(b) Technical Early in the period, forecasters considering only the vorticity advection pattern might have underestimated the potential for strong upward vertical velocities associated with the shape of the warm advection field (also called "overrunning"). This often catches forecasters unawares who assume that large scale lifting mechanisms (often termed "dynamics") can be entirely estimated from the vorticity advection pattern. This often shows up in forecast discussions when the forecaster, confronted with heavy rainfall and strong upward omega with weak or absent cyclonic vorticity advection, states "dynamics poorly initialized by models". In reality, the shape of the temperature advection field (maximum in warm advection = forcing for upward motion) is equally an important consideration when estimating vrtical motion.
Since a consideration of the isothermal vorticity advection pattern essentially combines both synoptic forcing terms for quasigeostrophic vertical motion into one (cyclonic vorticity advection by the thermal wind = upward vertical motion and vice versa), a combined thickness/vorticity chart can provide an overview of the synoptic forcing for this event. We have included such charts in our map section.
11 12 Bodega Bay 2.96 3.71 Concord 2.41 1.29 Danville 3.32 1.78 Fairfield 3.27 4.11 Fremont 1.73 0.93 Half Moon Bay 3.02 1.61 Kentfield 7.35 3.93 Livermore 1.69 0.91 Los Gatos 3.44 1.84 Martinez 2.20 1.18 Mountain View 2.96 1.58 Napa 2.54 3.18 Oakland 4.21 1.21 Pacifica 3.09 1.65 Pittsburg 1.53 0.82 San Francisco 3.27 1.75 SF Intl Airport 3.06 1.63 SF State U 3.67 1.69 San Jose 1.13 1.41 San Rafael 5.76 3.08 Santa Rosa 2.75 3.45 Sonoma 4.82 2.58 Stinson Beach 4.43 2.37 Vallejo 3.64 4.56 Walnut Creek 1.64 2.06
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