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Winter 2013-14 Pattern Discussion


CAD_Wedge_NC

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Look out below. At 240 GFS looks to have a potential major snow for the SE. With cold air filtering in we have a nice low tracking across the middle of FL.

Sent from my HTC One

 

This?

 

Yep I'll gladly take that look this far out. I'd be willing to bet that's a good timing situation.

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Don't see any great blocking, but it looks good anyway. :)

 

Yeah, I'm not seeing it either.  I'm starting to doubt that the models are really picking up on any true west based Greenland blocking.  It seems that the ridging on the west coast goes to the pole clearly, but the true block that we need to keep the PV south never shows up.  It has maybe a more neutural -NAO look maybe??

 

However even though the block isn't there, the PV stays close enough to put us on the cool side of things on the model. 

 

2CPrBfYl.png

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Well, as ST said, we may be starting to see some cracks in the armor of the +AO/+NAO regime. While positive in the near term, both look to dive torward neutral, with indications of negative values in the LR. Looking at the guidance over the last couple of days, this appears in-step with the latest trends.

The CFS (posted below) has now taken a turn back to the colder side in the east for the month of Jan. Precipitation looks lower than average after Week 1.

The PII index still remains negative but continues to trend toward neutral.

The 0z GFS didn't snow as much in the way of a west-based -NAO through the period, but it looked ok. The 6z (below), IMO, was better and had a Greenland Block. The Euro looked ok toward the end of its run, but I didn't pick up on any winter storm potential, like the 0z/6z GFS had.

The 6z GFS at at 360 hrs (bottom image) is a good illustration of a -NAO and why it's important. It helps to flatten the SE ridge, pressing the PV to the south and east. It also allows high pressure to generally enter the US and travel across the norther tier, instead of slamming straight south to the GOM. This promotes a cold air feed into the SE, and it leaves the Gulf available to be tapped by any energy that comes along. You can see here that we have somewhat of a STJ. The arctic front has passed through most of the SE, and even Waycross is on the verge of *gasp* winter. I posted this map to show that, not because I believe this will actually be the case at 360 hours (ahem, Metallica!).

Above that is today's dramtic CFS turn around bright eyes from yesterday's run.

That is actually a neutral/positive NAO transitioning into a more positive NAO. That trough should lift in the last frames. Below is the later frame. 

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Here we go! A lot to talk about today, so lets break it down.

 

This weekend, early next week: A front is going to push into the southeast, bringing the chance of some very heavy rain and possibly storms at the beginning of the front. Then, it stalls. Yes, the models show this front stalling for 12-18 hours over the southeast. This provides rounds of heavy rain east of the Appalachians through Tuesday. Rain totals with this storm could approach 2-4 inches through the Carolinas, Georgia, and Virginia if this was to happen. Usually the models break down a ridge to quickly, so I always knew this was a possibility. 

 

Once the front passes, it will be cool for Christmas Eve and Day. There will be a few snow showers in the mountains of NC due to northwest flow; however, accumulations will be light.

 

The GFS keeps the cold air lurking just to our north through next week with a piece of energy moving along the Gulf Coast. This could be something to watch next weekend as the chance of having an east coast storm is possible in this pattern.

 

The blocking is not great in the long term, but it does appear to be better than what we have seen. The teleconnections on the CPC page shows all of the indices moving towards a neutral state, and the NAO and AO  possibly moving into  a negative state. This is the first time in a long time that we can say there is a chance of a negative NAO. The picture Wow posted is a little upsetting because it does show the big vortex over Greenland, but this could change as we do move through this active period.

 

Finally, we have something excited to talk about in the southeast. But, do not overlook the storm this weekend. There will be a lot of heavy rain through the southeast United States.

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12z GFS at the end is a classic +NAO with below normal over Greenland and above normal south of it over the Atlantic basin.  These anomalies need to be the exact opposite of this to get what we're after.

 

HYydc5s.gif

 

Yeah it seems like the the AO is going to improve in the long range but not the NAO.  That's still quite problematic for the SE, IMO. 

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Yeah it seems like the the AO is going to improve in the long range but not the NAO. That's still quite problematic for the SE, IMO.

I guess it shows how important the influence of the NAO compared to the AO. This year the extremely positive AO hasn't produced a torch, while last year the extremely negative AO did nothing to enhance winter weather.

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Reasoning?

 

Maybe he thinks he will win WOTY (if the contest is ever actually fully run; I'm confused about it now as it seems to be in limbo) and that would be a bang in a way to end 2013 and start 2014? Or maybe he's indirectly referring to his 2nd movie? Opinion?

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That is actually a neutral/positive NAO transitioning into a more positive NAO. That trough should lift in the last frames. Below is the later frame.

 

Yep, that 12z image you posted there is a very positive NAO. Not the best thing for us, but it can be overcome if other features are present/properly aligned.

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12z Euro doesn't look awful. No blocking, of course, but not a grotesque look either.

 

Sounds like a relieved guy waking up next to a gal after a night out.  I think the key thing to look for here is the ridging off the west coast...does it push boldly up through Alaska, or does it stay kind of muted - that keys whether cold air is driven south, with potential storminess along a stalled boundary along the gulf.  No strong ridging, and the cold air for wintry weather stays to our north in this west-based +NAO regime.

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Sounds like a relieved guy waking up next to a gal after a night out. I think the key thing to look for here is the ridging off the west coast...does it push boldly up through Alaska, or does it stay kind of muted - that keys whether cold air is driven south, with potential storminess along a stalled boundary along the gulf. No strong ridging, and the cold air for wintry weather stays to our north in this west-based +NAO regime.

Haha! I guess that's pretty much the sentiment. The whole "pattern change" is still a precarious situation right now. At least the Euro wasn't completely in the other direction, which I'm still half expecting at any time.

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Haha! I guess that's pretty much the sentiment. The whole "pattern change" is still a precarious situation right now. At least the Euro wasn't completely in the other direction, which I'm still half expecting at any time.

 

Is it really a pattern change?  -EPO just reloads and the NAO stays positive.  Is the AO going to neutral really a big pattern change?  I still think, kinda like grit already said, that we're going to live and die by the PNA this winter.  Blocking just isn't working in our favor so far.  We have to depend on a tall GREAT placement ridge to push the trough so storms go south of us.  That's alot to expect. 

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Is it really a pattern change? -EPO just reloads and the NAO stays positive. Is the AO going to neutral really a big pattern change? I still think, kinda like grit already said, that we're going to live and die by the PNA this winter. Blocking just isn't working in our favor so far. We have to depend on a tall GREAT placement ridge to push the trough so storms go south of us. That's alot to expect.

Yeah, I'm with ya...it's why I put "pattern change" in quotes. It's a change from the current garbage, but it's more of a reversion back to the earlier pattern *unless* we get some blocking, which is kind of showing up off and on. But yeah, more of the same, with maybe some slightly better opportunities.

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Euro ensembles completely folded to the gefs. Ridge bridge !

 

Yep, now if we could just get the PV to drop south some, we would be in business..  A -NAO would be great to slow the storms down and allow things to develop deeper/stronger but we still can get a nice event with what is being shown in the day 10-15 setup, assuming it comes to fruition, the analogs still look good, IMO.  We just need to get to January.

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Yep, now if we could just get the PV to drop south some, we would be in business..  A -NAO would be great to slow the storms down and allow things to develop deeper/stronger but we still can get a nice event with what is being shown in the day 10-15 setup, assuming it comes to fruition, the analogs still look good, IMO.  We just need to get to January.

 

Good analysis PB.  IF, IF cold air is driven far enough south (I will bo-lieve it when I see it), two prior storms that would fit with the 500mb pattern would be 1/10/62 and 12/23/93 (two that were in your analog list yesterday - or if not, they were on there today).  Both light snow events.  You can see the similarities with the 500mb pattern for those from the links below.  12/23/93 was the warmer of the two - probably a more realistic comparison

 

1/10/62 - http://docs.lib.noaa.gov/rescue/dwm/1962/19620110.djvu

12/23/93 - http://docs.lib.noaa.gov/rescue/dwm/1993/19931220-19931226.djvu

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