Tuesday, 31 July 2001: 11:45 AM
The impact of California's coastal mountains on the observed frontal evolution during a major land-falling winter storm
The California Land-falling Jets Experiment (CALJET) was carried out along the California coast, and up to 1000 km offshore, during the winter of 1998 to study the underlying physical processes that cause flooding rains and high winds in the orographically complex coastal zone, and to explore the impact of potential future observing systems on short-term (<24 h) quantitative precipitation and wind forecasts during the land-fall of winter storms from the data-sparse eastern Pacific Ocean. Using the suite of experimental and operational observing systems that were available during CALJET, we were able to document the mesoscale modification of land-falling cyclone structures, and precipitation distributions, by California's steep coastal orography. This presentation will focus on the land-fall phase of the storm of 2-3 February 1998, which heavily impacted the populated areas of the California coast with flooding rains, violent winds, and major beach erosion. A NOAA P-3 research aircraft interrogated this intense storm over the open ocean, while the P-3 and a network of coastal wind profilers provided unique mesoscale observations of this storm in the coastal zone adjacent to the steep terrain. A pair of land-falling cold-frontal zones produced most of the severe weather, while the primary cyclone circulation remained offshore. Special attention will be given to the development of blocking of the low-level flow by the steep coastal mountains of southern California, and the influence of this blocked flow on the observed near-shore frontal evolution. The resulting mesoscale distributions of precipitation in the coastal zone will also be discussed, and its societal impacts described. Additional examples of frontal modulation by the coastal mountains will be presented to highlight the repeatability of this phenomenon in California's coastal zone.