6B.6 Linked extreme weather events: Severe cold and record-breaking rains in Mexico and disruptive wild fires in California in late October 2007

Tuesday, 2 June 2009: 5:15 PM
Grand Ballroom West (DoubleTree Hotel & EMC - Downtown, Omaha)
Lance Bosart, SUNY, Albany, NY; and H. M. Archambault and J. M. Cordeira

he purpose of this presentation is to document the large-scale flow variability over the North Pacific Ocean in October 2007 that was a catalyst for several linked severe weather events downstream, including destructive wildfires in California and severe cold and record-breaking rains in Mexico. These linked severe weather events occurred in conjunction with a typhoon-assisted acceleration and eastward displacement of the North Pacific jet stream. Amplification of the upper-level flow and associated downstream development resulted in strong Santa Ana conditions in southern California and an ensuing cold surge and heavy rains in Mexico.

The California wildfires occurred in conjunction with dynamic anticyclogenesis over western North America. Downstream trough development triggered a Mexican cold surge and subsequent record-breaking heavy rains in the Mexican states of Chiapas and Tabasco. The focus for the heavy rains was strong low-level warm-air advection along the southeastern margin of the cold surge in the presence of westward-moving tropical moisture, in part from developing Tropical Cyclone (TC) Noel situated near Hispaniola. The cold surge-induced sea level pressure difference between northern and southern Mexico resulted in an exceptionally strong and moist northerly upslope flow that allowed sustained heavy rainfall to occur in Chiapas and Tabasco.

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