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December Medium/Long Range Discussion

WxUSAF

By WxUSAF,
in Mid Atlantic

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psuhoffman

psuhoffman

Posted
Posted
14 minutes ago, C.A.P.E. said:

Not much of a warm up on the 18z GEFS. Maybe a few days approaching 50? That is a couple degrees above avg for mid Dec. Not a favorable pattern for winter weather, but far from having the look of an early winter torch. Looks like the pattern should be moving towards more favorable as we approach the holidays.

If you look at how the ensembles are correcting and retrograding the features if that continues just a bit more we will end up in a -AO/epo +PNA by the 20th. Lol 

 

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Bob Chill

Bob Chill

Posted
Posted
6 minutes ago, psuhoffman said:

If you look at how the ensembles are correcting and retrograding the features if that continues just a bit more we will end up in a -AO/epo +PNA by the 20th. Lol 

 

It's interesting. We can live with AN heights in Canada with BN heights across the southern tier. Not a cold look but it's not impossible to get snow like that in an otherwise AN temp pattern. 

I'm expecting a shutout pattern for at least a week but the gefs and eps are both gradually shifting towards a pattern that isn't a shutout even though it looks pretty crappy on the means. I can envision closed ulls and southern storm tracks underneath blocking hp in central Canada. Temps would be really dicey but mid Dec onward can be forgiving

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psuhoffman

psuhoffman

Posted
Posted
Just now, Bob Chill said:

It's interesting. We can live with AN heights in Canada with BN heights across the southern tier. Not a cold look but it's not impossible to get snow like that in an otherwise AN temp pattern. 

I'm expecting a shutout pattern for at least a week but the gefs and eps are both gradually shifting towards a pattern that isn't a shutout even though it looks pretty crappy on the means. I can envision closed ulls and southern storm tracks underneath blocking hp in central Canada. Temps would be really dicey but mid Dec onward can be forgiving

That's kind of how I read it.  Actually sounds like a typical nino pattern...

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CAPE

CAPE

Posted
Posted
13 minutes ago, psuhoffman said:

If you look at how the ensembles are correcting and retrograding the features if that continues just a bit more we will end up in a -AO/epo +PNA by the 20th. Lol 

 

I am looking forward to pulling up a day 12-15 h5 panel and not seeing a gigantic ball of blue around AK. It has been retrograding somewhat on the means recently, but for now it still sticks out like a sore thumb when looking at h5 height anomaly panels. I like seeing the indication of some ridging building downstream in the PNA region on recent runs. Good sign.

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MillvilleWx

MillvilleWx

Posted
Posted
Yes It does. No member runs the primary into western KY either. One runs up into WV but almost all the others have a great track. 


THIS! Primary into Tennessee is the most preferred. If you want snow, primary to East-Central Tennessee and secondary off Wilmington, NC. If you want a big snow, you want an ULL hiking through the Smokies and into SW VA while a secondary drunkenly staggers from Myrtle to OC MD while on a coastal bar tour.


.
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CAPE

CAPE

Posted
Posted
29 minutes ago, MillvilleWx said:

 


THIS! Primary into Tennessee is the most preferred. If you want snow, primary to East-Central Tennessee and secondary off Wilmington, NC. If you want a big snow, you want an ULL hiking through the Smokies and into SW VA while a secondary drunkenly staggers from Myrtle to OC MD while on a coastal bar tour.


.

 

Perfect. Except I would prefer it if the secondary drunkenly staggers about a hundred miles offshore of OC on a yacht.

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psuhoffman

psuhoffman

Posted
Posted

My random thoughts on this where we stand right now. It's still forever away. It's fun to analyze the guidance but these 50-100 mile jumps in a mid latitude cyclone run to run at day 7+ on operationals is nothing.  Noise. The ensembles have been fairly consistent in targeting the mid Atlantic. 

There are a few things I think I thInk right now. From past nino climo I think the odds of the stj just completely crapping the bed like last December is lower. I think history with these kinds of stj systems crashing Southern California during a cold pattern in a nino says this is a legit threat to the mid Atlantic. It's a fairly typical setup for this region.  My goalposts have narrowed to this not being completely squashed to im significance or a full cutter. I do think someone in the mid Atlantic sees a warning criteria snow from this.  But whether that is Richmond, DC, or somewhere in PA is way too small an adjustment to the longwave pattern from this range to say. 

Finally from past similar situations if this is going to get squashed it's likely to show that in the next couple days. Once we get to about 120 hours if it still looks healthy it's very unlikely to just go poof. Beyond that from about 48-72 hours in these trend north "some" more often then not. Models often underestimate the expanse of precip. They often underplay the intensity and ratios on the nw fringe. And they often adjust the surface track just a little north at the very end. All that usually adjusts the northern edge of snowfall north in the final endgame stages. So going into the final countdown being on the northern side of the snowfall is ok, you don't want to be riding the rain/snow line.  

After this storm my gut says we moderate for about a week to slightly above normal. No prolonged torch but as the pattern retrogrades we will have to suffer a transient period where Pacific air floods across. But I think it's temporary and by Xmas or abouts the Alaska vortex retrogrades enough that we are back in a more favorable pattern. I also think it's not completely out of the realm of possibility that during the "relax" something in the stj could cut under and perhaps create a threat for something wintery if it's just cold enough. Something like Xmas 2002 comes to mind. 

For the record I didn't once consider adjusting my seasonal snowfall prediction down. I did consider bumping it up slightly but let it ride!

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Maestrobjwa

Maestrobjwa

Posted
Posted
27 minutes ago, psuhoffman said:

My random thoughts on this where we stand right now. It's still forever away. It's fun to analyze the guidance but these 50-100 mile jumps in a mid latitude cyclone run to run at day 7+ on operationals is nothing.  Noise. The ensembles have been fairly consistent in targeting the mid Atlantic. 

There are a few things I think I thInk right now. From past nino climo I think the odds of the stj just completely crapping the bed like last December is lower. I think history with these kinds of stj systems crashing Southern California during a cold pattern in a nino says this is a legit threat to the mid Atlantic. It's a fairly typical setup for this region.  

Great post as usual, PSU!

Now, that portion there... @Bob Chill also mentioned this feature of waves that crash into southern California having a good history here...and got my attention. Any analogs of past big storms that started there?

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psuhoffman

psuhoffman

Posted
Posted

And of course not everything ends up an HECS. These went on to be 2 run of the mill secs systems in the end of the 2005 winter and the Dec 5 secs in 2002. But same theme. Stj system in a nino out of the southwest with a trough in the east and either blocking or some kind of 50/50 or PV lobe to suppress the pattern somewhat. 

IMG_7859.thumb.GIF.317aab21f63a1369f47bf842dd043f99.GIFIMG_7860.thumb.GIF.c7b7d35181f6c9106fcf91db7f2a50b1.GIFIMG_7861.thumb.GIF.7c626c0ccb1f2765a33fe0e40f012589.GIF

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Bob Chill

Bob Chill

Posted
Posted

Jan 2016 came in pretty far north but the table was set so perfectly for us. The only time we had a legit block all winter and the antecedent airmass was the coldest we had that entire winter. I'll never forget onset that afternoon. Temps in the low-mid 20's. Every single flake stuck and the roads caved 5 minutes after it started snowing. 

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psuhoffman

psuhoffman

Posted
Posted
Just now, Bob Chill said:

Jan 2016 came in pretty far north but the table was set so perfectly for us. The only time we had a legit block all winter and the antecedent airmass was the coldest we had that entire winter. I'll never forget onset that afternoon. Temps in the low-mid 20's. Every single flake stuck and the roads caved 5 minutes after it started snowing. 

Yea it came into Northern California vs southern but the blocking compensated and forced it to exit south of the latitude it came in at. There are lots of variables that change what "ideal" for any one factor is. You know this. Just pointing it out for the rookies. But in general in a nino a system crashing into the west with a cold trough in the east is a winning formula. 

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psuhoffman

psuhoffman

Posted
Posted
4 minutes ago, Maestrobjwa said:

Now I'm trying to read this (novice here!)...can't tell where the low is on some of those (don't suppose you could highlight it for amateur eyes? Lol)

It's hard to capture perfectly because those maps are only available in 24 hour increments so it's often impossible to catch it as it comes into Cali. and sometimes the systems are discreet coming into Southern California. But on the top what will be the energy for our hecs in 2016 is about to crash in around San Francisco. In the second what will be the feb 6 2010 hecs had just crossed southern cal and is in southern Arizona. The third that system about to hit southern cal will become PDII. 

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Ji

Ji

Posted
Posted
Jan 2016 came in pretty far north but the table was set so perfectly for us. The only time we had a legit block all winter and the antecedent airmass was the coldest we had that entire winter. I'll never forget onset that afternoon. Temps in the low-mid 20's. Every single flake stuck and the roads caved 5 minutes after it started snowing. 
Top 10 storm since 2007 for sure
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Maestrobjwa

Maestrobjwa

Posted
Posted
3 minutes ago, psuhoffman said:

It's hard to capture perfectly because those maps are only available in 24 hour increments so it's often impossible to catch it as it comes into Cali. and sometimes the systems are discreet coming into Southern California. But on the top what will be the energy for our hecs in 2016 is about to crash in around San Francisco. In the second what will be the feb 6 hecs had just crossed southern cal and is in southern Arizona. The third that system about to hit southern cal will become PDII. 

Gotcha. Now...the next question is...what was the difference between those that became HECS and those that were merely SECS? (Or was it a variety of things?)

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caviman2201

caviman2201

Posted
Posted
1 minute ago, Ji said:
14 minutes ago, Bob Chill said:
Jan 2016 came in pretty far north but the table was set so perfectly for us. The only time we had a legit block all winter and the antecedent airmass was the coldest we had that entire winter. I'll never forget onset that afternoon. Temps in the low-mid 20's. Every single flake stuck and the roads caved 5 minutes after it started snowing. 

Top 10 storm since 2007 for sure

I dunno about you but Jan 16 is top 5 all time for me... 

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Maestrobjwa

Maestrobjwa

Posted
Posted
1 minute ago, Ji said:
14 minutes ago, Bob Chill said:
Jan 2016 came in pretty far north but the table was set so perfectly for us. The only time we had a legit block all winter and the antecedent airmass was the coldest we had that entire winter. I'll never forget onset that afternoon. Temps in the low-mid 20's. Every single flake stuck and the roads caved 5 minutes after it started snowing. 

Top 10 storm since 2007 for sure

And it was the most enjoyable to track too--because every model locked in around day 7 and never looked back, lol So there was no model drama at all...just discussions about 2 feet versus 3! :lol:

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Maestrobjwa

Maestrobjwa

Posted
Posted
Just now, caviman2201 said:

I dunno about you but Jan 16 is top 5 all time for me... 

Same--at least for my brief 27 years of life, anyway, lol (I only have faint memories of 96). But Snowmageddon is always gonna be my #1 because...well, twin blizzards, lol Gonna be kinda hard to top that!! But Jan 2016 would definitely be my number 2!

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Bob Chill

Bob Chill

Posted
Posted
2 minutes ago, Maestrobjwa said:

Gotcha. Now...the next question is...what was the difference between those that became HECS and those that were merely SECS? (Or was it a variety of things?)

There's a ton of things that can happen in all directions. Conditions have to stay favorabe during the trip across the country for a big storm. The strength of the storm when it hits the west coast doesn't matter much. Phasing with the northern stream can make a tiny pac shortwave become a monster. A giant storm coming into socal can get shredded to pieces from confluence in the east. Possibilities are endless and that's one of the reasons that ops lose skill quickly beyond 4 days. 

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psuhoffman

psuhoffman

Posted
Posted
6 minutes ago, Maestrobjwa said:

Gotcha. Now...the next question is...what was the difference between those that became HECS and those that were merely SECS? (Or was it a variety of things?)

Simplest answer is it just didn't come together at all levels perfectly. An hecs requires engines firing on all cylinders at the surface mid and upper levels. 

Dec 5 2002 and feb 25 2005 had very little upper level support. If I remember correctly both looked fairly innocuous at h5 and what energy there was even tracked north of ideal. We got by on a WAA thump alone pretty much. 

The feb 28/mar1 2005 storm was convoluted. The upper energy kind of split with the main trough digging in pretty far west and a piece out in front. The storm kind of was disconnected and not synced up at all levels.  The surface storm was along the VA capes but the h5 low was back in the Midwest. The whole system got stretched out and prevented heavy banding from developing in the ccb. 

Thats just my memory of those 3 off the top of my head. 

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