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Old 22-02-2021, 03:49   #1
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Weather

Good day all,
Reading the theory is great. Many books and online resources explain fundamentals, fronts, sea state etc. But how do you translate all of this into passage plans? Questions like, do you skirt a low if you can? Head for highs?
Is there anything out there that can help with practical planning?
Many thanks
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Old 22-02-2021, 05:22   #2
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Re: Weather

There are lots of routing programs that can use a Grib file, the boats polars, and try and give you an optimal route. They do not take into account many things that are important to a cruiser. You can play with one here https://fastseas.com/

Another interesting armchair approach is to look at the routes and blogs of cruisers who are doing, or did the same route you are interested in. Lots of boats do US east coast to eastern Varibm or US west coast to Hawaii for example.
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Old 22-02-2021, 05:53   #3
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Re: Weather

The Atlas of Pilot Charts is a great source, for preliminary voyage planning.
Pilot Charts depict averages in prevailing winds and currents, air and sea temperatures, wave heights, ice limits, visibility, barometric pressure, and weather conditions at different times of the year. The information used to compile these averages was obtained from oceanographic and meteorologic observations over many decades during the late 18th and 19th centuries.
The Atlas of Pilot Charts set is comprised of five volumes, each covering a specific geographic region. Each volume is an atlas of twelve pilot charts, each depicting the observed conditions for a particular month of any given year.
The charts are intended to aid the navigator in selecting the fastest and safest routes with regards to the expected weather and ocean conditions.
Available [Free] Herehttps://msi.nga.mil/Publications/APC
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Old 22-02-2021, 07:26   #4
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Re: Weather

I just got the predict wind app on my iPad, supposed to work fairly well with Iridium Go. It supposedly will do trip planning based on weather. I have not had a chance to use it yet, still on an inland lake, but come November I will be (my boat) on a trailer headed for the coast!
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Old 04-03-2021, 08:53   #5
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Re: Weather

Good post. I was wondering the same things. Can anyone post a 'now is a good time to go' on passage post so those of us who don't know what to look for on all these weather charts and graphs can start to learn? I know there would be multiple departure points so post them all!!
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Old 04-03-2021, 09:00   #6
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Re: Weather

The Dashew's are incredibly generous in providing encylcopedic knowledge in their free online books including "Mariners Guide to Weather" and "Surviving the Storm." These are not short books, and they are not digestible in a single seating. They are the types of books that you can read every year for a lifetime and takeaway knowledge you missed the time before.

https://setsail.com/free-books/

I like and use forecasting products such as Fastseas, PredictWind, Windy, etc. But being able to understand the synoptic level influences will be helpful.

Peter
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Old 04-03-2021, 09:26   #7
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Re: Weather

If you are planning long passages, I think you need Cornell's Ocean Atlas. And, you should have some way to get updated weather and forecasts. Sources can be Iridium GO, ham or SSB nets, or offshore internet connections (e.g. from proximate oil rigs, ham radio, etc.). Unfortunately, Musk's Starlink only is available now to customers at fixed locations. But, that should change soon which will give cruisers a new option. You can download long range GRIB projections, but don't rely on these too much, unless you have no choice, past a day or so. In any case, GRIB files don't show synoptic weather, which can show fronts moving through or stalling out. And, you'll need information about hurricanes and tropical storms. Finally, it would be good to get local weather when you're departing, and the forecast of local weather for when you plan to arrive.
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Old 04-03-2021, 10:32   #8
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Re: Weather

Sailing from Mexico to French Polynesia we used a professional weather router and Predict Wind via IridiumGo.

The weather router delayed our departure by about 7 days past our planned date because winds were expected to be "light and variable" for several days. Ultimately, during a 29 day passage we motored only 18h because we were able to stay "in the wind". There were some light air days but as long as the boat was moving 3 to 4kts we did not start the engine. Actually there were probably many hours of 2kts, but on a sailboat, why hurry?

Nadine Slavinski has written about her families passages from NA to Australia and her question, which provided guidance to our strategy, was "why motor from one place with no wind to another place with no wind". We had lots of food and a watermaker. Being at sea was great.

The weather router and PW provided advice regarding where to cross the ITCZ and we used radar to avoid the most intense squalls or at least be prepared for them.

There are also sites like: https://www.ghradio.co.nz/ that provide good advice on weather, departure planning and routing plus run SSB/HF nets to keep people informed.

In addition to the Pilot charts mentioned by others the Cornell books are also useful (World Cruising Routes) regarding best departure and route windows.
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Old 04-03-2021, 11:10   #9
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Re: Weather

An interesting and potentially dangerous factor has been introduced by some Governments, that being the requirement for passages to be of a minimum length to satisfy quarantine requirements on arrival. In addition visiting a safe haven whilst underway (even when uninhabited) is forbidden.
Yet all the modelling tools and books are predicated on the fastest passage possible is the safest.
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Old 04-03-2021, 21:02   #10
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Re: Weather

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Originally Posted by grantmc View Post
An interesting and potentially dangerous factor has been introduced by some Governments, that being the requirement for passages to be of a minimum length to satisfy quarantine requirements on arrival. In addition visiting a safe haven whilst underway (even when uninhabited) is forbidden.
Yet all the modelling tools and books are predicated on the fastest passage possible is the safest.
Most countries that let yachts in but require quarantine also have quarantine anchorages. Some count passage time toward quarantine time and some don't.
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Old 06-03-2021, 08:00   #11
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Re: Weather

Quote:
Originally Posted by floater88 View Post
Good post. I was wondering the same things. Can anyone post a 'now is a good time to go' on passage post so those of us who don't know what to look for on all these weather charts and graphs can start to learn? I know there would be multiple departure points so post them all!!
It would take a book to post them all. There are thousands of possible passages one can do on a sailboat and it is quite unreasonable to ask someone cover them all on a forum.

If you are serious about actually making a passage it would pay you to do the actual reading, learning and research. It isn't that difficult and there are plenty of books written from a practical point of view without a lot of complex science and theory.
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Old 06-03-2021, 08:41   #12
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Re: Weather

Quote:
Originally Posted by skipmac View Post
It would take a book to post them all. There are thousands of possible passages one can do on a sailboat and it is quite unreasonable to ask someone cover them all on a forum.

If you are serious about actually making a passage it would pay you to do the actual reading, learning and research. It isn't that difficult and there are plenty of books written from a practical point of view without a lot of complex science and theory.
Jimmy Cornell's "World Cruising Routes..." is THE book for this info.
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Old 06-03-2021, 15:16   #13
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Re: Weather

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Originally Posted by sv_pelagia View Post
Jimmy Cornell's "World Cruising Routes..." is THE book for this info.
Agree. Have a copy of this as well as a 45 year old copy of Ocean Passages for the World.

But if one wanted to figure this out on the cheap, reading the various versions of pilot charts online is free.
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