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- Title
Orographic Precipitation Forcing along the Coast of Northern California during a Landfalling Winter Storm.
- Authors
Valenzuela, Raul A.; Kingsmill, David E.
- Abstract
This study documents orographic precipitation forcing along the coastal mountains of Northern California during the landfall of a significant winter storm over the period 16-18 February 2004. The primary observing asset is a scanning X-band Doppler radar deployed on the coast at Fort Ross, California, which provides low-level (e.g., below 1 km MSL) horizontal and vertical scans of radial velocity and reflectivity to characterize airflow and precipitation structures. Further context is provided by a wind-profiling radar, a radio acoustic sounding system (RASS), balloon soundings, buoys, a GPS receiver, and surface meteorological sensors. The winter storm is divided into two episodes, each having pre-cold-frontal low-level jet (LLJ) structures and atmospheric river characteristics. Episode 1 has a corridor of terrain-trapped airflow (TTA) that forms an interface with the LLJ. The interface extends ~25 km offshore in a ~0.5-km vertical layer, and the western edge of this interface near the ocean surface advances toward the coast over the course of ~5 h. The TTA acts as a dynamically driven barrier, so that the incoming LLJ slopes upward offshore below 1.5 km MSL and precipitation is enhanced over the ocean and near the coast. The absence of a TTA in episode 2 allows the cross-barrier flow to slope upward and enhance precipitation directly over the coastal mountains. A theoretical analysis favors the hypothesis that a gap flow exiting the Petaluma Gap forces the TTA.
- Subjects
NORTHERN California; METEOROLOGICAL precipitation; OROGRAPHIC clouds; DOPPLER radar; MESOSCALE convective complexes; WINTER storms
- Publication
Monthly Weather Review, 2015, Vol 143, Issue 9, p3570
- ISSN
0027-0644
- Publication type
Article
- DOI
10.1175/MWR-D-14-00365.1