California (and west coast)

[CaWx]

I figured since California and the immediate west coast in general doesn't have its own forum, thought I'd start a new one. Since the dry season is coming to a close, and the possibility of an active upcoming pattern, I was hoping to get some members to discuss. Generally the weather out here is sun sun sun, and it gets a little boring. 

First bay area disturbance to track this year. 

 

.DISCUSSION...as of 02:35 PM PDT Saturday...Satellite imagery
depicts a 543DM upper level trough positioned off the Pacific
coastline this afternoon, with the core of the upper low offshore
of Washington state and the base of the trough offshore of central
California. A series of vorticity lobes will traverse this upper
level feature through the coming days and bring unsettled weather
to the region.

The first of these vorticity pulses moved through the region
yesterday and the associated dry cold frontal passage brought
cooler temperatures, breezy onshore winds, and clear skies to the
area. Fair weather conditions are being observed today as the upper
level feature`s energy level has weakened slightly in between
vorticity pulses. Temperatures have warmed slightly across the
board, winds have eased, and skies remained clear for today.

The upper low resurges tomorrow to dominate our local weather.
This comes as a result of the lows upper core descending into our
region from the northwest, bringing with it much cooler unstable
air and more energetic dynamics aloft. These factors will combine
to bring cooler temperatures to the surface, increased onshore
winds, and the first rain of the season for some locations.
Surface temperatures are anticipated to be 10-15 degrees below
seasonal normals tomorrow, with -23C at 500MB, -5C at 700MB, and
4-5C at 850MB. Winds should be similar to those experienced on
Friday, with the strongest winds over north/east bay ridge tops
and along the immediate coast. Precipitation will come in the form
of isolated to scattered rain showers, predominately located over
the Greater Bay Area. Short term models also indicate the
potential for some rain showers to stray further south over the
Santa Cruz mountains, and possibly into portions of the Monterey
Bay region. That said, the bulk of the precipitation is expected
over the North Bay, where around a tenth of an inch of rain is
possible, but locally higher amounts of up to a quarter of an
inch are possible. Furthermore, convective parameters are bringing
sufficient cape and instability into the region to warrant a
mention of isolated thunderstorms for Sunday primarily over the
north/east SF Bay.

The upper low then shifts further inland on Monday, allowing for
cold air to settle in. Monday should be just as, if not colder
than, Sunday. A moist northwest flow will develop in the wake of
the upper low late Monday into early Tuesday. A series of weak
vorticity maxima will couple with a considerably moist
precipitable plume (on the order of 1.3-1.4") to bring a second
round of rain showers to portions of the region through Monday
night into early Tuesday.

 

 

Maybe a .10" if things go perfect. Nice to see the reservoirs in the north by Shasta will have a good start. 

[Monsoonchaser]

Your discussion didn't format correctly! *for tapatalk

ECMWF and GFS have been really inconsistent, but the ULL looks pretty good dropping down into the NW. Will have to watch the Mesoscale models.

Looking forward to some real strong surface lows!

Sent from my SAMSUNG-SM-G891A using Tapatalk
 

[andyhb]

Might be fixing to get hammered up here this weekend depending on the exact track of the system enhanced by Songda's remnants. Liable to have a very deep surface low somewhere off the Pacific NW coast. Closer in to the coast and wind damage would be highly likely.

[Chinook]

Here is (yesterday's) 7-day precip forecast from the NWS. It looks like this week could be considered a big dog for the Pacific Northwest, including extratropical Typhoon Songda  on Saturday, possibly. The GFS predicts the Songda low to be in the 950's.

[Roger Smith]

Yep, looks like 80-90 mph wind gusts likely on coasts of WA, OR and possibly southwest Vancouver Island by Saturday morning to mid-day, possibly spreading into Puget Sound and the Strait of Georgia also, and it's full moon so that storm surge will be a big issue too. This on top of a moderate storm coming in Thursday morning. 

The central pressure falls into the 950s similar to the Columbus Day storm of 1962 (Freda) and while I don't expect anything quite that destructive (winds gusted over 120 mph in some places in that one), this could blow down trees throughout the Pacific northwest. Hundreds of thousands could lose power in this storm. 

[Roger Smith]

12z GFS and GEM have almost identical scenarios of a strong windstorm event for Saturday, with near 960 mb low approaching southern WA coast and swerving northeast into central Vancouver Island. Gradient looks extreme for anywhere north of about Newport OR especially Astoria to Tofino BC. This jumps the Olympic peninsula and hits full force in Puget Sound and what we now call the Salish Sea (southern Strait of Georgia, eastern Strait of Juan de Fuca) where southerly storm force winds appear likely. 

Currently (15z) Typhoon Songda is a 945 mb low at 34.8 N, 158.8 E, with winds of 85 kts gusting 120, but is expected to fill to 984 mbs near the IDL at 42N same time tomorrow. From there it cruises along in a very low-latitude subarctic jet to reach an explosion point on Friday night near 42N 150W. This is rather similar to Freda (Oct 12, 1962) except that Freda came from the central Pacific (west of Hawaii) family of hurricanes (it was not a typhoon) and joined the jet stream closer to 35-37 deg N. This storm is known as the Columbus Day storm in WA and OR where it did tremendous damage to forests (same result in Vancouver's Stanley Park). Gusts of 120-150 mph were estimated from tree damage. I think this one could be almost that bad.

I think this will be a large enough weather event to put a thread onto the main page later today. The general public will become interested in this and search engines should direct them here. 

 

[andyhb]

Important to note that the track of the Columbus Day storm was absolutely paramount in it being a damaging as it was. The almost due N track close to the coast enabled intense winds to funnel up the Willamette Valley and Puget Sound. The GFS looks less dangerous than the Euro since the system occludes and swings N fairly far offshore. It would definitely be windy, but not the widespread damaging idea that the Euro has.

[Roger Smith]

Those are really low 500-mb heights on the coast (sub 520 dm) and I think the most likely track is a blend of all three models, landfall will most likely be near or just north of Tofino. I agree it won't be as intense as 1962 especially for inland Oregon, but coastal and perhaps Puget Sound winds may be damaging. 

[TPAwx]

Early 0z models have a closer to coast track, so that's not good for PNW.  Depth is prob tough to nail at this point, but could be some mayhem on Saturday.

[Roger Smith]

GFS looks a little more intense, GEM loses the system on final approach and would suggest more moderate windstorm only south of Hoquiam WA. Await the ECM with interest. 

[andyhb]

49 minutes ago, Roger Smith said:

GFS looks a little more intense, GEM loses the system on final approach and would suggest more moderate windstorm only south of Hoquiam WA. Await the ECM with interest. 

Er what? The GEM would be worse than the GFS (further south, closer to the coast). That's much closer to where the Euro has been recently.

[TPAwx]

That's a disaster euro run.  Could be epic.

[andyhb]

New Euro run is real nasty towards Portland. 80+ kt H85 flow right over the area. Can't see in between frames, but would assume the backside occlusion lashes further N with significant gusts as well.

[TPAwx]

The 12z/1013 GFS continues that model's trend of tracking the typhoon remnant low closer to the Oregon and Washington coasts.  The latest run is not as deep as previous solutions,  but this would still be a potentially devastating storm along the PNW coast from NorCal up through WA and Vancouver.  The major population centers in OR and WA would get battered on Saturday, and while not yet 62-esque it could be comparable.

[TPAwx]

In the Seattle area deciduous trees have been dropping leaves but most are still on the fuller side.  This evening's appetizer could bring enough wind and rain to strip most of the remaining leaves, which will or course plug gutters and drains.  Beyond the Olympics the Saturday threat is primarily high winds, but any significant rain in the metro area could create drainage issues, on top of the falling tree risk.

Looking for an upside, at least my view of Lake Washington will clear out a bit more  :-)

[Roger Smith]

It is one ugly morning here, low scudding cloud and pelting rain, at times hard to see the tops of nearby 40-storey high rises. Almost twilight darkness at 0830h, it has lightened up a bit since then.

We have had bursts of heavy rain all morning here (near Vancouver BC) and I would estimate 40-50 mm has fallen since midnight. Similar situation with leaves and drainage. Any strong wind gusts will encounter half-loaded trees and saturated ground conditions, making it easier to bring large trees down.

The 12z GEM looks a bit more robust than I thought the 00z looked, and has a landfall in central WA but I don't trust that, I think it's coming in at a sharper angle as shown on the GFS, and therefore will track into southern or central Vancouver Island putting greater Vancouver and Victoria in the path of damaging wind gusts too. The most damaging tracks for Seattle however are probably those that clip the nw corner of WA state and this may do that too. GFS while not as intense on central pressure still has the rapid deepening phase and a tight gradient that would suggest gusts to 80 knots at Astoria and Hoquiam, probably 55-60 in Puget Sound and 50-55 in Portland. 

Satellite imagery shows the center of the low making very rapid eastward progress. The 12z CMC analysis (and satellite imagery) showed a center around 42 N 177E but already (16z) it looks close to 43 N 175 W. That is 2 deg of longitude per hour, maybe not surprising given that it is under a 250-mb jet of 175-200 knots. But unless it slows down a bit, it will be at 130W by this time tomorrow, where the models are more like this time Saturday. I imagine it will slow down but I wonder if this is a sign that the actual timing will move ahead on future model runs. 

[TPAwx]

The 0z EPS and 12z GEFS are very similar in keeping the track offshore of WA Saturday afternoon and evening.  Still a significant storm for the region, but obviously not as intense for the population centers and lowlands as are the recent op runs.

[Roger Smith]

This link should illustrate the much faster motion, this thing (43 N 174 W) is already 5 deg east of where the 12z GFS placed it at 17z. 

A rough calculation shows that with an assumption of 1.5 deg per hour that places the center near 128 W by 00z Saturday.

http://weather.gc.ca/satellite/satellite_anim_e.html?sat=goes&area=pac&type=1070

 

[Chinook]

NWS WPC is predicting 15 to 24.6" of rain at the northwest corner of California in 5 days. You usually don't see the 15" contour used.

[Roger Smith]

With any luck this will help fill up some half-empty reservoirs in north-central CA. But I imagine there would be some bad flooding in nw CA and parts of western OR (I was there in the summer, it seemed bone dry around Crater Lake). 

[TPAwx]

No clue how else the hi res Nam does this far out, but we could be looking at a large population exposed to very severe conditions at Saturday progresses.  Round 1 is tonight with sustained winds possibly to 40 and gusts to 60.  Concerned about this knocking out power and taking down trees, and people literally being "in the dark" WRT communications as the situation develops on Saturday.  Chaos is already setting in, with many stores out of batteries and firewood already.  Just hope that people take this seriously and stay inside, as flying debris and falling tree limbs will be really dangerous.

[Roger Smith]

The 12z Euro apparently convinced the Seattle WFO to issue a high wind warning and monitor for storm surge although they think highest potential may be mitigated by low tide Saturday evening. Would imagine that areas like Ladner BC more at risk a bit later and closer to high tides. 

The 18z RGEM really bombs out on both tonight's low and the Saturday feature, showing 965 mb west of Astoria by 18z Saturday after bringing a 968 mb low inland late tonight. The 18z GFS is somewhat less extreme than earlier on Saturday, but adds a wind max on Friday afternoon, meaning that we are into almost continual moderate south to southwest winds from tonight to Sunday now. 

As to my observation of faster motion, that seems to be slowing down somewhat, the past six hours have seen about 9 deg further eastward tracking to 165 W. The 18z map positions were fairly close to what I had been saying although with an elongated wave crest you have a range of very similar low pressures over about 5 deg. 

Tonight's 500 mb and 250 mb maps will be interesting. My local weather has remained mostly dry this afternoon but it's getting dark about an hour before sunset. 

[Jim Martin]

Impressive 850 MB & Infrared Satellite this evening...

[Jim Martin]

Already getting multiple reports of 80 to 90 MPH wind with this storm in and near the Oregon Pacific Coast. It is only beginning, too.

[1900hurricane]

Potent looking storm on WV. Songda's remnants look like it's waiting in the wing back around 160*W.

[andyhb]

Man the 00z Euro and NAM just want to absolutely drop the hammer in W WA and SW BC Saturday. The former has widespread storm to hurricane force gusts around the Sound and northward into the Lower Mainland. Haven't seen anything like that since 2006, if not before then.

[TPAwx]

The euro depiction looks very intense and with high potential for damage and destruction Oregon coast up thru Vancouver and western WA.  This should play at a national level if it comes to pass.

[andyhb]

Multiple tornado warnings over the OR and WA coast this morning. The environment there is actually fairly impressive with 500 J/kg MLCAPE and very strong shear.

Edit: Tornado damage reported in Manzanita, OR via law enforcement.

[janetjanet998]

[andyhb]

This is absolutely incredible.