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December Med/Long Range Disco

WinterWxLuvr

By WinterWxLuvr,
in Mid Atlantic

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BTRWx

BTRWx

Posted
Posted

You (and others) have made many posts in the past week+ about model solutions changing at longer ranges.  

 

I'm obsessed with computer models because this is what I do for a living.  More precisely, I am quite interested in data assimilation, model initialization, and inherit predictability.  I have several peer-reviewed papers on the current scheme used in the NCEP GDAS, and several research projects trying to continue to move things forward...including the upcoming implementation of hybrid 4D EnVar.

 

For what it's worth, this has nothing to do with the GFS and I'm not defending anything...the same comments apply to the deterministic ECMWF, Canadian, etc.  The mean, hemispheric ACC skill for wavenumbers 4-9 (large scale down to high end synoptic scale) is only <0.65 at day 7, and for wavenumbers 10-20 the monthly skill is < 0.3 (for all models).  Anything below 0.6 is almost useless.  I'll leave my feelings about the current version of the GFS aside, since it leaves a lot to be desired.

 

This is why the operational centers run ensemble systems.  There are things that exhibit predictability at ranges beyond 6-7 days, but individual events are not high on the list.  You absolutely need to understand predictability at various time ranges in order to understand how to use the tools (the models).  Bob had some good comments on this the other day so I won't reiterate, but using ensembles at longer ranges to identify patterns is much more useful than worry about what a deterministic model shows for a highly nonlinear cyclogenesis event at 7+ days.  

Link us with some of those papers please. I'd love to read them!

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dtk

dtk

Posted
Posted

Link us with some of those papers please. I'd love to read them!

 

Original baseline for 3DVar scheme that replaced the old SSI:

Kleist, D.T., D.F. Parrish, J.C. Derber, R. Treadon, W.-S. Wu, and S. Lord, 2009: Introduction of the GSI into the operational NCEP Global Data Assimilation System.Wea. Forecasting., 24, 1691–1705 (doi: http://dx.doi.org/10.1175/2009WAF2222201.1).

 

The GSI is a community based data assimilation code: http://www.dtcenter.org/com-GSI/users/

 

Normal-mode based initialization procedure that is used:

Kleist, D.T., D.F. Parrish, J.C. Derber, R. Treadon, R.M. Errico, and  R. Yang, 2009: Improving incremental balance in the GSI 3DVAR analysis system. Mon. Wea. Rev.,137, 1046-1060 (doi: http://dx.doi.org/10.1175/2008MWR2623.1).

 

Tests of hybrid at low resolution:

Wang, X., D. Parrish, D. Kleist, and J. S. Whitaker, 2013: GSI 3DVar-based ensemble-variational hybrid data assimilation for NCEP Global Forecast System: single resolution experiments. Mon. Wea. Rev., 141, 4098–4117 (doi: http://dx.doi.org/10.1175/MWR-D-12-00141.1).

 

More hybrid and extension to 4D in a controlled OSSE:

Kleist, D. T., and K. Ide, 2015: An OSSE-based evaluation of hybrid variational-ensemble data assimilation for the NCEP GFS, Part I: System description and 3D-hybrid results. Mon. Wea. Rev., 143, 433-451 (doi: http://dx.doi.org/10.1175/MWR-D-13-00351.1).

 

Kleist, D. T., and K. Ide, 2015: An OSSE-based evaluation of hybrid variational-ensemble data assimilation for the NCEP GFS, Part II: 4D EnVar and hybrid variants.Mon. Wea. Rev., 143, 452-470 (doi: http://dx.doi.org/10.1175/MWR-D-13-00350.1).

 

Another paper on the testing of the 4D at low resolution by some collaborators of mine:

Xuguang Wang and Ting Lei, 2014: GSI-Based Four-Dimensional Ensemble–Variational (4DEnsVar) Data Assimilation: Formulation and Single-Resolution Experiments with Real Data for NCEP Global Forecast System. Mon. Wea. Rev., 142, 3303–3325. (doi: http://dx.doi.org/10.1175/MWR-D-13-00303.1)
 
And I have two more manuscripts in preparation describing the impact of the 4D for the GFS related to 3D hybrid in a dual-resolution framework and including stochastic physics to represent model uncertainty.
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Eskimo Joe

Eskimo Joe

Posted
Posted

Next Friday looks like something worth watching. Trailing wave on gfs, euro, and Canadian. Temps obviously a major issue but it's not like there's something else to watch. Snowtv?

I'm the biggest snob in this region and even I would take Snowtv on the 24th / 25th.  Even if it's a cartopper it's instantly 10x better because of the date.

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Heisy

Heisy

Posted
Posted

 

 

Not trying to bust on ya, but what exactly do you find good about this image? All I see is a transient cold shot with a -PNA, +AO, and a ridge about to head eastward. 

 

Oh and also a pig of an Alaskan ULL ..

 

I mean, I'm not a met. but the images you posted would be a type of pattern we would NOT WANT by any stretch of the imagination, what exactly do you see good about it? 

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Bob Chill

Bob Chill

Posted
Posted

DTK, I can't thank you enough for the intense knowledge about NWP products that you bring to this sub forum and the board as a whole. The range of products at our (weenies) fingertips is amazing. And to think that these models are able to turn the incredibly complex physics of our atmosphere using mathematics and algorithms into a pretty weather movie every 6 hours that almost anyone can understand is really something. 

 

I've spent way to much time looking at the movies too. lol. But just like anything you do over and over again...you eventually learn something...and then actually develop skills with the tools. Such an odd hobby.

 

I've always taken a simpleton approach with ops vs ensembles and of course combining both to make logical assumptions. It's really not that hard to use a logical "pecking order". Ops are great out to 4 days. Don't really need to use ensembles too much unless you are trying to determine which of the different ops are most likely right with fine details. Fine details meaning specifically my back yard. haha

 

I always use a blend of ops and ens d4-7. Ens really help smooth out the run over run jumps and wobbles with ops in that range. D8+ is heavyweight to exclusively ensembles. I totally understand that error growth over time make using ops as sensible wx tools ineffective. Exceptions maybe with stable/stagnant setups. Ops can do ok at longer ranges with blocked flow. We forget that there was a time when an op basically locked in at d7-8 and never let go. Man it's been a long time. Progressive flow reeks havoc on op runs and that's all we've had for 3+ years. ugh

 

I think most weenies when they start using all the tools don't like ensembles because they don't show sensible weather. That's what makes ops so appealing at long ranges. Fantasy snowstorms are fun to look at. And once you see one you start thinking it might actually happen. I was as guilty as the next guy for years with that stuff. Learning to use ensembles has made this hobby much more enjoyable. I like reviewing all the ens mean plots and drawing up my own weather movie in my head.  haha. Not to mention ens mean plots have far more skill at long ranges. It's pretty mind boggling how well they do in d10-15 range imo. 

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BTRWx

BTRWx

Posted
Posted

 

Original baseline for 3DVar scheme that replaced the old SSI:

Kleist, D.T., D.F. Parrish, J.C. Derber, R. Treadon, W.-S. Wu, and S. Lord, 2009: Introduction of the GSI into the operational NCEP Global Data Assimilation System.Wea. Forecasting., 24, 1691–1705 (doi: http://dx.doi.org/10.1175/2009WAF2222201.1).

 

The GSI is a community based data assimilation code: http://www.dtcenter.org/com-GSI/users/

 

Normal-mode based initialization procedure that is used:

Kleist, D.T., D.F. Parrish, J.C. Derber, R. Treadon, R.M. Errico, and  R. Yang, 2009: Improving incremental balance in the GSI 3DVAR analysis system. Mon. Wea. Rev.,137, 1046-1060 (doi: http://dx.doi.org/10.1175/2008MWR2623.1).

 

Tests of hybrid at low resolution:

Wang, X., D. Parrish, D. Kleist, and J. S. Whitaker, 2013: GSI 3DVar-based ensemble-variational hybrid data assimilation for NCEP Global Forecast System: single resolution experiments. Mon. Wea. Rev., 141, 4098–4117 (doi: http://dx.doi.org/10.1175/MWR-D-12-00141.1).

 

More hybrid and extension to 4D in a controlled OSSE:

Kleist, D. T., and K. Ide, 2015: An OSSE-based evaluation of hybrid variational-ensemble data assimilation for the NCEP GFS, Part I: System description and 3D-hybrid results. Mon. Wea. Rev., 143, 433-451 (doi: http://dx.doi.org/10.1175/MWR-D-13-00351.1).

 

Kleist, D. T., and K. Ide, 2015: An OSSE-based evaluation of hybrid variational-ensemble data assimilation for the NCEP GFS, Part II: 4D EnVar and hybrid variants.Mon. Wea. Rev., 143, 452-470 (doi: http://dx.doi.org/10.1175/MWR-D-13-00350.1).

 

Another paper on the testing of the 4D at low resolution by some collaborators of mine:

Xuguang Wang and Ting Lei, 2014: GSI-Based Four-Dimensional Ensemble–Variational (4DEnsVar) Data Assimilation: Formulation and Single-Resolution Experiments with Real Data for NCEP Global Forecast System. Mon. Wea. Rev., 142, 3303–3325. (doi: http://dx.doi.org/10.1175/MWR-D-13-00303.1)
 
And I have two more manuscripts in preparation describing the impact of the 4D for the GFS related to 3D hybrid in a dual-resolution framework and including stochastic physics to represent model uncertainty.

 

Wow, thanks a bunch!

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BTRWx

BTRWx

Posted
Posted

Not trying to bust on ya, but what exactly do you find good about this image? All I see is a transient cold shot with a -PNA, +AO, and a ridge about to head eastward. 

 

Oh and also a pig of an Alaskan ULL ..

 

I mean, I'm not a met. but the images you posted would be a type of pattern we would NOT WANT by any stretch of the imagination, what exactly do you see good about it? 

I was focusing on those particular frames and the 540 line with precipitation in our vicinity. I agree the pattern still has to make for a fairly large shift to get things where we want them, but it's a small step forward away from current positive anomalies.

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CAPE

CAPE

Posted
Posted

6z gfs one of the most hideous model runs I've ever seen

Any glimmers of hope that the op runs were advertising in the long range have vanished. The ens runs have been steadfast with the current pattern staying locked in. December is toast, save for a transient seasonal cold shot or two. Every important index looks to remain the opposite of what we want. PV is a cold, consolidated monster. I just hope we can get things to shift some by mid January, esp on the Pacific side. I have zero confidence in seeing a sustained -AO this winter.

 

I never care much about December honestly, because even when its chilly/cold its mostly wasted. Rather have the current weather than cold rain.

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Scarlet Pimpernel

Scarlet Pimpernel

Posted
Posted

6z gfs one of the most hideous model runs I've ever seen

 

Eee-gads, it was indeed awful!  The 00Z was very similar, too.

 

 

Don't recall ever seeing a worse run for that length of time in a winter month. The ensembles must be horrific

 

I somehow recall seeing the same kind of look during 2001-02, with a perpetual trough in the inter-mountain west area and southeast ridging here.  That's a scary thought.

 

 

It's best not to look at the overnight runs across the board. Except for 1 thing I guess. Euro op blows up a -epo in fantasy land. Everything else is horrifying.

 

Last night's runs should be banned!  I didn't see the Euro, and thus far have not even bothered to look at the ensembles, but those two GFS deterministic runs were a nightmare to see.  Wall-to-wall nothing, not even a hint of something good down the line.  Even the ensembles the past several days didn't look quite that bad, as I recall (not great, but still).

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BristowWx

BristowWx

Posted
Posted

Hey man...I'm down here by you now...we need to represent...buck up brother...it's going to be alright

Welcome. Always enjoy your posts. Funny I would always use your obs and Ji's and compare to mine during events. As you know, We are not that much different than where you were although not sure where you were exactly and how far west on 7 you were. Under normal conditions better than EZF or DCA in snow to rain or rain to snow situations. CAD holds on pretty well. Hopefully we will get to experience some of these conditions before spring.

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usedtobe

usedtobe

Posted
Posted

Eee-gads, it was indeed awful!  The 00Z was very similar, too.

 

 

 

I somehow recall seeing the same kind of look during 2001-02, with a perpetual trough in the inter-mountain west area and southeast ridging here.  That's a scary thought.

 

 

 

Last night's runs should be banned!  I didn't see the Euro, and thus far have not even bothered to look at the ensembles, but those two GFS deterministic runs were a nightmare to see.  Wall-to-wall nothing, not even a hint of something good down the line.  Even the ensembles the past several days didn't look quite that bad, as I recall (not great, but still).

To me the Euro was pretty bad especially the eps.   The GEFS was also pretty bad, low heights over AK and western Canada and high over eastern NA.   Plus,  the stratospheric polar vortex is still stronger than normal.  Bob will tell you there is a little warming over Siberia but it's minor compared to all the below normal temps elsewhere around the poles.  The only good think I've seen is the euro weeklies do have the southern stream starting to show up and climo cooling things off.   

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midatlanticweather

midatlanticweather

Posted
Posted

To me the Euro was pretty bad especially the eps.   The GEFS was also pretty bad, low heights over AK and western Canada and high over eastern NA.   Plus,  the stratospheric polar vortex is still stronger than normal.  Bob will tell you there is a little warming over Siberia but it's minor compared to all the below normal temps elsewhere around the poles.  The only good think I've seen is the euro weeklies do have the southern stream starting to show up and climo cooling things off.   

I have nothing to add to this but a sad face and a thumbs down (to the pattern and models.. Not Wes! He is awesome)! I apologize for the lack of anything meaningful!  :cry:  :thumbsdown:

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Bob Chill

Bob Chill

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Posted

To me the Euro was pretty bad especially the eps. The GEFS was also pretty bad, low heights over AK and western Canada and high over eastern NA. Plus, the stratospheric polar vortex is still stronger than normal. Bob will tell you there is a little warming over Siberia but it's minor compared to all the below normal temps elsewhere around the poles. The only good think I've seen is the euro weeklies do have the southern stream starting to show up and climo cooling things off.

No way to spin it. It's godawful ugly as far as the eye can see. I'm only interested in the strat because the massive symmetrical field of bad is getting a bump. Certainly nothing exciting. Just holding a shred of hope that it's the beginning of something more meaningful.

I feel bad for the local ski areas. If they don't open for the holiday week it's a major financial blow.

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wxdude64

wxdude64

Posted
Posted

No way to spin it. It's godawful ugly as far as the eye can see. I'm only interested in the strat because the massive symmetrical field of bad is getting a bump. Certainly nothing exciting. Just holding a shred of hope that it's the beginning of something more meaningful.

I feel bad for the local ski areas. If they don't open for the holiday week it's a major financial blow.

Snowshoe opened yesterday, but if you look at the webcams, it really is sad looking. 

I don't see how many are even going to open until first of the year.

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snowman19

snowman19

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Posted

To me the Euro was pretty bad especially the eps. The GEFS was also pretty bad, low heights over AK and western Canada and high over eastern NA. Plus, the stratospheric polar vortex is still stronger than normal. Bob will tell you there is a little warming over Siberia but it's minor compared to all the below normal temps elsewhere around the poles. The only good think I've seen is the euro weeklies do have the southern stream starting to show up and climo cooling things off.

I was reading HM on Twitter last night, he said the stratosphere is horrible and he sees absolutely no hopeful signs currently or any coming up anytime soon in the forecasts
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