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Potential Thanksgiving Day Storm?


Snow_Miser

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I thought I should post a topic for this storm, since it seems increasingly likely that a storm will probably be impacting the area around the Thanksgiving timeframe, or a little bit earlier.

gfs_namer_180_10m_wnd_precip.gif

The 12z GFS is similar to the 6z GFS in a sense that it has a storm, except on the 12z GFS the storm is more amplified than on the 6z GFS. However, it does not seem very likely that this storm will blow up into anything exceptional, since there will be a +NAO during this timeframe, and this would not have a full blown storm along the East Coast.

nao.sprd2.gif

Interestingly, the PNA should be spiking positive during this timeframe, and remaining near neutral levels after that, which is not a terrible sign for a storm along the East Coast.

pna.sprd2.gif

This storm should definitely be watched IMO, since there are several details that still need to be worked out with the computer guidance, and I think it seems pretty likely that places N of I-80 would probably see some flakes from this if the scenario materializes as seen on the models, but there are plenty of questions that do not have a solid answer yet on this storm, so P Types should not be the primary concern ATM. Once the storm gets into the mid range, then we can start worrying about P Types and who gets snow and who gets rain.

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This threat is pretty much garbage. The pattern is very fast and timing would have to be picture perfect for the 12z gfs scenario. Even then, this would only be a New England threat at best in my opinion.

I think it still needs to be watched IMO since it is still 8 days out, and a lot can change from today to then.

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I think it still needs to be watched IMO since it is still 8 days out, and a lot can change from today to then.

I agree with snow. Way too early to say anything about this storm. Just watch it on the models and see how it evolves.

True, it is silly to call anything off 8 days out...But it is not too early to say this is a HIDEOUS pattern for ANY type of winter event..

f168.gif

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Looks like this potential storm may end up around the same time that a transient cold spell affects the region... the colder air mass isn't expected to be as strong or as far south as the one for tomorrow/Friday though, and with the awful pattern still in place, I can see how parts of New England may see snow out of any possible storm in this time frame, but IMO snow in NYC is very unlikely in this time frame.

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True, it is silly to call anything off 8 days out...But it is not too early to say this is a HIDEOUS pattern for ANY type of winter event..

Yeah, the pattern is absolutely terrible for this storm with a raging +EPO, a -PNA, a +AO and a +NAO. At this moment, if the solution were to occur verbatim what the NCEP teleconnections and the Global models are spitting out right now, it would definitely be all rain for NYC and the surrounding areas.

However, since it is still 8 days out, there's still that hopeful optimism that some aspects of the storm could possibly change ;)

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Pattern still looks just terrible, almost as bad as you can get if you want any chance of snow in late November, early December. Things show some improvement the week after Thanksgiving but it's still pretty bad and the signals are still rather weak right now. I do think we may eventually get a more favorable pattern going but it's going to take longer than any of us anticipated. This is almost a reverse of last winter where all the METS were calling for a blowtorch January and instead winter trekked on after December but it did eventually come to a half as soon as we hit February.

This time it's going to be a waiting game for us until we get a favorable pattern, I'm thinking by Dec 15-20, we should have a much more favorable pattern for east coast snows with December 25-January 15 being the ideal time frame for a good snowstorm or two.

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Yeah, the pattern is absolutely terrible for this storm with a raging +EPO, a -PNA, a +AO and a +NAO. At this moment, if the solution were to occur verbatim what the NCEP teleconnections and the Global models are spitting out right now, it would definitely be all rain for NYC and the surrounding areas.

However, since it is still 8 days out, there's still that hopeful optimism that some aspects of the storm could possibly change ;)

If we could get a freak snowstorm in late October with a raging warm fall, anything is possible. It wouldn't surprise me the least if we got another freak event in a very unfavorable pattern.

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Yeah, the pattern is absolutely terrible for this storm with a raging +EPO, a -PNA, a +AO and a +NAO. At this moment, if the solution were to occur verbatim what the NCEP teleconnections and the Global models are spitting out right now, it would definitely be all rain for NYC and the surrounding areas.

However, since it is still 8 days out, there's still that hopeful optimism that some aspects of the storm could possibly change ;)

Sure, just completely reverse every ridge/trough anomaly predicted to be in place around the globe in 8 days and were in business! :gun_bandana:

In all seriousness though, we're talking about very unfavorable large/synoptic scale weather patterns that are largely agreed upon right now by each model and their ensembles 8 days out...These arent smaller scale short wave placement / storm track and strength details that will change drastically 8 days out.

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Looks like a lot of details are going to have to be sorted out before we can determine P Types, as the latest guidance suggests.

The 12z Euro is a massive hit for NW NJ and surrounding locations. They get a nice snowstorm on the 12z Euro, wheras NYC sees rain, but NYC is not all that far away from the rain/snow line. post-3451-0-02107800-1321561839.png

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Interesting... looking at the recent 12z teleconnections, the PNA looks to possibly spike towards positive territory during this timeframe, wheras the NAO goes down to neutral levels. The pattern for this storm does not look as terrible as yesterday's ensembles depicted. We'll have to see if this is a trend, or if this is simply an anomaly.

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Interesting... looking at the recent 12z teleconnections, the PNA looks to possibly spike towards positive territory during this timeframe, wheras the NAO goes down to neutral levels. The pattern for this storm does not look as terrible as yesterday's ensembles depicted. We'll have to see if this is a trend, or if this is simply an anomaly.

The October storm had a pna spike and a Davis strait block. It was beautiful regardless of what the cute Nao bar graphs showed. It was anything but ugly especially for October.

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The October storm had a pna spike and a Davis strait block. It was beautiful regardless of what the cute Nao bar graphs showed. It was anything but ugly especially for October.

According to the CPC, the PNA was slightly negative, the NAO slightly positive, and the AO positive during the October 29th 2011 storm. It wasn't a horrible pattern, but it certainly was not a beautiful pattern by any means.

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According to the CPC, the PNA was slightly negative, the NAO slightly positive, and the AO positive during the October 29th 2011 storm. It wasn't a horrible pattern, but it certainly was not a beautiful pattern by any means.

look at the 500mb charts for North America. There was a definitive ridge out west that got the pattern to buckle and there was a 540dm strait block.

As I said, those charts do not accurately describe the situation.

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look at the 500mb charts for North America. There was a definitive ridge out west that got the pattern to buckle and there was a 540dm strait block.

11102912_sathts_500_alt.gif

Meh, not so much of anything with regard to the PNA. There certainly is a trough in the east, but there is no distinct ridging in the west. From what I can see from this image, there was blocking in the Davis Straight, but there is troughing near Greenland, which is indicative of a +NAO. These two conflicting signals probably led the CPC Analysis of the NAO to be netural/slightly positive instead of negative.

modes.jpg

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Meh, not so much of anything with regard to the PNA. There certainly is a trough in the east, but there is no distinct ridging in the west. From what I can see from this image, there was blocking in the Davis Straight, but there is troughing near Greenland, which is indicative of a +NAO. These two conflicting signals probably led the CPC Analysis of the NAO to be netural/slightly positive instead of negative.

That's a positive PNA on the chart posted. The Davis straight block is also extremely anomalous. In a situation like that, what happens over Greenland doesn't mean much because the huge ridge over the DS controls the pattern. The upcoming pattern is completely different with a broad longwave trough over Eastern Canada extending up towards the DS and Greenland.

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According to the CPC, the PNA was slightly negative, the NAO slightly positive, and the AO positive during the October 29th 2011 storm. It wasn't a horrible pattern, but it certainly was not a beautiful pattern by any means.

The CPC calculation really doesn't tell the tale. What does tell the tale is thel presence of a positive height anomaly in Davis Straight for that storm. Can't just look at bar graphs and calculated numbers, but if you do, please use the CDC NAO graph...it is much more indicative of the nao and its effects on the sensible weather around here.

nao.png

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That's a positive PNA on the chart posted. The Davis straight block is also extremely anomalous. In a situation like that, what happens over Greenland doesn't mean much because the huge ridge over the DS controls the pattern. The upcoming pattern is completely different with a broad longwave trough over Eastern Canada extending up towards the DS and Greenland.

It's not an extremely anomalous PNA, and whether it was slightly negative or slightly positive would make little to no difference in the overall pattern.

The NAO Index is not just calculated through the amount of blocking in the Davis Straight though. It takes into consideration the height anomalies near Greenland as well, so while there was blocking, there was a trough near Greenland, which is probably why the CPC Analysis of the NAO shows the NAO as slightly positive to neutral during that timeframe.

I concur that Blocking in the Davis Straight would influence the weather patterns in the east substantially more than the troughing near Greenland would, and is what gave us that historical snowstorm.

please use the CDC NAO graph...it is much more indicative of the nao and its effects on the sensible weather around here.

Thank you for your recommendation. I'll try and use those graphs in the future when calculating the NAO than the CPC graphs. Could you answer as to why the CPC maps would show the NAO as being slightly positive, if the NAO is largely calculated off of how much blocking is occuring in the Davis Straight?

I think I can learn from a lot of people that post here.

REPLY TO EARTHLIGHT BELOW:

Nobody said it was an extremely anomalous PNA. But right now we have an extremely anomalous situation in the Pacific, which is completely controlling the pattern. Not just here, but around the globe. And with the absence of any type of blocking (let alone anything near the davis straight block we had in late Oct), there is virtually no correlation to that pattern with the one forecast to unfold next week.

You are missing my point regarding the NAO--I know how it's calculated, my point was that the Davis Straight anomaly controlled the pattern regardless of what the CPC Analysis data said.

Back to the vortex over the NE Pac and Alaska--this is the most anomalous feature on the globe at the time of our potential storm system.

Regarding your first point, I would solidly agree. The -PNA is simply off of the charts right now, and there would need to be a near perfect situation in order for the NYC area to see even a few flakes.

However, it is interesting to look at that in past history, during terrible patterns, perfect scenarios can happen at perfect times occasionally (February 2006), with transient troughs, so I don't think we can completely write this threat off completely, just because we are in a terrible pattern right now.

You are missing my point regarding the NAO--I know how it's calculated, my point was that the Davis Straight anomaly controlled the pattern regardless of what the CPC Analysis data said.

Agree 100% with the DS anomalies controlling the October 29th 2011 Pattern.

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It's not an extremely anomalous PNA, and whether it was slightly negative or slightly positive would make little to no difference in the overall pattern.

The NAO Index is not just calculated through the amount of blocking in the Davis Straight though. It takes into consideration the height anomalies near Greenland as well, so while there was blocking, there was a trough near Greenland, which is probably why the CPC Analysis of the NAO shows the NAO as slightly positive to neutral during that timeframe.

I concur that Blocking in the Davis Straight would influence the weather patterns in the east substantially more than the troughing near Greenland would, and is what gave us that historical snowstorm.

Nobody said it was an extremely anomalous PNA. But right now we have an extremely anomalous situation in the Pacific, which is completely controlling the pattern. Not just here, but around the globe. And with the absence of any type of blocking (let alone anything near the davis straight block we had in late Oct), there is virtually no correlation to that pattern with the one forecast to unfold next week.

You are missing my point regarding the NAO--I know how it's calculated, but my point was that the Davis Straight anomaly controlled the pattern regardless of what the CPC Analysis data said (CDC is the better option btw)

Back to the vortex over the NE Pac and Alaska--this is the most anomalous feature on the globe at the time of our potential storm system.

f144.gif

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Nobody said it was an extremely anomalous PNA. But right now we have an extremely anomalous situation in the Pacific, which is completely controlling the pattern. Not just here, but around the globe. And with the absence of any type of blocking (let alone anything near the davis straight block we had in late Oct), there is virtually no correlation to that pattern with the one forecast to unfold next week.

You are missing my point regarding the NAO--I know how it's calculated, but my point was that the Davis Straight anomaly controlled the pattern regardless of what the CPC Analysis data said (CDC is the better option btw)

Back to the vortex over the NE Pac and Alaska--this is the most anomalous feature on the globe at the time of our potential storm system.

f144.gif

Looks like records will continue to fall in Alaska in the week ahead.....that is one impressive +EPO.

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