P47 Multiscale Simulations of the Dynamics associated with the 27 September 2010 Los Angeles/Southern California Extreme Heat Event

Tilley, Jeffrey S., University of North Georgia, and Michael L. Kaplan, Desert Research Institute

An extraordinary mesoscale extreme heat event occurred during the afternoon of 27 September 2010 in Southern California, setting numerous temperature records for the date. The event was unusual that the extreme temperatures occurred well before typical diurnal heating maximum times as well the fact that the heat extended to the Pacific coastline with minimal modification. In this presentation we examine in depth a series of simulations, with domains covering from the synoptic scale down through the urban scale, to uncover the multiscale dynamics and interactions that led to this unique event unfolding as it did during the 27th of September.

The series of model simulations performed also includes sensitivity studies, including some basic FDDA and cycled 3DVAR runs, to determine what potential factors might be important for future forecasting and to determine if there is a sufficient paradigm in the multiscale dynamics that might allow for the development of improved forecasting models and other tools such as checklists.

We will provide a brief observational overview of the event and our simulation methodology, followed by selected modeling results from the "best case" simulation and some of the sensitivity studies as a means of presenting the dynamics and examining the potential for a multiscale modeling system to adequately predict the detailed evolution of the event.