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Model Potpourri


bluewave

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Chris, nice post. This is the period I've been mentioning for awhile now re enhanced potential of a Northeast snow event. Modelling seems to be keying in on a temporary, albeit weak, dip in the NAO. A pseudo-neg NAO of sorts develops D 7-9 with a strong north atlantic ridge, not really stretching all the way up to Greenland, but it would be sufficient in holding marginal cold air over the Northern CONUS.

We also see guidance over the past couple days trending away from blowtorch solutions. While next week's temperatures will be on the upswing, and certainly warmer than this weekend, they're not likely to be any warmer than we saw this week (mid 40s, slightly above normal).

By next weekend we see a gradual decline in PNA values but also NAO values, which ends up yielding a somewhat zonal flow across the country. However, as you correctly pointed out, the STJ will be energizing, and this is due in large part IMO to the strong MJO wave currently propagating ewd in the trop pacific. This wave should be in latter stage 8/phase 1 by Pres day weekend, putting the East coast in a pretty conducive position for a snow event. Obviously synoptic factors will need to be examined as we approach the time frame, but as it stands, I think the stage is set for something next weekend (depending on track, potentially producing more snow than this weekend).

Note fairly decent agreement b/t the ECMWF and GFS on the north atlantic ridge, a weak neg nao signal, with lower heights being detected in the central/sern US via the southern stream energy ejecting eastward. This wouldn't work a month from now probably, but luckily, marginal cold is still ok to produce snow at this time of year.

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Also of interest is the mid week WAA/weak event which could end up similar to yesterday's minor C-1"/2" deal for many folks.

18z GFS has the progression similar to this week's light event. We'll have to see if it trends stronger as we approach the time frame, but right now it looks like a Tues aft-evening light snow, minor accum deal.

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If we can get some phasing of the streams, next weekend has the potential to produce much more snow for some areas of the Northeast, dependent upon track of course. However, much more moisture to work with, given a very potent/juiced STJ impulse, as Chris already talked about in the OP. Both the ECMWF and GFS indicate that STJ wave will be propagating W-E through the SE US then off the east coast; the 00z Euro from last night bombs the low off Hatteras but is too far east to impact the NE US. Again, the torch isn't happening next week; there is marginal cold air around, the NAO will be briefly dipping negative, and the MJO will be phase 8/1. If we can get even some partial phasing and intensification on the east coast, next weekend has good potential. Will be interesting to track this one over the next several days.

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I posted this in the main thread but I think it applies here too, with regards to next weekend,

Note the day 10 and 14 GFS ensemble AO forecasts versus actual observations (black line) over the past month. In strong contrast to Dec/Jan, the AO has now been negative to much more negative than progged in the D 10-15 range. Even out at D7, there is a slight positive bias to GFS ensembles. What this may mean is the current proggs for a slightly positive AO in the D 10-15 time frame could bust on the high side. I wouldn't be surprised if the AO reaches or exceeds neutral, but then I'd expect it to generally stay neutral-slightly negative. The strat vortex has been pretty thoroughly destroyed, so I don't think we're looking at a mod/strongly positive AO any time soon at least.

fy1jf8.jpg

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Note on the CMC H5 progression, the nern stream s/w diving into the sern s/w and phasing over the TN/OH valleys, energizing the system and closing it off at H5 once near the MA coast. Perfect timing. This is what we'd like to see on other guidance as we move forward.

It is the perfect outcome, thankfully it is a week out again. :axe:

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Note on the CMC H5 progression, the nern stream s/w diving into the sern s/w and phasing over the TN/OH valleys, energizing the system and closing it off at H5 once near the MA coast. Perfect timing. This is what we'd like to see on other guidance as we move forward.

as of now you can see why even though its a beautiful system it slips a little too far SE for us to get major snow. That s/w that rolls through beforehand on wed into thurs doesn't allow the heights to amplify that much ahead of the trailing s/w that becomes our storm. It basically serves as a transient 50/50 low that is just slightly too far SW to allow the trailing s/w to climb the coast as it amplifies.

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It is the perfect outcome, thankfully it is a week out again. :axe:

Yeah it is a week out, though I don't believe this threat will simply fade away into the wind like most of the D5+ storms that have shown up on modelling this winter. I'm fairly confident we'll see a potent STJ wave moving across the sern US, the question is, can the H5 energy phase in time to intensify the sfc low on the east coast. The MJO supports a storm somewhere on the east coast, and our transient albeit weak ridging in the north atlantic should sustain sufficient cold in the Northeast.

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This period definitely looks interesting with the 2 streams and some cold air running around. Euro does eventually get a storm off the coast at hr 222, but thats way out, and a storm could easily come before that

The MJO traversing through phases 8-1 is a good sign for something.

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Ok so the models are hinting at something big for the east coast for next weekend. We got a juicy sub tropical jet that when it phases with the northern stream at the right time we can gets a MECS. Its a week away an we still got plenty of time to iron out details. This will be one of those timing issues between those two streams and we'll have to watch it closely over the next several days. One good thing supported for this storm stated already in this thread mjo phases 8-1 good phases for easy coast cyclogenesis, air mass looks to be able to hold some cold air in to keep p-type issues to a minimum. IMO we should really take a cautious approach till wednesday/thursday to really take any model run as its worth. Fun times ahead guys. Btw isotherm and bluewave some really great input regarding this threat too, really very informative.

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Ok so the models are hinting at something big for the east coast for next weekend. We got a juicy sub tropical jet that when it phases with the northern stream at the right time we can gets a MECS. Its a week away an we still got plenty of time to iron out details. This will be one of those timing issues between those two streams and we'll have to watch it closely over the next several days. One good thing supported for this storm stated already in this thread mjo phases 8-1 good phases for easy coast cyclogenesis, air mass looks to be able to hold some cold air in to keep p-type issues to a minimum. IMO we should really take a cautious approach till wednesday/thursday to really take any model run as its worth. Fun times ahead guys. Btw isotherm and bluewave some really great input regarding this threat too, really very informative.

Btw the weekend, mid week, and possible late week action flakes could be in the air a fair bit.... It's about time good grief

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I have a good feeling about this storm if we can get it closer to the coast. Even though we have been snow and storm starved there have been several bombs the last few weeks that have gone east of the maritimes. The low that gave us a coating Wednesday bombed out big time and produced hurricane force winds and some huge seas NE of the maritimes. So the pattern is capable of producing a big storm we just need it closer to home. Also there is the historical date its just a great time climatologicaly for us for a big storm.

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