Extratropical cyclone

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A powerful extratropical cyclone over the North Pacific Ocean in January 2018, with an eye-like feature and a long cold front extending to the tropics Northwest Pacific cyclone 2018-01-23 0230Z.png
A powerful extratropical cyclone over the North Pacific Ocean in January 2018, with an eye-like feature and a long cold front extending to the tropics

Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of producing anything from cloudiness and mild showers to heavy gales, thunderstorms, blizzards, and tornadoes. These types of cyclones are defined as large scale (synoptic) low pressure weather systems that occur in the middle latitudes of the Earth. In contrast with tropical cyclones, extratropical cyclones produce rapid changes in temperature and dew point along broad lines, called weather fronts, about the center of the cyclone. [1]

A low-pressure area, low, depression or cyclone is a region on the topographic map where the atmospheric pressure is lower than that of surrounding locations. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the troposphere. The formation process of a low-pressure area is known as cyclogenesis. Within the field of meteorology, atmospheric divergence aloft occurs in two areas. The first area is on the east side of upper troughs, which form half of a Rossby wave within the Westerlies. A second area of wind divergence aloft occurs ahead of embedded shortwave troughs, which are of smaller wavelength. Diverging winds aloft ahead of these troughs cause atmospheric lift within the troposphere below, which lowers surface pressures as upward motion partially counteracts the force of gravity.

Anticyclone opposite to a cyclone

An anticyclone is a weather phenomenon defined by the United States National Weather Service's glossary as "a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere". Effects of surface-based anticyclones include clearing skies as well as cooler, drier air. Fog can also form overnight within a region of higher pressure. Mid-tropospheric systems, such as the subtropical ridge, deflect tropical cyclones around their periphery and cause a temperature inversion inhibiting free convection near their center, building up surface-based haze under their base. Anticyclones aloft can form within warm core lows such as tropical cyclones, due to descending cool air from the backside of upper troughs such as polar highs, or from large scale sinking such as the subtropical ridge. The evolution of an anticyclone depends on a few variables such as its size, intensity, moist-convection, Coriolis force etc.

High-pressure area region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment

A high-pressure area, high or anticyclone is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment.

Contents

Terminology

This animation shows an extratropical cyclone developing over the United States, starting late on October 25 and running through October 27, 2010.

The term "cyclone" applies to numerous types of low pressure areas, one of which is the extratropical cyclone. The descriptor extratropical signifies that this type of cyclone generally occurs outside the tropics and in the middle latitudes of Earth between 30° and 60° latitude. They are termed mid-latitude cyclones if they form within those latitudes, or post-tropical cyclones if a tropical cyclone has intruded into the mid latitudes. [1] [2] Weather forecasters and the general public often describe them simply as "depressions" or "lows". Terms like frontal cyclone, frontal depression, frontal low, extratropical low, non-tropical low and hybrid low are often used as well.

Cyclone large scale air mass that rotates around a strong center of low pressure

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 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.

Latitude The angle between zenith at a point and the plane of the equator

In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle which ranges from 0° at the Equator to 90° at the poles. Lines of constant latitude, or parallels, run east–west as circles parallel to the equator. Latitude is used together with longitude to specify the precise location of features on the surface of the Earth. On its own, the term latitude should be taken to be the geodetic latitude as defined below. Briefly, geodetic latitude at a point is the angle formed by the vector perpendicular to the ellipsoidal surface from that point, and the equatorial plane. Also defined are six auxiliary latitudes which are used in special applications.

A post-tropical cyclone is a former tropical cyclone. Two classes of post-tropical cyclones are:

Extratropical cyclones are classified mainly as baroclinic, because they form along zones of temperature and dewpoint gradient known as frontal zones. They can become barotropic late in their life cycle, when the distribution of heat around the cyclone becomes fairly uniform with its radius. [3]

Baroclinity A measure of misalignment between the gradient of pressure and the gradient of density in a fluid

In fluid dynamics, the baroclinity of a stratified fluid is a measure of how misaligned the gradient of pressure is from the gradient of density in a fluid. In meteorology a baroclinic atmosphere is one for which the density depends on both the temperature and the pressure; contrast this with a barotropic atmosphere, for which the density depends only on the pressure. In atmospheric terms, the barotropic zones of the Earth are generally found in the central latitudes, or tropics, whereas the baroclinic areas are generally found in the mid-latitude/polar regions.

Gradient Multi-variable generalization of the derivative of a function

In vector calculus, the gradient is a multi-variable generalization of the derivative. Whereas the ordinary derivative of a function of a single variable is a scalar-valued function, the gradient of a function of several variables is a vector-valued function. Specifically, the gradient of a differentiable function of several variables, at a point , is the vector whose components are the partial derivatives of at .

Formation

Approximate areas of extratropical cyclone formation worldwide Extratropical formation areas.jpg
Approximate areas of extratropical cyclone formation worldwide
An upper level jet streak. DIV areas are regions of divergence aloft, which will lead to surface convergence and aid cyclogenesis. Jetstreak.png
An upper level jet streak. DIV areas are regions of divergence aloft, which will lead to surface convergence and aid cyclogenesis.

Extratropical cyclones form anywhere within the extratropical regions of the Earth (usually between 30° and 60° latitude from the equator), either through cyclogenesis or extratropical transition. A study of extratropical cyclones in the Southern Hemisphere shows that between the 30th and 70th parallels, there are an average of 37 cyclones in existence during any 6-hour period. [4] A separate study in the Northern Hemisphere suggests that approximately 234 significant extratropical cyclones form each winter. [5]

Equator Intersection of a spheres surface with the plane perpendicular to the spheres axis of rotation and midway between the poles

An equator of a rotating spheroid is its zeroth circle of latitude (parallel). It is the imaginary line on the spheroid, equidistant from its poles, dividing it into northern and southern hemispheres. In other words, it is the intersection of the spheroid with the plane perpendicular to its axis of rotation and midway between its geographical poles.

Southern Hemisphere part of Earth that lies south of the equator

The Southern Hemisphere is the half of Earth that is south of the Equator. It contains all or parts of five continents, four oceans and most of the Pacific Islands in Oceania. Its surface is 80.9% water, compared with 60.7% water in the case of the Northern Hemisphere, and it contains 32.7% of Earth's land.

30th parallel south circle of latitude

The 30th parallel south is a circle of latitude that is 30 degrees south of the Earth's equatorial plane. It crosses the Atlantic Ocean, Africa, the Indian Ocean, Australasia, the Pacific Ocean and South America.

Cyclogenesis

Extratropical cyclones form along linear bands of temperature/dewpoint gradient with significant vertical wind shear, and are thus classified as baroclinic cyclones. Initially, cyclogenesis, or low pressure formation, occurs along frontal zones near a favorable quadrant of a maximum in the upper level jetstream known as a jet streak. The favorable quadrants are usually at the right rear and left front quadrants, where divergence ensues. [6] The divergence causes air to rush out from the top of the air column. As mass in the column is reduced, atmospheric pressure at surface level (the weight of the air column) is reduced. The lowered pressure strengthens the cyclone (a low pressure system). The lowered pressure acts to draw in air, creating convergence in the low-level wind field. Low-level convergence and upper-level divergence imply upward motion within the column, making cyclones tend to be cloudy. As the cyclone strengthens, the cold front sweeps towards the equator and moves around the back of the cyclone. Meanwhile, its associated warm front progresses more slowly, as the cooler air ahead of the system is denser, and therefore more difficult to dislodge. Later, the cyclones occlude as the poleward portion of the cold front overtakes a section of the warm front, forcing a tongue, or trowal, of warm air aloft. Eventually, the cyclone will become barotropically cold and begin to weaken.

Wind shear

Wind shear, sometimes referred to as wind gradient, is a difference in wind speed or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal wind shear. Vertical wind shear is a change in wind speed or direction with change in altitude. Horizontal wind shear is a change in wind speed with change in lateral position for a given altitude.

Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere. Cyclogenesis is an umbrella term for at least three different processes, all of which result in the development of some sort of cyclone, and at any size from the microscale to the synoptic scale.

Surface weather analysis

Surface weather analysis is a special type of weather map that provides a view of weather elements over a geographical area at a specified time based on information from ground-based weather stations.

Atmospheric pressure can fall very rapidly when there are strong upper level forces on the system. When pressures fall more than 1 millibar (0.030  inHg ) per hour, the process is called explosive cyclogenesis, and the cyclone can be described as a (weather) bomb. [7] [8] [9] These bombs rapidly drop in pressure to below 980 millibars (28.94 inHg) under favorable conditions such as near a natural temperature gradient like the Gulf Stream, or at a preferred quadrant of an upper level jet streak, where upper level divergence is best. The stronger the upper level divergence over the cyclone, the deeper the cyclone can become. Hurricane-force extratropical cyclones are most likely to form in the northern Atlantic and northern Pacific oceans in the months of December and January. [10] On 14 and 15 December 1986, an extratropical cyclone near Iceland deepened to below 920 hectopascals (27 inHg), [11] which is a pressure equivalent to a category 5 hurricane. In the Arctic, the average pressure for cyclones is 980 millibars (28.94 inHg) during the winter, and 1,000 millibars (29.53 inHg) during the summer. [12]

Atmospheric pressure, sometimes also called barometric pressure, is the pressure within the atmosphere of Earth. The standard atmosphere is a unit of pressure defined as 1013.25 mbar (101325 Pa), equivalent to 760 mm Hg (torr), 29.9212 inches Hg, or 14.696 psi. The atm unit is roughly equivalent to the mean sea-level atmospheric pressure on Earth, that is, the Earth's atmospheric pressure at sea level is approximately 1 atm.

Bar (unit) non-SI unit of pressure

The bar is a metric unit of pressure, but is not approved as part of the International System of Units (SI). It is defined as exactly equal to 100,000 Pa, which is slightly less than the current average atmospheric pressure on Earth at sea level.

Inch of mercury is a unit of measurement for pressure. It is still used for barometric pressure in weather reports, refrigeration and aviation in the United States.

Extratropical transition

Hurricane Cristobal (2014) in the north Atlantic after completing its transition to an extratropical cyclone from a hurricane Cristobal Aug 29 2014 1615Z.jpg
Hurricane Cristobal (2014) in the north Atlantic after completing its transition to an extratropical cyclone from a hurricane

Tropical cyclones often transform into extratropical cyclones at the end of their tropical existence, usually between 30° and 40° latitude, where there is sufficient forcing from upper-level troughs or shortwaves riding the Westerlies for the process of extratropical transition to begin. [13] During this process, a cyclone in extratropical transition (known across the eastern North Pacific and North Atlantic oceans as the post-tropical stage), [14] [15] will invariably form or connect with nearby fronts and/or troughs consistent with a baroclinic system. Due to this, the size of the system will usually appear to increase, while the core weakens. However, after transition is complete, the storm may re-strengthen due to baroclinic energy, depending on the environmental conditions surrounding the system. [13] The cyclone will also distort in shape, becoming less symmetric with time. [16] [17] [18]

During extratropical transition, the cyclone begins to tilt back into the colder airmass with height, and the cyclone's primary energy source converts from the release of latent heat from condensation (from thunderstorms near the center) to baroclinic processes. The low pressure system eventually loses its warm core and becomes a cold-core system. [18] [16]

The peak time of subtropical cyclogenesis (the midpoint of this transition) in the North Atlantic is in the months of September and October, when the difference between the temperature of the air aloft and the sea surface temperature is the greatest, leading to the greatest potential for instability. [19] On rare occasions, an extratropical cyclone can transit into a tropical cyclone if it reaches an area of ocean with warmer waters and an environment with less vertical wind shear. [20] An example of this happening is in the 1991 Perfect Storm. [21] The process known as "tropical transition" involves the usually slow development of an extratropically cold core vortex into a tropical cyclone. [22] [23]

The Joint Typhoon Warning Center uses the extratropical transition (XT) technique to subjectively estimate the intensity of tropical cyclones becoming extratropical based on visible and infrared satellite imagery. Loss of central convection in transitioning tropical cyclones can cause the Dvorak technique to fail; [24] the loss of convection results in unrealistically low estimates using the Dvorak technique. [25] The system combines aspects of the Dvorak technique, used for estimating tropical cyclone intensity, and the Hebert-Poteat technique, used for estimating subtropical cyclone intensity. [26] The technique is applied when a tropical cyclone interacts with a frontal boundary or loses its central convection while maintaining its forward speed or accelerating. [27] The XT scale corresponds to the Dvorak scale and is applied in the same way, except that "XT" is used instead of "T" to indicate that the system is undergoing extratropical transition. [28] Also, the XT technique is only used once extratropical transition begins; the Dvorak technique is still used if the system begins dissipating without transition. [27] Once the cyclone has completed transition and become cold-core, the technique is no longer used. [28]

Structure

Surface pressure and wind distribution

QuikSCAT image of typical extratropical cyclones over the ocean. Note the maximum winds are on the outside of the occlusion. Quikscatcyclone.jpg
QuikSCAT image of typical extratropical cyclones over the ocean. Note the maximum winds are on the outside of the occlusion.

The windfield of an extratropical cyclone constricts with distance in relation to surface level pressure, with the lowest pressure being found near the center, and the highest winds typically just on the cold/poleward side of warm fronts, occlusions, and cold fronts, where the pressure gradient force is highest. [29] The area poleward and west of the cold and warm fronts connected to extratropical cyclones is known as the cold sector, while the area equatorward and east of its associated cold and warm fronts is known as the warm sector.

Extratropical cyclones spin clockwise in the Southern Hemisphere, just like tropical cyclones. Extratropical cyclone off Australia 2016-12-28 0230Z.jpg
Extratropical cyclones spin clockwise in the Southern Hemisphere, just like tropical cyclones.

The wind flow around an extratropical cyclone is counterclockwise in the northern hemisphere, and clockwise in the southern hemisphere, due to the Coriolis effect (this manner of rotation is generally referred to as cyclonic). Near this center, the pressure gradient force (from the pressure at the center of the cyclone compared to the pressure outside the cyclone) and the Coriolis force must be in an approximate balance for the cyclone to avoid collapsing in on itself as a result of the difference in pressure. [30] The central pressure of the cyclone will lower with increasing maturity, while outside of the cyclone, the sea-level pressure is about average. In most extratropical cyclones, the part of the cold front ahead of the cyclone will develop into a warm front, giving the frontal zone (as drawn on surface weather maps) a wave-like shape. Due to their appearance on satellite images, extratropical cyclones can also be referred to as frontal waves early in their life cycle. In the United States, an old name for such a system is "warm wave". [31]

In the northern hemisphere, once a cyclone occludes, a trough of warm air aloft—or "trowal" for short—will be caused by strong southerly winds on its eastern periphery rotating aloft around its northeast, and ultimately into its northwestern periphery (also known as the warm conveyor belt), forcing a surface trough to continue into the cold sector on a similar curve to the occluded front. The trowal creates the portion of an occluded cyclone known as its comma head, due to the comma-like shape of the mid-tropospheric cloudiness that accompanies the feature. It can also be the focus of locally heavy precipitation, with thunderstorms possible if the atmosphere along the trowal is unstable enough for convection. [32]

Vertical structure

Extratropical cyclones slant back into colder air masses and strengthen with height, sometimes exceeding 30,000 feet (approximately 9 km) in depth. [33] Above the surface of the earth, the air temperature near the center of the cyclone is increasingly colder than the surrounding environment. These characteristics are the direct opposite of those found in their counterparts, tropical cyclones; thus, they are sometimes called "cold-core lows". [34] Various charts can be examined to check the characteristics of a cold-core system with height, such as the 700 millibars (20.67 inHg) chart, which is at about 10,000 feet (3,048 meters) altitude. Cyclone phase diagrams are used to tell whether a cyclone is tropical, subtropical, or extratropical. [35]

Cyclone evolution

A hurricane-force extratropical cyclone in January 2016 with a distinct eye-like feature, caused by a warm seclusion Alex 2016-01-10 1635Z.jpg
A hurricane-force extratropical cyclone in January 2016 with a distinct eye-like feature, caused by a warm seclusion

There are two models of cyclone development and lifecycles in common use—the Norwegian model and the Shapiro-Keyser Model. [36]

Norwegian cyclone model

Of the two theories on extratropical cyclone structure and life cycle, the older is the Norwegian Cyclone Model, developed during World War I. In this theory, cyclones develop as they move up and along a frontal boundary, eventually occluding and reaching a barotropically cold environment. [37] It was developed completely from surface-based weather observations, including descriptions of clouds found near frontal boundaries. This theory still retains merit, as it is a good description for extratropical cyclones over continental landmasses.

Shapiro-Keyser model

A second competing theory for extratropical cyclone development over the oceans is the Shapiro-Keyser model, developed in 1990. [38] Its main differences with the Norwegian Cyclone Model are the fracture of the cold front, treating warm-type occlusions and warm fronts as the same, and allowing the cold front to progress through the warm sector perpendicular to the warm front. This model was based on oceanic cyclones and their frontal structure, as seen in surface observations and in previous projects which used aircraft to determine the vertical structure of fronts across the northwest Atlantic.

Warm seclusion

A warm seclusion is the mature phase of the extratropical cyclone lifecycle. This was conceptualized after the ERICA field experiment of the late 1980s, which produced observations of intense marine cyclones that indicated an anomalously warm low-level thermal structure, secluded (or surrounded) by a bent-back warm front and a coincident chevron-shaped band of intense surface winds. [39] The Norwegian Cyclone Model, as developed by the Bergen School of Meteorology, largely observed cyclones at the tail end of their lifecycle and used the term occlusion to identify the decaying stages.

Warm seclusions may have cloud-free, eye-like features at their center (reminiscent of tropical cyclones), significant pressure falls, hurricane-force winds, and moderate to strong convection. The most intense warm seclusions often attain pressures less than 950 millibars (28.05 inHg) with a definitive lower to mid-level warm core structure. [39] A warm seclusion, the result of a baroclinic lifecycle, occurs at latitudes well poleward of the tropics.

As latent heat flux releases are important for their development and intensification, most warm seclusion events occur over the oceans; they may impact coastal nations with hurricane force winds and torrential rain. [38] [40] Climatologically, the Northern Hemisphere sees warm seclusions during the cold season months, while the Southern Hemisphere may see a strong cyclone event such as this during all times of the year.

In all tropical basins, except the Northern Indian Ocean, the extratropical transition of a tropical cyclone may result in reintensification into a warm seclusion. For example, Hurricane Maria of 2005 reintensified into a strong baroclinic system and achieved warm seclusion status at maturity (or lowest pressure). [41]

Motion

A zonal flow regime. Note the dominant west-to-east flow as shown in the 500 hPa height pattern. Zonalflow.gif
A zonal flow regime. Note the dominant west-to-east flow as shown in the 500 hPa height pattern.
A February 24, 2007 radar image of a large extratropical cyclonic storm system at its peak over the central United States. Feb242007 blizzard.gif
A February 24, 2007 radar image of a large extratropical cyclonic storm system at its peak over the central United States.

Extratropical cyclones are generally driven, or "steered", by deep westerly winds in a general west to east motion across both the Northern and Southern hemispheres of the Earth. This general motion of atmospheric flow is known as "zonal". [42] Where this general trend is the main steering influence of an extratropical cyclone, it is known as a "zonal flow regime".

When the general flow pattern buckles from a zonal pattern to the meridional pattern, [43] a slower movement in a north or southward direction is more likely. Meridional flow patterns feature strong, amplified troughs and ridges, generally with more northerly and southerly flow.

Changes in direction of this nature are most commonly observed as a result of a cyclone's interaction with other low pressure systems, troughs, ridges, or with anticyclones. A strong and stationary anticyclone can effectively block the path of an extratropical cyclone. Such blocking patterns are quite normal, and will generally result in a weakening of the cyclone, the weakening of the anticyclone, a diversion of the cyclone towards the anticyclone's periphery, or a combination of all three to some extent depending on the precise conditions. It is also common for an extratropical cyclone to strengthen as the blocking anticyclone or ridge weakens in these circumstances. [44]

Where an extratropical cyclone encounters another extratropical cyclone (or almost any other kind of cyclonic vortex in the atmosphere), the two may combine to become a binary cyclone, where the vortices of the two cyclones rotate around each other (known as the "Fujiwhara effect"). This most often results in a merging of the two low pressure systems into a single extratropical cyclone, or can less commonly result in a mere change of direction of either one or both of the cyclones. [45] The precise results of such interactions depend on factors such as the size of the two cyclones, their strength, their distance from each other, and the prevailing atmospheric conditions around them.

Effects

Preferred region of snowfall in an extratropical cyclone Snowcsi.gif
Preferred region of snowfall in an extratropical cyclone

General

Extratropical cyclones can bring mild weather with a little rain and surface winds of 15–30 km/h (9.3–18.6 mph), or they can be cold and dangerous with torrential rain and winds exceeding 119 km/h (74 mph), [46] (sometimes referred to as windstorms in Europe). The band of precipitation that is associated with the warm front is often extensive. In mature extratropical cyclones, an area known as the comma head on the northwest periphery of the surface low can be a region of heavy precipitation, frequent thunderstorms, and thundersnows. Cyclones tend to move along a predictable path at a moderate rate of progress. During fall, winter, and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall.

Severe weather

Squall lines, or solid bands of strong thunderstorms, can form ahead of cold fronts and lee troughs due to the presence of significant atmospheric moisture and strong upper level divergence, leading to hail and high winds. [47] When significant directional wind shear exists in the atmosphere ahead of a cold front in the presence of a strong upper level jet stream, tornado formation is possible. [48] Although tornadoes can form anywhere on Earth, the greatest number occur in the Great Plains in the United States, because downsloped winds off the north-south oriented Rocky Mountains, which can form a dryline, aid their development at any strength.

Explosive development of extratropical cyclones can be sudden. The storm known in Great Britain and Ireland as the "Great Storm of 1987" deepened to 953 millibars (28.14 inHg) with a highest recorded wind of 220 km/h (140 mph), resulting in the loss of 19 lives, 15 million trees, widespread damage to homes and an estimated economic cost of £1.2 billion (US$2.3 billion). [49]

Although most tropical cyclones that become extratropical quickly dissipate or are absorbed by another weather system, they can still retain winds of hurricane or gale force. In 1954, Hurricane Hazel became extratropical over North Carolina as a strong Category 3 storm. The Columbus Day Storm of 1962, which evolved from the remains of Typhoon Freda, caused heavy damage in Oregon and Washington, with widespread damage equivalent to at least a Category 3. In 2005, Hurricane Wilma began to lose tropical characteristics while still sporting Category 3-force winds (and became fully extratropical as a Category 1 storm). [50]

In summer, extratropical cyclones are generally weak, but some of the systems can cause significant floods overland because of torrential rainfall. The July 2016 North China cyclone never brought gale-force sustained winds, but it caused devastating floods in mainland China, resulting in at least 184 deaths and ¥33.19 billion (US$4.96 billion) of damage. [51] [52]

Climate and general circulation

In the classic analysis by Edward Lorenz (the Lorenz energy cycle), [53] extratropical cyclones (so-called atmospheric transients) acts as a mechanism in converting potential energy that is created by pole to equator temperature gradients to eddy kinetic energy. In the process, the pole-equator temperature gradient is reduced (i.e. energy is transported poleward to warm up the higher latitudes).

The existence of such transients are also closely related to the formation of the Icelandic and Aleutian Low — the two most prominent general circulation features in the mid- to sub-polar northern latitudes. [54] The two lows are formed by both the transport of kinetic energy and the latent heating (the energy released when water phase changed from vapor to liquid during precipitation) from the extratropical cyclones.

Historic storms

Cyclone Oratia showing the comma shape typical of extratropical cyclones, over Europe in October 2000. Storm Oratia 30 Oct 2000.jpg
Cyclone Oratia showing the comma shape typical of extratropical cyclones, over Europe in October 2000.

A violent storm during the Crimean War on November 14, 1854, wrecked 30 vessels, and sparked initial investigations into meteorology and forecasting in Europe. In the United States, the Columbus Day Storm of 1962, one of many Pacific Northwest windstorms, led to Oregon's lowest measured pressure of 965.5  hPa (96.55 kPa; 28.51 inHg), violent winds, and US$170 million in damage (1964 dollars). [55] The "Wahine storm" was an extratropical cyclone that struck Wellington, New Zealand on April 10, 1968, so named after causing the inter-island ferry TEV Wahine to strike a reef and founder at the entrance to Wellington Harbour, resulting in 53 deaths. On November 10, 1975, an extratropical storm on Lake Superior contributed to the sinking of the SS Edmund Fitzgerald near the Canada–US border, 15 NM northwest of the entrance to Whitefish Bay. [56] A rapidly strengthening storm struck Vancouver Island on October 11, 1984, and inspired the development of moored buoys off the western coast of Canada. [57] The Braer Storm of January 1993 was the strongest extratropical cyclone known to occur across the northern Atlantic Ocean, with a central pressure of 914 millibars (27.0 inHg). [58] In 2012, Hurricane Sandy transitioned to a post-tropical cyclone on the night of October 29; a few minutes later it made landfall on the New Jersey coast as an extratropical storm with winds similar to a Category 1 hurricane and a wind field of over 1,150 miles (1,850 km).

In the Southern Hemisphere, a violent extratropical storm hit Uruguay on August 23–24, 2005, killing 10 people. [59] The system's winds exceeded 100 mph (160 km/h) while Montevideo, the country's capital with 1.5 million inhabitants, was affected by tropical storm-force winds for over 12 hours and by hurricane-force winds for nearly four hours. [60] Peak gusts were registered at Carrasco International Airport as 107 mph (172 km/h) and at the Harbour of Montevideo as 116 mph (187 km/h). The lowest reported pressure was 991.7 hPa (99.17 kPa; 29.28 inHg). Extratropical cyclones are common in this part of the globe during fall, winter and spring months. The winds usually peak to 80–110 km/h (50–68 mph), and winds of 116 mph (187 km/h) are very uncommon. [60]

See also

Related Research Articles

Subtropical cyclone

A subtropical cyclone is a weather system that has some characteristics of a tropical and an extratropical cyclone.

The synoptic scale in meteorology is a horizontal length scale of the order of 1000 kilometers or more. This corresponds to a horizontal scale typical of mid-latitude depressions. Most high and low-pressure areas seen on weather maps such as surface weather analyses are synoptic-scale systems, driven by the location of Rossby waves in their respective hemisphere. Low-pressure areas and their related frontal zones occur on the leading edge of a trough within the Rossby wave pattern, while high-pressure areas form on the back edge of the trough. Most precipitation areas occur near frontal zones. The word synoptic is derived from the Greek word συνοπτικός, meaning seen together.

Westerlies

The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes and trend towards the poles and steer extratropical cyclones in this general manner. Tropical cyclones which cross the subtropical ridge axis into the westerlies recurve due to the increased westerly flow. The winds are predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere.

1957 Atlantic hurricane season hurricane season in the Atlantic Ocean

The 1957 Atlantic hurricane season featured the one of longest travelling tropical cyclones in the Atlantic basin, Hurricane Carrie. Nevertheless, the season was generally inactive with eight tropical storms – two of which went unnamed – and three hurricanes, two of which intensified further to attain major hurricane intensity. The season officially began on June 15 and ended on November 15, though the year's first tropical cyclone developed prior to the start of the season on June 8. The final storm dissipated on October 27, well before the official end of the season. The strongest hurricane of the year was Carrie, which reached the equivalent of a Category 4 hurricane on the Saffir–Simpson hurricane scale on two separate occasions in the open Atlantic; Carrie later caused the sinking of the German ship Pamir southwest of the Azores, resulting in 80 deaths.

Hurricane Catarina South Atlantic tropical cyclone of March 2004

Hurricane Catarina was an extremely rare South Atlantic tropical cyclone that hit Southern Brazil in late March 2004. The storm developed out of a stationary cold-core upper-level trough on March 12. Almost a week later, on March 19, a disturbance developed along the trough and traveled towards the east-southeast until March 22 when a ridge stopped the forward motion of the disturbance. The disturbance was in an unusually favorable environment with a slightly below-average wind shear and above-average sea surface temperatures. The combination of the two led to a slow transition from an extratropical cyclone to a subtropical cyclone by March 24. The storm continued to obtain tropical characteristics and became a tropical storm the next day while the winds steadily increased. The storm attained wind speeds of 75 mph (120 km/h)—equivalent to a low-end Category 1 hurricane on the Saffir–Simpson scale—on March 26. At this time it was unofficially named Catarina and was also the first hurricane-strength tropical cyclone ever recorded in the Southern Atlantic Ocean. Unusually favorable conditions persisted and Catarina continued to intensify and was estimated to have peaked with winds of 100 mph (155 km/h) on March 28. The center of the storm made landfall later that day at the time between the cities of Passo de Torres and Balneário Gaivota, Santa Catarina. Catarina rapidly weakened upon landfall and dissipated on the next day.

1940 Atlantic hurricane season hurricane season in the Atlantic Ocean

The 1940 Atlantic hurricane season was a generally average period of tropical cyclogenesis in 1940. Though the season had no official bounds, most tropical cyclone activity occurred during August and September. Throughout the year, fourteen tropical cyclones formed, of which nine reached tropical storm intensity; six were hurricanes. None of the hurricanes reached major hurricane intensity. Tropical cyclones that did not approach populated areas or shipping lanes, especially if they were relatively weak and of short duration, may have remained undetected. Because technologies such as satellite monitoring were not available until the 1960s, historical data on tropical cyclones from this period are often not reliable. As a result of a reanalysis project which analyzed the season in 2012, an additional hurricane was added to HURDAT. The year's first tropical storm formed on May 19 off the northern coast of Hispaniola. At the time, this was a rare occurrence, as only four other tropical disturbances were known to have formed prior during this period; since then, reanalysis of previous seasons has concluded that there were more than four tropical cyclones in May before 1940. The season's final system was a tropical disturbance situated in the Greater Antilles, which dissipated on November 8.

Hurricane Linda (1997) Category 5 Pacific hurricane in 1997

Hurricane Linda was the second-strongest eastern Pacific hurricane on record. Forming from a tropical wave on September 9, 1997, Linda steadily intensified and reached hurricane status within 36 hours of developing. The storm rapidly intensified, reaching sustained winds of 185 mph (295 km/h) and an estimated central pressure of 902 millibars (26.6 inHg); both were records for the eastern Pacific until Hurricane Patricia surpassed them in 2015. The hurricane was briefly forecast to move toward southern California, but instead, it turned out to sea and lost its status as a tropical cyclone on September 17, before dissipating on September 21. Linda was the fifteenth tropical cyclone, thirteenth named storm, seventh hurricane, and fifth major hurricane of the 1997 Pacific hurricane season.

Rainband

A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as banded structure. Rainbands within tropical cyclones are curved in orientation. Tropical cyclone rainbands contain showers and thunderstorms that, together with the eyewall and the eye, constitute a hurricane or tropical storm. The extent of rainbands around a tropical cyclone can help determine the cyclone's intensity.

Rapid intensification

Rapid intensification is a meteorological condition that occurs when a tropical cyclone intensifies dramatically in a short period of time. The United States National Hurricane Center (NHC) defines rapid intensification as an increase in the maximum 1-min sustained winds of a tropical cyclone of at least 30 knots in a 24-hour period.

Tropical cyclogenesis

Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which temperate cyclogenesis occurs. Tropical cyclogenesis involves the development of a warm-core cyclone, due to significant convection in a favorable atmospheric environment.

1996 Lake Huron cyclone

The 1996 Lake Huron cyclone was a strong cyclonic storm system that developed over Lake Huron in September 1996. The system resembled a subtropical cyclone at its peak, having some characteristics of a tropical cyclone.

Explosive cyclogenesis rapidly deepening extratropical cyclonic low-pressure area

Explosive cyclogenesis is the rapid deepening of an extratropical cyclonic low-pressure area. The change in pressure needed to classify something as explosive cyclogenesis is latitude dependent. For example, at 60° latitude, explosive cyclogenesis occurs if the central pressure decreases by 24 mbar (hPa) or more in 24 hours. This is a predominantly maritime, winter event, but also occurs in continental settings, even in the summer. This process is the extratropical equivalent of the tropical rapid deepening. Although their cyclogenesis is totally different from that of tropical cyclones, bombs can produce winds of 74–95 mph, the same order as the first categories of the Saffir-Simpson scale and give heavy precipitation. Even though only a minority of the bombs become so strong, some have caused significant damage.

1975 Pacific Northwest hurricane Category 1 Pacific hurricane in 1975

The 1975 Pacific Northwest hurricane was an unusual Pacific tropical cyclone that attained hurricane status farther north than any other Pacific hurricane. It was officially unnamed, with the cargo ship Transcolorado providing vital meteorological data in assessing the storm. The twelfth tropical cyclone of the 1975 Pacific hurricane season, it developed from a cold-core upper-level low merging with the remnants of a tropical cyclone on August 31, well to the northeast of Hawaii. Convection increased as the circulation became better defined, and by early on September 2 it became a tropical storm. Turning to the northeast through an area of warm water temperatures, the storm quickly strengthened, and, after developing an eye, it attained hurricane status late on September 3, while located about 1,200 miles (1,950 km) south of Alaska. After maintaining peak winds for about 18 hours, the storm rapidly weakened, as it interacted with an approaching cold front. Early on September 5, it lost its identity near the coast of Alaska.

Inflow (meteorology) in meteorology, the flow of a fluid into a large collection of that fluid

Inflow is the flow of a fluid into a large collection of that fluid. Within meteorology, inflow normally refers to the influx of warmth and moisture from air within the Earth's atmosphere into storm systems. Extratropical cyclones are fed by inflow focused along their cold front and warm fronts. Tropical cyclones require a large inflow of warmth and moisture from warm oceans in order to develop significantly, mainly within the lowest 1 kilometre (0.62 mi) of the atmosphere. Once the flow of warm and moist air is cut off from thunderstorms and their associated tornadoes, normally by the thunderstorm's own rain-cooled outflow boundary, the storms begin to dissipate. Rear inflow jets behind squall lines act to erode the broad rain shield behind the squall line, and accelerate its forward motion.

Cold-core low cyclone aloft which has an associated cold pool of air residing at high altitude within the Earths troposphere

A cold-core low, also known as an upper level low or cold-core cyclone, is a cyclone aloft which has an associated cold pool of air residing at high altitude within the Earth's troposphere. It is a low pressure system that strengthens with height in accordance with the thermal wind relationship. If a weak surface circulation forms in response to such a feature at subtropical latitudes of the eastern north Pacific or north Indian oceans, it is called a subtropical cyclone. Cloud cover and rainfall mainly occurs with these systems during the day. Severe weather, such as tornadoes, can occur near the center of cold-core lows. Cold lows can help spawn cyclones with significant weather impacts, such as polar lows, and Kármán vortices. Cold lows can lead directly to the development of tropical cyclones, owing to their associated cold pool of air aloft or by acting as additional outflow channels to aid in further development.

Mediterranean tropical-like cyclone meteorological phenomenon observed over the Mediterranean Sea

Mediterranean tropical-like cyclones, often referred to as medicanes but sometimes also as Mediterranean cyclones or as Mediterranean hurricanes, are meteorological phenomena observed over the Mediterranean Sea. On a few rare occasions, some storms have been observed reaching the strength of a Category 1 hurricane. The main societal hazard posed by Medicanes is not usually from destructive winds, but through life-threatening torrential rains and flash floods.

Glossary of tropical cyclone terms

The following is a glossary of tropical cyclone terms.

References

  1. 1 2 DeCaria (2005-12-07). "ESCI 241 – Meteorology; Lesson 16 – Extratropical Cyclones". Department of Earth Sciences, Millersville University. Archived from the original on 2008-02-08. Retrieved 2009-06-21.
  2. Robert Hart; Jenni Evans (2003). "Synoptic Composites of the Extratropical Transition Lifecycle of North Atlantic TCs as Defined Within Cyclone Phase Space" (PDF). American Meteorological Society . Retrieved 2006-10-03.
  3. Ryan N. Maue (2004-12-07). "Chapter 3: Cyclone Paradigms and Extratropical Transition Conceptualizations". Archived from the original on 2008-05-10. Retrieved 2008-06-15.
  4. Ian Simmonds; Kevin Keay (February 2000). "Variability of Southern Hemisphere Extratropical Cyclone Behavior, 1958–97". Journal of Climate. 13 (3): 550–561. Bibcode:2000JCli...13..550S. doi:10.1175/1520-0442(2000)013<0550:VOSHEC>2.0.CO;2. ISSN   1520-0442.
  5. S. K. Gulev; O. Zolina; S. Grigoriev (2001). "Winter Storms in the Northern Hemisphere (1958–1999)". Climate Dynamics. 17 (10): 795–809. Bibcode:2001ClDy...17..795G. doi:10.1007/s003820000145.
  6. Carlyle H. Wash; Stacey H. Heikkinen; Chi-Sann Liou; Wendell A. Nuss (February 1990). "A Rapid Cyclogenesis Event during GALE IOP 9". Monthly Weather Review. 118 (2): 234–257. Bibcode:1990MWRv..118..375W. doi:10.1175/1520-0493(1990)118<0375:ARCEDG>2.0.CO;2. ISSN   1520-0493 . Retrieved 2008-06-28.
  7. Jack Williams (2005-05-20). "Bomb cyclones ravage northwestern Atlantic". USA Today. Retrieved 2006-10-04.
  8. Glossary of Meteorology (June 2000). "Bomb". American Meteorological Society. Retrieved 2009-06-21.
  9. Frederick Sanders; John R. Gyakum (October 1980). "Synoptic-Dynamic Climatology of the "Bomb"". Monthly Weather Review . 108 (10).
  10. Joseph M. Sienkiewicz; Joan M. Von Ahn; G. M. McFadden (2005-07-18). "Hurricane Force Extratropical Cyclones" (PDF). American Meteorology Society. Retrieved 2006-10-21.
  11. "Great weather events — A record-breaking Atlantic weather system". U.K. Met Office. Archived from the original on 2008-07-07. Retrieved 2009-05-26.
  12. Brümmer B.; Thiemann S.; Kirchgässner A. (2000). "A cyclone statistics for the Arctic based on European Centre re-analysis data (Abstract)". Meteorology and Atmospheric Physics. 75 (3–4): 233–250. Bibcode:2000MAP....75..233B. doi:10.1007/s007030070006. ISSN   0177-7971 . Retrieved 2006-10-04.
  13. 1 2 Robert E. Hart; Jenni L. Evans (February 2001). "A climatology of extratropical transition of tropical cyclones in the North Atlantic". Journal of Climate. 14 (4): 546–564. Bibcode:2001JCli...14..546H. doi:10.1175/1520-0442(2001)014<0546:ACOTET>2.0.CO;2.
  14. "Glossary of Hurricane Terms". Canadian Hurricane Center. 2003-07-10. Archived from the original on 2006-10-02. Retrieved 2006-10-04.
  15. National Hurricane Center (2011-07-11). "Glossary of NHC Terms: P". National Oceanic and Atmospheric Administration . Retrieved 2011-07-23.
  16. 1 2 Jenni L. Evans; Robert E. Hart (May 2003). "Objective indicators of the life cycle evolution of extratropical transition for Atlantic tropical cyclones". Monthly Weather Review. 131 (5): 909–925. Bibcode:2003MWRv..131..909E. doi:10.1175/1520-0493(2003)131<0909:OIOTLC>2.0.CO;2.
  17. Robert E. Hart (April 2003). "A Cyclone Phase Space Derived from Thermal Wind and Thermal Asymmetry". Monthly Weather Review. 131 (4): 585–616. Bibcode:2003MWRv..131..585H. doi:10.1175/1520-0493(2003)131<0585:ACPSDF>2.0.CO;2.
  18. 1 2 Robert E. Hart; Clark Evans; Jenni L. Evans (February 2006). "Synoptic composites of the extratropical transition lifecycle of North Atlantic tropical cyclones: Factors determining post-transition evolution". Monthly Weather Review. 134 (2): 553–578. Bibcode:2006MWRv..134..553H. CiteSeerX   10.1.1.488.5251 . doi:10.1175/MWR3082.1.
  19. Mark P. Guishard; Jenni L. Evans; Robert E. Hart (July 2009). "Atlantic Subtropical Storms. Part II: Climatology". Journal of Climate. 22 (13): 3574–3594. Bibcode:2009JCli...22.3574G. doi:10.1175/2008JCLI2346.1.
  20. Jenni L. Evans; Mark P. Guishard (July 2009). "Atlantic Subtropical Storms. Part I: Diagnostic Criteria and Composite Analysis". Monthly Weather Review. 137 (7): 2065–2080. Bibcode:2009MWRv..137.2065E. doi:10.1175/2009MWR2468.1.
  21. David M. Roth (2002-02-15). "A Fifty year History of Subtropical Cyclones" (PDF). Hydrometeorological Prediction Center. Retrieved 2006-10-04.
  22. Michelle L. Stewart, COAPS, Tallahassee, FL; and M. A. Bourassa (2006-04-25). "Cyclogenesis and Tropical Transition in decaying frontal zones" . Retrieved 2006-10-24.CS1 maint: Uses authors parameter (link)
  23. Christopher A. Davis; Lance F. Bosart (November 2004). "The TT Problem — Forecasting the Tropical Transition of Cyclones". Bulletin of the American Meteorological Society . 85 (11): 1657–1662. Bibcode:2004BAMS...85.1657D. doi:10.1175/BAMS-85-11-1657.
  24. Velden, C.; et al. (Aug 2006). "The Dvorak Tropical Cyclone Intensity Estimation Technique: A Satellite-Based Method that Has Endured for over 30 Years" (PDF). Bulletin of the American Meteorological Society . 87 (9): 1195–1210. Bibcode:2006BAMS...87.1195V. CiteSeerX   10.1.1.669.3855 . doi:10.1175/BAMS-87-9-1195 . Retrieved 2008-11-07.
  25. Lander, Mark A. (2004). "Monsoon depressions, monsoon gyres, midget tropical cyclones, TUTT cells, and high intensity after recurvature: Lessons learned from the use of Dvorak's techniques in the world's most prolific tropical-cyclone basin" (PDF). 26th Conference on Hurricanes and Tropical Meteorology. Retrieved 2008-11-08.
  26. "JTWC TN 97/002 Page 1". Archived from the original on 2012-02-08.
  27. 1 2 "JTWC TN 97/002 Page 8". Archived from the original on 2012-02-08.
  28. 1 2 "JTWC TN 97/002 Page 2". Archived from the original on 2012-02-08.
  29. "WW2010 - Pressure Gradient Force". University of Illinois. 1999-09-02. Retrieved 2006-10-11.
  30. "The Atmosphere in Motion" (PDF). University of Aberdeen. Archived from the original (PDF) on 2013-09-07. Retrieved 2011-09-11.
  31. "The Atmosphere in motion: Pressure & mass" (PDF). Ohio State University. 2006-04-26. Archived from the original (PDF) on 2006-09-05. Retrieved 2009-06-21.
  32. "What is a TROWAL?". St. Louis University. 2003-08-04. Archived from the original on 2006-09-16. Retrieved 2006-11-02.
  33. Andrea Lang (2006-04-20). "Mid-Latitude Cyclones: Vertical Structure". University of Wisconsin-Madison Department of Atmospheric and Oceanic Sciences. Archived from the original on 2006-09-03. Retrieved 2006-10-03.
  34. Robert Hart (2003-02-18). "Cyclone Phase Analysis and Forecast: Help Page". Florida State University Department of Meteorology. Retrieved 2006-10-03.
  35. Robert Harthi (2006-10-04). "Cyclone phase evolution: Analyses & Forecasts". Florida State University Department of Meteorology. Retrieved 2006-10-03.
  36. David M. Roth (2005-12-15). "Unified Surface Analysis Manual" (PDF). Hydrometeorological Prediction Center (NOAA). Retrieved 2006-10-11.
  37. Shaye Johnson (2001-09-25). "The Norwegian Cyclone Model" (PDF). University of Oklahoma, School of Meteorology. Archived from the original (PDF) on 2006-09-01. Retrieved 2006-10-11.
  38. 1 2 David M. Schultz; Heini Werli (2001-01-05). "Determining Midlatitude Cyclone Structure and Evolution from the Upper-Level Flow". Cooperative Institute for Mesoscale Meteorological Studies. Retrieved 2006-10-09.
  39. 1 2 Ryan N. Maue (2006-04-25). "Warm seclusion cyclone climatology". American Meteorological Society Conference. Retrieved 2006-10-06.
  40. Jeff Masters (2006-02-14). "Blizzicanes". JeffMasters' Blog on Wunderground.Com. Retrieved 2006-11-01.
  41. Richard J. Pasch; Eric S. Blake (2006-02-08). "Tropical Cyclone Report — Hurricane Maria" (PDF). National Hurricane Center (NOAA). Retrieved 2006-10-30.
  42. Glossary of Meteorology (June 2000). "Zonal Flow". American Meteorological Society. Archived from the original on 2007-03-13. Retrieved 2006-10-03.
  43. Glossary of Meteorology (June 2000). "Meridional Flow". American Meteorological Society. Archived from the original on 2006-10-26. Retrieved 2006-10-03.
  44. Anthony R. Lupo; Phillip J. Smith (February 1998). "The Interactions between a Midlatitude Blocking Anticyclone and Synoptic-Scale Cyclones That Occurred during the Summer Season". Monthly Weather Review. 126 (2): 502–515. Bibcode:1998MWRv..126..502L. doi:10.1175/1520-0493(1998)126<0502:TIBAMB>2.0.CO;2. hdl:10355/2398. ISSN   1520-0493.
  45. B. Ziv; P. Alpert (December 2003). "Theoretical and Applied Climatology — Rotation of mid-latitude binary cyclones: a potential vorticity approach". Theoretical and Applied Climatology. 76 (3–4): 189–202. Bibcode:2003ThApC..76..189Z. doi:10.1007/s00704-003-0011-x. ISSN   0177-798X . Retrieved 2006-10-21.
  46. Joan Von Ahn; Joe Sienkiewicz; Greggory McFadden (April 2005). "Mariners Weather Log, Vol 49, No. 1". Voluntary Observing Ship Program. Retrieved 2006-10-04.
  47. "WW2010 - Squall Lines". University of Illinois. 1999-09-02. Retrieved 2006-10-21.
  48. "Tornadoes: Nature's Most Violent Storms". National Severe Storms Laboratory (NOAA). 2002-03-13. Archived from the original on 2006-10-26. Retrieved 2006-10-21.
  49. "The Great Storm of 1987". Met Office. Archived from the original on 2007-04-02. Retrieved 2006-10-30.
  50. Richard J. Pasch; Eric S. Blake; Hugh D. Cobb III & David P Roberts (2006-01-12). "Tropical Cyclone Report — Hurricane Wilma" (PDF). National Hurricane Center (NOAA). Retrieved 2006-10-11.
  51. "华北东北黄淮强降雨致289人死亡失踪" (in Chinese). Ministry of Civil Affairs. July 25, 2016. Archived from the original on July 25, 2016. Retrieved July 25, 2016.
  52. "西南部分地区洪涝灾害致80余万人受灾" (in Chinese). Ministry of Civil Affairs. July 25, 2016. Archived from the original on July 25, 2016. Retrieved July 25, 2016.
  53. Holton, James R. 1992 An introduction to dynamic meteorology / James R. Holton Academic Press, San Diego : https://www.loc.gov/catdir/toc/els032/91040568.html
  54. Linear Stationary Wave Simulations of the Time-Mean Climatological Flow, Paul J. Valdes, Brian J. Hoskins, Journal of the Atmospheric Sciences 1989 46:16, 2509–2527
  55. George Taylor; Raymond R. Hatton (1999). The 1962 Windstorm. The Oregon Weather Book: A State of Extremes. Oregon State University Press. ISBN   978-0-87071-467-2. Archived from the original on 2006-09-07. Retrieved 2009-06-21.
  56. "Archived copy". Archived from the original on 2015-11-13. Retrieved 2015-11-20.CS1 maint: Archived copy as title (link)
  57. S. G. P. Skey; M. D. Miles (1999-11-08). "Advances in Buoy Technology for Wind/Wave Data Collection and Analysis" (PDF). AXYS Technologies. Archived from the original (PDF) on 2006-10-18. Retrieved 2006-11-25.
  58. Stephen Burt (April 1993). "Another new North Atlantic low pressure record". Weather. 48 (4): 98–103. Bibcode:1993Wthr...48...98B. doi:10.1002/j.1477-8696.1993.tb05854.x.
  59. NOAA (2009-07-31). "State of the Climate Global Hazards August 2005". National Oceanic and Atmospheric Administration. Retrieved 2009-09-21.
  60. 1 2 Gary Padget (2005-07-31). "Monthly Global Tropical Cyclone Summary August 2005". Australian Severe Weather. Retrieved 2009-09-21.