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Jan 11-12 Model/Forecasting Discussion


Ji

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Agreed...I'll go with the Euro ensembles at this point...even though that is a cop out. But they are king even in this model-troubled winter. I would actually be worried about a further north and more robust solution. The -NAO is impressive but its in the process of breaking down....we are seeing one of the few breakdowns this winter (then it will probably build back after 7-10 days). But most big snowstorms over the EC occur when the nao breaks down...not when it ramps up.

The Archambault events are when it ramps up to negative, but that is precip and not snow....a lot of the snowstorms were when it went from negative to positive. Or negative to neutral.

Yeah good points. The GFS has seemingly had the most trouble adjusting to the breakdown of the -NAO amongst the globals and has been the least bullish in developing a more amplified height field pattern in the mid/upper levels. What confounds me is the way it comes in more impressive each run from a dynamic standpoint yet it seems to produce the same result. It is very weird, and this run really looked much better overall even though it paints a similar eventual scenario. The height field, the much more curved jet max (also stronger through 84), a fatter mid level S/W and a more diffluent upper level height field into the upstream ridge. It all screams stronger development...and it seems sooner or later the GFS will have to shift in a big way.

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Yeah I see that now, the upper wave is too flat. I still honestly don't buy the GFS and the way it plows the wave through that ridge and remains so flat and pathetic. GFS op continues to remains a stalwart though.

The GFS hasn't looked right to me for a couple of days now with how it handles the interaction between the southern shortwave and the energy diving down. I have been thinking that it leaves the duel low or strung out low to long and that it should consolidate better with a more westerly track. The current 06Z run seems a little better then previous runs though and it looks like a more westerly track because of that. Also the ensemble members have seemed to be better then the OP on a quicker consolidation and with that they have also had a more westerly track on the means.

Question I have is, is my thinking right as far as my assumption and if so is the delaying of the merging of duel structure strung out low a realistic option.

Thanks in advance.

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The GFS hasn't looked right to me for a couple of days now with how it handles the interaction between the southern shortwave and the energy diving down. I have been thinking that it leaves the duel low or strung out low to long and that it should consolidate better with a more westerly track. The current 06Z run seems a little better then previous runs though and it looks like a more westerly track because of that. Also the ensemble members have seemed to be better then the OP on a quicker consolidation and with that they have also had a more westerly track on the means.

Question I have is, is my thinking right as far as my assumption and if so is the delaying of the merging of duel structure strung out low a realistic option.

Thanks in advance.

This is basically what I am talking about. This is the current 06Z and it seems to do a better job then the previous runs of merging the duel structured low but it still seems to slow to me.

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The GFS hasn't looked right to me for a couple of days now with how it handles the interaction between the southern shortwave and the energy diving down. I have been thinking that it leaves the duel low or strung out low to long and that it should consolidate better with a more westerly track. The current 06Z run seems a little better then previous runs though and it looks like a more westerly track because of that. Also the ensemble members have seemed to be better then the OP on a quicker consolidation and with that they have also had a more westerly track on the means.

Question I have is, is my thinking right as far as my assumption and if so is the delaying of the merging of duel structure strung out low a realistic option.

Thanks in advance.

A lot of different scenarios can still play out. It is almost a sure bet though, even based off the GFS and its own dynamic/kinematic fields, is that there will be a more impressive and stronger primary surface low/inverted trough over the OV as it heads E. It is seemingly impossible to have a low amplitude S/W like the GFS does interacting with an amplified upper level ridge and simply passing through it in such a weak way. Forced ascent aloft with that shortwave (DPVA) will develop a stronger low level circulation NW and will also enhance the warm air advection off the coast. It is likely that the low off the coast tracks closer inland as a result of the stronger primary circulation. The coastal should tank out quickly off the VA coast but prolly a tad N, at least IMO. As ORH said there is a legitimate chance the inland low actually tracks well NW of its current position. DC/BA and NOVA is once again in the middle under such a scenario, but I do believe snow is likely with much better eventual totals along the coast and Delmarva. Trends with the development of the inland primary will need to be watched. It does seem possible there will be a minor screwzone somewhere in between all the chaos of the coastal developing low and the inland primary. Exactly where tough to tell still. For now, the type of snow totals Ian/Wes suggested are pretty good overall IMO with a solid 2-4" inland, chance for 5".

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A lot of different scenarios can still play out. It is almost a sure bet though, even based of the GFS and its own dynamic/kinematic fields, is that there will be a more impressive and stronger primary surface low/inverted trough over the OV as it heads E. It is seemingly impossible to have a low amplitude S/W like the GFS does interacting with a amplified upper level ridge and simply passing through it in such a weak way. Forced ascent aloft with that shortwave (DPVA) will develop a stronger low level circulation NW and will also enhance the warm air advection off the coast. It is likely that the low off the coast tracks closer inland as a result of the stronger primary circulation. The coastal should tank out quickly off the VA coast but prolly a tad N, at least IMO. As ORH said there is a legitimate chance the inland low actually tracks well NW of its current position. DC/BA and NOVA is once again in the middle under such a scenario, but I do believe snow is likely with much better eventuial totals along the coast and Delmarva. Trends with the development of the inland primary will need to be watched. It does seem likely there will be a minor screwzone somewhere in between all the chaos of the coastal devleoping low and the inland primary. Exactly where tough to tell still.

Thanks for the follow up.

Been in the back of my mind for a while that we may have rain/snow/sleet issues fairly far inland on the coast and now reading your reply it sounds like we may have issues with it to the south as well.

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one thing that was concerning about the op euro at 0z was the miller b precip pattern.. we had good bit more qpf here but we're right on the line. i think either way we're locking in for some snow.. i guess i may need to raise my number a bit if 'trends' hold, but i'm nervous about the evolution still.

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one thing that was concerning about the op euro at 0z was the miller b precip pattern.. we had good bit more qpf here but we're right on the line. i think either way we're locking in for some snow.. i guess i may need to raise my number a bit if 'trends' hold, but i'm nervous about the evolution still.

Can't see the members of the Euro but looking at the 06Z GFS members most show the precip starting to kick in around the DC and Baltimore area. It's a concern of mine as well that we could actually see the low crank a little farther north and take us out of that zone.

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one thing that was concerning about the op euro at 0z was the miller b precip pattern.. we had good bit more qpf here but we're right on the line. i think either way we're locking in for some snow.. i guess i may need to raise my number a bit if 'trends' hold, but i'm nervous about the evolution still.

The wetter but closer the edge scenario was the one that I guess several of us were asking for. Hope I don't pay for my wish for that with 33 and rain. Course, as dry as its been, I still didn't want to see another one slide by with us fringed and dry.

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The wetter but closer the edge scenario was the one that I guess several of us were asking for. Hope I don't pay for my wish for that with 33 and rain. Course, as dry as its been, I still didn't want to see another one slide by with us fringed and dry.

My thinking is still, that the coastal will be right on the coast but if we do get a stronger low to the west I think that would take away any benefit of that for our area as well as cause precip type issues farther inland.

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Is there a long analog list of strong Nina's where there was the degree of blocking we have this year? I am not sure we can simply rely on climo for a nina to discout any threat as unlikely because climo for a nina also argued the NAO should average positive this year.

My issue with Nina years isn't whether or not you can get persistent high lat blocking. It's the tendency for a relatively quiet s-stream. This means the chances of meaningful snowfall in DC are reliant on a split n-stream or a very rare s-stream s/w. Alas when Nina years offer a one of the two prior chances they also tend to feature an already in place, fairly strong HP from Canada, and a tendency of any east coast trough to be pretty dramatically deep, albeit transient. Thus the SE, SNE and eastern NE tend to do far better than we. As do points along and west of the Apps and into the OV as the other path for southern systems would tend to be along somewhere to our west as the usually transient block lifts out and NE.

Take for instance the position of today's and the last block's, center of greatest height anomalies. They started further east well over GL. They're now well back over Hudson's Bay. This puts the core of the greatest negative anomalies right over, or very near, us. This isn't the perfect scenario for a coastal hugging nor'easter.

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