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post #1 of Old 06-19-2001 Thread Starter
Michael Carr
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Assessing Weather via Satellite

Looking forward on Spirit's maiden voyage in the middle of the Bermuda High.

In early April, the brand new, 960-foot cruise ship Carnival Spirit departed Helsinki, Finland bound for Miami, FL, a voyage of over 5,000 miles. To obtain weather data during this voyage, Spiritís crew depended upon Inmarsat satellite communications, which allowed them to download compressed weather files from Ocean Routes, a commercial routing service, as well as access the Internet and obtain National Weather Service Marine Prediction Center products.

I was aboard for this voyage and I brought along a Global Star satellite phone and a laptop computer loaded with the latest version of SeaStation 2000, a premier weather access software ( Global Star provides satellite voice and data communications and allows both ftp and http access to the Internet at a data rate of 9,600 baud.

What can this do for a mariner? Within SeaStation is a directory of all world meteorological organization (WMO) weather charts available on the Internet. This directory is linked with the specific Internet addresses (URLs) of each chart and so that when a desired chart is selected and the "download" button clicked in SeaStation, the GlobalStar phone allows that chart to be saved into the SeaStation directory. With this portable system, a single chart requires approximately 20 seconds or less to download.

The author downloaded this weather chart via his GlobalStar phone and used SeaStation 2000 software to plot the vessel's rhumbline route.

Why do I mention this and is this capability useful to mariners? Well for myself and others who have struggled with obtaining charts via weatherfax, where one chart takes 10 to 15 minutes to print out, and is often so unreadable as to be nearly useless, this SeaStation-GlobalStar capability is truly impressive due to its speed and reception quality.

Accompanying this article is the 96-hour, surface-forecast chart that I downloaded on April 17 while on that trip. During the downloading process I had the choice of viewing each chart on line or downloading a batch of charts, logging off, and then opening each chart within SeaStation. For cost effectiveness the recommended process is to create a "batch download" menu within SeaStation, essentially a shopping cart of charts you would like to obtain. When a batch has been created, and the "download" button clicked within SeaStation, the software goes out to the Internet using the GlobalStar connection and without further action by you the user, downloads each chartóone by oneóinto the SeaStation download directory. Within the directory charts are ordered by date and type.

This screen grab from the SeaStation 2000 program shows projected satellite coverage.

While I wrote this article, the Spirit was positioned at 39N/32W on a heading of 249 degrees true, 20.6 knots. We were abeam of Flores, Azores, sitting in the middle of the Azores-Bermuda high pressure. There was a low swell coming in from the west, about four to six feet, while local seas were less than a foot since the winds were below 10 knots. That was good weather for a large steamship since we wanted to avoid head winds and large swells as much as possible.

Using the Marine Prediction Centerís 24, 48 and 96-hour surface and 500-mb charts we were able to determine an optimal route for reaching Miami by the morning of April 24. Spirit is the Carnival cruise lineís newest ship and there was a busy schedule planned upon arrival in the US. The owners had made clear that avoiding heavy weather on this maiden Atlantic crossing was a priority.

SeaStationís weather chart directory assists greatly in obtaining the most appropriate charts regardless of the time of day because within each product listing there are choices listed by valid time as well as by "most current." How is this useful? Because I no longer need to be concerned with broadcast schedules as I was when using wefax. Regardless of the time I always chose "most current" when downloading either individual charts or building a batch download. I allow SeaStation to compare the time of chart release to the present time and pull down the "most current" product.

An example of real-time weather presented via the SeaStation 2000 program.

Once my selected charts are downloaded, I open them within SeaStation, overlay a latitude/longitude grid, and then input GPS data, which places a cursor at Spiritís present position. I have turned a weather chart into an electronic chart on which I can navigate until the next appropriate weather chart is downloaded. For me, thereís no better way to navigate on the open ocean than by using a weather chart since wind, waves, swells, clouds are the most important navigational features in this setting.

Of course, once I finished this article I had two options: send it to SailNet via GlobalStar as an attachment to my e-mail, or transfer it to a floppy disc, take it up to Spiritís bridge, and send it via the shipís Inmarsat system. Since I am always looking for reasons to spend time on the bridge (there is a terrific espresso machine in the pantry), I chose the option of sending via the ship's satellite communications system.

I remember the satisfaction I had being able to send the article off with full confidence that it would arrive easily by the deadline. I wasnít actually sure when that was, but at that particular moment, life under the Bermuda-Azores high pressure was extremely pleasant and I wasnít too concerned. All our navigation concerns were attended to, and I had a great cup of espresso in my immediate future.

Over the Horizon

The author's preference for SeaStation 2000 notwithstanding, there are a number of products on the market that allow enhanced navigation by way of integrating satellite weather data with charting software.

The key for mariners is knowing which bells and whistles you need and want (ie. bathymetric data, radar overlays, etc.), and making sure you get a system compatible with your computer. Here's a quick take on a few of these programs:

  • MaxSea, used by around-the-world racers, is the only program available for PowerMac. (
  • Nobletec's Visual Navigation Suite 6.0 offers three levels of sophistication for weather information (from basic, to coastal, to offshore). (
  • RayTech's Navigator is easily expandable, and comes in additional versions for racers (Sail Racer) and anglers (Fishing Pro). (

Suggested Reading:

Performance Basics for Routing by Michael Carr

Advanced Electronic Charting by Jim Sexton

WAAS Up? by Don Casey


Buying Guide: Chartplotters

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