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December 14/15 winter storm threat part II


Typhoon Tip

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We are definitely dryslotting quick, but those VVs should be indicative of big moisture punching pretty far up in the atmosphere. This almost looks like a S-N warm conveyor belt look. I do think most of this is over by dawn, ESP BOS to FIT and points SW.

 

It wouldn't be surprising to see a lot of these areas switch over to sleet / freezing drizzle around this time even as the column remains completely below freezing. VVs are impressive, but if they only exist in the low-levels it doesn't matter. If static stability is strong (as it always is with strong inversions) the might not see enough upward penetration of the vertical circulation to get into the snow growth zone by the latter half of the storm evolution.

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It wouldn't be surprising to see a lot of these areas switch over to sleet / freezing drizzle around this time even as the column remains completely below freezing. VVs are impressive, but if they only exist in the low-levels it doesn't matter. If static stability is strong (as it always is with strong inversions) you might not see enough upward penetration to get into the snow growth zone by the latter half of the storm evolution.

If it is as modeled I would agree with this. We may see one of those super intense bands that flips to a snow sleet waivering mix as some parcels mix enough before finally succumbing to non frozen.

Nam was first to lead far NW, maybe it is doing a better job with the cold air. The Gfs should help clarify

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If it is as modeled I would agree with this. We may see one of those super intense bands that flips to a snow sleet waivering mix as some parcels mix enough before finally succumbing to non frozen.

Nam was first to lead far NW, maybe it is doing a better job with the cold air. The Gfs should help clarify

Do you mean Euro?  Or did I miss something?

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Ratios will be good initially.

 

Yes, and I think that can't be undersold yet... this system will be able to work with a 300-400 hPa deep -10 to -20 C snow growth region early on. That's very impressive and will persists up to 03z before that zone shrinks on down... while isentropic lift dominates early on, frontogenetically enhanced precipitation at this point could really enhance totals until the inversion intensifies beyond this period.

 

21cbjq1.gif

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Its amazingly cold for the track it takes...it keeps Ray pretty much all snow despite a track over Messenger.

 

 

This is getting a very convective look on the hi res models. Just these billows of intense VVs. So naturally when that happens all sorts of weird sh*t goes on. Areas that should be rain are snow, Areas that should have snow have a gravity wave induced toaster bath etc. I'm not saying that will happen...but it's getting that intense look for a time after 3z- 6z.

I mentioned last night, and Will this morning that this was trending into a 12/9/05 type of deal...still looks that way.

Probably not quite to anomalous, but headed that way..

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Phil I saw a lot of deep lift in the 700-500mb range which is what I meant. Towards the end we certainly could have IP or FZDZ as the more shallow lift takes over and we lose the ice in the prime snow growth layer, but I think the damage is done at that point.

 

Oh I agree with you. I think the thing I am trying to key on is that it might end earlier than suggested... You can see the main axis of VV on the NAM is north of MA by 9z. The GFS is admittedly more aggressive but even it has the max VV north of the area by 12z. 

 

namNE_700_vvel_045.gif

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Phil I saw a lot of deep lift in the 700-500mb range which is what I meant. Towards the end we certainly could have IP or FZDZ as the more shallow lift takes over and we lose the ice in the prime snow growth layer, but I think the damage is done at that point.

 

Even at 45 hours on the GFS, the column is still impressive...the soundings don't go to sh** until literally the precip is about to shutoff.

 

GFS_3_2013121312_F45_42_5000_N_71_5000_W

 

 

 

 

 

 

Of course, that is the GFS...NAM tries to dry out a smidge earlier,

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This is why we could use

Some blocking. Arctic high retreating FTL.

Ya im not sold on frozen for the 128 area from 3-6 am thump. Some see this as a lock or NBD. I think 128 flips to rain if 850 goes over bos.

No guidance has that. Pl or zr sure but not plain rain in the 128 belt. I think that thought is wrong and I'll be prepared to eat crow if otherwise.

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This is getting a very convective look on the hi res models. Just these billows of intense VVs. So naturally when that happens all sorts of weird sh*t goes on. Areas that should be rain are snow, Areas that should have snow have a gravity wave induced toaster bath etc. I'm not saying that will happen...but it's getting that intense look for a time after 3z- 6z.

This things began looking thundery to me yesterday for other synoptic reasons ... we'll see

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Must we keep throwing out 12/9/05? That had a rediculous bombing low <970 mb with +TSSN not to mention the wind on the Cape in particular. Looks like a solid event at least for anyone N/W fof Boston for now, but lets not get carried away,

Snow amounts for some might be similar, but not the hole in the atmosphere to be sure

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Oh I agree with you. I think the thing I am trying to key on is that it might end earlier than suggested... You can see the main axis of VV on the NAM is north of MA by 9z. The GFS is admittedly more aggressive but even it has the max VV north of the area by 12z.

namNE_700_vvel_045.gif

Do you have axis to a 850-500 RH type

Product? That nails the start and end times. Probably done after 09z for most. The further NE you are the later it ends naturally.

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Even at 45 hours on the GFS, the column is still impressive...the soundings don't go to sh** until literally the precip is about to shutoff.

 

GFS_3_2013121312_F45_42_5000_N_71_5000_W

 

 

 

 

 

 

Of course, that is the GFS...NAM tries to dry out a smidge earlier,

 

Honestly the GFS soundings (at least at the resolution that you are given which only picks limited isobaric levels) are total crap... they have little to no reflection of the strong low-level inversion that should be setting up with the strong WAA occurring in the wind profile. Look at the NAM at the same time in contrast.

 

jt9dtf.gif

Buyer beware when you look at soundings from different sites... if the vertical resolution is limited, you are not going to pick up on the final scale features. The NAM clearly shows a dry slot trying to move in between 700-500 hPa. The GFS in contrast doesn't show this feature.

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