The current pressure as shown on the env. Canada pressure slope grid is in the left corner of the chart the pattern is read from right to left. Wind direction will follow the arrows on the picture displayed...The LARGER the number the STRONGER the winds to be encountered. BIG WAVE DAVE provides a wind prediction just below current conditions...This grid is most consistent when calling for a WEST wind. Invariably if the pressure between Smith Island (E. end of Juan De Fuca) and Tatoosh (West side of Olympic Pen.) is significant, say 2.5 Millibars LOWER at Smith then race rocks will experience winds 10 times Higher than the drop..Air moves from high to low pressure areas like when you pop the cap of a carbonated beverage therefor in this example 2.5 X 10 = 25 KNOTS at Race rocks! Jim. p.s. I find that if I use the phone 363-6880 (just one of many) I can use these numbers (Tatoosh/Smith) to make my own decision re: Juan De Fuca...If I see a fog bank distant that just adds to the wind due to moist air meeting dry!

I thought that's how it all worked. Jimmy/Marvin, you are 'Da man!'

Hey Jimmy. Thanks fo the explanation. I've got a few questions though. Doesn't the EC pressure slope chart just tell you what is happening now and what has happened up until now?? Are you trying to determine a pattern using this data? What's the difference between using the lighthouse report graphs and the pressure slope?? I usually track the wind by the lighthouse reports to see if it's following what the forecast called for.
I know the pressure slope is an extremely valuable tool....if you know how to read it
Thanks.
Rob

One more question....in your example, you said that if Smith Island was 2.5mb higher than Tatoosh, the wind at Race Rocks would be 25 knots. Since the wind blows from high to low, I'm assuming that would be an easterly outflow type wind. If TAtoosh was higher than Smith, then Race Rocks would be westerly??
Is there any relationship between what Race Rocks receives and what Sheringham or Cook St would get?? Or Kelp Reef and Discovery in an east wind??
Thanks
Rob

Oops! Your right 247 it goes high -low. YES follow the pattern and apply it to the wind at the light houses..Make a mental note for the next time the pattern appears!(the best part of writing here is when I mess up I can correct my original post!) Jim