Sunday, December 02, 2012

Places That Have Seen More Rain Than You: California

Continuing our theme of places that have been rained on a bit more heavily than your backyard of late, the northern third of California has been dealing with a few days of consistent and persistent heavy rainfall.  A combination of a powerful jet streak and tropical moisture that is originating near Hawaii have fed one soaker into the West Coast already, sending a second one in now, and feeding a third in a couple of days.

Parts of California have picked up several inches of rain so far -- with more on the way as heavy rain is moving onshore today with the second storm in the series of three that should impact through Wednesday. You can see that storm system moving through the West on the satellite image up above -- this storm system will send a cold front east through our region on Tuesday night and early Wednesday and help mitigate the warmup that's in place overhead.

One of the cool features that's worth sharing is that water moisture loop from CIMSS at the University of Wisconsin -- it shows the amount of precipitable water in the atmosphere in a given point.  The brighter the color, the more moisture available.  Not only is it a good indicator of how much "juice" is available in the ocean to work with for tropical systems, but it gives you a good idea of the source of moisture when a mid latitude storm latches onto tropical moisture.  In the case of the West Coast storms, this moisture train is coming from Hawaii.  A large storm is spinning in the Central Pacific and pulling moisture northward above the island chain.  It is then shunted east along a frontal boundary and the northern jet.  The moisture then zooms east towards the US.  Not quite your typical "Pineapple Express" but it does show the strong influx of moisture from a tropical source region -- and with another heavier batch strengthening near Hawaii, more rain will be forthcoming as it shoves east in the next couple of days.

Rainfall totals through Wednesday probably exceed a foot in parts of California or Southwest Oregon.  The Tuesday/Wednesday system that's projected to hit the West Coast probably hits farther north than today's system does (hitting more into Oregon and less into California) as a ridge tries to nudge up into California.

Over the next two or three days, you may hear about mudslides and flooding across Oregon and California from these storms as they move through.   Moisture from these will not impact our region at the same clip as they impact the West Coast although some rain is definitely possible later tonight and again on Tuesday night as frontal boundaries cross the region.