January 12-14 Potential storm

[RogueWaves]

GFS remains super late with the northern branch.

Or super fast with the southern cut-off more likely..its a known bias.

[snowstormcanuck]

Or super fast with the southern cut-off more likely..its a known bias.

Thing just spins over TX for 24 hours around ~120 but by 144 the GFS has the H5 center over AL while the EURO has it in NE LA. Of course, the EURO's bias is that it's too slow in ejecting energy from the SW.

Could cut the difference but I'd just wait see.

[Ajdos]

The good news DTX is still calling for a pattern change...and possible phase...plenty of time for things to change..

THE MEDIUM RANGE MODEL SUITE CONTINUE TO SHOW AMPLIFICATION OF AN

UPPER WAVE DIVING INTO THE SWRN US/NRN MEXICO EARLY NEXT WEEK...WITH

MID LEVEL HEIGHTS BUILDING ACROSS THE GREAT LAKES. THIS WILL SUSTAIN

MILD TEMPS ACROSS THE FORECAST AREA INTO MIDWEEK. A MAJOR PATTERN

SHIFT CONTINUES TO BE ADVERTISED MID TO LATE NEXT WEEK AS MID LEVEL

RIDGE AMPLIFICATION ACROSS WESTERN CANADA LEADS TO THE DEVELOPMENT

OF A HIGH AMPLITUDE NORTHERN STREAM TROUGH/POLAR VORTEX OVER THE

UPPER MIDWEST/NRN GREAT LAKES LATE NEXT WEEK. THIS WILL OPEN THE

DOOR FOR ARCTIC AIR TO PLUNGE INTO THE REGION. MODELS WILL LIKELY

CONTINUE TO STRUGGLE THE NEXT SEVERAL DAYS ON TIMING AND POTENTIAL

PHASING OF THE SOUTHERN STREAM SYSTEM SYSTEM LIFTING OUT OF THE

SWRN US AND THE POLAR VORTEX DIVING OUT OF CANADA. THE POSSIBLE

INTERACTION OF THESE TWO SYSTEM WILL WARRANT A CHANCE OF RAIN/SNOW

IN THE WED/THURS TIME PERIOD.

[Nic]

18z gfs shows NORMAL temperatures for a few days. lol

[snowstormcanuck]

This isn't the case this time. The ECMWF bias is when it leaves a cutoff over the southwest.

I am not sure how far west this goes. I suspect the northern stream will be further west as well. A rain storm in the ohio valley wouldn't surprise me while a trough digs into the rockies, it would fit this pattern to a "t". Maybe a little slushy snow at the end?

I was led to understand that it's a general bias, not one that applies exclusively to cutoff lows. Can anybody shed some light?

[cyclone77]

Even though the GEM will probably be wrong, it sure is pretty looking looping the phase on this thing.

[Harry]

That is key, also where the southern stream cuts off/digs will be key. The Euro/GGEM are further SW compared to the GFS.

And what have the models tended to do with these southern systems all season? Also what is lacking in the Atlantic?

Also a slew of the euro ensembles do bomb this thing ( sub 980mb ) on this side of the apps.

So yeah i would not be writing this thing off at all.

[Harry]

I was led to understand that it's a general bias, not one that applies exclusively to cutoff lows. Can anybody shed some light?

The euro was/has been known to leave these type of systems hanging too long in the sw. See my last reply about what the models have done with these systems this season so far.

[Powerball]

It would be quite fitting to top off a less than stellar start to the season with a storm like the GGEM is suggesting...

[Stevo6899]

Gulf low gets shunted east by the northern piece on gfs. Was looking good for a phase as the low came north before going due east once it got to Kentucky.

[cyclone77]

Yeah the op GFS looks like it's not too far off from a nice phasing. Ensembles should be interesting.

[Ajdos]

Gfs=Puke...another delay to the cold basically... models are lost I think... because of the potential pattern change?

[Stebo]

GFS finding new ways to kick that low out of the SW too quickly, Tonight's run features another cut off low diving south into the Baja on its heels causing it to eject out. No other model has this low or ejects out the Southern stream wave as quickly.

[Rainman]

Gfs=Puke...another delay to the cold basically... models are lost I think... because of the potential pattern change?

The models are doing great. There is every reason to think that there will be a pattern change, and every run of every model continues to advertise it that it will occur. If it's the phased mid week system that you're worried about, then check back 60 hours before event time.

[Ajdos]

The models are doing great. There is every reason to think that there will be a pattern change, and every run of every model continues to advertise it that it will occur. If it's the phased mid week system that you're worried about, then check back 60 hours before event time.

I agree..

[baroclinic_instability]

Thing just spins over TX for 24 hours around ~120 but by 144 the GFS has the H5 center over AL while the EURO has it in NE LA. Of course, the EURO's bias is that it's too slow in ejecting energy from the SW.

Could cut the difference but I'd just wait see.

This is really no longer a real bias with the ECMWF.

[baroclinic_instability]

I was led to understand that it's a general bias, not one that applies exclusively to cutoff lows. Can anybody shed some light?

This is one of those supposed "biases" that has just been over-played and continued through time. It really is no longer a bias of the ECMWF, and the model itself has gone through massive data assimilation and modeling changes since this was a supposed bias. In fact, from a plain subjective POV, I have not seen any evidence that would suggest the ECMWF is "too slow" ejecting cutoff lows out of the SW keeping in mind all models struggle with both cutting lows off and kicking them out...whether it is the SW or the plains.

[Thundersnow12]

GFS finding new ways to kick that low out of the SW too quickly, Tonight's run features another cut off low diving south into the Baja on its heels causing it to eject out. No other model has this low or ejects out the Southern stream wave as quickly.

Yeah noticed that too. It actually had a nice looking wave offshore the pac NW before it broke off and went due south to CA.

[baroclinic_instability]

dtk, on the GFS data assimilation team, says it much better:

"

dtk

• 
  
• 
  
• 363 posts
  
• Joined November 23, 2010
  

• Location:Alexandria, VA
  

Chinook, on 08 November 2011 - 12:45 PM, said:

"I read years ago that the GFS had a cold bias and a progressive bias, implying the polar jet was over-represented. I also read that the ECMWF has a less-than-progressive bias and a warm bias, also it tended to be not progressive enough with lows in the SW USA. Is this still true? Now that we have a trough in the western USA, I am starting to wonder again about long-range stuff for the West."

I always struggle to answer these kinds of questions/comments because people tend to overgeneralize "model bias". You need to be more specific about what portion of the atmosphere you are talking about, what lead time you're interested in, and even be specific about which geographic regions you're curious about.

With that caveat, the GFS certainly doesn't have the documented "cold bias" it used to have. If you look at the long term trend, just in terms of NH 500 hPa height bias, you can see for the past two years the GFS actually has a warm bias:

http://www.emc.ncep....H500mb_day5.png

The figure isn't labeled well, but the interval for the x-axis is yearly. The time series shows bumps toward warmer bias around 2007, and then again in 2010. Both of these jumps correspond to significant implementations (2007 was a model coordinate change and DA overhaul, 2010 was a resolution increase and physics overhaul). This is also demonstrated in the figure here:

http://www.emc.ncep....00mb_dieoff.png

These plots also show that the ECMWF model does tend to have a small, warm bias (in this hemispheric metric). Keep in mind that this doesn't mean that either of the models has the same bias at the surface (or other regions of the atmosphere for that matter).

I believe the issue you bring up with the ECWMF model over the SW US has more to do with long-duration, cutoff type events (I don't think it is accurate to say that the model is always "not progressive enough" with any low over the SW US). In fact, I'm not certain this is even an issue with recent versions of the model (they do very regular, fairly frequent upgrades) "

[PatrickSumner]

The 00Z GFS actually seems to have taken a step in the right direction. The southern energy was slower on this run and there was even a partial phase...

[mnweather]

0Z GEFS quite a bit west of the op run

[PatrickSumner]

0Z GEFS quite a bit west of the op run

Yeah GFS ensembles are pretty far west of the op run...

[Hoosier]

Cutoff is fairly far east on the Euro at 120 hours. I doubt it ends up a favorable phase for most of us on this run.

[PatrickSumner]

Cutoff is fairly far east on the Euro at 120 hours. I doubt it ends up a favorable phase for most of us on this run.

:(

[baroclinic_instability]

GFS was first to lead to some sort of cutoff low breaking off the main upper wave day 4-5...now the ECMWF does this as well...albeit 300 miles eastward. Throws in even more variability with an already highly variable pattern.

[Justin]

With a projected pattern change these models are going to be all over the place, making any possible storm potential very hard to pin down this far out. Again, I'll watch to see if the push of cold coming shoots more South through the Plains states (meaning a likely left track) or if the push of cold initially comes charging Southeastward (which would mean any potential system goes right). Cold air coming in initially tends to be very shallow and seep South through the Plains before bodily moving Eastward. Seen it happen time after time after time over the years. Models shoving everything East on the nose of an Arctic outbreak only to correct back to the left.

[baroclinic_instability]

With a projected pattern change these models are going to be all over the place, making any possible storm potential very hard to pin down this far out. Again, I'll watch to see if the push of cold coming shoots more South through the Plains states (meaning a likely left track) or if the push of cold initially comes charging Southeastward (which would mean any potential system goes right). Cold air coming in initially tends to be very shallow and seep South through the Plains before bodily moving Eastward. Seen it happen time after time after time over the years. Models shoving everything East on the nose of an Arctic outbreak only to correct back to the left.

Yeah agreed. Not to mention the overall volatility with the projected baroclinity and a southern stream anomaly with ample GOM/Gulf stream latent energy. In terms of potential energy, the mass response location/strength at day 7 is strongly correlated to small scale perturbations in the Pacific and the process of wave splitting (possibly as much as two times according to the ECMWF/GFS deterministic). No solution will have much of an idea at this juncture. I am personally just happy to see a change in the Pacific if anything.

[cmichweather]

Yeah agreed. Not to mention the overall volatility with the projected baroclinity and a southern stream anomaly with ample GOM/Gulf stream latent energy. In terms of potential energy, the mass response location/strength at day 7 is strongly correlated to small scale perturbations in the Pacific and the process of wave splitting (possibly as much as two times according to the ECMWF/GFS deterministic). No solution will have much of an idea at this juncture. I am personally just happy to see a change in the Pacific if anything.

At this time frame I'd say toss it... these split stream waves have either been late to phase or non existent, I learned real quick earlier this season how tough it was to get the two streams to phase when we had a cut off southern wave trying to merge with a northern to get a storm up here. Until day 10 or so when we finally get a break in that ugly ridge out west i'd say no good I could see a late phase for the OH and east but the trend is your friend these n/s stream phases have been too far east or way to late.

[baroclinic_instability]

At this time frame I'd say toss it... these split stream waves have either been late to phase or non existent, I learned real quick earlier this season how tough it was to get the two streams to phase when we had a cut off southern wave trying to merge with a northern to get a storm up here. Until day 10 or so when we finally get a break in that ugly ridge out west i'd say no good I could see a late phase for the OH and east but the trend is your friend these n/s stream phases have been too far east or way to late.

I guess I meant I agreed choosing any model at this juncture is a waste, not that it was necessarily going to make a late westward jog.

[Harry]

At this time frame I'd say toss it... these split stream waves have either been late to phase or non existent, I learned real quick earlier this season how tough it was to get the two streams to phase when we had a cut off southern wave trying to merge with a northern to get a storm up here. Until day 10 or so when we finally get a break in that ugly ridge out west i'd say no good I could see a late phase for the OH and east but the trend is your friend these n/s stream phases have been too far east or way to late.

1. Go back to the early Nov system. Models took that thing all the way across the south and off the Mid Atlantic coast. Similar deal with the NM/TX/CO storm. Top that off we have no blocking in the Atlantic?

2. Pay CLOSE attention to the trend with the models especially the euro. Note the northern system dropping out of Canada and BE SURE to look at the 500 maps. THAT really jumped out at me.

You think i am gonna just ignore that and or toss it especially when a good number of euro ensembles are suggesting things go boom?

Lastly check out the strato thread on the main forum. Changes taking place already with the PV, across Asia etc.

NOT saying it is gonna happen but the chances ( for now..IMO ) are growing for a pretty decent storm. Models continue this same trend for another day or so then yeah my excitement is gonna really start to grow.