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December Medium/Long Range Discussion


yoda
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6 minutes ago, WxUSAF said:

6z GFS is pretty close to an event next Monday :weenie:

Still out there but the GEFS has a whopping 3lps in the location of the GFS :p

gfs-ensemble-all-avg-ne-mslp_with_low_locs-8584400.thumb.png.97dae7ffc10a2e5ea2c7de9d485fd09c.png

Although these lps seem to be overshadowed by a cluster of consensus around the great lakes. Seems like a recipe for nothing? Stale airmass, great lakes low. I guess there's time to iron out the details though

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06z GEFS relaxes the NA blocking regime around D10 only to really bring it back toward the end of the run....

That Aleutian low is a very stable feature.  A shift east with that low just a bit could send this pattern into a very cold, classic pattern for snow.  As it is, plenty of positives to be taken from the advertised pattern.... 

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7 minutes ago, poolz1 said:

06z GEFS relaxes the NA blocking regime around D10 only to really bring it back toward the end of the run....

That Aleutian low is a very stable feature.  A shift east with that low just a bit could send this pattern into a very cold, classic pattern for snow.  As it is, plenty of positives to be taken from the advertised pattern.... 

Yeah that's a pretty nice look at the end of the run. EPAC looks about as good as we could hope for, and  the Atlantic ridge builds further north/west into southern Greenland. Looks like the 0z EPS might be heading in that direction too.

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15 minutes ago, poolz1 said:

06z GEFS relaxes the NA blocking regime around D10 only to really bring it back toward the end of the run....

That Aleutian low is a very stable feature.  A shift east with that low just a bit could send this pattern into a very cold, classic pattern for snow.  As it is, plenty of positives to be taken from the advertised pattern.... 

 
As you mentioned, positives regarding snowfall and cold. Big differences versus last year at this time. 
We track. 
 
I've annotated the 35-day GEFS (note this is yesterday's run) with my thoughts on the evolution of the U-wind...
 
 
 
 
 
Image
 
 
Significant wave-1 "attack" on the stratospheric vortex toward late December in recent GFS runs. Z500 anomalies constructively interfere with climo wave-1 pattern. Leads to sig. deceleration & warming in this run & could open door to further wave-2 activity if trop. conducive
 
 
Image
 
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Image
 
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Yeah yeah, even though I grew up in  South Philly, I always get pissed when Philly gets crushed with 6 or 14 inches and I get 2 inch or 4 inch events here below the Canal in Middletown. But, anyway you view the event from yesterday I believe it is more of a positive , even for our region, versus a negative. The stat below is interesting from a Philly perspective. 

  

 

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24 minutes ago, osfan24 said:

I wonder if that's a timing issue for these maps. Everything I've seen shows a cold front coming through with possibly some precipitation, and then it getting very cold behind the front.

Good point sir.  Wondered that myself.  Timing because the pattern could look great for days but a missed connection and whammy shows up

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7 minutes ago, BristowWx said:

Good point sir.  Wondered that myself.  Timing because the pattern could look great for days but a missed connection and whammy shows up

The GFS and Euro are pretty in sync with the dump of cold air at Christmas.  I'd like to see maybe a reinforcement of that and then a storm running into it.

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3 minutes ago, MN Transplant said:

The GFS and Euro are pretty in sync with the dump of cold air at Christmas.  I'd like to see maybe a reinforcement of that and then a storm running into it.

Probably a brief warm up before the re-load? If it's a day or two that'd be fine, so long as we don't torch back into the 60s or something.

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5 hours ago, Ji said:

Did eps lose the blocking and ao?

 

5 hours ago, CAPE said:

The AO trends basically neutral and the NAO slightly positive by the end of the month. Btw that area of +heights on the means focused in the WA is not exactly the block we want.  50-50 high!

It is very encouraging that all 3 major ensembles temporarily spike the AO as two TPV lobes merge but all 3 immediately give it the boot and tank the AO again within a couple days.  The best news is we are well into the point where the last few years there was ample evidence the look up top was going to be trouble.  Especially last year when huge warning flags were there.  This year we have the opposite with every sign pointing to a favorable base state of the NAM.  

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4 minutes ago, psuhoffman said:

It is very encouraging that all 3 major ensembles temporarily spike the AO as two TPV lobes merge but all 3 immediately give it the boot and tank the AO again within a couple days.  The best news is we are well into the point where the last few years there was ample evidence the look up top was going to be trouble.  Especially last year when huge warning flags were there.  This year we have the opposite with every sign pointing to a favorable base state of the NAM.  

Yea by this time last year it was pretty evident that we were in store for a pretty sucko winter, even by Mid Atlantic standards.

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37 minutes ago, poolz1 said:

If we can just get some energy to hang back a bit for a x-mas miracle......

A fair number of the 12z GEFS members show decent snowfall on xmas eve/xmas morning.  Hard to capture it all in a single panel because of timing differences, but you can sort of see it here.  EC6381C2-287C-49A8-BCD9-B7C820D11A16.thumb.png.ac755c4eff31fe875a42613d0ab562a9.png

BF1EFB6F-1C97-4747-9679-763B96ACEC9F.png

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5 minutes ago, JakkelWx said:

How it started vs how it's going

1020091992_ao.sprd2(5).thumb.gif.4e9f9024b5da29bb098b9960a1bd762e.gif

Ensemble Mean AO Outlooks

 

 

Today's forecast has a greater spread out in time,  although I doubt we achieve some of the upper member's forecasts.

May very well consolidate in a more narrow channel, more so negative versus + or neutral, in a few days. That has happened twice in the last 11 days. 

 

315726440_ao.sprd2(12).thumb.gif.ca3dc53f4a3e6a5db57ab1acad9ea5d1.gif

 

 

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