Explosive cyclogenesis

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The Braer Storm of January 1993 explosively deepened to a record low of 913 mbar (hPa) BraerStorm1993.png
The Braer Storm of January 1993 explosively deepened to a record low of 913 mbar (hPa)

Explosive cyclogenesis (also referred to as a weather bomb, [1] [2] [3] meteorological bomb, [4] explosive development, [1] bomb cyclone, [5] [6] or bombogenesis [7] [8] [9] ) 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 millibars (0.71 inHg) or more in 24 hours. [10] [11] This is a predominantly maritime, winter event, [10] [12] but also occurs in continental settings. [13] [14] This process is the extratropical equivalent of the tropical rapid deepening. Although their cyclogenesis is entirely different from that of tropical cyclones, bomb cyclones can produce winds of 74 to 95 mph (120 to 155 km/h), the same order as the first categories of the Saffir–Simpson scale, and yield heavy precipitation. Even though only a minority of bomb cyclones become this strong, some weaker ones can also cause significant damage.

Contents

History

In the 1940s and 1950s, meteorologists at the Bergen School of Meteorology began informally calling some storms that grew over the sea "bombs" because they developed with a great ferocity rarely seen over land.

By the 1970s, the terms "explosive cyclogenesis" and even "meteorological bombs" were being used by MIT professor Fred Sanders (building on work from the 1950s by Tor Bergeron), who brought the term into common usage in a 1980 article in the Monthly Weather Review . [5] [10] In 1980, Sanders and his colleague John Gyakum defined a "bomb" as an extratropical cyclone that deepens by at least (24 sin φ / sin 60°) mb in 24 hours, where φ represents latitude. This is based on the definition, standardised by Bergeron, for explosive development of a cyclone at 60°N as deepening by 24 mb in 24 hours. [15] Sanders and Gyakum noted that an equivalent intensification is dependent on latitude: at the poles this would be a drop in pressure of 28 mb/24 hours, while at 25 degrees latitude it would be only 12 mb/24 hours. All these rates qualify for what Sanders and Gyakum called "1 bergeron". [10] [13] Sanders' and Gyakum's 1980 definition, which is used in the American Meteorological Society's Glossary of Meteorology, said that the "bomb" was "predominantly" a "maritime, cold season event". [10] [12]

In October 2010, an unusual weather system that reached the strength of a Category 3 hurricane and spanned 31 states in the United States and six Canadian provinces, underwent bombogenesis, according to Environment Canada. [16] Severe weather warnings included "tornadoes, blustery blizzards, powerful gales, wind-driven rains, heavy snows and thunderstorms". [16] The storm had the greatest impact in the Canadian province of Manitoba with the city of Winnipeg setting an "all-time record for its lowest-ever barometric pressure". [16]

In early 2014 in the North Atlantic, fourteen wind events out of twenty that had reached hurricane-force, underwent bombogenesis, the process that creates a bomb cyclone, according to National Oceanic and Atmospheric Administration (NOAA). [17] NOAA said that bombogenesis "occurs when a midlatitude cyclone rapidly intensifies, dropping at least 24 millibars over 24 hours." [17]

Formation

Baroclinic instability has been cited as one of the principal mechanisms for the development of most explosively deepening cyclones. [18] However, the relative roles of baroclinic and diabatic processes in explosive deepening of extratropical cyclones have been subject to debate (citing case studies) for a long time. [19] Other factors include the relative position of a 500-hPa trough and thickness patterns, deep tropospheric frontogenetic processes which happen both upstream and downstream of the surface low, the influence of air–sea interaction, and latent heat release. [20]

Regions and motion

Absorbing the remnants of a powerful tropical cyclone can trigger explosive cyclogenesis Northwest Pacific cyclone 2017-10-24 2350Z.png
Absorbing the remnants of a powerful tropical cyclone can trigger explosive cyclogenesis

The four most active regions where extratropical explosive cyclogenesis occurs in the world are the Northwest Pacific, the North Atlantic, the Southwest Pacific, and the South Atlantic. [21]

In the Northern Hemisphere the maximum frequency of explosively deepening cyclones is found within or to the north of the Atlantic Gulf Stream and Kuroshio Current in the western Pacific, [10] and in the Southern Hemisphere it is found with Australian east coast lows above the East Australian Current, which shows the importance of air-sea interaction in initiating and rapidly developing extratropical cyclones. [22]

Explosively deepening cyclones south of 50°S often show equator-ward movement, in contrast with the poleward motion of most Northern Hemisphere bombs. [20] Over the year, 45 cyclones on average in the Northern Hemisphere and 26 in the Southern Hemisphere develop explosively, mostly in the respective hemisphere's winter time. Less seasonality has been noticed in bomb cyclogenesis occurrences in the Southern Hemisphere. [20]

Other uses of "weather bomb"

The term "weather bomb" is popularly used in New Zealand to describe dramatic or destructive weather events. Rarely are the events actual instances of explosive cyclogenesis, as the rapid deepening of low pressure areas is rare around New Zealand. [23] [24] This use of "bomb" may lead to confusion with the more strictly defined meteorological term. In Japan, the term bomb cyclone (爆弾低気圧, bakudan teikiatsu) is used both academically and commonly to refer to an extratropical cyclone which meets the meteorological "bomb" conditions. [25] [26]

The term "bomb" may be somewhat controversial. When European researchers protested that it was a rather warlike term, Fred Sanders, the coauthor of the paper which introduced the meteorological usage quipped: "So why are you using the term 'front'?" [27]

See also

Related Research Articles

<span class="mw-page-title-main">Cyclone</span> Large scale rotating air mass

In meteorology, a cyclone is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above. 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 the smaller mesoscale.

<span class="mw-page-title-main">Subtropical cyclone</span> Cyclonic storm with tropical and extratropical characteristics

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

<span class="mw-page-title-main">Low-pressure area</span> Area with air pressures lower than adjacent areas

In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather, while high-pressure areas are associated with lighter winds and clear skies. Winds circle anti-clockwise around lows in the northern hemisphere, and clockwise in the southern hemisphere, due to opposing Coriolis forces. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the atmosphere (aloft). The formation process of a low-pressure area is known as cyclogenesis. In meteorology, atmospheric divergence aloft occurs in two kinds of places:

<span class="mw-page-title-main">1959 Atlantic hurricane season</span>

The 1959 Atlantic hurricane season featured near normal tropical cyclone activity overall. The season officially began on June 15, 1959 and lasted until November 15, 1959. These dates historically described the period in each year when most tropical cyclogenesis occurs in the Atlantic basin. However, the formation of a tropical cyclone is possible at any time of the year, as shown in 1959, by the formation of Tropical Storm Arlene on May 28. Arlene struck Louisiana and brought minor flooding to the Gulf Coast of the United States. The next tropical storm, Beulah, formed in the western Gulf of Mexico and brought negligible impact to Mexico and Texas. Later in June, an unnamed hurricane, caused minor damage in Florida, and then devastated parts of Maritime Canada, resulting in what became known as the Escuminac disaster. Hurricane Cindy brought minor impact to The Carolinas. In late July, Hurricane Debra produced flooding in the state of Texas. Tropical Storm Edith in August and Hurricane Flora in September caused negligible impact on land.

<span class="mw-page-title-main">Westerlies</span> Prevailing winds from the west

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.

<span class="mw-page-title-main">Tropical wave</span> Type of atmospheric trough

A tropical wave, in and around the Atlantic Ocean, is a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which moves from east to west across the tropics, causing areas of cloudiness and thunderstorms. Tropical waves form in the easterly flow along the equatorial side of the subtropical ridge or belt of high air pressure which lies north and south of the Intertropical Convergence Zone (ITCZ). Tropical waves are generally carried westward by the prevailing easterly winds along the tropics and subtropics near the equator. They can lead to the formation of tropical cyclones in the north Atlantic and northeastern Pacific basins. A tropical wave study is aided by Hovmöller diagrams, a graph of meteorological data.

<span class="mw-page-title-main">Cyclogenesis</span> The development or strengthening of cyclonic circulation in the atmosphere

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.

<span class="mw-page-title-main">Fujiwhara effect</span> Meteorological phenomenon involving two cyclones circling each other

The Fujiwhara effect, sometimes referred to as the Fujiwara effect, Fujiw(h)ara interaction or binary interaction, is a phenomenon that occurs when two nearby cyclonic vortices move around each other and close the distance between the circulations of their corresponding low-pressure areas. The effect is named after Sakuhei Fujiwhara, the Japanese meteorologist who initially described the effect. Binary interaction of smaller circulations can cause the development of a larger cyclone, or cause two cyclones to merge into one. Extratropical cyclones typically engage in binary interaction when within 2,000 kilometres (1,200 mi) of one another, while tropical cyclones typically interact within 1,400 kilometres (870 mi) of each other.

<span class="mw-page-title-main">Tropical cyclogenesis</span> Development and strengthening of a tropical cyclone in the atmosphere

Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occur 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.

<span class="mw-page-title-main">Extratropical cyclone</span> Type of cyclone

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 severe 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.

<span class="mw-page-title-main">Tropical cyclone</span> Type of rapidly rotating storm system

A tropical cyclone is a rapidly rotating storm system with a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its location and strength, a tropical cyclone is called a hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply cyclone. A hurricane is a strong tropical cyclone that occurs in the Atlantic Ocean or northeastern Pacific Ocean. A typhoon occurs in the northwestern Pacific Ocean. In the Indian Ocean and South Pacific, comparable storms are referred to as "tropical cyclones". In modern times, on average around 80 to 90 named tropical cyclones form each year around the world, over half of which develop hurricane-force winds of 65 kn or more.

<span class="mw-page-title-main">Cold-air damming</span>

Cold air damming, or CAD, is a meteorological phenomenon that involves a high-pressure system (anticyclone) accelerating equatorward east of a north-south oriented mountain range due to the formation of a barrier jet behind a cold front associated with the poleward portion of a split upper level trough. Initially, a high-pressure system moves poleward of a north-south mountain range. Once it sloshes over poleward and eastward of the range, the flow around the high banks up against the mountains, forming a barrier jet which funnels cool air down a stretch of land east of the mountains. The higher the mountain chain, the deeper the cold air mass becomes lodged to its east, and the greater impediment it is within the flow pattern and the more resistant it becomes to intrusions of milder air.

<span class="mw-page-title-main">Sting jet</span> Narrow airstream of strong winds in cyclones

A sting jet is a narrow, transient and mesoscale airstream that descends from the mid-troposphere to the surface in some extratropical cyclones. When present, sting jets produce some of the strongest surface-level winds in extratropical cyclones and can generate damaging wind gusts in excess of 50 m/s. Sting jets are short-lived, lasting on the order of hours, and the area subjected to their strong winds is typically no wider than 100 km (62 mi), making their effects highly localised. Studies have identified sting jets in mid-latitude cyclones primarily in the northern Atlantic and western Europe, though they may occur elsewhere. The storms that produce sting jets have tended to follow the Shapiro–Keyser model of extratropical cyclone development. Among these storms, sting jets tend to form following storm's highest rate of intensification.

<span class="mw-page-title-main">1992 New Year's Day Storm</span> European windstorm in 1992

The New Year's Day Storm, known in Scotland as the 'Hogmanay Hurricane', was an extremely powerful and record-breaking European windstorm, comparable to a category 4 major hurricane, that affected much of northern Scotland and western Norway on 1 January 1992. DNMI estimated the strongest sustained winds and the strongest gusts to have reached 103 mph and 138 mph, respectively. Unofficial records of gusts in excess of 170 knots (87 m/s) were recorded in Shetland, while Statfjord-B in the North Sea recorded wind gusts in excess of 145 knots (75 m/s). There were very few fatalities, mainly due to the rather low population of the islands, the fact that the islanders are used to powerful winds, and because it struck in the morning on a public holiday when people were indoors. In Norway there was one fatality, in Frei, Møre og Romsdal county. There were also two fatalities on Unst in the Shetland Isles. Despite being referred to by some as a 'Hurricane', the storm was Extratropical in origin and is classified as an Extratropical Cyclone.

<span class="mw-page-title-main">Upper tropospheric cyclonic vortex</span>

An upper tropospheric cyclonic vortex is a vortex, or a circulation with a definable center, that usually moves slowly from east-northeast to west-southwest and is prevalent across Northern Hemisphere's warm season. Its circulations generally do not extend below 6,080 metres (19,950 ft) in altitude, as it is an example of a cold-core low. A weak inverted wave in the easterlies is generally found beneath it, and it may also be associated with broad areas of high-level clouds. Downward development results in an increase of cumulus cloudy and the appearance of circulation at ground level. In rare cases, a warm-core cyclone can develop in its associated convective activity, resulting in a tropical cyclone and a weakening and southwest movement of the nearby upper tropospheric cyclonic vortex. Symbiotic relationships can exist between tropical cyclones and the upper level lows in their wake, with the two systems occasionally leading to their mutual strengthening. When they move over land during the warm season, an increase in monsoon rains occurs

<span class="mw-page-title-main">Cold-core low</span> Cyclone with an associated cold pool of air at high altitude

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, without a frontal structure. 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.

<span class="mw-page-title-main">Australian east coast low</span>

Australian east coast lows are extratropical cyclones or low-pressure systems on the coast of southeastern Australia that may be caused by both mid-latitude and tropical influences over a variety of levels in the atmosphere. These storms should not be confused with Australian region tropical cyclones which typically affect the northern half of the continent.

<span class="mw-page-title-main">October 2017 nor'easter</span> Meteorological bomb that affected United States and Canada

The October 2017 nor'easter was a major explosive cyclogenesis storm, also called a bomb cyclone, in the Northeastern United States and Atlantic Canada from October 29–31, 2017. Forming from an extratropical cyclone on October 29 the system moved rapidly up the East Coast of the United States, bombing out with a minimum pressure of 975 millibars (28.8 inHg) on October 30. It brought heavy rain and extremely strong winds, and power outages, over 1.3 million customers being without power in the Northeast. Hurricane-force wind gusts resulted in downed trees, power lines, and widespread damage to buildings. The number of power outages in the state of Maine surpassed the Ice Storm of 1998.

<span class="mw-page-title-main">Cyclolysis</span> The process of dissipation of a cyclone

Cyclolysis is a process in which a cyclonic circulation weakens and deteriorates. Cyclolysis is the opposite of cyclogenesis.

<span class="mw-page-title-main">October 2022 Southern Ocean cyclone</span>

The October 2022 Southern Ocean cyclone, also referred to as the Peter I storm or EC2022 was the most intense extratropical cyclone on record. Forming as a weak depression near Tonga late on 9 October, the extratropical cyclone tracked slowly southeastward across the South Pacific, remaining weak. Starting on 14 October, the cyclone began rapid deepening as it moved towards Antarctica. Deepening rates peaked on 16 October, where the pressure fell as rapidly as 19 mbar (0.56 inHg) over a six-hour period. The storm peaked early on 17 October in the Bellingshausen Sea, with a minimum pressure of around 900 mbar (26.58 inHg). The cyclone moved slowly in a loop, rising in pressure over the next few days before dissipating on 20 October.

References

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  3. ↑ Edwards, Tim (9 December 2011). "Scotland storm: what is a weather bomb?". The Week . London, United Kingdom: Dennis Publishing . Retrieved 4 April 2013.
  4. ↑ O'Hanlon, Larry (25 February 2013). "Look out -- 'meteorological bomb' is on the way!". NBC News. Retrieved 21 March 2013.
  5. 1 2 Williams, Jack (20 May 2005). "Bomb cyclones ravage northwestern Atlantic". USA Today. Retrieved 22 March 2013.
  6. ↑ Feltman, Rachel (3 January 2018). "What the heck is a bomb cyclone?". Popular Science. Retrieved 6 January 2018.
  7. ↑ "Ryan explains Bomb Cyclogenesis". WBRZ News 2 Louisiana. Archived from the original on 12 April 2013. Retrieved 21 March 2013.
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  9. ↑ Rodman, Kristen (23 January 2014). "What is Bombogenesis?". Accuweather. Retrieved 31 January 2014.
  10. 1 2 3 4 5 6 Sanders, Frederick; Gyakum, John R (1980). "Synoptic-Dynamic Climatology of the 'Bomb'". Monthly Weather Review. 108 (10): 1589–606. Bibcode:1980MWRv..108.1589S. doi: 10.1175/1520-0493(1980)108<1589:SDCOT>2.0.CO;2 .
  11. ↑ Chelsea Harvey (November 10, 2014). "Here's What Caused The 'Bomb Cyclone' That's About To Freeze The Northern US". Business Insider. Retrieved October 8, 2017.
  12. 1 2 "Bomb". American Meteorological Society . Glossary of Meteorology. 20 February 2012. Retrieved 27 December 2022.
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  14. ↑ MacDonald, Bruce C; Reiter, Elmar R (1988). "Explosive Cyclogenesis over the Eastern United States". Monthly Weather Review. 116 (8): 1568–86. Bibcode:1988MWRv..116.1568M. doi: 10.1175/1520-0493(1988)116<1568:ECOTEU>2.0.CO;2 .
  15. ↑ Baker, Laura (2011). Sting Jets in Extratropical Cyclones (Ph.D.). University of Reading.
  16. 1 2 3 Government of Canada (16 December 2010). "Freak Canada-U.S. 'Weather Bomb'". Environment and Climate Change Canada: Weather and Meteorology. Retrieved 27 December 2022.
  17. 1 2 "What is bombogenesis?". US Department of Commerce and National Oceanic and Atmospheric Administration. n.d. Retrieved 27 December 2022.
  18. ↑ Weng, H. Y.; Barcilon, A. (1987). "Favorable environments for explosive cyclogenesis in a modified two-layer Eady model". Tellus A. 39A (3): 202–214. Bibcode:1987TellA..39..202W. doi:10.1111/j.1600-0870.1987.tb00301.x.
  19. ↑ Fink, Andreas H.; Pohle, Susan; Pinto, Joaquim G.; Knippertz, Peter (2012). "Diagnosing the influence of diabatic processes on the explosive deepening of extratropical cyclones" (PDF). Geophysical Research Letters. 39 (7): n/a. Bibcode:2012GeoRL..39.7803F. doi: 10.1029/2012GL051025 . Retrieved 2 June 2013.
  20. 1 2 3 Lim, Eun-Pa; Simmonds, Ian (2002). "Explosive Cyclone Development in the Southern Hemisphere and a Comparison with Northern Hemisphere Events". Monthly Weather Review. 130 (9): 2188–2209. Bibcode:2002MWRv..130.2188L. doi: 10.1175/1520-0493(2002)130<2188:ECDITS>2.0.CO;2 .
  21. ↑ Black, Mitchell Timothy; Pezza, Alexandre Bernardes (2013). "A universal, broad-environment energy conversion signature of explosive cyclones". Geophysical Research Letters. 40 (2): 452–7. Bibcode:2013GeoRL..40..452B. doi: 10.1002/grl.50114 .
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