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Wintry December 28-29th Possible Winter Storm

Webberweather53 said:
The reason the GFS is further NW of the Euro has to do w/ its handling of a shortwave trough currently over Manitoba, Saskatchewan, and northern Alberta. This system will determine how much suppression we observe w/ our storm on the 28-29th, the more it digs around the base of the low pressure gyre over the Hudson Bay and the slower it moves (as shown by the Euro) the more suppression we get and vis versa. The GFS is faster/more progressive w/ the shortwave in the northern stream and already has it off New England by day 3, whereas the Euro keeps it centered over the eastern seaboard, which imparts more confluence & shearing on our s/w that ultimately rips it to shreds.

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Interesting. Would the Euro's slow bias with energy be in play here? Also, if the cold high doesn't press quite as much as modeled (which often happens), would that cause less suppression?
 
tractor girl said:
How did NAVGEM perform for our mid Dec storm?
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One of the best models for that particular system. However, I wouldn't think it should be taken as seriously as the other major models necessarily. The last storm just happened to verify on the upper end of the model guidance. That doesn't usually happen...
 
packfan98 said:
Interesting. Would the Euro's slow bias with energy be in play here? Also, if the cold high doesn't press quite as much as modeled (which often happens), would that cause less suppression?
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This trough is in the northern stream, far removed from the southwestern US where the Euro's slow bias comes into play in most occasions. If anything, I'm a little more concerned about the GFS's progressive bias w/ the northern stream (which is inherently related to its low level cold bias). The high not pressing as strongly to the south & east would be related to the depth & placement of the trough over New England because the more cold air advection that's pushed into the base of the trough the more it digs, and the more suppressed our storm becomes & vis versa. We need less CAA into the trough base to hinder more digging & for this s/w to speed up more like the GFS shows to give us a good chance & reduce the confluence over the eastern seaboard.
 
Webberweather53 said:
This trough is in the northern stream, far removed from the southwestern US where the Euro's slow bias comes into play in most occasions. If anything, I'm a little more concerned about the GFS's progressive bias w/ the northern stream (which is inherently related to its low level cold bias). The high not pressing as strongly to the south & east would be related to the depth & placement of the trough over New England because the more cold air advection that's pushed into the base of the trough the more it digs, and the more suppressed our storm becomes & vis versa. We need less CAA into the trough base to hinder more digging & for this s/w to speed up more like the GFS shows to give us a good chance & reduce the confluence over the eastern seaboard.
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Thanks for the explanation. Let's see if we can get it trending in a better directions. Do you think think the storm will get sheared out like the recent trends suggest?
 
Blue_Ridge_Escarpment said:
My question is, how in the world has the GEFS stayed so high with qpf. Heck look at the 6Z run, one of the better runs I’ve seen.
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It's a little OT but with the bad maps I thought the 0Z GEFS looked decent for NYD too.

Also: This may not be a "normal" trend away situation for reasons already talked about. This one may not be coming back. I suspect the HP isn't as strong as modeled but if the northern stream is dominant this is going to be dry.
 
packfan98 said:
Thanks for the explanation. Let's see if we can get it trending in a better directions. Do you think think the storm will get sheared out like the recent trends suggest?
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It's possible because it will go over the Rocky Mountains (which induces shrinking of the column and an anticyclonic vorticity tendency in concurrence w/ absolute vorticity conservation, at the same token stretching in the Lee of the Rockies strengthens our trough), into and just over a ridge crest over the Rockies (again yet more anticyclonic vorticity tendency due to anticyclonic vorticity advection near and just beyond the ridge crest) & confluence underneath the base of the trough over the Canadian Rockies. From a large scale standpoint there's not much help being given to intensify our system, sticking a trough over New England just adds yet more insult to injury and shears apart whatever is left of our s/w thus it becomes suppressed like no tomorrow. We need the shortwave to slow down and intensify some before moving over the Rockies and the crest of the ridge, &/or for that s/w over central-western Canada to speed up s.t our s/w isn't longitudinally aligned with the northern stream (which optimizes confluence and shearing which we don't want if u would like a storm.). The separation of the two disturbances and/or a stronger s/w would reduce the confluence on the eastern seaboard and give our storm some breathing room which it desperately needs
 
Webberweather53 said:
This shortwave in the northern stream over central Canada has already been sampled by the RAOB network...

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Preemptive attack on the "it hasn't been sampled yet" grasping at straws reasoning? Lol
Rah NWS took the simple keep it short Christmas write up this morning....

Trends are drier and more suppressed with the winter precipitation
threat for Thu-Fri. There remains a threat and it will have to be
watched as the models may go back the other way etc...
 
I know it's different setups and all but models losing a storm to only bring it back isn't entirely new. Although NS shearing out a s/w is probably the one that has the least chance of heading back in the right direction, but I'm not throwing in the towel just yet, there is still enough out there to support some precip so let's see what the day brings
 
The Euro and NAM still trying to get some precip in here with the minor overrunning event on Wednesday.... maybe this one will trend NW and over perform since the 28th is looking like a dud.
 
Webberweather53 said:
12z NAM vs 6z NAM out to 45 hours. Inside 48 hours the NAM isn't too bad and worth looking at, the trough over New England looks weaker & is lifting out faster this time, definitely something we need to see on all the 12z suites today...

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Good call Webber. I was just about to say the same thing about the 12z NAM.


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Webberweather53 said:
12z NAM vs 6z NAM out to 45 hours. Inside 48 hours the NAM isn't too bad and worth looking at, the trough over New England looks weaker & is lifting out faster this time, definitely something we need to see on all the 12z suites today...

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So maybe the models hearts grew 10x this day! I'm with you the NAM is not bad at H5 within 48-60 hrs so that is good to see hopefully a good start to a great 12z suite
 
Webberweather53 said:
12z NAM vs 6z NAM out to 45 hours. Inside 48 hours the NAM isn't too bad and worth looking at, the trough over New England looks weaker & is lifting out faster this time, definitely something we need to see on all the 12z suites today...

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That's a great point. If that trof dampens out quicker we have a shot
 
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