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An update: Useful public weather websites

Apr 21, 2016

When I first began writing these newsletters in 2007, in one of the first issues I wrote about the availability of weather data for mariners on the Internet. In particular, I presented information about three websites, all of which are U.S. government websites that all mariners should be familiar with. These were the Ocean Prediction Center website, the Tropical Prediction Center website and the National Data Buoy Center website. Fast forward to 2016, and all three websites still exist, but they have all been redesigned and have had some changes in the data that they make available. This newsletter will revisit those three websites with an updated look at what they have to offer.

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 website, along with links to many other marine-related websites. All of the information that is available on the “old-fashioned” (even more old-fashioned now than it was in 2007!) radio weatherfax service is also available here, and often is 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 UTC (same as GMT, or Zulu time) and the other starting at 1200 UTC. The forecast cycle begins with the collection of data, including weather balloon data, surface weather observations and 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, it means that the chart is based on real, observed data.

The gathered, analyzed data is then input into several computer models that are run to 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 “Issued” date and time indicates the date and time that the chart was made available, which can be anywhere from one to six hours after the start of the forecast cycle. The difference between the start time of the forecast cycle and the “Issued” time on the charts 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. The “Valid” date and time is the time in the future when the data shown on the chart is expected to occur.

Now we can look at some of the products found on the Ocean Prediction Center website. There are several tabs on the front page, each of which will present many links to products related to the tabs, but I prefer to access the products by using the links on the left-hand side. For example, by clicking on the “Atlantic” or “Pacific” links under the “Marine Weather” header, you will be taken to a list of links for either region. By clicking the “High Seas” link, 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 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. Within this section, regional charts can be found covering just the western Atlantic or eastern Pacific, and if your interest is even more local, then near-coastal text forecasts can be obtained from this section as well. These are the same forecasts that are heard on local NOAA weather radio.

There is also a “Base Map” link to obtain blank copies of all the different plotting charts that are used, and these can be very useful to plot vessel progress on charts with the same background as the weather charts. There are several other links here, which some may find interesting and useful such as experimental products. The “Briefing” link will bring up the latest version of all charts, which can be handy, but it is important to make sure that you know which forecast cycle the charts are from since it is possible to click on this in the middle of a forecast cycle when some charts have been made available but others have not, in which case the previous version will be displayed.

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

The National Hurricane Center, also known as 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 website 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 website available for the tropical latitudes of the Atlantic and the Pacific. To access them, scroll down and click on the “Marine Products from NHC’s Tropical Analysis and Forecast Branch” in the lower left portion of the front page. This will take you to a page with graphic links to text forecasts; while scrolling down, there will be links to surface charts and sea-state charts for the tropical regions.

Back on the front page of the National Hurricane Center website, drop-down menus at the top of the page offer much more information. There’s “Educational Resources,” including naming conventions, safety rules and precautions; “Data and Tools,” including blank plotting charts; and an archive where information on systems from previous years can be accessed. At the bottom of the front page are 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 access individual buoys. Using the regional links on the right-hand side will zoom the map into a particular area, which will make it easier to select the buoy of interest. The map interface is now a Google Earth-compatible product, but the older map interface is still available by clicking the “Recent” link under “Classic Maps” in the menu on the right-hand side. I actually prefer this interface. Many buoys record wind speed and direction and temperature along with detailed sea-state information, but some have more limited information. 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.

There are other organizations that have set up their own weather web pages. In most cases, these pages use many of the resources that are found on the web pages above, but the pages are designed 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. With the approaching sailing season in the northern hemisphere, it is a perfect time to become familiar with these websites and all that they offer. Frequent visits will allow the products to be of greater use when they are needed to help make decisions.

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