More on Shilshole Bay

This is an article written by Jack Christiansen from North Sails prior to the US Nationals in 2006.

What to Expect For Conditions at the Shilshole

Racing will take place on Puget Sound ideally in the waters just North of Meadow point and South of Richmond Beach.

The Olympic Mountains to the west and the Cascade Mountains to the east funnel the weather systems into flowing either from the North or south primarily. The Northerly winds are Òfair weatherÓ winds during May and June. As the barometric pressure climbs when the high moves over Washington the Northerlies begin a 3 to 4 day cycle. The first day will see the Northerly develop later in the day and it will typically top out at 10 to 13 knots. The second day is usually the strongest day of the cycle with winds building from 1pm or 2pm until shutting off after dark at 9 pm to 9:30 pm. This breeze will get additional boost if there has been early morning clouds that burn off quickly. The continual heating of downtown Seattle will add 2 to 4 knots of Sea breeze effect to the Northerly. Day 3 and four follow the pattern of day 2 of the northerly cycle except with an ever decreasing top wind speed should be expected. Part of the reason for the Sea breeze thermal boost is due to the cold Puget Sound temperature. The sound is 48 to 52 degrees year-round, so plan your sailing gear accordingly.

Southerly and Southwesterly winds have the potential to be much stronger breeze for racing. The winds from these directions are caused by low pressure systems moving onshore. These winds will typically come in with more southeasterly direction at the beginning of the front and move to southerly and then southwesterly as the low pressure ridge passes between Shilshole and the Cascades. Winds will blow 12 knots to 25knots in May from any part of the southerly direction.

The rare westerly is a strong front in which you will not see high winds due to the mountains to the west, but you will see the wind really just on the way from Southerly to Northerly.

As we say about the East, trust it least. With water depth at 150 to 650 feet deep in the course area, the committee should not be in a hurry to set marks in the easterly or westerly since it will only delay getting the course set in a worthwhile wind from the North or South.  

Currents and Tides

For the nationals racing will primarily be in Flood tides with up to 1.25 knots of current pushing from North to South as the tide floods into Puget Sound. If we are in Northerlies then this will make the beats longer and runs shorter putting a premium on getting and holding a lane and good tacking. As the tide changes to an ebb there will be an ever increasing eddy form North of and off of Meadow point that can lead to ÒelevatorsÓ of currents breaking off the eddy and onto the course area. Keep your eyes peeled for changes in the water surface. Since, however, we are not racing in mid June during the highest tide changes of the year we will not see the race tactics dictated by the current, especially if the winds are stronger.

MAY 2004 CLIMATOLOGICAL REPORT FOR SEA-TAC AIRPORT NATIONAL WEATHER SERVICE SEATTLE WA  

TEMPERATURE DATA (Degrees F)
Average Monthly Temperature.... 57.0
DEPARTURE FROM NORMAL... +1.2
Average Maximum Temperature.... 64.8
Average Minimum Temperature.... 49.1
Highest Temperature was 76 on day 1
Lowest Temperature was 44 on day 5
The average wind speed for the month was 7.4 MPH.
The fastest two minute wind was 23 MPH from the south on day 8.
The highest instantaneous wind gust was 28 MPH from the south on day 8.

JUNE 2004 CLIMATOLOGICAL REPORT FOR SEA-TAC AIRPORT NATIONAL WEATHER SERVICE SEATTLE WA
TEMPERATURE DATA...... (Degrees F)
Average Monthly Temperature.... 63.4
departure from normal...+2.7
Average Maximum Temperature.... 72.9
Average Minimum Temperature.... 53.8
Highest Temperature was 88 on days 20,21
Lowest Temperature was 46 on day 12
The average wind speed for the month was 7.6 MPH.
The fastest two minute wind was 25 MPH from the northeast on day 19.
The highest instantaneous wind gust was 31 MPH from the northeast on day 19.

Written by Jack Christiansen North Sails Seattle