There are several categories of decisions each Winlink/Saildocs user must deal with to gain effective use of this data:

1. Which weather documents to retrieve.  This decision is a function of both the bandwidth available when connected (how many files and of what size can be downloaded) and the ability of the sailor to use the reports.  The limited bandwidth of both the networks and the sailor's brain make it necessary to restrict the number of documents requested to those that are most important to the voyage.
2. When to acquire specific weather documents.  This decision is a function of both the existing propagation conditions (what time of data can you reliably connect) and the scheduled availability of the requested documents.  The later issue is very important as weather data is very perishable.  A forecast that was prepared 6 hours ago may no longer represent the current outlook of the forecaster. 

In the process of determining a document's availability we need to take into account the different ways Saildocs and Winlink acquire the documents from the Internet.  While I've not seen anything documented for either system, it appears that Saildocs has a scheduled retrieval time for most documents in its library.  At a scheduled time the Saildocs server will download the document from its URL.  When Saildocs receives a request for some documents that are downloaded frequently (every hour or less), the request may be held until the next schedule retrieval of the document.  Then when that retrieval takes place the weather document is forwarded back to the requestor.  For other documents with less frequent retrievals (e.g., every 6 hours) Saildocs may immediately send what ever version of the document is currently stored on the server.

Winlink appears to retrieve the document from the Internet at the time of the request and sends it to the requestor within minutes.

So with Saildocs your are assured of getting a recent version of the requested document, but you may have to wait up to an hour after your request for some documents to be available.  With Winlink you can expect to receive the document within a few minutes of your request, but that document may be updated shortly after you receive it and your copy may be obsolete before you even have a chance to review it.

I believe this document is generated at least every 6 hours by the NOAA duty forecaster, but the schedule is not very  precise.  It appears to be posted anywhere from 1 to 2 hours after the GRIB under discussion is available from Saildocs.  So the discussion of the model output contained in the 00z GRIB forecast is posted between 06 - 07z.  If I wanted to acquire both this discussion and the associated GRIB in a single connection I would wait until 07z to make that connection.

In this case WL2K retrieved the document from the Internet at the time it generated this message.  That is, WL2K does not store this document on its server, but retrieves it at the time the system responds to the request.  This document was retrieved from the NOAA web server at 07:50z (green highlight), the same time this message was sent to my email address.  The document was published on the NOAA server at 04:04z (yellow highlight).  This is the 00z Surface Analysis.

So it would appear that the Surface Analysis is available a little over 4 hours after the valid period of the data and about 50 minutes prior to the availability of the GRIB file based on the same data.

Once again WL2K has retrieved this document from the French Meteo web site at the time of my request (green highlight).  The forecast valid time is 09z and was last updated on the Meteo web site at 08:30z.

Therefore early in the voyage I will be looking to connect to Winlink or SailMail between 02:00z and 04:00z in the morning and between 22:00z to 00:00z in the evening.  As we progress further west those connection times will shift to later hours.  As we near the East Coast of the USA the connection times will likely be between 07:00z and 09:00z in the morning and 03:00z and 05:00z in the evening.  Therefore the likely connection times during the entire voyage will be somewhere between 22:00z and 09:00z.  The following table summarizes the document availability during those connections times.

In developing a connection and document retrieval schedule, one other thing needs to be kept in mind - the difference between a subscription for a Winlink document and a Saildocs document.  A document subscription is one of the best ways to implement a document retrieval schedule.  However, the differences between Winlink and Saildocs have implemented document scheduling have an effect on not only how you set up those subscriptions, but also on when and how often you connect to the network.

These differences reflect the basic differences that exist in many client-server applications, whether to put the application on the server or the client.  There is seldom one best choice and the differences between Winlink and Saildocs demonstrate this.  Winlink uses a client-driven subscription process and Saildocs is server-driven.  Each approach has its advantages and disadvantages for the cruising sailor.

So Winlink has the advantage when connections are frequent or when the schedule changes often.  Saildocs has the advantage of requiring minimal connections to acquire the required documents.  Of course subscriptions are not necessary to manage a document retrieval schedule, they just automate the process.  Sometimes that automation is of significant benefit, but sometimes it gets in the way.  I use subscriptions sparingly, primarily for the GRIB and ship reports from Saildocs.

Below are links to the two Excel Workbooks I used as logs of my connections to Winlink and SailMail.