geog 300 mid-latitude cyclones - university of...
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Mid-‐La,tude Cyclones
Introduc,on to Climatology GEOGRAPHY 300
Tom Giambelluca University of Hawai‘i at Mānoa
Basics • Mid-‐la,tude cyclone, aka wave cyclone • Form along the polar front • Energy for mid-‐la,tude cyclones is derived from the
poten,al energy created by the strong temperature across the polar front
• Each cyclone has a life cycle • Cyclone forma,on, “cyclogenesis” is favored beneath areas
of upper level divergence • Cyclogenesis occurs downstream of Rossby wave troughs,
where upper level divergence occurs • Cyclones are steered by upper level winds, generally
moving toward the northeast in the northern hemisphere
• “The Hurricane Future: Science and Policy” by Thomas A. Schroeder
Mid-‐La,tude Cyclone Life Cycle Ini,al stage
Mid-‐La,tude Cyclone Life Cycle Incipient stage
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Mid-‐La,tude Cyclone Life Cycle Mature stage
Mid-‐La,tude Cyclone Life Cycle Par,ally-‐occluded stage
Mid-‐La,tude Cyclone Life Cycle Occluded stage • Storm life cycle lasts 5-‐7 days
• Energy stored as poten,al energy along the polar front is dissipated by the storm
• During its life cycle, the air density distribu,on is rearranged; star,ng from cold (dense) and warm (less dense) air si]ng side by side, the dense air ends up below the less dense air at the end of the storm’s life cycle
Mid-‐La,tude Cyclone Life Cycle
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Circula,on and Weather in a Mid-‐La,tude Cyclone
Frontal li`ing and convergence li`ing create areas of clouds and rain in a dis,nct paaern.
Rossby Wave In the figure at le`, transi,on zone A is an area of upper level convergence and downward mo,on. Transi,on zone B is an area of upper level divergence and upward mo,on. Cyclogenesis occurs beneath transi,on zone B.