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A look ahead at the Feb 3-10 Period - Technical Discussion (Updated to Feb 15th)

ORH_wxman

By ORH_wxman,
in New England

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REDMK6GLI

REDMK6GLI

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I don't see PDII as a great analog to the Feb 9th threat, at least right now...there are a few similarities, however, the pattern to the north is not the same as that storm. There is currently less of an arctic high anchored to the north on guidance...however that could still change. There is some east-based -NAO ridging showing up that could try and pin the PV further southeast than it currently modeled. IF that is the case as we get closer, then the storm could take on more of a PDII synoptic setup...I try to avoid historic storm analogs in general until it becomes more clear that such comparisons are warranted since it often will get people's expectations up. The flow during PDII was quite slow as it was southern stream dominated...as it often the case during El Nino winters (esp February)....that is one reason so much snow fell along the east coast. It would be hard to get a storm moving that slowly in this pattern.

 

great points and I appreciate your response to help clarify the possibilities of this storm.

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ORH_wxman

ORH_wxman

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A 50/50 low is a storm that is positioned around the latitude/longitude of 50/50.  It can act as a block/confluence to force systems to move out S of the New England coastline.  It is one key feature needed for larger east coast systems.  Here is a representation of it.

 

attachicon.gif192.jpg

 

 

Yeah...good visual there. In a classic east coast snowstorm, you'd want that low to be further south closer to New Foundland. Kind of like where the "o" is in the word "low" on that map.

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ORH_wxman

ORH_wxman

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The 00z Feb 2nd guidance continued to come into better agreement for both the February 5th and February 9th widespread winter storm threats. The details of the February 5th threat are in the other specific thread for it.

 

 

As for February 9th, the 00z guidance suite shows a major winter storm threat for New England. The ECMWF ensemble mean showed a low pessure to the southeast fo LI for 12z Feb 9th and a high pressure systme situation tot he north. The guidance has mean hitting the PV a bit harder SE which holds in the cold air a bit better. This is thanks to some modest -NAO ridging in addition o the very strong EPO/WPO block that extends well into the Arctic Ocean. The spread was below average for the D6-7 timeframe on the ensembles as well suggesting that this may be a higher confidence threat at this time range than is normally seen.

 

However, even with that, the confidence at this time frame is normally very low, so improvement there doesn't mean there are any slam dunks by any means.

 

The evolution of the Feb 9 threat is dependent on many factors. In addition to the weak NAO ridging showing up, the strong EPO/WPO block rolls over itself and helps generate a temporary split flow out over the western CONUS/Canada by Feb 6-7. This allows the shortwave to begin its trek east without phasing with the PV which starts to get locked into SE Canada creating a supply of cold air for New England.

 

 

Here is the ECMWF ensemble mean 5H pattern for 00z Feb 4th and then 00z Feb 5th with some labels on it to explain what is happening for the seeds being planted for the Feb 9th threat:

 

Feb2_00z_ECMWFmean_1.png

 

 

 

Now as we move ahead to 00z Feb 7th, you can see how the split flow out west has sort of left that shortwave to trek on its own disconnected from the polar vortex...this gives the PV a chance to setup shop out in SE Canada without being stretched/phased into the storm which would make a warmer/west solution solution more likely...instead, the PV setting up shop in SE Canada gives a colder look and higher threat to a major winter storm for the northeast.

 

See below:

 

Feb2_00z_ECMWFmean_2.png

 

 

 

 

 

You can see how complicated the anatomy is for the Feb 9th threat. So there's a lot of things that can "wrong" between now and then. The good news is that a lot of these pieces are high confidence to occur...but the shortwave itself and the PV positioning are a bit lower confidence and those details matter quite a lot in terms of where this storm ultimately tracks.

 

 

 

Remember the images above and we'll revisit them as we get closer and see how many of the features change.

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CoastalWx

CoastalWx

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Good description of what is going on and the kind of stuff we have to look at. In addition to what is posted above, the features highlighted do not contain a lot of spread for a 7 day prog. We have had very good agreement with these storms lately. Sometimes with blocking features you can have good agreement far out there.

 

What I do question is the two part system the euro has. Obviously that will be determined by the s/w's embedded in the flow.

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ORH_wxman

ORH_wxman

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Good description of what is going on and the kind of stuff we have to look at. In addition to what is posted above, the features highlighted do not contain a lot of spread for a 7 day prog. We have had very good agreement with these storms lately. Sometimes with blocking features you can have good agreement far out there.

 

What I do question is the two part system the euro has. Obviously that will be determined by the s/w's embedded in the flow.

 

 

Yeah that probably isn;t happening. We usually see those consolidate into one system. I think confidence is fairly high of a significant storm moving out of the southern plains/southeast right now...but obviously for our own sensible wx up here, the confidence remains low as we'd expect for 7 days out.

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mahk_webstah

mahk_webstah

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The 00z Feb 2nd guidance continued to come into better agreement for both the February 5th and February 9th widespread winter storm threats. The details of the February 5th threat are in the other specific thread for it.

 

 

As for February 9th, the 00z guidance suite shows a major winter storm threat for New England. The ECMWF ensemble mean showed a low pessure to the southeast fo LI for 12z Feb 9th and a high pressure systme situation tot he north. The guidance has mean hitting the PV a bit harder SE which holds in the cold air a bit better. This is thanks to some modest -NAO ridging in addition o the very strong EPO/WPO block that extends well into the Arctic Ocean. The spread was below average for the D6-7 timeframe on the ensembles as well suggesting that this may be a higher confidence threat at this time range than is normally seen.

 

However, even with that, the confidence at this time frame is normally very low, so improvement there doesn't mean there are any slam dunks by any means.

 

The evolution of the Feb 9 threat is dependent on many factors. In addition to the weak NAO ridging showing up, the strong EPO/WPO block rolls over itself and helps generate a temporary split flow out over the western CONUS/Canada by Feb 6-7. This allows the shortwave to begin its trek east without phasing with the PV which starts to get locked into SE Canada creating a supply of cold air for New England.

 

 

Here is the ECMWF ensemble mean 5H pattern for 00z Feb 4th and then 00z Feb 5th with some labels on it to explain what is happening for the seeds being planted for the Feb 9th threat:

 

Feb2_00z_ECMWFmean_1.png

 

 

 

Now as we move ahead to 00z Feb 7th, you can see how the split flow out west has sort of left that shortwave to trek on its own disconnected from the polar vortex...this gives the PV a chance to setup shop out in SE Canada without being stretched/phased into the storm which would make a warmer/west solution solution more likely...instead, the PV setting up shop in SE Canada gives a colder look and higher threat to a major winter storm for the northeast.

 

See below:

 

Feb2_00z_ECMWFmean_2.png

 

 

 

 

 

You can see how complicated the anatomy is for the Feb 9th threat. So there's a lot of things that can "wrong" between now and then. The good news is that a lot of these pieces are high confidence to occur...but the shortwave itself and the PV positioning are a bit lower confidence and those details matter quite a lot in terms of where this storm ultimately tracks.

 

 

 

Remember the images above and we'll revisit them as we get closer and see how many of the features change.

Thank you Will.  The way you present this is very clear and laid out in an easy to understand way.  It is a great learning opportunity over the next week.  Look forward to seeing how globals represent this, and then being able to look at shorter term models to see if it is developing in the way it was modelled 8 days out.

 

It would be awesome if the -NAO developed.  It keeps showing up and if it develops, even weakly, we could have a lot of fun post Feb 9.

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jamesnichols1989

jamesnichols1989

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Look at that huge 1030mb high over Quebec, Canada, storm splits and heads to the coastline while a 992mb low just sits near Chicago, ILL and dumps on them while the best QPF splits to the coastline and redevelops.  Thinking this might be overdone in some capacity for Chicago, IL but the way this winter has gone, who knows.

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Typhoon Tip

Typhoon Tip

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Euro and GGEM all but completely abandoned the Feb 9 signal... suppose that is par for the course to behave that way.  We see these systems get dropped only to re-appear.  

 

Sufficed it is to say, however, the tele's don't really favor a system on that date.  All we have had, to date, is some consistency in the GFS operational, and off-and-on nodding by the Euro.   

 

We'll see... not having complete tele support isn't always necessary -- it just helps to have it. 

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REDMK6GLI

REDMK6GLI

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gfs has becs, nyc thread suggests we may only see the tops of the telephone poles should that verify..........its nice to dream:)

don't know about BECS but the signal for a pretty big snowstorm is there. don't think we're going to know whats going on until Tuesday/Wednesday when the models agree with what to do with the mid week storm. 50/50 is key to help lock that HP in SE Canada to get redevelopment early off the mid atlantic coast to deliver the goods from PHL-NYC

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