NOAA Magazine | NOAA Home Page MARINE SERVICES PROVIDED BY NOAA's NATIONAL WEATHER SERVICE July 3, 2002 — Whether it involves a comfortable day recreating or the potential loss of millions of dollars in cargo, weather information has a very direct impact on the boating public. What information does NOAA's National Weather Service provide? How does the NWS produce this information? Where can people get this information? Read on and find the answers. Since the late 19th century when the government began issuing official marine forecasts, most weather information has been given in text format (i.e., forecasters used words to describe those conditions he/she believes will occur over a particular geographic area throughout the next day or two and/or more general conditions for a day or two thereafter in an extended forecast). Forecasters would issue these forecasts a set number of times a day unless conditions begin to deviate from what was expected — then they issue updates. Although text forecasts will continue to be used into the foreseeable future, many other ways of depicting current and future weather are evolving, including those specifically geared toward the marine community. For example, boaters will soon be able to: watch a graphic display depicting clouds and/or precipitation as they move into a given area, see when wind changes are expected in that area and identify the best location to protect themselves from these changes. The NWS issues three basic marine text products. These include: Forecasts and warnings (Coastal Waters, Offshore, and High Seas Forecasts and Near shore and Open Lakes Forecasts for the Great Lakes), Special Marine Warnings, and Marine Weather Statements. 1. Coastal/Near Shore Waters, Offshore, and High Seas Forecasts and Warnings Coastal/Near Shore Waters, Offshore, and High Seas Forecasts and Warnings continue to provide all the basic information needed to inform boaters of what weather should be expected. The major weather elements impacting boaters (i.e., winds, waves, precipitation, and visibility) are given for each 12-hour period out to five days. Forecasters will include headlines of more important weather conditions (e.g., gale, storm, or hurricane force winds, low visibilities, and/or ice accretions) to alert mariners of potentially life threatening conditions. Each forecast covers a different type of area. The Coastal and Near shore Forecasts are relatively small. Coastal Forecasts extend no more than 60 miles from shore, while the Near shore Forecasts—issued for the Great Lakes—extend only 5 miles from the beach. This allows forecasters to provide more detail in these areas. This is important considering the fact that large variations in topography and/or interaction between land and water can cause large variations in weather conditions within a relatively small distance. Furthermore, boaters traveling though coastal and near shore waters tend to be in smaller boats, which stay closer to shore and, therefore, need this greater level detail. Local NWS offices, with greatest access to very detailed weather information, typically issue these forecasts. The Offshore Forecasts, extending from 60 to more than 200 miles from shore, cover large areas with little topographic influence. The surface homogeneity over these vast waters produces less horizontal differences in weather conditions, thus allowing for large forecast areas. Commercial fishermen, barge operators, and/or mariners who are usually in bigger, more rugged boats, are the principal users of these products. The Great Lakes, although more impacted than the ocean areas, still cover areas that are less influenced by local topography. Thus, each Lake receives its own individual Open Lakes Forecast. Again, these forecasts are aimed at cargo vessels, barges and large pleasure craft. The NWS relies on the National Centers for Environmental Prediction, the Marine Prediction Center, the Tropical Prediction Center, and two larger forecast offices (i.e., Anchorage and Honolulu), for issuing the offshore products. Additionally, five selected forecast offices are responsible for the Open Lake Forecasts. High Seas Forecasts cover the largest areas. After the Titanic sank in 1912, the nations of the world decided that they had to work cooperatively to make ocean travel safer. Through its membership in the United Nations, the United States has taken responsibility for issuing weather forecasts for most of the North Atlantic, North Pacific Oceans and small parts of the Arctic and South Pacific Oceans. Such products are generally directed at the mariners who transit the open oceans. Because of the vast distances involved, only the most significant weather features are described in the High Seas Forecasts. Areas with light winds and low wave heights are briefly mentioned. The Marine Prediction Center, the Tropical Prediction Center and the Honolulu forecast office produce the High Seas Forecasts. Of all weather elements, winds are most important to mariners. Therefore, all marine forecasts will contain headlines alerting mariners whenever threatening wind speeds are expected. GALE, STORM, and HURRICANE FORCE WIND WARNINGS are issued for winds of 34 knots, 48 knots, and 63 knots or greater, respectively. Additionally, headlines may be used to alert mariners of dangerous icing conditions, high swells or low visibilities. 2. Special Marine Warnings What happens if a tornado moves off land over the water? What happens if a local thunderstorm produces down burst winds strong enough to overturn boats? Local NWS offices will issue a Special Marine Warning. This text product alerts boaters of any conditions that could kill or harm them. Because this information is often not available for far offshore waters, these products are only issued for the Great Lakes and for the coastal waters. 3. Marine Weather Statements When some unusual weather phenomenon occurs or is possible, or when more information than is available in the forecast is required, forecasters issue a Marine Weather Statement. Note, however, that this text product is only issued by local offices on an as need basis. How do NOAA forecasters produce these products? Much goes into the forecast preparation process. Raw weather data must first be collected and processed so the forecaster is knowledgeable about current conditions. The physical properties of the atmosphere are then examined using numerical models to provide the forecaster with guidance as to how the atmosphere will change in the hours and days to come. Then finally, the forecaster must combine all the available information with his/her acquired knowledge to generate an understandable, accurate, and timely forecast. Raw Data The raw data for all weather forecasts are an observation. Although people still look outside and manually record existing conditions, more and more automated sensors are now fulfilling this task. Unlike land-based systems, marine observations pose a special challenge. Although ships travel across the oceans and provide the NWS with observed conditions, people do not live out on the ocean. Hence, a stable observation network over water is dependent on hearty devices that can be anchored offshore for extended periods of time—often a very costly endeavor. The NWS manages more than 50 data buoys and 80 Coastal Marine Automated Network (C-MAN) sites scattered throughout or along U.S. waters. By continuously sampling air temperature, air moisture, pressure, winds and wave conditions, these systems provide the best data available to the marine forecaster. Unfortunately, in some locations there are significant distances between buoys and storms have been known to sneak between them. Fortunately, satellite photography has been used over the past 40 years to fill in the gaps between the data buoys. Some satellites are in geosynchronous orbit (i.e., these satellites are so far out in space above the equator that they fall around the Earth at the same rate the Earth is turning. Hence, the satellite is always viewing the Earth's same side.). A series of photographs taken from such satellites allows forecasters to watch systems, far away from land, grow, die and move. Other satellites orbit the Earth by crossing the poles. Much lower in altitude, these satellites can provide very detailed pictures. In clear areas, they can actually provide a profile of atmospheric conditions from the surface up to several thousand feet. These atmospheric profiles are very important in the forecast process because weather seen at the Earth's surface is often generated by features existing only several thousand feet above the Earth. Some polar orbiting satellites can even provide detailed surface wind information out over the open ocean using a system called a micro-wave scatterometer. Others are capable of measuring wave height using a radar altimeter and can help locate oceanographic features, such as the Gulf Stream or Kuroshio Current, by using thermal imaging. Numerical Models The atmosphere is in a constant state of change. Although there is some randomness in the atmosphere and how it moves, it is generally governed by certain physical ‘laws,"which can be described in mathematical equations. When weather observations, physical laws and mathematical equations are combined, they are called numerical models. Generating these models requires some of the most powerful computers in the world. By solving these equations across space and time, and mapping the solutions, forecasters can see how conditions may change. Since there is no single absolutely correct numerical model, forecasters base their forecasts on solutions produced by several different numerical models. By understanding the strengths and weaknesses of the various models, forecasters at NOAA's National Center for Environmental Prediction can effectively analyze them to come up with the most likely composite forecast. The U.S. Navy and several other countries also run their own numerical models. Fortunately, the NWS has agreements with many of them to exchange the output from their models. All of this information combined gives marine forecasters an in depth look at systems impacting their forecast area. In the end, however, the forecaster is the person who must make the final forecast. Thus, NWS forecasters take the observations and model guidance and utilize the knowledge they have acquired through education and experience to generate a final product. Product Dissemination Forecasts are worthless, however, if they don't get to the person who needs it. Radio is the major vehicle through which mariners receive most weather information. Although the Coast Guard disseminates most marine weather information, NOAA Weather Radio is also available along all coasts and across the Great Lakes allowing mariners close to shore to receive weather information directly from local forecast offices. The Internet is another effective method for disseminating weather information (i.e., graphics and text). Mariners can also get text information through e-mail systems and personal digital assistants (PDAs). And finally, National Weather Service forecast offices are open 24 hours a day and can be reached by telephone. What Does the Future Hold? Although words are useful, graphics are the wave of the future. The old adage, a picture is worth a thousand words, still holds true in the world of weather. Weather maps of oceans surrounding the United States have been available for more than a decade and are especially useful to mariners in the high seas. A new tool, the Automated Weather Interactive Processing System (AWIPS), provides a powerful aid in developing graphic and gridded products. This system allows forecasters to view weather in several different ways to better understand current and future events. It also allows them to issue forecasts and warnings more quickly than is currently possible. Gridded data files will allow ships at sea to quickly and cheaply receive the latest forecast information (i.e., on-ship computers will process the data through programs supplied by private sector partners to display information in a convenient and informative way). No matter what the future holds, NOAA products will be there for you whenever you are in, on, or near the water. Relevant Web Sites National Weather Service marine forecast services National Weather Service Coastal and Near shore Forecasts Offshore Forecasts Open Lakes Forecast National Centers for Environmental Prediction Marine Prediction Center Tropical Prediction Center High Seas Forecasts Special Marine Warnings Marine Weather Statements NOAA Weather Radio Internet Access to Marine Weather Telephone Access to Marine Weather Automated Weather Interactive Processing System (AWIPS) Media Contacts: Curtis Carey or John Leslie, NOAA National Weather Service, (301) 713-0622