Severe weather terminology (United States)

This article describes severe weather terminology used by the National Weather Service (NWS) in the United States, a government agency operating within the Department of Commerce as an arm of the National Oceanic and Atmospheric Administration (NOAA).

The NWS provides weather forecasts, hazardous weather alerts, and other weather-related products for the general public and special interests through a collection of national and regional guidance centers (including the Storm Prediction Center, the National Hurricane Center and the Aviation Weather Center), and 122 local Weather Forecast Offices (WFO). Each Weather Forecast Office is assigned a designated geographic area of responsibility—also known as a county warning area—that are split into numerous forecast zones (encompassing part or all of one county or equivalent thereof) for issuing forecasts and hazardous weather products.

The article primarily defines precise meanings and associated criteria for nearly all weather warnings, watches, advisories, statements, and other products not associated with hazardous weather issued by the NWS and its sub-organizations (some of which may be specific to certain cities or regions). Related weather scales and general weather terms used by the agency are also addressed.

The NWS divides severe weather alerts into several types of hazardous/hydrologic events:

The following advisories are issued by the National Weather Service Aviation Weather Center (outside of Alaska) or Alaska Aviation Weather Unit. Atmospheric ash plume advisories/warnings are also issued by the United States Geological Survey (Aviation Color Codes).

VAAs are standardized worldwide by the International Civil Aviation Organization.

The National Weather Service also relays messages for non-weather related hazardous events in text products and NOAA Weather Radio broadcasts:

Wind alerting is classified into groups of two Beaufort numbers, beginning at 6–7 for the lowest class of wind advisories. The last group includes three Beaufort numbers, 14–16. The actual alerts can be categorized into three classes: maritime wind warnings, land wind warnings, and tropical cyclone warnings. Advisory-force and gale-force winds will not trigger a separate wind advisory or warning if a Blizzard warning is already in effect. However, as seen with Hurricane Sandy, if widespread high wind warnings are in effect prior to the issuance of a blizzard warning, the high wind warnings may be continued.