High winds::Severe weather


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High winds {{#invoke:main|main}}

Panorama of a strong shelf cloud, which can precede the onset of high winds

High winds are known to cause damage, depending upon their strength.

Wind speeds as low as {{safesubst:#invoke:convert|convert}} may lead to power outages when tree branches fall and disrupt power lines.<ref name="LightningPrinciples2009">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> Some species of trees are more vulnerable to winds. Trees with shallow roots are more prone to uproot, and brittle trees such as eucalyptus, sea hibiscus, and avocado are more prone to branch damage.<ref name="Derek2006">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Wind gusts may cause poorly designed suspension bridges to sway. When wind gusts harmonize with the frequency of the swaying bridge, the bridge may fail as occurred with the Tacoma Narrows Bridge in 1940.<ref name="Grazulis2001">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref>

Hurricane-force winds, caused by individual thunderstorms, thunderstorm complexes, derechos, tornadoes, extratropical cyclones, or tropical cyclones can destroy mobile homes and structurally damage buildings with foundations. Winds of this strength due to downslope winds off terrain have been known to shatter windows and sandblast paint from cars.<ref name="boulder">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Once winds exceed {{safesubst:#invoke:convert|convert}} within strong tropical cyclones and tornadoes, homes completely collapse, and significant damage is done to larger buildings. Total destruction to man-made structures occurs when winds reach {{safesubst:#invoke:convert|convert}}. The Saffir-Simpson scale for cyclones and Enhanced Fujita scale (TORRO scale in Europe) for tornados were developed to help estimate wind speed from the damage they cause.<ref name="NHC SSHS">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="EF SPC">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>



The F5 tornado that struck Elie, Manitoba in 2007.

A dangerous rotating column of air in contact with both the surface of the earth and the base of a cumulonimbus cloud (thundercloud) or a cumulus cloud, in rare cases. Tornadoes come in many sizes but typically form a visible condensation funnel whose narrowest end reaches the earth and surrounded by a cloud of debris and dust.<ref name="Renno">{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref>

Tornadoes' wind speeds generally average between {{safesubst:#invoke:convert|convert}} and {{safesubst:#invoke:convert|convert}}. They are approximately {{safesubst:#invoke:convert|convert}} across and travel a few miles (kilometers) before dissipating. Some attain wind speeds in excess of {{safesubst:#invoke:convert|convert}}, may stretch more than two miles (3.2 km) across, and maintain contact with the ground for dozens of miles (more than 100 km).<ref name=autogenerated2>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="fastest wind">

A tornado can pose threats to both humans and buildings. {{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="widest tornado">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Tornadoes, despite being one of the most destructive weather phenomena, are generally short-lived. A long-lived tornado generally lasts no more than an hour, but some have been known to last for 2 hours or longer (for example, the Tri-State Tornado). Due to their relatively short duration, less information is known about the development and formation of tornadoes.<ref name="Tornadoes2008">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Downburst and derecho


Downbursts are created within thunderstorms by significantly rain-cooled air, which, upon reaching ground level, spreads out in all directions and produce strong winds. Unlike winds in a tornado, winds in a downburst are not rotational but are directed outwards from the point where they strike land or water.
Illustration of a microburst. The air moves in a downward motion until it hits ground level. It then spreads outward in all directions.
"Dry downbursts" are associated with thunderstorms with very little precipitation,<ref name="micro">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> while wet downbursts are generated by thunderstorms with large amounts. Microbursts are very small downbursts with winds that extend up to 2.5 miles (4 km) from their source, while macrobursts are large-scale downbursts with winds that extend in excess of 2.5 miles (4 km).<ref name="Microburst">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The heat burst is created by vertical currents on the backside of old outflow boundaries and squall lines where rainfall is lacking. Heat bursts generate significantly higher temperatures due to the lack of rain-cooled air in their formation.<ref name="Oklahomaheat1999">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref> Derechos are longer, usually stronger, forms of downburst winds characterized by straight-lined windstorms.<ref name="noaa">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="EW">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref>

Downbursts create vertical wind shear or microbursts, which are dangerous to aviation.<ref name="National1992">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> These convective downbursts can produce damaging winds, lasting 5 to 30 minutes, with wind speeds as high as {{safesubst:#invoke:convert|convert}}, and cause tornado-like damage on the ground. Downbursts also occur much more frequently than tornadoes, with ten downburst damage reports for every one tornado.<ref name=columbia>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Squall line

Cyclonic vortex over Pennsylvania with a trailing squall line.

{{#invoke:main|main}} A squall line is an elongated line of severe thunderstorms that can form along or ahead of a cold front.<ref name="Glossary2009a">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Glossary2009b">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The squall line typically contains heavy precipitation, hail, frequent lightning, strong straight line winds, and possibly tornadoes or waterspouts.<ref name="Office2008">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Severe weather in the form of strong straight-line winds can be expected in areas where the squall line forms a bow echo, in the farthest portion of the bow.<ref name="Glossary2009c">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Tornadoes can be found along waves within a line echo wave pattern (LEWP) where mesoscale low pressure areas are present.<ref name="Glossary2009d">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> Some{{ safesubst:#invoke:Unsubst||$N=Which |date=__DATE__ |$B= {{#invoke:Category handler|main}}[which?] }} summer bow echoes are called derechos, and move quickly over large territories.<ref name="noaa" /> A wake low or a mesoscale low pressure area forms behind the rain shield (a high pressure system under the rain canopy) of a mature squall line and is sometimes associated with a heat burst.<ref name="Glossary2009e">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref>

Squall lines often cause severe straight-line wind damage, and most non-tornadic wind damage is caused from squall lines.<ref name=Louisville>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Although the primary danger from squall lines is straight-line winds, some squall lines also contain weak tornadoes.<ref name=Louisville/>

Tropical cyclone

Hurricane Isabel (2003) as seen from orbit during Expedition 7 of the International Space Station.

{{#invoke:main|main}} Very high winds can be caused by mature tropical cyclones (called hurricanes in the United States and Canada and typhoons in eastern Asia). A tropical cyclone's heavy surf created by such winds may cause harm to marine life either close to or upon the surface of the water, such as coral reefs.<ref name="Dan2004">{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref> Coastal regions may receive significant damage from a tropical cyclone while inland regions are relatively safe from the strong winds, due to their rapid dissipation over land. However, severe flooding can occur even far inland because of high amounts of rain from tropical cyclones and their remnants.



File:Great Lakes Waterspouts.jpg
Formation of numerous waterspouts in the Great Lakes region.

Waterspouts are generally defined as tornadoes or non-supercell tornadoes that develop over bodies of water.<ref name="Glossary">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Waterspouts are not known for inflicting much damage because they are not commonly exposed to land, but they are capable of traveling over land. Some waterspouts are known to produce hurricane-strength winds and are capable of producing equivalent damage. Vegetation, weakly constructed buildings, and other infrastructure may be destroyed by waterspouts. Automobiles may be lifted by advancing waterspouts. Heavy precipitation may be noted, developed from the water raised by the wind currents. Waterspouts do not generally last long over terrestrial environments as the friction produced easily dissipates the winds. Strong horizontal winds cause waterspouts to dissipate,<ref name="">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> destroying the concentration of the updrafts. While not generally as dangerous as "classic" tornadoes, waterspouts can overturn boats, and they can cause severe damage to larger ships.<ref name=spc-faq/>

Strong extratropical cyclones

File:Intense Nor'Easter over the N. Alantic on Mar 26, 2014.png
GOES-13 Imagery of an intense Nor'Easter that impacted the North East US on Mar 26, 2014 and produced recorded gusts of 101mph+

{{#invoke:main|main}} Severe local windstorms in Europe that develop from winds off the North Atlantic. These windstorms are commonly associated with the destructive extratropical cyclones and their low pressure frontal systems.<ref name="EuropeanWindstorms">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> European windstorms occur mainly in the seasons of autumn and winter.<ref name="EuroWind">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

A synoptic-scale extratropical storm along the East Coast of the United States and Atlantic Canada is called a Nor'easter. They are so named because their winds come from the northeast, especially in the coastal areas of the Northeastern United States and Atlantic Canada. More specifically, it describes a low pressure area whose center of rotation is just off the East Coast and whose leading winds in the left forward quadrant rotate onto land from the northeast. Nor'easters may cause coastal flooding, coastal erosion, and hurricane force winds.

Dust storm

{{#invoke:main|main}} An unusual form of windstorm that is characterized by the existence of large quantities of sand and dust particles carried by moving air.<ref name="Glossary_a">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Dust storms frequently develop during periods of droughts, or over arid and semi-arid regions.

A massive dust storm cloud is close to enveloping a military camp as it rolls over Al Asad, Iraq, just before nightfall on April 27, 2005.

Dust storms have numerous hazards and are capable of causing deaths. Visibility may be reduced dramatically, so risks of vehicle and aircraft crashes are possible. Additionally, the particulates may reduce oxygen intake by the lungs,<ref name="Duststorms">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> potentially resulting in suffocation. Damage can also be inflicted upon the eyes due to abrasion.<ref name="DustStorm">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Dust storms can produce many issues for agricultural industries as well. Soil erosion is one of the most common hazards and decreases arable lands. Dust and sand particles can cause severe weathering of buildings and rock formations. Nearby bodies of water may be polluted by settling dust and sand, killing aquatic organisms. Decrease in exposure to sunlight can affect plant growth, as well as decrease in infrared radiation may cause decreased temperatures.



Wildfire in Yellowstone National Park produces a pyrocumulus cloud

The most common cause of wildfires varies throughout the world. In the United States, Canada, and Northwest China, lightning is the major source of ignition. In other parts of the world, human involvement is a major contributor. For instance, in Mexico, Central America, South America, Africa, Southeast Asia, Fiji, and New Zealand, wildfires can be attributed to human activities such as animal husbandry, agriculture, and land-conversion burning. Human carelessness is a major cause of wildfires in China and in the Mediterranean Basin. In Australia, the source of wildfires can be traced to both lightning strikes and human activities such as machinery sparks and cast-away cigarette butts."<ref name=Krock>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Wildfires have a rapid forward rate of spread (FROS) when burning through dense, uninterrupted fuels.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> They can move as fast as {{safesubst:#invoke:convert|convert}} in forests and {{safesubst:#invoke:convert|convert}} in grasslands.<ref>Billing, 5-6</ref> Wildfires can advance tangential to the main front to form a flanking front, or burn in the opposite direction of the main front by backing.<ref>Graham, et al.., 12</ref>

Wildfires may also spread by jumping or spotting as winds and vertical convection columns carry firebrands (hot wood embers) and other burning materials through the air over roads, rivers, and other barriers that may otherwise act as firebreaks.<ref name = underfire>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Graham, et al.., 16.</ref> Torching and fires in tree canopies encourage spotting, and dry ground fuels that surround a wildfire are especially vulnerable to ignition from firebrands.<ref>Graham, et al.., 9, 16.</ref> Spotting can create spot fires as hot embers and firebrands ignite fuels downwind from the fire. In Australian bushfires, spot fires are known to occur as far as {{safesubst:#invoke:convert|convert}} from the fire front.<ref>Billing, 5</ref> Since the mid-1980s, earlier snowmelt and associated warming has also been associated with an increase in length and severity of the wildfire season in the Western United States.<ref name="Westerling2006">{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref>

Severe weather sections
Intro  Terminology  Causes  Categories  High winds  Hail  Heavy rainfall and flooding  Severe winter weather  Heat and drought  References  

High winds
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