olympics. The direction the weather systems take (weather gurus can predict this) will typically dictate whether the wind in Puget Sound blows from either the north or south. Sometimes the weather systems decide to go both north and south and creates a "Convergence Zone". This is a condition where you see a northerly wind in the North Puget Sound and a southerly wind in South Puget Sound. In between these two winds, the conditions are generally light and variable.

To the east of Puget Sound are Lake Washington and the Cascade Mountain Range (max elevation 15,000 ft). The Cascade and Olympic ranges are oriented in a north-south direction and setup a corridor wherein the wind almost always blows either Northerly or Southerly. I heard Bill Buchan say once "If the wind on Puget Sound begins blowing from the east or west, keep your head up for the 90 degree shift that will surely follow."

SHILSHOLE BAY (see chart on last page)

90% of the small boat sailing in Seattle occurs in Shilshole Bay. The sailing area is bordered by the Puget Sound shipping lanes to the west, Shilshole Bay Marina to the east, West Point to the South, and Meadow Point to the North. Occasionally, the sailing area extends north of Meadow Point. Topographical features of note are Meadow Point and the high bluffs to the east and south of Shilshole Bay. The only saltwater entrance to Lake Washington occurs in the valley (gorge) between the Ballard and Fort Lawton bluff. This ship canal has a set of Army Corps Locks that allow vessel movement between salt and sweet water. The water depth in Shilshole Bay varies from 100 to 600 ft. North of Shilshole Bay the water depth increases to 800 ft. The current on the race course is significantly affected by the tidal flow and possibly by other factors such as the winds affect on the surface water, and the outflow of fresh water from the Locks. Shilshole Bay has two tidal cycles per day and the peak to peak differential can be up to 15 ft. For example here are the tides for mid June 2005:

19 June	0159	0931	1707	2141
	10.9 ft	-1.2 ft	10.3 ft	7.6 ft
20 June	0235	1012	1756	2237
	11.0 ft	-2.3 ft	11.2 ft	8.0 ft

In Shilshole Bay during a flood current the water generally moves southbound, while the opposite is true during ebb. The racing area in the vicinity of Meadow Point has a unique set of current gradients that sometimes resembles a back eddy, at other times resembles an eddy fence, and most times a cross between the two. Much mystery and speculation surrounds the exact location and shape of these eddies and watching the water surface is the best advice. Conventional wisdom like "choppy water means current is opposite wind" and "smooth water means current and wind are same" will generally serve the sailor well to apply. It is safe to say that current dynamics should play a major role in strategic decisions when sailing in Shilshole Bay. There is one rule of thumb that is almost universally agreed upon with respect to the current. During a northerly with a flood, it is almost always favored to go to the right hand (east) side of the beat. The reasons for this can be partially explained by the affect of the Meadow Point back eddy, but may also have to do with the Meadow Point thermal described later. The neighborhood park at the top of the bluff in Ballard (34th Ave NW) is an excellent place to view the current swirls in Shilshole Bay.

As described earlier, the wind is either predominantly Northerly or Southerly, generated by the weather systems that pass through the region. There are two exceptions to this standard trend. First is a Southeasterly breeze that blows through the valley created by the ship canal to the Ballard Locks. This mostly winter-time breeze is typically characterized by gusty and shifty winds near the breakwater and more steady lighter winds as you get further from the breakwater. The second exception is a thermal wind known colloquially as the "Meadow Point Hurricane". This mostly summer time condition occurs due to thermal gradients between Meadow Point and the valley described earlier. As Meadow Point heats up, the warm air seeks the path of least resistance toward the vacuum created by the ship canal gorge. The wind direction is predominantly northwest; however, it can be very shifty as you approach Meadow Point. It is not uncommon in the summer for the Sound to be like a mirror pond with the hurricane blowing 12 - 15 knots.

During the times when the weather system is producing a nice Northerly, the Meadow Point hurricane can still occur and this is a strong reason, in the absence of any other reasons, you will see most local sailors heading to the right hand corner on the beats.

Race Management

This venue is as challenging for the race management as for the racers. Setting a square starting line in 500 ft of water with variable current and wind is no small task. We locals are blessed with professional race management that have very specialized equipment for rapidly setting marks in 500 ft of water. I want to recognize the skills of the mark set whaler drivers who have become proficient at their craft using some of the same skill sets required to become a proficient sailor. Be aware of the new whaler driver who puts out too much scope as this can drastically change the starting line if the anchor line is near a current swirl.

Conclusion

As stated in the beginning, this is only one sailor's opinion and I hope to hear other views on this subject. I encourage others to send me their comments, opinions, and theories that can be added. Mike Johnson mjohns77@aol.com Seattle Laser Fleet Figure 1. The outlined area is the part of Puget Sound where most of the small boat sailboat racing occurs. This figure is a scan from NOAA chart 18446 and the soundings are in feet. Do not use this for navigation.