Mesoscale Organization of ConvectionMesoscale Organization of Convection

Squall LineSquall Line• Is a set of individual intense thunderstorm cells

arranged in a line. • Thy occur along a boundary of unstable air –

e.g. a cold front. • Strong environmental wind shear causes the

updraft to be tilted and separated from thedowndraft.

• The dense cold air of the downdraft forms a ‘gust front’.

Squall line from SpaceSquall line from Space

Image courtesy of http://cnls.lanl.gov.

http://cnls.lanl.gov

This image has been removed due to copyright restrictions.

Please see: http://www.floridalightning.com/Hurricane_Wilma.html

http://www.floridalightning.com/Hurricane_Wilma.html

This image has been removed due to copyright restrictions.

Please see similar images on: http://www.bom.gov.au/wa/sevwx/

http://www.bom.gov.au/wa/sevwx/

Mesoscale ConvectiveMesoscale Convective ComplexComplex

• A Mesoscale Convective Complex iscomposed of multiple single-cell storms indifferent stages of development.

• The individual thunderstorms must supportthe formation of other convective cells

• In order to last a long time, a good supplyof moisture is required at low levels in teatmosphere.

Infrared image of a mesoscale convectiveInfrared image of a mesoscale convective complex over Kansas, July 8 1997.complex over Kansas, July 8 1997.

This image has been removed due to copyright restrictions.

Please see similar images on: http://cimss.ssec.wisc.edu/goes/misc/970708.html

http://cimss.ssec.wisc.edu/goes/misc/970708.html

TYPES OF THUNDERSTORMTYPES OF THUNDERSTORM

• SINGLE-CELL THUNDERSTORM

• MULTICELL THUNDERSTORM

• MESOSCALE CONVECTIVE C0MPLEX

• SUPERCELL THUNDERSTORM

Non-equilibrium Convection

SUPERCELL THUNDERSTORMSSUPERCELL THUNDERSTORMS

• SINGLE CELL THUNDERSTORM THAT

PRODUCES DANGEROUS WEATHER

• REQUIRES A VERY UNSTABLE ATMOSPHEREAND STRONG VERTICAL WIND SHEAR - BOTH SPEED AND DIRECTION

• UNDER THE INFLUENCE OF THE STRONG WIND SHEAR MUCH OF THE THUNDERSTORM ROTATES

• FAVORED IN THE SOUTHERN GREAT PLAINS IN THE SPRING

Wind ShearWind ShearShear VectorShear Vector

HodographHodograph

This image has been removed due to copyright restrictions.

Please see similar images on: http://www.bom.gov.au/wa/sevwx/

http://www.bom.gov.au/wa/sevwx/

Visible image of a supercell thunderstormVisible image of a supercell thunderstorm

Image courtesy of NASA.

InfraInfra--red image of a supercell thunderstormred image of a supercell thunderstorm

This image has been removed due to copyright restrictions.

Please see similar images on: http://jrscience.wcp.muohio.edu/coriolis/hurricanearchives.html

http://jrscience.wcp.muohio.edu/coriolis/hurricanearchives.html

Supercell SkematicSupercell Skematic

This image has been removed due to copyright restrictions.

Please see: http://weather.cod.edu/sirvatka/tstorm.gif

http://weather.cod.edu/sirvatka/tstorm.gif

This image has been removed due to copyright restrictions.

Please see similar image on: http://weatherfreaks.net/images/mesocyclone1.jpg

http://weatherfreaks.net/images/mesocyclone1.jpg

Northeast

This image has been removed due to copyright restrictions.

Please see: http://earthstorm.mesonet.org/materials/graphics/SupercellSlice.gif

http://earthstorm.mesonet.org/materials/graphics/SupercellSlice.gif

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12.103 Science and Policy of Natural Hazards Spring 2010

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