Weather Software

By Daniel Piltch, Marine Computer Systems
(as originally published in Ocean Navigator Issue #106) 
  

 

Weather software plays an increasingly important role for the offshore sailor. The options for getting weather information at sea have been proliferating rapidly. As with many other marine technologies, weather software is quickly becoming faster, easier to use and less expensive.

Weather Fax

Most marine weather software can be classified into one of the following categories: weather fax, satellite weather, and weather routing. Weather fax imagery has been around since the 1950s and is the most widely used type of marine weather software. In the US, synoptic weather charts originate at the National Weather Service's Marine Prediction Center and are disseminated to the Coast Guard for transmission over marine single sideband frequencies. The Coast Guard maintains transmitters at Marshfield, MA (outside Boston) for North Atlantic weather, Belle Chase, LA (outside New Orleans) for Gulf of Mexico and tropical Atlantic weather, and Point Reyes, CA (outside San Francisco) for Pacific weather. There are also transmitting stations in Kodiak, Alaska (for the Gulf of Alaska) and Honolulu, Hawaii (for tropical Pacific waters). Each station transmits weather charts according to a daily schedule. An excerpt of the schedule from Marshfield, MA can be seen in figure 1.

While there are still a limited number of dedicated units that focus solely on receiving and printing weather fax charts such as the Furuno Weather Facsimile Receiver/Printer, most people choose to interface their single sideband (SSB) radio with their computer instead. The computer based option offers a number of advantages over the dedicated receiver/printer. With the dedicated units, you're limited to seeing the image directly as it arrives off the radio waves. There is no opportunity to clean the image or tweak it to be clearer or more readable. However, by using a computer and software to receive the images, you have the ability to perform many different operations to try and improve the quality of the incoming weather chart. As an example, consider the image in figure 2. This is an image of a chart as it was received onboard from the Belle Chase/New Orleans transmitting station. By using weather fax software to clear away some of the "snow" or "static" in the image, and re-aligning the image, we can improve the image to look like it does in figure 3.

While you can try and piece together homegrown hardware and publicly available software to assemble your own weather fax decoding equipment, most people find it more convenient to buy an off the shelf package that includes all the hardware and software necessary to start receiving weather fax images. You provide the single sideband radio - the package does all the rest. The most popular commercial weather fax packages are Coretex's Weather Fax for Windows (originally made by Xaxero in New Zealand), Software Systems Consulting or SSC's PC HF Facsimile, OCENS' Weather Station HW, and - for the Macintosh - Quintessence Designs' WeathermaQ.

Coretex and SSC both include a demodulator with cable that connect it to the external speaker (or headphone) jack of your SSB receiver and a spare serial port on your computer (see diagram). One common problem with these systems is that they require the use of a serial port in order to connect to your single sideband receiver. If you have a laptop computer on board, chances are it has only one serial port, and chances are you're already using this serial port to provide a GPS signal to your electronic charting program. If this is the case, you'll need to look into buying an extra serial port which can be provided through a PC Card or a USB device.

WeathermaQ avoids the problem entirely by connecting your SSB receiver's external speaker jack directly to the "audio in" connection on the computer. There is no external demodulator; it's functions are handled within the computer.

The Ocean and Coastal Environmental Sensing (OCENS) company developed an interesting product called WeatherStation 2000 HW late last year that allows for weather fax reception without the need of an extra serial port. Instead it uses a credit card sized PC (or PCMCIA) card that fits into your laptop (or into your desktop with an adapter) to make the connection to the SSB. While their product is a bit more pricey than Coretex or SSC's products, it costs about the same when you consider the cost for the extra serial port that's sometimes needed with the other products.

Any of these systems should provide high quality weather charts from various stations around the world. In addition to the rapidly changing software, the transmitting stations have also been in a state of flux lately with many going off the air restricting their transmission to times of military need. The de facto web site standard for finding weather fax stations is http://www.hffax.de/. The site is maintained privately by Marius Rensen in Hannover, Germany and contains a wealth of information about weather fax stations as well as weather fax equipment. Though not officially sanctioned by any governmental authority as a source for station frequencies - the US National Weather Service Marine Prediction Center's web site will send you here if you're looking for information on overseas weather fax. For domestic stations, the Weather Service maintains a very informative web site at http://www.mpc.ncep.noaa.gov/. This site not only lists the frequencies and schedules for the Coast Guard's transmitting stations, it also allows you to use your Internet connection to download the same charts that are broadcast over the radio waves. This is great for practicing your weather interpretation skills at home without the need to bring your SSB with you! In January 2000, the National Weather Service issued a 94 page publication entitled, Worldwide Marine Radiofacsimile Broadcast Schedules, which contains information about all known transmitting weather fax stations. The publication is available for free on the Internet at http://www.nws.noaa.gov/om/marine/radiofax.htm and will prove useful for anyone considering an International voyage. For information on other radio transmissions, consider the British Admiralty's multi-volume publication: List of Signals, which contains information not only about weather fax stations, but about all other radio transmissions of interest to the mariner.

Satellite Weather

The next step up in sophistication for gathering weather information is to use satellite imagery. These images are produced by orbiting weather satellites that are continually photographing the earth. There is some confusion as to what type of satellite imagery is available to mariners. There are two types of weather satellites that scan the earth - one is a geostationary type of satellite which is in a very high orbit (22,3000 miles high) and stays constantly over one spot on earth's surface. Due to it's high orbit and distance from the earth, it can see almost one third of the globe at any one time. However, because it is so far away, a fairly sophisticated tracking antenna is required to capture the relatively weak signal. These antennae are generally too large for most yachts. The other type of weather satellite is a polar orbiting satellite which circles Earth in a north-south direction and is in a much lower orbit (500 miles). Since these satellites are much closer to the surface, their signal can be picked up with a relatively small, non-tracking antenna (figure 3.5) that will fit on just about any boat. The signal is available anytime the satellite is in view. These polar orbiting satellites circle the earth about once every 90 minutes, offering several passes a day over any given location.

Each satellite has a number of different sensors used to collect information - the two most important types for mariners are the sensors used to collect visible and infrared imagery. Visible satellite imagery can show textures in cloud tops that yield significant clues as to the weather in their vicinity. Infrared imagery allows you to measure the temperature for each point in the image. In areas covered in clouds you can measure the temperature of the cloud tops, which in turn signifies how high the clouds reach in the atmosphere and what type of clouds they are. For example, a dense thundercell is typically composed of cumulonimbus clouds that reach into the upper limits of the atmosphere. As a result of being so high, the tops of these clouds are very cold and they show up very distinctively in a satellite image that's been colorized to show cloud top temperatures. The ability to see this detail in an otherwise featureless cold front could prove invaluable to the ocean cruiser.

Consider the image in figure 4 which shows a chart that arrived via weather fax, showing a long cold front stretching to the southwest off the US east coast. This information alone is invaluable to any sailor in the vicinity. Now consider the image in figure 5 which was obtained from SeaStation 2000 - this image shows the same cold front, but it has additional detail because it shows the cloud top temperatures. The green area highlighted by the black arrow is significantly colder than the surrounding clouds. This suggests that it is a taller group of clouds which in turn suggest greater convective activity and a greater likelihood of bad weather. This kind of detailed information isn't available on any weather fax chart, and can only be found by analyzing satellite imagery.

In areas not covered by clouds, you can measure the temperature of the earth's surface - or in our case, the ocean's surface. These sea surface temperatures can be colorized to show warmer water traveling in the midst of colder water. This allows you to actually see ocean currents like the Gulf Stream quite clearly on satellite imagery. In figure 6, the Gulf Stream appears as a deep red, while the waters to the north are significantly cooler and show up as mostly yellow and blue. There are two large warm eddies that have spun off the Gulf Stream - one eddy is south of Long Island and its clockwise circulation is shown clearly in the red color indicating the warm water. The other eddy is southeast of Nantucket, and appears as an orange circular pattern.

In order to receive satellite imagery directly, you'll need an antenna (preferably with a pre-amplifier), a receiver to tune in to the correct signal, and a demodulator to extract the data from the radio signal. In addition you'll need to have software that allows you to process the image. Most mariners who choose to have satellite capture equipment onboard wind up getting a complete package that includes all of the hardware, software, and components necessary to get up and running. Some of the software packages available will also allow you to download satellite imagery from an on-line archive that NOAA maintains on the Internet (http://www.saa.noaa.gov). This is a useful feature as you can practice analyzing imagery at home and compare your analysis with TV meteorologists and other public weather sources. It can also be useful to download several images before departure to get a feel for the current weather patterns. Another advantage to this approach of downloading imagery from the Internet is that you can get very detailed information on ocean currents which aren't likely to change very much over the course of a short passage (say to Bermuda) - all without the expense of installing direct capture equipment onboard.

Some of the more popular packages include SeaStation 2000 from Ocean and Coastal Environmental Sensing, Inc. (OCENS) in Seattle, WeatherTrac from SFWX, Inc. in Allentown, Pennsylvania, Wefax (hardware) and Qfax (software) from Quorum Communications, Inc. in Irving, Texas, and various packages from Systems West, Inc. in Marina, California.

Weather Routing

The object of weather routing software is to suggest a route that will get you and your boat to your destination within the shortest possible time period without encountering adverse weather. In order to do this, the software generally needs to know what the weather will be like for the next several days as well as something about how your boat (and its crew) perform in various different weather conditions. For instance, if the appropriate software is armed with a computer-readable three day weather forecast along with some information on your boat's polars (how it should perform in varying wind speeds and varying true wind angles), it should be able to predict the shortest-time route. Note that this will not always be the same as the shortest distance route.

Consider the two heavy black lines in figure 7 from Lunamar's OCEAN routing program. The image shows two routes from the Bay of Biscay to Land's End in England. The straight line running to the northeast shows the shortest distance (great circle) route from the starting location to the destination - 834 miles in this case.

 

The route to the west of this is much longer, at 975 miles, but suggests that your time enroute will almost 27 hours less than the great circle route. In this case, the weather for the next several days was predicted to veer from the west around through north to northeast. The original great circle route would put you in a position to be bucking headwinds for the last day of the trip, while the longer route has you reaching for the whole trip.

The recreational weather routing software market is in the midst of an interesting change as the software from one of the players - Kiwitech - has recently been acquired by Raytheon. Kiwitech, based in New Zealand, had been providing a weather routing software package that had been used in a number of ocean races. In merging the Kiwitech software into their Raytech Navigator program, Raytheon has removed the weather routing features. A future version of Raytech Navigator is expected to make these features available again.

The other formidable player is Lunamar, Inc. which developed the OCEAN routing program for the BOC singlehanded around the world race. The program includes two modules - the routing module and the polar editing program. The polar editing program allows you to enter your boat's performance characteristics with respect to various wind speeds and directions.

Larger yachts might be interested in the Orion routing system from WNI-Ocean Routes in Sunnyvale, California. Originally developed for commercial shipping, Orion focused on the impact that wind, waves, and swells would have on a particular hull shape. It doesn't take into account any polar information for sailboats, but would be useful for large power yachts.

Entering polar information into any routing program requires careful consideration. Though your boat may sail at high speeds in 45 knots of wind, this might not be your idea of a comfortable passage. Not knowing this, the software might suggest a route that takes advantage of the higher speeds available in 45 knot winds. You'll need to adjust the polar information to take into account your personal preferences.

Another interesting program for weather routing is Visual Passage Planner from Digital Wave. In a slightly different category than other weather routing programs, Visual Passage Planner works by using pilot charts rather than actual weather forecasts. When planning a passage, the software will tell you the conditions expected for each part of your route based on the average conditions in that area of the world for many years. It does not analyze the current weather forecast to suggest a route, but rather uses historical average weather to report on expected conditions.

The Internet

Though not technically a category of software, the Internet has rapidly become a primary source of weather information for many mariners - both recreational and professional. It is very common to hear of sailors spending the morning of a departure at their computer downloading the latest weather charts and forecasts to have on file before leaving port. Though the download-before-departure approach has diminishing returns as you're at sea for longer periods it is invaluable for short passages.

The information available on the Internet is typically much more detailed than that available while underway, and also offers a great opportunity to get familiar with weather patterns without actually having to sail through them. For instance, if there's a storm coming - the first thing I usually do is start looking at weather charts from the Internet. Once you get familiar with how "real" weather relates to weather depicted on charts, you'll be in a better position to route your vessel safely through troubled waters. What better way to find out what kind of weather you don't want to sail through than to experience it from your front yard rather than your foredeck?

Mariners are finding that it is becoming easier to access the Internet in different ways while at sea. While many systems offer the capability to send and receive email messages from the high seas, a few will even allow you to browse the web - albeit at very, very slow speeds. If you have an Inmarsat A, B, Mini-M, or AMSC satellite system, you should be able to connect to a provider that will get you access to the Internet. Be very cautious about doing this, as the fees can add up rapidly due to the frustratingly slow access times for most of these systems. Here are some tips to help keep costs down if you choose to do this:

Bookmark the site with the information you actually need. If you usually go to the Marine Prediction Center's web site, and then click on the "Forecast Products" link, and then click on the "Current High Seas Forecast" link, don't bother to bookmark the first few pages - just bookmark the page with the forecast on it. The fewer pages you look at, the less time you'll spend online, and the lower the costs will be.
Avoid downloading images. Images take up an exponentially larger amount of space than text. The 48 hour surface forecast for the North Atlantic is anywhere from 4 to 15 times larger than the text forecast for the same area. Larger files mean longer download times which mean higher costs. If you do need the charts, be selective about which ones you need - many of the charts are available over the weather fax. Find sites with smaller images or lots of text information before you leave, and make bookmarks for them.
Most browsers will automatically download both text and images from each web page. Since many of these images are advertisements, or other uninteresting graphics, you shouldn't have to wait to download them. Or pay to download them. In the options setting of your browser (Edit/Preferences/Advanced for Netscape Navigator and Tools/Internet Options/Advanced for Internet Explorer), you'll find a check box for "Automatically Load Images" (in Netscape) or "Show Pictures" (Internet Explorer). Uncheck this box, and you'll be able to avoid downloading graphics and images that you don't want. To view a specific image, right click on the box where the image normally appears and choose "Show Image" (Netscape) or "Show Picture" (Internet Explorer). While you're here, you might also want to uncheck the boxes that enable Java (but not JavaSript). Leave JavaScript enabled as this won't save you much and some sites won't work without it. This will be a little awkward when you first use it. Get used to it while you're still on shore, rather than fumble around from your satellite connection.
Don't browse aimlessly. While the web is a great medium for finding things you didn't even know you were looking for - "Oh, I didn't know I could find that on the Internet". Do most of your browsing at home, and bookmark the pages that you think will be useful underway. Some sites such as Gocruising.Net (see below for web site address) cater to boaters looking for no-frills, text only weather information.
Here is a short list of valuable web sites providing weather information for mariners:

 Web Site Name  Internet Address (URL)  Description

 Marine Prediction Center (National Weather Service) http://www.mpc.ncep.noaa.gov/  Excellent source of analysis and forecast charts. Original source of weather fax charts.

 National Hurricane Center and Tropical Prediction Center http://www.nhc.noaa.gov/  Excellent source of up-to-date information about existing and developing hurricanes. Also has marine weather for tropical areas.

 Marine Computer Systems http://www.MarineComputer.com/Weather/WeatherLinks.html An almost all text (no images) list of many, many different web sites providing marine weather information. 

 Gocruising.Net http://www.gocruising.net/  A text-only page with links to text-only weather information.

 National Data Buoy Center http://www.ndbc.noaa.gov/  Provides detailed information on weather conditions at several buoys, including historical data and graphical plots.

 

Selecting the Right Software

Like other software markets, the marine computing market is changing almost daily with new features developed, new versions planned, and new bugs found (and hopefully fixed). Most companies offer evaluation versions of their programs which you can try out for a while to see if the software meets your expectations. You should feel comfortable with the operation of any software you purchase. Sometimes in an effort to pack in as many features as possible, vendors lose sight of making the product easy to use. A high quality software vendor will spend some time testing their software for usability, and incorporate the feedback they receive from their user tests. You'll notice this extra effort when you can easily find out how to accomplish a task as opposed to having to dig out the manual and thumbing through the index in frustration. If a program seems unusually complex even after you've spent some time trying to learn how it works, you might want to try an alternative.

Software training is slowly becoming available. Ocean Navigator's School of Ocean Seamanship offers a two day seminar focused on onboard computing where you'll be able to get hands-on training with a number of different software packages. Some software vendors are starting to offer their own training courses to help their customers better understand their product's operation.

While word-of-mouth can be a big help in selecting the right software, be careful of negative opinions from people who didn't spend the time to learn how to use their software. It's not uncommon for an opinion such as, "I just spent five hundred dollars on this new fangled software and it doesn't seem to do anything worthwhile," to change into something like, "This new software is so useful, I don't know how I ever got along without it," once someone makes the effort to understand how to use the program.

Weather software can add a tremendous amount of utility and safety to an offshore passage. Choosing the right software for your needs, and learning how to use the software properly is critical. Don't be afraid to ask for help.
 

 

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