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Storm Warning
At sea, a storm warning is a warning issued by the National Weather Service of the United States when winds between 48 knots (89 km/h, 55 mph) and 63 knots (117 km/h, 73 mph) are occurring or predicted to occur soon. The winds must not be associated with a tropical cyclone. If the winds are associated with a tropical cyclone, a tropical storm warning will be substituted for the storm warning and less severe gale warning. In US maritime warning flag systems, a red square flag with a black square taking up the middle ninth of the flag is used to indicate a storm warning (the use of two such flags denotes a hurricane force wind warning or a hurricane warning). The same flag as a storm warning is used to indicate a tropical storm warning. On land, the National Weather Service issues a 'high wind warning' (Specific Area Message Encoding code: HWW) for storm-force winds, which also encompasses the lesser gale-force and greater hurricane force winds. In most c ...
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Severe Thunderstorm Warning
A severe thunderstorm warning ( SAME code: SVR) is a severe weather warning product issued by regional offices of weather forecasting agencies throughout the world to alert the public that severe thunderstorms are imminent or occurring. A severe thunderstorm warning is issued when Doppler weather radar, trained storm spotters or local emergency management personnel indicate that a thunderstorm is producing large hail and high winds capable of causing significant damage, and is expected to continue producing severe weather along the storm's projected track. Flooding is also sometimes caused by torrential rainfall produced by a thunderstorm. (In these cases, a flood advisory or flash flood warning may be issued to alert the public of the flooding threat.) Definition A severe thunderstorm warning indicates the warned area is in impending danger from hail or wind speeds meeting warning criteria as well as from lightning and hydrological impacts associated with the storm cell. S ...
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Hurricane Force Wind Warning
A hurricane force wind warning is a warning issued by the National Weather Service of the United States when sustained winds or frequent gusts of 64 knots (118 km/h, 74 mph) or greater are either being observed or are predicted to occur. The winds must not be directly associated with a tropical cyclone, or a hurricane warning will be issued. If winds are lighter than 64 knots, a storm warning or gale warning will be issued. The hurricane force wind warning is only used to warn of the possibility of wind which reaches hurricane-level severity, but lacks direct connection with a hurricane system. The hurricane force wind can either signal sustained winds of 64 knots, or gusts of 64 knots lasting for two or more hours. In US maritime warning flag systems, two red square flags with a black square taking up the middle ninth of each flag is used to indicate a hurricane force wind warning (the use of one such flag denotes a storm warning or a tropical storm warning). The flags used to de ...
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Hurricane Force Wind Warning
A hurricane force wind warning is a warning issued by the National Weather Service of the United States when sustained winds or frequent gusts of 64 knots (118 km/h, 74 mph) or greater are either being observed or are predicted to occur. The winds must not be directly associated with a tropical cyclone, or a hurricane warning will be issued. If winds are lighter than 64 knots, a storm warning or gale warning will be issued. The hurricane force wind warning is only used to warn of the possibility of wind which reaches hurricane-level severity, but lacks direct connection with a hurricane system. The hurricane force wind can either signal sustained winds of 64 knots, or gusts of 64 knots lasting for two or more hours. In US maritime warning flag systems, two red square flags with a black square taking up the middle ninth of each flag is used to indicate a hurricane force wind warning (the use of one such flag denotes a storm warning or a tropical storm warning). The flags used to de ...
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Weather Warning Flag (United States)
Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmosphere, the troposphere, just below the stratosphere. Weather refers to day-to-day temperature, precipitation, and other atmospheric conditions, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time. When used without qualification, "weather" is generally understood to mean the weather of Earth. Weather is driven by air pressure, temperature, and moisture differences between one place and another. These differences can occur due to the Sun's angle at any particular spot, which varies with latitude. The strong temperature contrast between polar and tropical air gives rise to the largest scale atmospheric circulations: the Hadley cell, the Ferrel cell, the polar cell, and the jet stream. Weather system ...
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Small Craft Advisory
A small craft advisory is a type of wind warning issued by the National Weather Service in the United States. In Canada a similar warning is issued by Environment Canada. It is issued when winds have reached, or are expected to reach within 12 hours, a speed marginally less than gale force. A Small Craft Advisory may also be issued when sea or lake ice exists that could be hazardous to small boats. The insignia that denotes a small craft advisory is one red, triangular flag (two such flags, one placed above the other, signify a gale warning). Inland, this advisory is known as a '' wind advisory''. A lake wind advisory is issued for winds just below this range, because unobstructed winds across the open waters of a lake are normally faster than across land. The wind speed that triggers the advisory has changed over time. Until the late 1960s, the threshold was 32 to 38 miles per hour (or 28 to 33 knots). At some point, the lower limit was reduced to 23 miles per hour (20 knots) ...
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Severe Weather Terminology (United States)
This article describes severe weather terminology used by the National Weather Service (NWS) in the United States. The NWS, a government agency operating as an arm of the National Oceanic and Atmospheric Administration (NOAA) branch of the United States Department of Commerce (DoC), defines precise meanings for nearly all of its weather terms. This article describes NWS terminology and related weather scales used by the agency. Some terms may be specific to certain cities or regions. Specific Area Message Encoding (SAME) product codes assigned to each term for NOAA Weather Radio (NWR) broadcasts are included in parentheses following the title of the described alert type if used; products that do not have a specified code are identified where applicable as Non-Precipitation Warnings/Watches/Advisories (NPW), Coastal Flood Warnings/Watches/Advisories (CFW), Marine Weather Statement (MWS), Surf Discussion (SRD) or Winter Weather Warnings/Watches/Advisories (WSW) as defined by NOAA. D ...
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Seattle
Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest region of North America. The Seattle metropolitan area's population is 4.02 million, making it the 15th-largest in the United States. Its growth rate of 21.1% between 2010 and 2020 makes it one of the nation's fastest-growing large cities. Seattle is situated on an isthmus between Puget Sound (an inlet of the Pacific Ocean) and Lake Washington. It is the northernmost major city in the United States, located about south of the Canadian border. A major gateway for trade with East Asia, Seattle is the fourth-largest port in North America in terms of container handling . The Seattle area was inhabited by Native Americans for at least 4,000 years before the first permanent European settlers. Arthur A. Denny and his group of travelers, subsequ ...
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Tornado Emergency
A tornado emergency is an enhanced version of a tornado warning, which is used by the National Weather Service (NWS) in the United States during imminent, significant tornado occurrences in highly populated areas. Although it is not a new warning type from the NWS, issued instead within a severe weather statement or in the initial tornado warning, a tornado emergency generally means that significant, widespread damage is expected to occur and a high likelihood of numerous fatalities is expected with a large, strong to violent tornado. These enhanced warnings are intended to convey the urgency of the weather situation to the general public, who are advised to take safety precautions immediately if they are in or near the projected path of a large tornado or its accompanying thunderstorm; tornado emergencies are usually identified following the preceding storm summary in the tornado warning product, which itself will denote visual or radar confirmation of "a large and extremely dang ...
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Tornado Warning
A tornado warning ( SAME code: TOR) is a severe weather warning product issued by regional offices of weather forecasting agencies throughout the world to alert the public when a tornado has been reported or indicated by weather radar within the parent severe thunderstorm. It can be issued after a tornado, funnel cloud and rotation in the clouds has been witnessed by the public, storm chasers, emergency management or law enforcement, and indicates that residents in the affected areas should take immediate safety precautions. A warning should not be confused with a tornado watch, issued in the United States by the Storm Prediction Center (SPC) and in other countries by applicable regional forecasting agencies or national severe weather guidance centers, which only indicates that conditions are favorable for the formation of tornadoes. Although a tornado warning is generally a higher alert level than a tornado watch, in the U.S., it can be surpassed by a higher-level alert—struc ...
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Derecho
A ''derecho'' (, from es, derecho, link=no , 'straight') is a widespread, long-lived, straight-line wind storm that is associated with a fast-moving group of severe thunderstorms known as a mesoscale convective system. Derechos can cause hurricanic and tornadic-force winds, heavy rains, and flash floods. In many cases, convection-induced winds take on a bow echo (backward "C") form of squall line, often forming beneath an area of diverging upper tropospheric winds, and in a region of both rich low-level moisture and warm-air advection. Derechos move rapidly in the direction of movement of their associated storms, similar to an outflow boundary (gust front), except that the wind remains sustained for a greater period of time (often increasing in strength after onset), and may exceed hurricane-force. A derecho-producing convective system may remain active for many hours and, occasionally, over multiple days. A warm-weather phenomenon, derechos occur mostly in summer, especial ...
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Eyewall
The eye is a region of mostly calm weather at the center of tropical cyclones. The eye of a storm is a roughly circular area, typically in diameter. It is surrounded by the ''eyewall'', a ring of towering thunderstorms where the most severe weather and highest winds occur. The cyclone's lowest barometric pressure occurs in the eye and can be as much as 15 percent lower than the pressure outside the storm. In strong tropical cyclones, the eye is characterized by light winds and clear skies, surrounded on all sides by a towering, symmetric eyewall. In weaker tropical cyclones, the eye is less well defined and can be covered by the central dense overcast, an area of high, thick clouds that show up brightly on satellite imagery. Weaker or disorganized storms may also feature an eyewall that does not completely encircle the eye or have an eye that features heavy rain. In all storms, however, the eye is the location of the storm's minimum barometric pressure—where the atmospheric pre ...
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Hurricane
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane (), typhoon (), tropical storm, cyclonic storm, tropical depression, or simply cyclone. A hurricane is a strong tropical cyclone that occurs in the Atlantic Ocean or northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean. In the Indian Ocean, South Pacific, or (rarely) South Atlantic, comparable storms are referred to simply as "tropical cyclones", and such storms in the Indian Ocean can also be called "severe cyclonic storms". "Tropical" refers to the geographical origin of these systems, which form almost exclusively over tropics, tropical seas. "Cyclone" refers to their winds moving in a circle, whirl ...
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