Mesoscale meteorology

Short description: Moderately sized weather phenomena

A meso-beta scale vortex

Mesoscale meteorology is the study of weather systems and processes at horizontal scales of approximately 5 kilometres (3 mi) to several hundred kilometres. It is smaller than synoptic-scale systems (1,000 km or larger) but larger than microscale (less than 1 km). At the small end, it includes storm-scale phenomena (the size of an individual thunderstorm[1]). Examples of mesoscale weather systems are sea breezes, squall lines, and mesoscale convective complexes.

Vertical velocity often equals or exceeds horizontal velocities in mesoscale meteorological systems due to nonhydrostatic processes such as buoyant acceleration of a rising thermal or acceleration through a narrow mountain pass.

## Contents

* 1 Classification
* 1.1 Subclasses
* 2 Dynamics
* 3 Mesoscale boundaries
* 4 See also
* 5 References

## Classification

Mesoscale meteorology studies weather systems like thunderstorm clusters too small to be resolved by the earliest weather observation networks.

The earliest networks of weather observations in the late 1800s and early 1900s could detect the movement and evolution of larger, synoptic-scale systems like high and low-pressure areas. However, smaller and potentially hazardous meteorological phenomena were not well-captured by the sparse observation networks. The emergence of weather radar in the mid-1900s and an improved understanding of thunderstorm behavior led to an increased recognition of a need to study phenomena between the scales studied in the extant disciplines of microscale and synoptic-scale meteorology.[2] The term "mesoscale" originated from M. G. H. Ligda at the Massachusetts Institute of Technology, who suggested a need to study phenomena at such scales in 1951:[2][3]

> It is anticipated that radar will provide useful information concerning the structure and behavior of that portion of the atmosphere which is not covered by either micro- or synoptic-meteorological studies. We have already observed with radar that precipitation formulations which are undoubtedly of significance occur on a scale too gross to be observed from a single station, yet too small to appear even on sectional synoptic charts. Phenomena of this size might well be designated as mesometeorological.

— M. G. H. Ligda, "Radar Storm Observation", Compendium of Meteorology (1951)[4]

### Subclasses

Mesoscale meteorology broadly concerns meteorological phenomena larger than a few kilometres across but smaller than could be resolved by the observation networks used in the earliest standardized weather maps.[5] The mesoscale regime is often divided into these subclasses based on the size of associated weather systems:[6]

* Meso-alpha (meso-α) – 200–2000 km scale of phenomena like fronts, squall lines, mesoscale convective systems (MCS), tropical cyclones at the smaller edge of synoptic scale.[6]
* Meso-beta (meso-β) – 20–200 km scale of phenomena like mesocyclones, sea breezes, and lake effect snow storms.[6] Mesocale often refers to meso-β scale specifically.[7]
* Meso-gamma (meso-γ) – 2–20 km scale of phenomena like thunderstorm convection, complex terrain flows (at the larger edge of microscale)

As a note, tropical and subtropical cyclones are classified by National Hurricane Center as synoptic scale rather than mesoscale.[8]

Features the size of an individual thunderstorm are also known somewhat informally as "storm-scale", typically meso-gamma but sometimes meso-beta[9] or microscale.

## Dynamics

Vertical motion is prominent in many mesoscale processes.

Mesoscale processes are characterized by having a relatively large Rossby number compared to synoptic scale processes. Thus, over shorter distances as implicated in mesoscale phenomena, the importance of geostrophic balance and the Earth's rotation in shaping atmospheric processes is small relative to synoptic-scale phenomena.[10] This is particularly true towards the smaller end of the mesoscale range.[11]: 8 Because the curvature of Earth is small at mesoscales, the physical models used to diagnose mesoscale phenomena often assume a constant Coriolis frequency.[10] Nonetheless, the Coriolis force is non-negligible and comparable to the influence of atmospheric buoyancy.[7]

Large-scale turbulence and eddies also play a large role in mesoscale meteorology.[10] The vertical movement of air (often expressed as omega) is larger at mesoscale than at synoptic scales, and the distribution of air pressure tends to be influenced by the behavior of winds at the mesoscale (as opposed to the converse at synoptic scales).[7] For many mesoscale phenomena, the vertical acceleration of air is sufficiently large enough that calculations cannot assume hydrostatic balance. This is often true of phenomena with a vertical dimension roughly equal to their horizontal dimensions.[11]: 9

## Mesoscale boundaries

As in synoptic frontal analysis, mesoscale analysis uses cold, warm, and occluded fronts on the mesoscale to help describe phenomena. On weather maps mesoscale fronts are depicted as smaller and with twice as many bumps or spikes as the synoptic variety. In the United States, opposition to the use of the mesoscale versions of fronts on weather analyses, has led to the use of an overarching symbol (a trough symbol) with a label of outflow boundary as the frontal notation.[12]

## See also

* Microscale meteorology
* Misoscale meteorology
* POLYGON experiment
* Surface weather analysis
* Synoptic scale meteorology

## References

1. ↑ NOAA Glossary entry for "Storm Scale"
2. ↑ 2.0 2.1 Trapp, Robert J. (2013). Mesoscale-Convective Processes in the Atmosphere. Cambridge: Cambridge University Press. ISBN 978-0-521-88942-1.
3. ↑ Fujita 1986, p. 23.
4. ↑ Ligda, Myron G. H. (1951). "Radar Storm Observation". Compendium of Meteorology. pp. 1265–1282. doi:10.1007/978-1-940033-70-9_103. ISBN 978-1-940033-70-9.
5. ↑ Markowski, Paul; Richardson, Yvette (2010). Mesoscale Meteorology in Midlatitudes. Chichester: Wiley-Blackwell. ISBN 978-0-470-74213-6.
6. ↑ 6.0 6.1 6.2 Orlanski, I. (1975). "A rational subdivision of scales for atmospheric processes". Bulletin of the American Meteorological Society 56 (5): 527–530. http://twister.caps.ou.edu/MM2015/docs/chapter1/Orlanski1975.pdf.
7. ↑ 7.0 7.1 7.2 Shou, Shaowen; Li, Shenshen; Shou, Yixuan; Yao, Xiuping (2023). An Introduction to Mesoscale Meteorology. Singapore: Springer Nature Singapore. doi:10.1007/978-981-19-8606-2. ISBN 978-981-19-8605-5.
8. ↑ "Glossary of NHC Terms". http://www.nhc.noaa.gov/aboutgloss.shtml.
9. ↑ "Subdividing the Mesoscale". The Pennsylvania State University. 2019. https://learningweather.psu.edu/node/88.
10. ↑ 10.0 10.1 10.2 Parker, D.J. (2015). "Mesoscale Meteorology | Overview". Encyclopedia of Atmospheric Sciences. pp. 316–322. doi:10.1016/B978-0-12-382225-3.00478-3. ISBN 978-0-12-382225-3.
11. ↑ 11.0 11.1 Markowski, Paul; Richardson, Yvette (2010). Mesoscale meteorology in midlatitudes. Chichester: Wiley-Blackwell. ISBN 978-0-470-74213-6.
12. ↑ Roth, David. "Unified Surface Analysis Manual". Hydrometeorological Prediction Center. http://www.wpc.ncep.noaa.gov/sfc/UASfcManualVersion1.pdf.

* Fujita, T.T. (1986). "Mesoscale classifications: their history and their application to forecasting". in Ray, P.S.. Mesoscale Meteorology and Forecasting. Boston: American Meteorological Society. pp. 18–35.

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Cyclones and anticyclones of the world (Centers of action)

Concepts|

* Anticyclonic storm
* Storm
* High-pressure area
* Low-pressure area
* Rapid intensification
* Central dense overcast
* Annular tropical cyclone
* Bar (tropical cyclone)
* Superstorm
* Hypercane

Anticyclone|

| Northern Hemisphere|

* North Polar High
* Siberian High
* Azores High
* North American High
* North Pacific High
* Ridiculously Resilient Ridge
* Subtropical ridge

|

Southern Hemisphere|

* South Polar High
* South Atlantic High
* South Pacific High
* Kalahari High
* Subtropical ridge

Cyclone|

| Synoptic scale|

| Surface-based|

| Polar|

* North Polar low
* South Polar low

|

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* e

Extratropical cyclones

Concepts|

* Anticyclonic storm
* Storm
* Cyclone
* Post-tropical cyclone
* Low-pressure area
* Weather bomb
* Sting jet
* List
* Rainband

Northern Hemisphere|

| North America|

| Continental|

| Lee Cyclone|

* Alberta clipper
* Colorado low
* Great basin low

|

Other|

* Panhandle hook
* Witch of November

Oceanic|

* Aleutian Low
* Hatteras low
* Nor'easter
* Gulf low
* Pacific Northwest windstorm

Europe|

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European windstorms

Historical|

* Grote Mandrenke
* Burchardi flood
* Great Storm of 1703
* Great Storm of 1824
* Night of the Big Wind
* Moray Firth fishing disaster
* Tay Bridge disaster
* Eyemouth disaster

20th century|

* Iberia 1941
* North Sea flood of 1953
* Hurricane Debbie 1961
* North Sea flood of 1962
* 1968 Scotland storm
* Quimburga 1972
* Gale of January 1976
* December 1981 windstorm
* Ex-Hurricane Charley 1986
* Great Storm of 1987
* Burns' Day storm 1990
* New Year's Day Storm 1992
* Braer Storm of January 1993
* Christmas Eve storm 1997
* Boxing Day Storm of 1998
* Anatol 1999
* Lothar and Martin 1999

2000s|

* Oratia 2000
* Jeanett 2002
* Gudrun 2005
* Per 2007
* Kyrill 2007
* Emma 2008
* Klaus 2009
* Xynthia 2010
* Berit 2011
* Friedhelm/Bawbag 2011
* Joachim 2011
* Dagmar 2011
* Andrea 2012
* St Jude 2013
* Xaver 2013
* Dirk 2013
* Tini 2014
* Elon and Felix 2015
* Niklas 2015
* Egon 2017
* Thomas (Doris) 2017
* Zeus 2017
* Xavier 2017
* Ophelia 2017
* Herwart 2017
* Eleanor (Burglind) 2018
* Friederike (David) 2018

2015–present|

* 2015–16
* 2016–17
* 2017–18
* 2018–19
* 2019–20

See also|

* List of European windstorms
* List of atmospheric pressure records in Europe

Other|

* Black Sea storms
* Icelandic Low
* Genoa low

Asia|

* Western Disturbance
* Continental North Asian storms
* East Asian-northwest Pacific storms

Other areas|

* Arctic
* Kona storm

Southern Hemisphere|

| Australia|

* Australian east coast low
* Black nor'easter

|

Other areas|

* Southern Ocean cyclone
* Sudestada

Subtropical|

* Kona storm
* Australian east coast Low
* Lake Huron cyclone
* Mediterranean tropical-like cyclone
* Thermal

Tropical
(List)|

| Northern Hemisphere|

* Atlantic hurricane
* Cape Verde hurricane
* Pacific hurricane
* Typhoon
* North Indian Ocean tropical cyclone
* Mediterranean tropical-like cyclone

|

Southern Hemisphere|

* South-West Indian Ocean tropical cyclone
* Australian region tropical cyclone
* South Pacific tropical cyclone
* South Atlantic tropical cyclone

Upper level|

* Cold-core low
* Polar vortex
* Upper tropospheric cyclonic vortex

Mesoscale|

| Mesoscale ocean eddies|

* Catalina eddy
* Haida Eddies

|

Mesoscale convective system|

* Wake Low
* Mesohigh
* Mesoscale convective vortex
* Line echo wave pattern

Whirlwind|

| Major|

* Mesocyclone
* Supercell
* Low-topped supercell
* Wall cloud
* Funnel cloud
* Tornado
* Multiple-vortex tornado
* Satellite tornado
* Anticyclonic tornado
* Landspout
* Waterspout

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Minor|

* Gustnado
* Dust devil
* Steam devil
* Fire whirl

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