Severe weather phenomena are weather conditions that are hazardous to human life and property.
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Severe weather can occur under a variety of situations, but three characteristics are generally needed: a temperature or moisture boundary, moisture, and (in the event of severe, precipitation-based events) instability in the atmosphere.
In meteorology, a cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure. Cyclones are characterized by inward spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes, and dust devils lie within smaller mesoscale. Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the tropical upper tropospheric trough during the summer months in the Northern Hemisphere. Cyclones have also been seen on extraterrestrial planets, such as Mars, Jupiter, and Neptune. Cyclogenesis is the process of cyclone formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones. These zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, extratropical cyclones occlude as cold air masses undercut the warmer air and become cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flow of the subtropical jet stream.
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers."NWS JetStream". National Weather Service. Retrieved 26 January 2019.</ref> Thunderstorms occur in a type of cloud known as a cumulonimbus. They are usually accompanied by strong winds, and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms produce little precipitation or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course at a right angle to the wind shear direction.
A storm is any disturbed state of a body especially affecting its surface, and strongly implying a wind force. It may be marked by significant disruptions and lightning, heavy precipitation, heavy freezing rain, strong winds, or wind transporting some substance through the atmosphere as in a dust storm, blizzard, sandstorm, etc.
These are some notable tornadoes, tornado outbreaks, and tornado outbreak sequences that have occurred around the globe.
At sea, a storm warning is a warning issued by the National Weather Service of the United States when winds between 48 knots and 63 knots 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.
This is a list of meteorology topics. The terms relate to meteorology, the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting.
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 severe weather terminology used by the Meteorological Service of Canada, a branch within Environment and Climate Change Canada. The article primarily describes various weather warnings, and their criteria. Related weather scales and general weather terms are also addressed in this article. Some terms are specific to certain regions.
A superstorm is a large, unusually-occurring, destructive storm without another distinct meteorological classification, such as hurricane or blizzard. As the term is of recent coinage and lacks a formal definition, there is some debate as to its usefulness.
Severe weather refers to any dangerous meteorological phenomena with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atmospheric conditions. High winds, hail, excessive precipitation, and wildfires are forms and effects of severe weather, as are thunderstorms, downbursts, tornadoes, waterspouts, tropical cyclones, and extratropical cyclones. Regional and seasonal severe weather phenomena include blizzards (snowstorms), ice storms, and duststorms.
European windstorms are the strongest extratropical cyclones which occur across the continent of Europe. They form as cyclonic windstorms associated with areas of low atmospheric pressure. They are most common in the autumn and winter months. On average, the month when most windstorms form is January. The seasonal average is 4.6 windstorms. Deep low pressure areas are relatively common over the North Atlantic, sometimes starting as nor'easters off the New England coast, and frequently track across the North Atlantic Ocean towards western Europe, past the north coast of Great Britain and Ireland and into the Norwegian Sea. However, when they track further south, they can affect almost any country in Europe. Commonly affected countries include the United Kingdom, Ireland, the Netherlands, Norway, the Faroe Islands and Iceland, but any country in Central Europe, Northern Europe and especially Western Europe is occasionally struck by such a storm system.
Hurricane Darby was the first Eastern Pacific major hurricane since Hurricane Kenna in 2002. The sixth tropical cyclone, fourth named storm, and second hurricane of the 2004 Pacific hurricane season, Darby developed from a tropical wave that emerged from the west coast of Africa on July 12. After crossing into the Eastern Pacific, the storm became a tropical depression on June 26. The system steadily intensified, and became a hurricane on 000 UTC July 28. Darby peaked as a Category 3 hurricane on the Saffir-Simpson Hurricane Scale, though it quickly deteriorated due to cooler waters and increasing wind shear. While Darby dissipated on August 1, the remnants of the tropical cyclone affected the Hawaiian Islands. The system produced high waves and heavy rainfall that led to extensive flash flooding. Numerous roads were closed, while minor landslides and rockslides were reported. Despite the effects, no fatalities or severe damages occurred.
The December 2009 Midwest blizzard was a powerful extratropical cyclone which was of a category which meteorologists refer to as a cyclogenic bomb, a system which shows a drop in central pressure similar to the rapid intensification cycle of a tropical cyclone, more than 1 mbar per hour for 12 to 24 hours or more. A sustained drop averaging more than 2.5 mbar/h is termed explosive deepening/intensification, and this was the case with this rapidly deepening and intensifying storm as it traversed the Midwest and Ontario and on to Québec, Greenland and vicinity. In many locations wind, snowfall, and precipitation moisture content records dating back to the December 2, 1990 storm, the 1976-1978 period, the 1949 blizzard, or even further back were broken, with barometric pressure records falling as well. Both the central pressure (depth) and rate of change and differential over a given distance (intensity) were remarkable, and both caused hurricane-force winds in places.
Global storm activity of 2006 profiles the major worldwide storms, including blizzards, ice storms, and other winter events, from January 1, 2006 to December 31, 2006. Winter storms are events in which the dominant varieties of precipitation are forms that only occur at cold temperatures, such as snow or sleet, or a rainstorm where ground temperatures are cold enough to allow ice to form. It may be marked by strong wind, thunder and lightning, heavy precipitation, such as ice, or wind transporting some substance through the atmosphere. Other major non winter events such as large dust storms, Hurricanes, cyclones, tornados, gales, flooding and rainstorms are also caused by such phenomena to a lesser or greater existent.
A severe thunderstorm outbreak, also called a severe weather outbreak or simply a severe outbreak, is an event in which a weather system or combination of weather systems produces a multitude of severe thunderstorms in a region over a continuous span of time. A severe outbreak which is most notable for its tornadoes is called a tornado outbreak. The four kinds of severe weather produced in these outbreaks are tornadoes, severe wind, large hail, and flash flooding.
The March 2014 North American winter storm, also known as Winter Storm Titan, was an extremely powerful Winter storm that affected much of the United States and portions of Canada. It was one of the most severe winter storms of the 2013–14 North American winter storm season, storm affecting most of the Western Seaboard, and various parts of the Eastern United States, bringing damaging winds, flash floods, blizzard conditions, icy conditions.
The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.
Storm Data and Unusual Weather Phenomena (SD) is a monthly NOAA publication with comprehensive listings and detailed summaries of severe weather occurrences in the United States. Included is information on tornadoes, high wind events, hail, lightning, floods and flash floods, tropical cyclones (hurricanes), ice storms, snow, extreme temperatures such as heat waves and cold waves, droughts, and wildfires. Photographs of weather and attendant damage are used as much as possible. Maps of significant weather are also included.
This glossary of meteorology is a list of terms and concepts relevant to meteorology and atmospheric science, their sub-disciplines, and related fields.
Hurricane Sergio was a powerful and long-lived tropical cyclone that affected the Baja California Peninsula as a tropical storm and caused significant flooding throughout southern Texas in early October 2018. Sergio became the eighth Category 4 hurricane in the East Pacific for 2018, breaking the old record of seven set in 2015. The twentieth named storm, eleventh hurricane, and ninth major hurricane of the season, Sergio originated from a system that was located over northwestern South America on September 24. The National Hurricane Center monitored the disturbance for several days as the system organized into a tropical storm on September 29. Sergio gradually strengthened for the next couple of days as it traveled west-southwestward, becoming a hurricane on October 2. The storm then turned towards the northwest as it underwent rapid intensification and an eyewall replacement cycle, before peaking as a Category 4 hurricane on October 4, with maximum sustained winds of 140 mph (220 km/h). The hurricane maintained peak intensity for 12 hours before undergoing a second eyewall replacement and turning towards the southwest. The system then began another period of intensification, achieving a secondary peak with winds of 125 mph (205 km/h) on October 6. The next day, Sergio began a third eyewall replacement cycle, falling below major hurricane strength. At the same time, the system unexpectedly assumed some annular characteristics. Over the next few days, the cyclone curved from the southwest to the northeast, weakening into a tropical storm on October 9. Sergio made landfall as a tropical storm on October 12 on the Baja California Peninsula, and later in northwestern Mexico as a tropical depression before dissipating early on October 13.