NYC/PHL Potential Jan 11-14 Event Discussion Part Two

[gkrangers]

stuff

Superb post.

[nzucker]

Superb post.

Agreed...it is a great post by John.

Earthlight should be given many congratulations for how much meteorological skill and time he has put into this winter. I believe he has raised the level of the NYC threads to some of the best on these boards. This has been a very active winter pattern with many storms and cold outbreaks to track, and Earthlight has stayed on top of this all. I think his participation will continue to be crucial, and thought provoking, as we experience a continued active pattern in early-mid January.

[Ralph Wiggum]

I'm burning one of my 3 remaining posts to say splendid, earthlight, simply splendid post!

[Tiburon]

There have been a slew of questions and posts over the past day or so regarding the "lack of precipitation" or "lack of QPF" on the models. First of all, I think the statement in itself is flawed. Most people here are probably looking for 2"+ QPF bombs we have been seeing so far this winter. Truth is, that won't happen here..we don't have the insane dynamics, phasing, and 970's mb surface low that we did with the last system. Everybody should try and do their best to get those numbers out of their heads. The fact is that 1" liquid is a significant winter storm and there are plenty of models heading towards those numbers.

Still, plenty have asked why the models are taking so long to develop the heavy precipitation. The problem lies in the initial surface low and initial 500mb flow. I included the 18z NAM depiction at 72 hours in a below image with the H5, SLP, and 6 hr QPF chart. There are several things to note here. First, the primary low into the Ohio Valley. This primary low is being driven by the initial burst of 500mb vorticity which you can see at the time over Southern Illinois. The secondary surface low is still forming over the Carolinas. Usually, we would have more significant precipitation associated with this feature. But the H5 forcing is still lagging back to the west. There is a favorable diffluent flow with the ridge axis over the East coast--which will help form the surface low northward and eventually develop the CCB. But we aren't going to get prolific amounts until that said cold conveyor belt can really develop and mature.

The details go beyond this though, as I mentioned how things should really get going once the dynamics come into play. I included the NAM high resolution graphics of the 250mb jet stream at the same valid time below. That's a 120kt 250mb jet streak already ejecting northeast out of the base of the trough towards the East coast. It doesn't really matter how strong the primary is, once that gets in play (it's not just at 250mb either, as we all know) things should really get going.

The other thing I wanted to hit on really quickly, without getting into too many details at this range, is the potential for banding. The NAM, as an example, is rapidly developing the cold conveyor belt and is bringing an area of enhanced frontogenic forcing up along the coast and into New Jersey and towards the Northern Mid Atlantic including Eastern PA, eventually NYC, etc. This could, as we all know, be an area where prolific snow amounts are recorded. The NAM in it's own right would advertise the potential for dynamic heavy wet snow..and the potential for thundersnow once again within the banding area. Here's the H7 vertical velocities below which show the rather broad area of support for heavy snow (as evidenced by the NCEP H7 UVV charts as well)..but a small area where very intense snowfall rates would be occurring at that time as well. There are also intense 850mb vertical velocities moving northeast over coastal NJ and towards LI/NYC at that time frame. The H85 low reforming and the surface low deepening rapidly just off the coast would likely create a prolific snow event even towards the coast despite some initial warmth.

So in general, there is really some dynamic potential here. As far as the models and their QPF..there are reasons why they haven't showed absolutely prolific amounts--and I wouldn't expect them with this type of event, either. But if the guidance trends are any indication, and this storm is going to tuck off the coast as depicted, somebody is going to get slammed with some prolific amounts underneath heavy frontogenic forcing and banding. Exciting possibilities here as we sit 78-84 hours away from the event.

Wow. Someone's been reading their copy of KU and paying attention in class, eh?

[forkyfork]

this will become more useful as we get closer to the event

http://moe.met.fsu.edu/banding/

[Edge Weather]

Thank you.

for good snow growth you want the higher neg numbers, or deeper colors like blues and purples and pinks, in the 700mb zone, this is the snow growth region.

[jm1220]

A blend between the NAM and GFS would be great. NAM would dryslot I-95 south and east fast and even change them to rain, while the GFS a little stronger would be perfect.

[SomeguyfromTakomaPark]

If you are a Jets fan....

Would you rather have this storm blow up and score big with 12-18 and strong winds on Wed and have the Jets lose?

Or a Jet win and storm somehow misses OTS?

[unknown]

18 hours from now

[Edge Weather]

No question about it. If John wants a job reference from me, he's got it.

Agreed...it is a great post by John.

Earthlight should be given many congratulations for how much meteorological skill and time he has put into this winter. I believe he has raised the level of the NYC threads to some of the best on these boards. This has been a very active winter pattern with many storms and cold outbreaks to track, and Earthlight has stayed on top of this all. I think his participation will continue to be crucial, and thought provoking, as we experience a continued active pattern in early-mid January.

[Edge Weather]

Fantastic stuff, thanks.

this will become more useful as we get closer to the event

http://moe.met.fsu.edu/banding/

[Edge Weather]

I guess you have to install the software?

check the northeast box, then click the station bubble closest to you.

[am19psu]

There have been a slew of questions and posts over the past day or so regarding the "lack of precipitation" or "lack of QPF" on the models. First of all, I think the statement in itself is flawed. Most people here are probably looking for 2"+ QPF bombs we have been seeing so far this winter. Truth is, that won't happen here..we don't have the insane dynamics, phasing, and 970's mb surface low that we did with the last system. Everybody should try and do their best to get those numbers out of their heads. The fact is that 1" liquid is a significant winter storm and there are plenty of models heading towards those numbers.

Still, plenty have asked why the models are taking so long to develop the heavy precipitation. The problem lies in the initial surface low and initial 500mb flow. I included the 18z NAM depiction at 72 hours in a below image with the H5, SLP, and 6 hr QPF chart. There are several things to note here. First, the primary low into the Ohio Valley. This primary low is being driven by the initial burst of 500mb vorticity which you can see at the time over Southern Illinois. The secondary surface low is still forming over the Carolinas. Usually, we would have more significant precipitation associated with this feature. But the H5 forcing is still lagging back to the west. There is a favorable diffluent flow with the ridge axis over the East coast--which will help form the surface low northward and eventually develop the CCB. But we aren't going to get prolific amounts until that said cold conveyor belt can really develop and mature.

The details go beyond this though, as I mentioned how things should really get going once the dynamics come into play. I included the NAM high resolution graphics of the 250mb jet stream at the same valid time below. That's a 120kt 250mb jet streak already ejecting northeast out of the base of the trough towards the East coast. It doesn't really matter how strong the primary is, once that gets in play (it's not just at 250mb either, as we all know) things should really get going.

The other thing I wanted to hit on really quickly, without getting into too many details at this range, is the potential for banding. The NAM, as an example, is rapidly developing the cold conveyor belt and is bringing an area of enhanced frontogenic forcing up along the coast and into New Jersey and towards the Northern Mid Atlantic including Eastern PA, eventually NYC, etc. This could, as we all know, be an area where prolific snow amounts are recorded. The NAM in it's own right would advertise the potential for dynamic heavy wet snow..and the potential for thundersnow once again within the banding area. Here's the H7 vertical velocities below which show the rather broad area of support for heavy snow (as evidenced by the NCEP H7 UVV charts as well)..but a small area where very intense snowfall rates would be occurring at that time as well. There are also intense 850mb vertical velocities moving northeast over coastal NJ and towards LI/NYC at that time frame. The H85 low reforming and the surface low deepening rapidly just off the coast would likely create a prolific snow event even towards the coast despite some initial warmth.

So in general, there is really some dynamic potential here. As far as the models and their QPF..there are reasons why they haven't showed absolutely prolific amounts--and I wouldn't expect them with this type of event, either. But if the guidance trends are any indication, and this storm is going to tuck off the coast as depicted, somebody is going to get slammed with some prolific amounts underneath heavy frontogenic forcing and banding. Exciting possibilities here as we sit 78-84 hours away from the event.

100% agree with all of this. Great post, earthlight.

[am19psu]

Sorry, I've been out the last 24 hours. Anyway, the big concern I have right now is a track further to the left. There is still some skew in the Euro ensemble to bring this back farther to the west, bringing more p-type problems to the coast, and maybe I-95.

[Edge Weather]

Tom, I would love the link for this as well now that you taught me how to read it.

i wasn't looking at the bufkit i was looking at the omega, UVV's in the snow growth region....ill post what im saying

phl nam

abe nam

[AbsoluteVorticity]

Tom, I would love the link for this as well now that you taught me how to read it.

I think thats from coolwx.com under model forecasts

[Analog96]

Sorry, I've been out the last 24 hours. Anyway, the big concern I have right now is a track further to the left. There is still some skew in the Euro ensemble to bring this back farther to the west, bringing more p-type problems to the coast, and maybe I-95.

I really dont think we have to worry about p-type issues all the way to the 95. The only way that would happen, IMO, is if the clipper-like system that the 18Z GFS has is stronger than the coastal and further North, which could produce sleet.

[ArtRosen]

There have been a slew of questions and posts over the past day or so regarding the "lack of precipitation" or "lack of QPF" on the models. First of all, I think the statement in itself is flawed. Most people here are probably looking for 2"+ QPF bombs we have been seeing so far this winter. Truth is, that won't happen here..we don't have the insane dynamics, phasing, and 970's mb surface low that we did with the last system. Everybody should try and do their best to get those numbers out of their heads. The fact is that 1" liquid is a significant winter storm and there are plenty of models heading towards those numbers.

Still, plenty have asked why the models are taking so long to develop the heavy precipitation. The problem lies in the initial surface low and initial 500mb flow. I included the 18z NAM depiction at 72 hours in a below image with the H5, SLP, and 6 hr QPF chart. There are several things to note here. First, the primary low into the Ohio Valley. This primary low is being driven by the initial burst of 500mb vorticity which you can see at the time over Southern Illinois. The secondary surface low is still forming over the Carolinas. Usually, we would have more significant precipitation associated with this feature. But the H5 forcing is still lagging back to the west. There is a favorable diffluent flow with the ridge axis over the East coast--which will help form the surface low northward and eventually develop the CCB. But we aren't going to get prolific amounts until that said cold conveyor belt can really develop and mature.

The details go beyond this though, as I mentioned how things should really get going once the dynamics come into play. I included the NAM high resolution graphics of the 250mb jet stream at the same valid time below. That's a 120kt 250mb jet streak already ejecting northeast out of the base of the trough towards the East coast. It doesn't really matter how strong the primary is, once that gets in play (it's not just at 250mb either, as we all know) things should really get going.

The other thing I wanted to hit on really quickly, without getting into too many details at this range, is the potential for banding. The NAM, as an example, is rapidly developing the cold conveyor belt and is bringing an area of enhanced frontogenic forcing up along the coast and into New Jersey and towards the Northern Mid Atlantic including Eastern PA, eventually NYC, etc. This could, as we all know, be an area where prolific snow amounts are recorded. The NAM in it's own right would advertise the potential for dynamic heavy wet snow..and the potential for thundersnow once again within the banding area. Here's the H7 vertical velocities below which show the rather broad area of support for heavy snow (as evidenced by the NCEP H7 UVV charts as well)..but a small area where very intense snowfall rates would be occurring at that time as well. There are also intense 850mb vertical velocities moving northeast over coastal NJ and towards LI/NYC at that time frame. The H85 low reforming and the surface low deepening rapidly just off the coast would likely create a prolific snow event even towards the coast despite some initial warmth.

So in general, there is really some dynamic potential here. As far as the models and their QPF..there are reasons why they haven't showed absolutely prolific amounts--and I wouldn't expect them with this type of event, either. But if the guidance trends are any indication, and this storm is going to tuck off the coast as depicted, somebody is going to get slammed with some prolific amounts underneath heavy frontogenic forcing and banding. Exciting possibilities here as we sit 78-84 hours away from the event.

Although I'm dreading yet ANOTHER snowstorm, you really made this upcoming event sound exciting! Thank you!

[Saturn510]

I really dont think we have to worry about p-type issues all the way to the 95. The only way that would happen, IMO, is if the clipper-like system that the 18Z GFS has is stronger than the coastal and further North, which could produce sleet.

I think it is also pretty wierd that so far this season has been either snow or no. Not one storm we had precip issues even on the coastal plain. It is also pretty neat that the majority of us are at or above our seasonal averages. Hopefully those that are not will get there with this storm. If that happens everything from Jan 12th and on is pure gravy.

[am19psu]

I really dont think we have to worry about p-type issues all the way to the 95. The only way that would happen, IMO, is if the clipper-like system that the 18Z GFS has is stronger than the coastal and further North, which could produce sleet.

Looking at the Euro ensemble members, about 20-30% put the 850 0C line near or west of PHL and NYC. It all depends on when the primary low dies out. If it hangs on much longer than currently progged, the coastal will tuck closer to the coast.

To your point though, the ensemble mean is lined up closely with the ops at 850.

[WxLover]

Sorry, I've been out the last 24 hours. Anyway, the big concern I have right now is a track further to the left. There is still some skew in the Euro ensemble to bring this back farther to the west, bringing more p-type problems to the coast, and maybe I-95.

Mentioned this in another thread. Snowgoose seems to think it will not come much further inside the BM. Due to the setup in the N. Atlantic.

[earthlight]

Thanks for all the thoughts and comments dudes. You guys rock.

By the way, if anyone is looking for some extra juice as we wait for tonight's 00z model suite, check out the SREF data from this afternoons 15z. All of them have a very weak southern stream connection heading towards the coast even after the first shortwave was squashed by the confluent flow. Pretty cool.

http://www.meteo.psu.edu/~gadomski/SREF21500US_15z/f48.gif

[nzucker]

I think it is also pretty wierd that so far this season has been either snow or no. Not one storm we had precip issues even on the coastal plain. It is also pretty neat that the majority of us are at or above our seasonal averages. Hopefully those that are not will get there with this storm. If that happens everything from Jan 12th and on is pure gravy.

I'm not near my seasonal average....have 18.5" so far and average annual snowfall is around 38" for here. I'm certainly running above average on the year-to-date, and another snowstorm would get me closer to my goal of a 50"+ season. I had 68" here in Dobbs Ferry last year.

Looking at the Euro ensemble members, about 20-30% put the 850 0C line near or west of PHL and NYC. It all depends on when the primary low dies out. If it hangs on much longer than currently progged, the coastal will tuck closer to the coast.

To your point though, the ensemble mean is lined up closely with the ops at 850.

This is why I'm a bit happy to be on the NW side of the storm. The 18z GFS does give heavier QPF to NJ and LI, but I could see the developing Miller B tucking a bit farther west than currently modeled and changing some of these areas over to sleet. I have a bit more breathing room in Westchester as the GFS is showing 850s around -4C/-5C during the storm with surface temperatures in the low to mid 20s.

[earthlight]

21z SREF's are nearly identical to the 15z run. The surface low may be a hair stronger, but it's still in an ideal position.

[tombo82685]

Tom, I would love the link for this as well now that you taught me how to read it.

heres the link, on the bottom left, just change your state and pick the closest town.

http://coolwx.com/cgi-bin/getbufr.cgi?region=PA&stn=KPHL&model=nam&time=current&field=omeg

[SnowGoose69]

Looking at the Euro ensemble members, about 20-30% put the 850 0C line near or west of PHL and NYC. It all depends on when the primary low dies out. If it hangs on much longer than currently progged, the coastal will tuck closer to the coast.

To your point though, the ensemble mean is lined up closely with the ops at 850.

I never really pay much attention since in these storms I'm focused on what is occurring with the coastal but it seems I always notice folks in the OH Valley going nuts complaining the primary is underperforming during these events or dying out early...it seems primary lows either remain dominant and little if any coastal forms or they die a bit earlier than they are progged to.

[Bluescat1]

The Nam is rolling.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/nam/00/fp0_012.shtml

[Analog96]

I think it is also pretty wierd that so far this season has been either snow or no. Not one storm we had precip issues even on the coastal plain. It is also pretty neat that the majority of us are at or above our seasonal averages. Hopefully those that are not will get there with this storm. If that happens everything from Jan 12th and on is pure gravy.

It is very interesting. Even during the blizzard, way out on the Forks, there was little to no mixing, and it was sleet, rather than rain, that mixed in. And the low was right on top of them!

[am19psu]

I never really pay much attention since in these storms I'm focused on what is occurring with the coastal but it seems I always notice folks in the OH Valley going nuts complaining the primary is underperforming during these events or dying out early...it seems primary lows either remain dominant and little if any coastal forms or they die a bit earlier than they are progged to.

Mt Holly made a good point in their AFD about surface lows not liking to track over snow covered land (because of poor WAA ahead - at least I assume that's their reasoning). That would seem to agree with your anecdote.

[Zir0b]

<br />21z SREF's are nearly identical to the 15z run. The surface low may be a hair stronger, but it's still in an ideal position.<br />

Only thing I don't like is the track of the H5 low on the mean. It is too far north of the area for my liking.