The climatology of synoptic-scale ascent over Western North America: a perspective on storm tracks

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Publication Type pre-print
School or College College of Mines & Earth Sciences
Department Atmospheric Sciences
Creator Horel, John D.
Other Author Lareau, Neil P.
Title The climatology of synoptic-scale ascent over Western North America: a perspective on storm tracks
Date 2012-01-01
Description The position and variability of storm tracks across western North America are examined during the October-April cool seasons spanning 1989-2010. The location and intensity of storms are represented by strong synoptic-scale ascent, which is diagnosed by the alternative balance omega equation applied to ECMWF Re-Analysis Interim data. This dynamically filtered method removes poorly resolved updrafts arising from subsynoptic-scale phenomena such as convection and mountain waves. The resulting vertical motions are illustrated for the case of a strong storm traversing the western United States. Summary statistics of synoptic-scale ascent are compiled over months, seasons, and the entire 21-yr period. Locations exhibiting high mean values of ascent are deemed to represent storm tracks. The climatological-mean storm track exhibits a sinusoidal shape across the eastern Pacific and western North America. The composite evolution of strong storms moving along specific segments of the storm track show regional differences (e.g., storms poleward of 508N tend to result from progressive low-amplitude troughs progressing through the mean planetary ridge, while storms over the western United States are initiated by digging troughs that temporarily suppress the mean ridge). Seasonal shifts in the storm track are pronounced and exhibit coherent regional patterns. Interannual variations in synoptic-scale ascent indicate meridional shifts in position as well as changes in the degree of amplification within the dominant sinusoidal storm track. These changes in structure are related to the phase of ENSO: El Nin˜ o (La Nin˜ a) winters favor zonal (amplified) and southern (northern) storm tracks.
Type Text
Publisher American Meteorological Society
Volume 140
Issue 6
First Page 1761
Last Page 1778
Dissertation Institution University of Utah
Language eng
Bibliographic Citation Lareau, N. P., & Horel, J. D. (2012). The climatology of synoptic-scale ascent over Western North America: a perspective on storm tracks. Monthly Weather Review, 140(6), 1761-78.
Rights Management (c)American Meteorological Society
Format Medium application/pdf
Format Extent 4,116,178 bytes
Identifier uspace,17718
ARK ark:/87278/s6vm4x1m
Setname ir_uspace
Date Created 2012-09-07
Date Modified 2021-05-06
ID 708098
Reference URL https://collections.lib.utah.edu/ark:/87278/s6vm4x1m
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