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Blocking Pattern Has Been A Challenge For the Models


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I just wanted to move this thread over form Eastern to follow how the models have been doing with the impressive blocking pattern.

Posted 10 November 2010 - 06:55 PM

It seems like the models have been really struggling with the impressive blocking that we have seen recently.

The models were back and forth with how they handled the big trough amplification in the East recently.

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Now updating for today.

You can see how the models struggled to pick up on the low that bombed out near BC today from earlier forecasts.

I reminds me of how the models had to play catch up with last Monday's big East Coast Cutoff that delivered

early snow to portions of the NE and a pounding surf for several days along the East Coast.

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I rarely see the models handle global blocking patterns or tele-connections that well...especially after 72-84 hrs. Many of the differential equations and advective schemes have some sort of delta t in the denominator...which generally don't want to allow large areas to remain stagnant for too long. Also...the manner in which things finally "get going again" allows for much error thermodynamically/physically in other geographical regions outside of the blocking locales leading to unrealistic tele-connections. Therefore...tele-connections should be increasingly inferred from model output and weighted moreso with theory and climo the farther out in time you go.                       

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Great example of the challenge is shown on the 11/17/2010 18Z GFS, vs. previous runs for the Thanksgiving storm... small change of the orientation of the features at 500mb makes a big difference! The op Euro has also been differing quite a bit with it's ensembles.

Wouldn't surprise me if the 11/17/2010 18Z GFS has right idea given Nina and November climo. Regardless, I'm sure they'll be flipping around quite a bit in the next several days.

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Wow...the Euro looks brutal, I cant remember the last time two H5 charts have been that far off

Yeah, we'll just have to play the ensemble means which at least look a bit closer than the OPS until

we get close enough to sort out the details.It sure does make the pattern more interesting to follow though.

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In comparison to how the models were looking a few days ago in the period after Thanksgiving, they have turned ugly. 11/20/2010 12Z GFS quickly evacuates the cold now from the midwest and plains, thanks to the ridging out by the Aluetians and resulting west coast trof. Instead of some great storm threats with the NAO help, we end up with zonal or WSW flow across the country. :arrowhead:

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In comparison to how the models were looking a few days ago in the period after Thanksgiving, they have turned ugly. 11/20/2010 12Z GFS quickly evacuates the cold now from the midwest and plains, thanks to the ridging out by the Aluetians and resulting west coast trof. Instead of some great storm threats with the NAO help, we end up with zonal or WSW flow across the country. :arrowhead:

Welcome to la nina.:arrowhead:

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In comparison to how the models were looking a few days ago in the period after Thanksgiving, they have turned ugly. 11/20/2010 12Z GFS quickly evacuates the cold now from the midwest and plains, thanks to the ridging out by the Aluetians and resulting west coast trof. Instead of some great storm threats with the NAO help, we end up with zonal or WSW flow across the country. :arrowhead:

12z GFS actually shows a cooler regime for much of the country in the extended than the last couple runs. Much closer to the Euro, in fact.

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Ultimately, the evacuation of Arctic air will be correct, but the solutions yesterday seemed too fast. The 12z GFS suite keeps the cold air in at a more respectable time frame. But let these occasional warm runs warn us now that when the NAO block dissipates and the wavelengths elongate-out from a Gulf of Alaska low.... well...not so pretty. But the cool thing about La Niña: just when you get bored, the pattern changes again in another 10 days. :)

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The Euro is still less gung-ho for a really good -NAO, Eastern cold lovers better hope the GFS is better:

post-357-0-49686700-1290453998.gif

Typical Nina lots of ridging but very little Blocking. There is no real southern Jet to undercut the ridges and really form a block. I'm ready for the disappointment already.

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Typical Nina lots of ridging but very little Blocking. There is no real southern Jet to undercut the ridges and really form a block. I'm ready for the disappointment already.

It does not look good early but that means nothing...I'd rather see these failed pattern developments now than in January or February....one thing is for sure, I don't think we're going to see any sort of sustained warmth or blow torching like December 1998 or 1999 but we may see massive frustration as far as the pattern being generally cold with no storms or when storms do occur they cut west like December 1989 or December 2000.

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This might just decide which signal is boss. I got my money on the -NAO, but not until December. With such a pronounced Nina, it will take a good west based block in conjunction with a 50/50 low to produce the pattern that puts the east in the deep freeze.

The fact that we are seeing a -NAO is a great sign, but I'm more worried about the pacific. You really need two blocks to get a strong cross polar flow going. The pacific firehose doesn't look like it wants to let up anytime soon. I think it's going to be one heck of a battle this winter between the two oceans. With an -PDO and strong Nina, I have a feeling the Pacific is going to win in the long run....

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The fact that we are seeing a -NAO is a great sign, but I'm more worried about the pacific. You really need two blocks to get a strong cross polar flow going. The pacific firehose doesn't look like it wants to let up anytime soon. I think it's going to be one heck of a battle this winter between the two oceans. With an -PDO and strong Nina, I have a feeling the Pacific is going to win in the long run....

Strongly agree. We are downstream of the Pacific, so it exerts more overall influence on the pattern.

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