25-29 October 2021


Weather systems moving across the ocean can produce life-threatening situations not only for mariners at sea but also for those living in coastal communities. Therefore, a National Weather Service (NWS) program monitors the weather, prepares weather forecasts, and issues warnings for marine and coastal interests. The NWS area of responsibility includes the coastal and open waters of the Atlantic and Pacific Oceans, the Gulf of Mexico, and the Great Lakes. Data used in preparing these forecasts are obtained from a variety of sources, including ships, buoys, and Earth-orbiting satellites.

Coastal or near shore forecasts are intended for those mariners staying in coastal waters that are roughly within 20 nautical mi of the coast. Offshore forecasts are for those mariners operating farther offshore, typically a day or more from safe harbor, or between 60 and 250 nautical mi offshore. Open seas forecasts are mainly geared for large ocean-going vessels operating more than 250 nautical mi out to sea.

In addition to the forecasts, various marine-related advisories, watches and warnings are issued to the public. These pertain to a variety of severe weather conditions as well as unusual water, wave, and current conditions that could affect life and property.


The Ocean Prediction Center (OPC), formerly known as the Marine Prediction Center (MPC), is the component of the National Centers for Environmental Prediction (NCEP) that issues marine forecasts for coastal and offshore waters as well as the high seas of the western North Atlantic and much of the North Pacific poleward of 30 degrees N. This center also issues marine warnings for situations not involving tropical weather systems.

The Tropical Prediction Center (TPC), another component of the National Centers for Environmental Prediction, is responsible for marine forecasts equatorward of 30 degrees N. This responsibility includes the tropical North Atlantic, the Caribbean Sea, the Gulf of Mexico and eastern portions of both the North and South Pacific Oceans. The Honolulu Forecast Office (HFO) has responsibility for central and western portions of the North and South Pacific Oceans that include the Hawaiian Islands and the Pacific Islands that are administered by the U.S. Government.

The National Hurricane Center (NHC) in Miami, FL, part of the Tropical Prediction Center, is responsible for issuing statements covering tropical storms and hurricanes for the North Atlantic Basin (including the Gulf of Mexico and the Caribbean Sea) and the eastern Pacific Basin (to 140 degrees W). The Pacific Hurricane Center in Honolulu, HI monitors the Central Pacific to the International Date Line (at 180 degrees). The Hawaiian Islands are located within this region.

The Pacific Tsunami Warning Center (PTWC) in Honolulu, HI and the West Coast/Alaska Tsunami Warning Center (WC/ATWC) in Palmer, AK issue tsunami watches and warnings for Pacific basin.


The following terminology is used by NOAA's National Weather Service for public statements pertaining to tropical weather:

The National Hurricane Center (Tropical Prediction Center) issues Tropical Weather Outlooks. The information contained in these guidance products is used on television weathercasts. These Outlooks include levels of risk.

The following statements can be issued for several types of events, not limited to tropical weather systems:

The following marine weather statements can be issued if conditions warrant:


Marine weather information, including forecasts and warnings, are transmitted to mariners and other interested parties by several methods. The U.S. Coast Guard transmits weather maps to ships at sea by HF Radiofax and forecasts by either voice (HF, VHF or MF radio) or text transmission (NAVTEX). Recently, marine weather information can be obtained using "Internet-Ready" digital cellular phones and Personal Data Assistants (PDAs). Coastal and near shore forecasts (typically within about 25 mi of shore) can be obtained from the NOAA Weather Radio network. Graphics and text are also available on the Internet through the National Weather Service.

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Prepared by Edward J. Hopkins, Ph.D.,
© Copyright, 2021, The American Meteorological Society.