Dynamical Aspects of Gulf Surge Events

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Thursday, 27 January 2011
Dynamical Aspects of Gulf Surge Events
Andrew J. Newman, NCAR, Boulder, CO; and R. H. Johnson

The North American Monsoon Experiment (NAME) produced a very extensive observational dataset of monsoon conditions throughout southwest Mexico and along the Gulf of California (GoC). The NAME captured two strong surge events and multiple weak surge events throughout the NAME enhanced observing period (EOP). This unique dataset provides the necessary observations for detailed comparisons to numerical simulations of gulf surge events, providing further understanding of their dynamics. Simulations of the strong 12-14 July 2004 surge event indicate that the initial surge was a Kelvin wave-like feature generated by convection moving off the SMO, which then propagated up the GoC on 13 July. The removal of evaporational cooling in the microphysics scheme during wave formation creates distinct changes in the evolution of the initial surge during the 12-14 July event. This, along with highly idealized simulations, lends further support to the convectively generated Kelvin wave concept. A weak surge event will also be examined to assess the applicability of the convectively generated Kelvin wave-like feature to surge events in general. Finally, the influence of upper level inverted troughs on surge events will be discussed briefly through the removal of the upper-level PV anomaly in surge simulations and related to the convectively generated Kelvin wave concept previously introduced.