The Mesoscale and Microscale Structure and Organization of Clouds and Precipitation in Midlatitude Cyclones. VII: Formation, Development, Interaction and Dissipation of Rainbands

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  • 1 Atmospheric Sciences Department, University of Washington. Seattle, 98195
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Abstract

Mesoscale measurements on five Pacific cyclones are used to investigate the formation, movement, development, interaction and dissipation of warm-sector, prefrontal cold-surge, narrow cold-frontal, wide cold-frontal, wavelike and postfrontal rainbands.

Warm-sector rainbands formed near the leading edge of the cold front and often moved away from the front. Prefrontal cold-surge and wide cold-frontal rainbands formed aloft and behind the surface cold front and they also advanced relative to the front. The clearest interactions between rainbands occurred when wide cold-frontal rainbands overtook narrow cold-frontal rainbands; in this case the narrow cold-frontal rainband may be either temporarily or permanently dissipated, or the wide cold-frontal rainband may be dissipated, depending on the relative strengths of the rainbands. Wavelike rainbands, with very uniform properties, were initiated primarily in the vicinity of the cold front aloft; despite their small scale, these rainbands were relatively long-lived. Postfrontal rainbands, some of which contained oriented precipitation cores, moved with the winds within the postfrontal airmass, and exhibited a variety of lifecycles.

Abstract

Mesoscale measurements on five Pacific cyclones are used to investigate the formation, movement, development, interaction and dissipation of warm-sector, prefrontal cold-surge, narrow cold-frontal, wide cold-frontal, wavelike and postfrontal rainbands.

Warm-sector rainbands formed near the leading edge of the cold front and often moved away from the front. Prefrontal cold-surge and wide cold-frontal rainbands formed aloft and behind the surface cold front and they also advanced relative to the front. The clearest interactions between rainbands occurred when wide cold-frontal rainbands overtook narrow cold-frontal rainbands; in this case the narrow cold-frontal rainband may be either temporarily or permanently dissipated, or the wide cold-frontal rainband may be dissipated, depending on the relative strengths of the rainbands. Wavelike rainbands, with very uniform properties, were initiated primarily in the vicinity of the cold front aloft; despite their small scale, these rainbands were relatively long-lived. Postfrontal rainbands, some of which contained oriented precipitation cores, moved with the winds within the postfrontal airmass, and exhibited a variety of lifecycles.

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