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» Online Classroom   »   » Public Discussion of Marine Weather   » Hawaii to Seattle route planning and timing

   
Author Topic: Hawaii to Seattle route planning and timing
flowers


 - posted February 08, 2014 02:14 PM      Profile for flowers           Edit/Delete Post 
I am planning to sail my 37 ft sloop back to Seattle from Hawaii (Kona Coast) sometime this year between May and August, completing a round trip to NZ.
Hurricane season starts 1 June.
COGOW pilot charts indicate much more favorable wind vectors and a much less obstructive NoPac high with a 16 May start compared to a 16 July start, but these are just averages and the 2000-2009 wind rose data may not tell the whole story, especially regarding stability of the weather.
How best to analyze this choice further?
Thanks for any ideas or insight.

David Burch


 - posted February 08, 2014 03:01 PM      Profile for David Burch           Edit/Delete Post 
I will be back shortly with more specifics. But for now the short answer.

Later is better.

The risk of hurricane is low because (1) it is rare they get that far west,

(2) you see them coming plenty early to work around them if one should start that way. Check our path data in the weather trainer program or go to NHC to see historic tracks. you do not have to get far north before out of the range.

there is the long shot of a TS evolving into a bad storm that coincides with deep dip in the winds aloft which brings it north, but these are rare occurrences to other statistical matters on your plate... and you would not avoid that scenario no matter when you leave.

COGOW is the best (bar none) climatic wind data... but you sail in the weather, not in the climate.

the High firms up in July even late July, but the high is better to deal with than the statistics of north pacific storms earlier in the season.

when using cogow for this type of analysis you need to look not just at the average pictures shown in color every 2 weeks, but widen out the screen and look at the actual plotted statistics of the probability of strong winds. I will try to capture some pictures to demonstrate this point when i can.

this is a common sailing route since all of the boats that race to hawaii have to get home. it is usually (and i would say rightfully) thought of as a delivery.

pack up as much extra fuel as possible in jerry cans, then point the boat to Cape Flatterly. you will end up sailing due north or so for some time because of the trades. not unheard of to end up even a bit west of north in worst conditions periodically.

then come up to the rhumbline course to the cape as you can.. even if pointed right into the High. then if needed, motor though the high. with light air sails, you can often even keep moving under sail. watch for actual ship reports on the surface analysis and use our ship reports free email service. needless to say, one has to look at the actual maps at the time and modify this as called for, but with 96h as the longest look forward, you have to make some more generic decisions ahead of time. i.e. where the high is when you depart is not likely to be where it is when you get there.

the trick is to for sure save 100 miles of fuel or more, as it might be fog when you approach the cape.

the key point to this approach is you do not just sail north with some plan to go "over the high" even when you could make good miles to the mark. You go for the mark.

i will come back with the stats pics as soon as i can, but they are rather unrelated to the tactics mentioned here. a cursory look might seem to allow a more direct route earlier rather than later, but that is what i suspect is misleading without more specific stats. i.e. is it better to motor though the high for a couple days or to sail in 50 kts of wind and high seas. we can never rule out a north pacific storm, any time of year... we are just looking at statistics.

From: Starpath, Seattle, WA
flowers


 - posted April 19, 2014 04:41 PM      Profile for flowers           Edit/Delete Post 
Thanks, David. You are clearly extracting more detail from COGOW than meets my eye and the advice is much appreciated.
I have planned the passage for approximately July 20 to August 20.
Now that El Nino is being predicted for this summer, how do you think the average predictions from COGOW will be affected?
Thanks again. JFF

David Burch


 - posted April 19, 2014 11:24 PM      Profile for David Burch           Edit/Delete Post 
First, i support your choice of date for the trip.

Second on the statistics i added notes on this question i had hoped to do earlier. Note it is dated last year as it is not a timely topic in our ongoing discussions there, but it is an easy way to post an answer.

Third, i do not think that El Nino can affect your decision making on planning the trip. Without evaluating the significance of that climatic pattern at the moment, it is important to remember that we sail in the weather and not in the climate. You could well buy new sails and rigging or take more or less water with you etc, and then find (even likely) conditions that are not at all representative of some extreme consequence of a climatic prediction.

From: Starpath, Seattle, WA


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