2009

Somewhat surprisingly, the much-advertised major fall storm is still very much on track. There have been some subtle changes in the models since late in the week, but the screaming headline remains the same: the potential for heavy to very heavy rainfall and strong to very strong winds exists over much of CA early this coming week. Recent model runs have expanded the area of significant impacts significantly to the south, with perhaps the northern 4/5 of the state receiving significant weather from this system. Rainfall totals and wind speeds will certainly be highest up north, but it does now appear that Los Angeles will see some rain and the mountains of SoCal could see heavy precip. There is still some question regarding the exact placement of the surface low which could have a large impact on rainfall and wind speeds in NorCal–if it deepens a bit more than expected, or is just slightly closer to the coast, as some recent GFS/ECMWF runs have suggested–impacts would be significantly greater. Widespread urban flooding and moderate wind damage–including downed trees and power lines–can be expected in NorCal. If that surface low is a bit deeper, though, wind damage could be more serious and flash flooding more dangerous. Again, this storm is still a couple of days out, but this is a system that has the potential for rapid cyclogenesis (something models are sometimes notorious for missing). Intuition tells us that this system could also be a bit weaker than expected, but the models have remained remarkably gung-ho regarding the magnitude of this storm (and the NAM, which had been weaker than the other models, just came into line with the others in the 12 and 0z runs).