, which can precede the onset of high winds High winds are known to cause damage, depending upon their strength. Wind speeds as low as may lead to power outages when tree branches fall and disrupt power lines. 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. 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. 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. Once winds exceed 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 . The
Saffir–Simpson scale for cyclones and
Enhanced Fujita scale (
TORRO scale in Europe) for tornadoes were developed to help estimate wind speed from the damage they cause.
Tornado , Canada, 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. Tornadoes' wind speeds generally average between and . They are approximately across and travel a few miles (kilometers) before dissipating. Some attain wind speeds in excess of , may stretch more than two miles (3.2 km) across, and maintain contact with the ground for dozens of miles (more than 100 km). The
Enhanced Fujita Scale and the
TORRO Scale are two examples of scales used to rate the strength, intensity and/or damage of a tornado. 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.
Waterspout Waterspouts are generally defined as tornadoes or non-
supercell tornadoes that develop over bodies of water. Waterspouts typically do not do much damage because they occur over open water, but they are capable of traveling over land. Vegetation, weakly constructed buildings, and other infrastructure may be damaged or destroyed by waterspouts. Waterspouts do not generally last long over terrestrial environments as the friction produced easily dissipates the winds. Strong horizontal winds will cause waterspouts to dissipate as they disturb the vortex. While not generally as dangerous as "classic" tornadoes, waterspouts can overturn boats, and they can cause severe damage to larger ships. while
wet downbursts are generated by thunderstorms with large amounts of rainfall.
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). 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.
Derechos are longer, usually stronger, forms of downburst winds characterized by straight-lined windstorms. Downbursts create vertical
wind shear or
microbursts, which are dangerous to aviation. These
convective downbursts can produce damaging winds, lasting 5 to 30 minutes, with wind speeds as high as , 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.
Squall line over Pennsylvania with a trailing squall line A squall line is an elongated line of
severe thunderstorms that can form along or ahead of a
cold front. The squall line typically contains heavy
precipitation,
hail, frequent
lightning, strong straight line winds, and possibly
tornadoes or
waterspouts. 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.
Tornadoes can be found along waves within a line echo wave pattern (LEWP) where mesoscale
low-pressure areas are present. Intense bow echoes responsible for widespread, extensive wind damage are called
derechos, and move quickly over large territories. Squall lines often cause severe straight-line wind damage, and most non-tornadic wind damage is caused from squall lines. Although the primary danger from squall lines is straight-line winds, some squall lines also contain weak tornadoes. Coastal regions usually take more serious wind damage than inland, due to rapid dissipation upon landfall, though heavy rain from their remnants may flood either.
Strong extratropical cyclones Imagery of an intense Nor'Easter that impacted the North East US on 26 March 2014 and produced recorded gusts of 101mph+ 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. European windstorms occur mainly in the seasons of autumn and winter. Severe European windstorms are often characterized by heavy precipitation as well. A
synoptic-scale extratropical storm along the upper
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 upper 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, heavy rain or snow, and
hurricane-force winds. The precipitation pattern of Nor'easters is similar to other mature
extratropical storms. Nor'easters can cause heavy rain or snow, either within their comma-head precipitation pattern or along their trailing cold or stationary front. Nor'easters can occur at any time of the year but are mostly known for their presence in the winter season.
Dust storm A dust storm is an unusual form of windstorm that is characterized by the existence of large quantities of sand and dust particles carried by the wind. Dust storms frequently develop during periods of droughts, or over arid and semi-arid regions. ) is close to enveloping a military camp as it rolls over
Al Asad Airbase,
Iraq, just before nightfall on 27 April 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, potentially resulting in suffocation. Damage can also be inflicted upon the eyes due to abrasion. Dust storms cause 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.
Wildfires 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." Wildfires have a rapid
forward rate of spread (FROS) when burning through dense, uninterrupted fuels. They can move as fast as in forests and in grasslands. 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. 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. Torching and fires in tree canopies encourage spotting, and dry ground fuels that surround a wildfire are especially vulnerable to ignition from firebrands. 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 from the fire front. 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. ==Hail==