Cold Air Still on Track

November 30, 2009

It’s like the good old days; checking out model updates for weather 5 days from now while totally missing the one day forecast.  As I suspected (but didn’t forecast), the low clouds that developed over us 24 hours ago just sat in the Valley all day.  So on the last day of November with onshore flow and no mixing of any sort, what oh what did I think would clear us out???  I don’t know.  But it did make for a great timelapse from our skycam at 1900′ in the West Hills.  It was above the cloud cover all day.

A bit of a change in the short term is strong easterly flow through the Gorge developing tomorrow afternoon and continuing through Thursday, or Friday.  This appears to be a classic chilly December east wind too.  So after a high near 50 tomorrow I think we’ll be cooler Wednesday and Thursday, with much colder nights where the wind goes calm.  Basically it’s going to get chilly, sunny, and windy for a few days.

Of great interest is the long range of course.  The usual twists and turns keep showing up in various models and model runs within the same models. 

The GENERAL pattern appears to  look like this:  We will see a shot of some sort of cold airmass this weekend and early next week.  Then we go into a much wetter pattern sometime next week as a warmer jet moves in.  My gut feeling is that it’ll be an El Nino-ish warm jet.  Of course the details are the BIG issue.  How cold?  When does it arrive?  When does moisture return?  Or is the ECMWF right (all by itself up through 12z today), showing troughing much farther offshore which doesn’t allow a blast of cold air.  For example, the 12z ECMWF showed 850 mb temps Sunday morning around -3.  The GFS at 12/18z showed -10 or so.  of There is SOME support so far for that warmer solution.  The new 00z NAM is tilting that direction.  More thoughts tomorrow, and Wednesday, and Thursday etc…

Chief Meteorologist Mark Nelsen


New ECMWF Link

November 30, 2009

I added a link to my weather page: http://www.cascadeaccess.com/~mnelsen/markswxlinks.html

About halfway down, right side, the ECMWF pulldown menu.  I put the images from the actual ECMWF site into a much easier format to look at.  That website they have is a real pain to navigate.  I’ve only got the 500mb heights working this evening, but I’ll make an 850mb/Sfc link in a day or two.


Sunday Night Extra…A Big Freeze Coming?

November 29, 2009

     Steve Pierce here with a “special guest blog post” tonight. Had to swing by Fox 12 tonight to take care of some business. I guess I picked a good night to swing in. Why? By now you have all likely viewed the 0z GFS model run showing the Pacific Northwest going from “cool” to downright “frigid” this coming weekend. Not that this is a “lock” at this point in time, but the changes on tonight’s GFS are pretty dramatic, wouldn’t you say? Most obvious change is the colder 850mb temps, along with reinforcing shot of cold air again early next week. A quick check of historical data (stored mostly in my brain) leads me to think, if verified, that this would be the coldest air this early in the season since 1985. There is plenty of time for future model runs to change things one way or the other, but a trend to much colder sure looks better tonight than it did last night. Could it be the “09/10 Cycle” that I spoke of at the fall AMS meeting? Only time will tell! Stay tuned! ~ Steve Pierce – Oregon AMS

So what Steve really meant to say is “Mark allowed me to geek out all evening but is about to kick me out”.  Actually Steve behaved pretty well.

The image above is the 6-10 day 500mb. height deviation from normal.  It shows a huge 500mb height anomaly (positive) over SE Alaska.  That allows cold air to stream down the eastern side of the high as Steve has already pointed out.  The trend is definitely faster with the arrival of cold air on both the GFS and GEM (Canadian Model).  They also don’t have moisture of any kind for snow or rain through early next week.  The 12z ECMWF was much slower and not nearly as cold, but had plenty of moisture in here by Monday.

Of course it’s Sunday evening, and we’re talking about something 6 days away.  I won’t get really jazzed up about a big arctic outbreak until another 24 hours of cold on the GFS and the ECMWF needs to come around as well.  That’s why I didn’t go crazy with high temps in the upper 20s or 30.  I figure a forecast high of 35 on Sunday when all other forecasts are 45-50 is wild enough for now.  Wait…I was almost shoving Steve out the door but he just told me the 00z ECMWF would be out by 11pm.

Chief Meteorologist Mark Nelsen


Spaghetti-Like Maps

November 28, 2009

Here’s a nice image that displays the challenges of the long term forecast.  It’s the various GFS ensemble members for Tuesday, December 8th (D+8 forecast).  A bit of confusion eh?

Okay, back at it this evening.  I just perused the 00z maps to compare with the last 24 hours.  There had been quite a bit of excitement with various models (Canadian and GFS) showing arctic air intrusions into the Pacific Northwest at differing time periods.  Of course each model run has been different.  Notice the spaghetti chart is a huge mess from the 12z GFS.    That’s unusually messy for Day 8.  Now the 00z models are in and I don’t see any sign of a big blast of cold air;  that’s due to models showing the upper level ridge staying quite close to the Coast.  What I do see is classic El Nino conditions.  High pressure nearby, a wet southerly jet across the USA, and cool offshore flow for more than half the 7 day forecast here in the Pacific Northwest.  Since the first week of December is just around the corner, any offshore flow will keep us chilly.  It’s tough to get high temps above about 52 at PDX with easterly flow December through January.  More likely in the 45-50 degree range later next week.  Add to that overnight lows down in the 20s in outlying areas and it’s going to really feel like December around here as we progress through the next 7-10 days.

Chief Meteorologist Mark Nelsen


A Thanksgiving Fantasy

November 25, 2009

Happy Thanksgiving! 

To celebrate the big day I found this map in tonight’s 00z GFS model run.  Click on it to see a much better view.  It’s the 324 hour forecast;  that’s ONLY two weeks from tonight!  The image includes surface pressure, rainfall, and 500-1000mb thickness.  It shows a cold arctic high dropping into Montana and southern British Columbia/Alberta.  At the same time warm and very wet Pacific flow is surging in from the southwest.  This is a great setup for an ice storm  in the Gorge and probably into the Metro Area as well.  One can only dream eh?  Well, something to dream about while enjoying the turkey.  Two other things quite obvious on recent maps; we are in ridging or split flow along the West Coast through the next 7-14 days.  There were hints on the ECMWF and a bit here on the 00z GFS that some slight retrogression may occur beyond 5 days.  That allows cooler air (probably not arctic) to come south for gusty east wind and sunshine Tuesday and beyond next week.    Other than that it’s dry, dry dry.    The 2nd regime I notice is an active southern jet stream.  Several systems move from Texas east through Florida during the next 10 days.  Possibly (as indicated on this map) California starts to get wet at some point too.  Of course all of this is classic El Nino weather.  But just as we can’t attribute any one weather event to Global Warming, we can’t just take the first week or two of this pattern and say “El Nino is here!”.  Now if this pattern recurs several times between now and early February?  That’s a different story and something we might expect with an ongoing El Nino episode.

I’ll be back at work Saturday, but no blog updates between now and then.  Enjoy the holiday.

Chief Meteorologist Mark Nelsen


S-L-O-W Weather

November 23, 2009

After the wild weekend, it seems appropriate that the weather would slow down for Thanksgiving Week.  But what a slowdown!  The next 7-10 days look real quiet.  The main message is ridging or split flow through at least early next week.  One system makes it through late Thursday and Friday and might give us a burst of wind (depending on the model), but otherwise it’s makeup time for all the busy weather apparently.

Chief Meteorologist Mark Nelsen


Storm Wrapup

November 22, 2009

Oh boy;  feels like I stayed up too much last night watching the wind.  I was up until 1am and then from 2:30 to 3:30 during the peak of the storm.  Now both kids are sick in bed and on the couch, so a good time to do a recap of our best inland wind so far this season.

As expected, it wasn’t a big windstorm.  Peak gusts from the Airports:

PDX: 51  HIO: 44  VUO: 43  TTD: 50  UAO: 48  SLE: 48  KLS: 39  SPB: 38

Of course there were some higher gusts recorded at some home weather stations:

Forest Grove: 52  Corbett: 46, Orchards: 50, Happy Valley: 52, Glen Jackson Bridge: 51

That 51 mph from PDX is the highest southerly wind since December 2006.  By the way, when looking for the highest gust at NWS observation sites, make sure you go to the RAW observation and look for the PKWND comment.  That’s the peak gust for the hour.  For example, the 4am observation from PDX: KPDX 221153Z 21020G31KT 10SM -RA FEW028 OVC040 08/05 A2953 AO2 PK WND 21044/1058.   It’s the direction (240=SW), speed (44kts=51mph), and time (10:58z=2:58am).

What went right?  Model performance…pretty good.  The mesoscale models did well on depth of the low.  It ended up coming inland slightly south of where it was expected, maybe right over Astoria and then inland to central Washington.  But still, very nicely done models!

What didn’t go right?  Observations are pitiful off our coastline this winter.  What is going on?   Buoys with no windspeeds, buoys that aren’t working or not in place, and the dirty little secret we never talk about; horrendous radar coverage offshore.  There’s no excuse to not have two radars in place along the Oregon and Washington Coastline.  That tornado that moved into Lincoln City?  Someone from the NWS can correct me if I am wrong, but I think the LOWEST the beam can see out there is about 15,000!  Even after some of the signal makes it through gaps in the Coast Range, we’re missing the entire lowest section of the atmosphere along the Pacific Northwest coastline.  At least they got organized enough in Washington to put in a coastal radar somewhere near Hoquiam within the next two years.  That would have shown us exactly where the low pressure center was.  There needs to be another radar near Newport or Florence to at least partly fill the gap between the Eureka radar and the new one coming up north.  I wish we had the willpower or leadership to get that done. 

Chief Meteorologist Mark Nelsen


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