Useful Weather Websites

By Ken McKinley

Last time I talked about the availability of weather data on the Internet in a general way. I finished that newsletter by promising to talk about some specific Web sites that are quite useful. So this time I will talk about three U.S. government Web sites with which all mariners should be familiar. These are the Ocean Prediction Center Web site, the Tropical Prediction Center Web site, and the National Data Buoy Center Web site.

The Ocean Prediction Center is the branch of NOAA's National Weather Service that is charged with providing forecasts and warnings for the high seas of both the North Atlantic and the North Pacific. There is a treasure trove of information on this Web site, along with links to many other marine-related Web sites. All of the information that is available on the old-fashioned radio weatherfax service is also available here, and is often able to be accessed significantly earlier than its transmission time on the radiofax. Surface and upper air charts as well as sea state charts are available. To best use this information, it is important to understand some basic information about the forecast process.

There are two forecast cycles each day, one starting at 0000 GMT (same as UTC, or Zulu time) and the other starting at 1200 GMT. The forecast cycle begins with the collection of data, including weather balloon data, surface weather observations, land-based stations, buoys and ships. Once this data is gathered, it is analyzed by meteorologists and several analysis charts are prepared. Therefore, anytime a chart has the word "analysis" in its header that means the chart is based on real, observed data. The gathered, analyzed data is then input into several computer models that produce a simulation of how the atmosphere will look in the future. Meteorologists use this computer output along with other data and their knowledge and expertise to generate forecasts, some of which are issued as text products, and others that are presented in graphic form. These are called "forecast" charts, and they will be so labeled in their header. The header will contain two date/time lines: the "from" date and time indicates the date and time of the start of the forecast cycle, and the "valid" date and time is the time in the future when the data shown on the chart is expected to occur. Keep in mind that forecast products will not be available until a couple of hours after the start of the forecast cycle. This corresponds to the time it takes to gather and analyze the data, run the computer models, and to have the meteorologist come up with his or her forecast.

Now we can look at some of the products found on the Ocean Prediction Center Web site. There are many links to products on the front page, but I prefer to access the products by using the links on the left hand side. For example, by clicking on the "High Seas" link under the "OPC Atlantic Products" header, tables can be found with all of the products arranged by forecast cycle. These tables group the charts by type (surface, upper air, sea state) and by valid time (analysis, 48-hour and 96-hour forecasts). The time of the latest update can be seen so it will be easy to tell if the current day's chart is available.

If your interest is not the high seas, but the nearshore waters, then click on the "Offshore/NAVTEX" link right above the high seas link. And if your interest is even more local, then near coastal text forecasts can be obtained for local areas by scrolling down to the "Multi-national Atlantic & Pacific Text Products" header and clicking on the "Coastal/Offshore/High Seas Forecast" link. From here, you can find the same forecasts that are heard on local NOAA weather radio stations.

These suggestions only scratch the surface of what is available on this Web site. Explanations of the various products are embedded throughout the site, and there are many links to other useful Web sites.

The Tropical Prediction Center is the branch of NOAA's National Weather Service charged with providing warnings and forecasts for the tropical regions of the Atlantic and eastern Pacific, and also with tracking tropical cyclones (tropical depressions, tropical storms, and hurricanes). The front page of this Web site has links to the latest tropical storm advisories when active systems are present. But even when there are not active tropical storms or hurricanes, there are analysis and forecast products similar to those on the Ocean Prediction Center Web site available for the tropical latitudes of the Atlantic and the Pacific. To access them, click on the "Forecasts and Analyses" link in the second line below the large type header for the Atlantic or Eastern Pacific regions. This line begins with the abbreviation "TAFB". This will take you to an easy-to-understand page where surface charts and sea state charts can be found.

The links on the left hand side of the Tropical Prediction Center Web site offer much information about hurricanes, including the history of previous seasons, naming conventions, and safety rules and precautions. There are also links to other tropical weather resources around the world, including, among others, the Joint Typhoon Warning Center in the Pacific.

The National Data Buoy Center is where data from weather buoys around the world can be found. By using the map interface, one can zoom into a particular area, and then look at current and past data from individual buoys. Many buoys record wind speed and direction along with temperature and detailed sea state information, but some have more limited information. There are links to many university-sponsored networks of research buoys, and in these regions the networks provide rather dense coverage. Because buoys are mostly in near coastal areas, this information is most useful for coastal sailors. It is a great resource to use to check on actual conditions before heading out for an afternoon of sailing.

Some yachting organizations have set up their own weather Web pages. An example that was emailed to me is www.clubcruceros.org/WeatherPages.htm. This page uses many of the resources that are found on the Web pages above, but has organized the links to be most useful for their user base.

The key with any of these Web pages is to be well aware of what is available, to be able to access it fairly quickly, and to understand what you are looking at. For those who are winding up their sailing season in the northern hemisphere, the coming colder months are a great opportunity to spend some time exploring and becoming familiar with these Web sites and all that they offer. Just a little bit of time every day will pay great dividends for next summer's sailing season.

In a future newsletter I will spend some time looking in detail at some of the specific products on these Web sites. Feel free to email me at locuswx@midcoast.com with questions about any of the products that you would like to have answered.