[Fosc] Big rain, big wind on the way!

Karen Paulsell kpaulsell at pacbell.net
Fri Jan 15 15:54:29 PST 2010


Here's an email from one of my weather-watching pals.  Sounds like 
we'll be getting some real weather, some serious rain, for quite a while.

We'll need to batten down the hatches at the nursery on Saturday, for sure!



>This FYI. It's quite a bit more vivid than what NOAA is putting out.
>It was emailed to me by a Pt Reyes neighbor who got it from a friend
>of hers who seems to work for Marin emergency services. Searching
>with Google I found the text or pieces of it replicated to various
>blogs, and verified the existence of the writer and the institution,
>but haven't located his original posting. It's consistent with the
>current NOAA briefing but takes more of a macro view.
>
>There's also an animated forecast from the Navy at: http:tinyurl.com/yzmchsk
>(When I first accessed this, my web browser made
>all sorts of noises about this being an unverified site, but I think
>you can safely ignore those-- it's seems to be as harmless as the
>Navy can be.)
>
>LJ
>
>
>>Currently, the strong El Nino is reaching its peak in the Eastern
>>Pacific, and now finally appears to be exerting an influence on our
>>weather. The strong jet has been apparent for quite some time out
>>over the open water, but the persistent block had prevented it from
>>reaching the coast. Now that the block has dissolved completely, a
>>200+ kt jet is barreling towards us. Multiple large and powerful
>>storm systems are expected to slam into CA from the west and
>>northwest over the coming two weeks, all riding this extremely
>>powerful jet stream directly into the state. The jet will itself
>>provide tremendous dynamic lift, in addition to directing numerous
>>disturbances right at the state and supplying them with an ample
>>oceanic moisture source. The jet will be at quite a low latitude
>>over much of the Pacific, so these storms will be quite cold, at
>>least initially.
>>
>>Very heavy rainfall and strong to potentially very strong winds
>>will impact the lower elevations beginning late Sunday and
>>continuing through at least the following Sunday. This will be the
>>case for the entire state, from (and south of) the Mexican border
>>all the way up to Oregon. Above 3000-4000 feet, precipitation will
>>be all snow, and since temperatures will be unusually cold for a
>>precipitation event of this magnitude, a truly prodigious amount of
>>snowfall is likely to occur in the mountains, possibly measured in
>>the tens of feet in the Sierra after it's all said and done. But
>>there's a big and rather threatening caveat to that (discussed
>>below).Individual storm events are going to be hard to time for at
>>least few more days, since this jet is just about as powerful as
>>they come (on this planet, anyway). Between this Sunday and the
>>following Sunday, I expect categorical statewide rainfall totals in
>>excess of 3-4 inches. That is likely to be a huge underestimate for
>>most areas. Much of NorCal is likely to see 5-10 inches in the
>>lowlands, with 10-20 inches in orographically-favored areas. Most
>>of SoCal will see 3-6 inches at lower elevations, with perhaps
>>triple that amount in favored areas.
>>
>>This is where things get even more interesting, though. The models
>>are virtually unanimous in "reloading" the powerful jet stream and
>>forming an additional persistent kink 2000-3000 miles to our
>>southwest after next Sunday. This is a truly ominous pattern,
>>because it implies the potential for a strong Pineapple-type
>>connection to develop. Indeed, the 12z GFS now shows copious warm
>>rains falling between days 12 and 16 across the entire state.
>>Normally, such as scenario out beyond day seven would be dubious at
>>best. Since the models are in such truly remarkable agreement,
>>however, and because of the extremely high potential impact of such
>>an event, it's worth mentioning now. Since there will be a massive
>>volume of freshly-fallen snow (even at relatively low elevations
>>between 3000-5000 feet), even a moderately warm storm event would
>>cause very serious flooding. This situation will have to monitored
>>closely. Even if the tropical connection does not develop, expected
>>rains in the coming 7-10 days will likely be sufficient to cause
>>flooding in and of themselves (even in spite of dry antecedent
>>conditions).
>>
>>In addition to very heavy precipitation, powerful winds may result
>>from very steep pressure gradients associated with the large and
>>deep low pressure centers expected to begin approaching the coast
>>by early next week. Though it's not clear at the moment just how
>>powerful these winds may be, there is certainly the potential for a
>>widespread damaging wind event at some point, and the high Sierra
>>peaks are likely to see gusts in the 100-200 mph range (since the
>>200kt jet at 200-300 mb will essentially run directly into the
>>mountains at some point). The details of this will have to be
>>hashed out as the event(s) draw closer.
>>
>>In short, the next 2-3 weeks (at least) are likely to be more
>>active across California than any other 2-3 week period in recent
>>memory. The potential exists for a dangerous flood scenario to
>>arise at some point during this interval, especially with the
>>possibility of a heavy rain-on-snow event during late week 2. In
>>some parts of Southern California, a whole season's worth of rain
>>could fall over the course of 5-10 days. This is likely to be a
>>rather memorable event. Stay tuned.
>>
>>Samuel Y. Johnson
>>Western Coastal and Marine Geology
>>U.S. Geological Survey
>>Pacific Science Center
>>400 Natural Bridges Drive
>>Santa Cruz, CA 95060
>>(831) 427-4746 voice
>>(831) 252-0812 cell
>>(831) 427-4709 FAX
>>sjohnson at usgs.gov




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