Weather Analysis, A Step-By-Step Guide—Part 2, Strategic

Strategic GRIB just after model run time.

In Part 1, I shared how I analyze the weather and plan out cruises accordingly for four to five days out from forecast time—tactical analysis.

In this chapter I'm going to move on to looking out as much as two weeks (strategic analysis) and how we can use that process to plan safer and more fun cruises.

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Geoff Armstrong

Great article – HOWEVER – I think you have an error in your Saildocs request string – according to Saildocs the syntax to request a time period is as follows:

send gfs:40N,60N,0W,20W/0.5,0.5/0,3,…, 72/
(comma dot dot dot comma) to request a forecast every 3 hours from T=0 to T=72 hours.

Your request string is missing the commas either side of the dots


Geoff Armstrong

Hi John
This is what I got back from Saildocs using the same string – I tried again with the commas and it worked fine – I think the “…” was interpreted as a different string but with the commas added is was interpreted OK.

I looked up the syntax and found what I sent you in the previous message which has the commas included.

Perhaps different locations interpret strings in the local language (I am in Portugal) and ned the correct syntax – just a thought.

Error: Incorrect syntax in the following grib request:
which parsed as follows:
Field 0: 41N,34N,7E,18W
Field 1: 1,1
Field 2: 0,12,24â€
Field 3: 384
Error: “24— is not a valid forecast-time
For more info on request formats, see or send a (blank) email to: moc.scodlias@ofnibirg

Thanks for using Saildocs, an Internet document retrieval
service for the bandwidth-impaired. By using this service
you agree to the Saildocs terms and conditions (send a
blank email to: moc.scodlias@smret for a copy).

Saildocs is a service of Sailmail, a membership-owned email
service built by cruising sailors for cruising sailors.
Sailmail provides world-wide email via marine-band radio,
internet and satellite including support for the Iridium GO!

For more information on SailMail see the web page at
or send a query to the office at moc.liamlias@posys.
More information on Saildocs is available by sending an email to
moc.scodlias@ofni, this will return the how-to document (about 5K).

Geoff Armstrong

Hi John

You are correct – the “…” was interpreted as a single character – I am using a Macbook Air and the default email client and the message format is set to “Rich Text”.
It might be worth mentioning that the email message should be sent as plain text.

Thanks for your help

Craig McPheeters

To stop the Mac mail program from converting triple dot to ellipsis, three characters to one character, you need to uncheck an option:
Edit -> Substitutions -> Smart Dashes.


Great stuff, John.
Being still a part-time charter sailor I just out of curiosity am regularly looking at the “greater picture” of weather forming west of and over Europe (I am mainly med bound). And having developed an eye for weather patterns I was able to predict Meltemi in Greece (which depends on a wider pressure structure) or the rare southwesterlies I encountered this September in the Aegean.
However, local effects that can be quite dangerous, such as a short-term Bora preparing in Croatia, can seldom or never be seen on a grib pattern if you don’t take the temperature coefficient into account. I have no experience with CAPE, maybe this might also help in local effects prediction.

Stein Varjord

Hi John.

Thanks for going through this stuff so thoroughly. I’ve been thinking along the same lines, but mostly just improvising and using memory from day to day. That way I obviously loose most of the important conclusions. Your conscious organisation, registration and analysis of info is obviously a huge improvement. I’ll definitely use this and stop being lazy about it.

Jamie Abdy Collins

UUPlus now support rain and a host of more parameters, in the Grib fetch. Beta version.

Craig McPheeters

Just a note – LuckGrib now supports downloading weather data via the Iridium GO! and the RedPort Optimizer, as well as with email through services such as UUPlus and XGate. (The Optimizer allows you to download data using most satellite phones.) The weather data is highly compressed using the new Offshore Compact File. Its worth checking out, and there is a 2 week free trial for everyone to evaluate it. See for many details. This is not a subscription service – pay a small fee once, and use it forever.

John, in this article you also mentioned a preference that your GRIB viewer show central pressures for weather systems (“LuckGrib are you listening?”) – I am, as you will have noticed, LuckGrib now provides this ability.