Interpreting Buoy Data and trip planning.

[s/v Beth]

As you can imagine, I have suddenly gained a great interest in buoy data. They speak of dominate wave period and average period of the waves. Which one should I use for my planning?
Also, one should ideally have some wind out there, so should I leave port at the end of a high- with winds calm and waves down but starting up again, or at the beginning of a high pressure area, with the assurance that there will always be some wind off the Washington coast?

[jackdale]

Buoy data is historical.

I would also suggest using the NOAA weatherfax for forecasts.

Northeast Pacific WX Briefing Package

For buoys use the wave height and wave period and wave direction. Low long period waves on the stern are much easier on the system than short high waves on the bow.

[s/v Beth]

Jack, the link you gave me is great. How accurate is NOAA beyond 24 hours? Having just been spanked, I am a little gun shy.

[jackdale]

I have used them offshore; they are like any forecast, as you go further out they become less reliable. I like the NOAA forecasts for HI to PNW. They give a sense of where you want to be in 4 days. The 500mb analysis is great to show how systems could track.

I also use Ugrib (GRIB.US > Home) for 7 day forecasts when I go around Vancouver Island.

It is essential to monitor current conditions; the buoys are great for that.

[ljsailing]

Howdy!
I use another NOAA product that does very well for isobar/wind predictions, try-

www.nws.noaa.gov

click on FORECAST - AVIATION
select FORECAST - WINDS-TEMPS
select the IMAGE for a graphic view

This has worked for me on a regular basis.

73

[cas206]

Originally Posted by s/v Beth

They speak of dominate wave period and average period of the waves.

I'm no expert here, but I did have some radio spectrum analysis classes decades ago. So total WAG here:

If there was just one sinusoid wave, then the dominant and average would be the same. When you get a mix of different period waves, then that is no longer so. If the dominant wave is very much stronger than any others, then the average should be close to the dominant. In this case, you might expect to see "regular" (uniform? predictable? smooth?) wave action.

In the case where the average is very different from dominant, then there must be many different period waves out there. So you might expect to be sailing through a "dishwasher like" situation.

cas

[Therapy]

Originally Posted by jackdale

Buoy data is historical.

I would also suggest using the NOAA weatherfax for forecasts.

Northeast Pacific WX Briefing Package

For buoys use the wave height and wave period and wave direction. Low long period waves on the stern are much easier on the system than short high waves on the bow.

That is awesome.

There is so much on NOAA but it is so hard to find.

Thanks.

[s/v Beth]

Thanks for all the info. I have now bookmarked the NOAH briefing and found it to be very accurate in describing the weather 2-3 days in advance. The dominate vs average wave explanation makes sense. Will try it out.

[barnakiel]

Originally Posted by jackdale

(...) The 500mb analysis is great to show how systems could track.(...)

This is already contained in forward sea level products.

At least this is what I heard from NOAA staff.

b.

[jackdale]

Originally Posted by barnakiel

This is already contained in forward sea level products.

At least this is what I heard from NOAA staff.

b.

That is true. There are some other redundancies in the weatherfax as well.

[s/v Beth]

jack, can you get the twice daily briefings over a HF radio receiver and graphed out on your laptop? How easy is that to do?

[jackdale]

Originally Posted by s/v Beth

jack, can you get the twice daily briefings over a HF radio receiver and graphed out on your laptop? How easy is that to do?

On the HI deliveries we have get our weather information emailed to us by the boat owners after they edit the file and compress it. We have been using Expedition, but that is fairly expensive software that assumes that boat is in race trim. I would recommend Ugrib (GRIB.US > Home) which is free. You might play with that a little through its internet connection.

In 2000 we used a SSB through a modem to a laptop and a printer. We used the NOAA station at Point Reyes.

You can get grib files sent to you via email through saildocs.

Requesting grib files from Saildocs (2010-07-08)

[barnakiel]

You can also request a radiofax img via email.

b.