NYC/PHL Jan 11-14 Threat Potential Part 3

[earthlight]

It's interesting to consider the Euro bringing .75" back to EWR..considering the GFS brought the .5" line to that location and delivered 7.1" on the bufkit data. I would be pretty comfortable predicting 5-8/5-10" throughout the area right now...which I have a hunch OKX will do this morning.

[tombo82685]

fwiw the hires arw and nmm are both slower at developing the h5 low than the nam. Nam developes it at hr 42 or before, and those models are still open at hr 42

[CTWeatherFreak]

lol yea, see johns above comments 126am lol...but yea hfd

S'all good.. aside from the late hour, you must also be suffering the pangs of the ignominious eagles loss, especially when the receiver stepped 1/4" out of bounds to negate the late game td!

[earthlight]

fwiw the hires arw and nmm are both slower at developing the h5 low than the nam. Nam developes it at hr 42 or before, and those models are still open at hr 42

They are closed off pretty dramatically at hr 45, though...so I would have to figure it ends up being something pretty much similar. They are actually identical (NMM and NAM) at 48 hours with the height lines and shortwave orientation.

[tombo82685]

S'all good.. aside from the late hour, you must also be suffering the pangs of the ignominious eagles loss, especially when the receiver stepped 1/4" out of bounds to negate the late game td!

lol hahaha yea its been a long day lol.

[tombo82685]

They are closed off pretty dramatically at hr 45, though...so I would have to figure it ends up being something pretty much similar. They are actually identical (NMM and NAM) at 48 hours with the height lines and shortwave orientation.

o ok, i was only out to hr 42, cause i know the nam is already closed off, and they arent like the gfs..

[baroclinic_instability]

I don't think the mesoscale models are out to lunch here. There has been a general trend with this storm threat from the start, and that is the global models were too flat in the height field. The mesoscale models were the first to correct and show a much more amplified height field and stronger primary low passing through the OV. With a stronger S/W directing DPVA into that amplified shortwave ridge, the primary low will act to strengthen WAA off the coast and support a stronger secondary low off the coast as the trough continues to propagate eastward. Second, the global models have been slow to correct, and I have noticed, for whatever reason, that the global models will correct their height fields first with the surface development following later. Does this make sense? Not to me, but that is how it generally has worked thus far, especially in the GFS. The mesoscale models have been more correct thus far, but some may have had too much amplification. All of the non-hydrostatic mesoscale models will have an edge over the global models, especially with respect to the intensity of the coastal low when it is undergoing rapid development. Given they are accurate with their initial conditions, I do believe something in between the global operationals and the mesoscale models is realistic--with the track favoring the mesoscale models.

The GFS/ECM operationals have been stalwarts, and they have been very useful because they have made slow trends/changes which are quite easy to interpret even though they have been slow to correct. This is why these models are so useful to forecasters--and why most forecasters don't use the CMC/UK in an operational sense.

[earthlight]

o ok, i was only out to hr 42, cause i know the nam is already closed off, and they arent like the gfs..

Yeah..the MM5 is in the same camp. As are several SREF members. So we have some ammo here...but the Euro ticking east was not what we wanted to see.

[green tube]

I don't think the mesoscale models are out to lunch here. There has been a general trend with this storm threat from the start, and that is the global models were too flat in the height field. The mesoscale models were the first to correct and show a much more amplified height field and stronger primary low passing through the OV. With a stronger S/W directing DPVA into that amplified shortwave ridge, the primary low will act to strengthen WAA off the coast and support a stronger secondary low off the coast as the trough continues to propagate eastward. Second, the global models have been slow to correct, and I have noticed, for whatever reason, that the global models will correct their height fields first with the surface development following later. Does this make sense? Not to me, but that is how it generally has worked thus far, especially in the GFS. The mesoscale models have been more correct thus far, but some may have had too much amplification. All of the non-hydrostatic mesoscale models will have an edge over the global models, especially with respect to the intensity of the coastal low when it is undergoing rapid development. Given they are accurate with their initial conditions, I do believe something in between the global operationals and the mesoscale models is realistic--with the track favoring the mesoscale models.

The GFS/ECM operationals have been stalwarts, and they have been very useful because they have made slow trends/changes which are quite easy to interpret even though they have been slow to correct. This is why these models are so useful to forecasters--and why most forecasters don't use the CMC/UK in an operational sense.

where have you been all my life?

[Absolute Humidity]

Not sure how much I trust the HIRESW as they ARW NMM had 6 to 10" for CTRL Jersey at 36 for Sats event. Think 2.2 was the highest for that area. Of cousre totally different setup.

[baroclinic_instability]

Here is a terrific example of how much the global operational GFS has corrected its height field in two days. Note both the huge amplfication change in the trough as well as the stronger jet max. This will all play a big role in rapid development--and all models are very beefy with the ejecting S/W over the coast. The tightness of the 850/700/surface low is amazing, and this storm will be compact. That is where the mesoscale models will have a distinct advantage.

0Z GFS two days ago verifying at 102 hours:

0Z GFS tonight verifying at 54:

[earthlight]

I don't think the mesoscale models are out to lunch here. There has been a general trend with this storm threat from the start, and that is the global models were too flat in the height field. The mesoscale models were the first to correct and show a much more amplified height field and stronger primary low passing through the OV. With a stronger S/W directing DPVA into that amplified shortwave ridge, the primary low will act to strengthen WAA off the coast and support a stronger secondary low off the coast as the trough continues to propagate eastward. Second, the global models have been slow to correct, and I have noticed, for whatever reason, that the global models will correct their height fields first with the surface development following later. Does this make sense? Not to me, but that is how it generally has worked thus far, especially in the GFS. The mesoscale models have been more correct thus far, but some may have had too much amplification. All of the non-hydrostatic mesoscale models will have an edge over the global models, especially with respect to the intensity of the coastal low when it is undergoing rapid development. Given they are accurate with their initial conditions, I do believe something in between the global operationals and the mesoscale models is realistic--with the track favoring the mesoscale models.

The GFS/ECM operationals have been stalwarts, and they have been very useful because they have made slow trends/changes which are quite easy to interpret even though they have been slow to correct. This is why these models are so useful to forecasters--and why most forecasters don't use the CMC/UK in an operational sense.

I agree with much of your post. Regarding the height field corrections and the surface lag, I have noticed this specifically this winter..but it's there almost every winter when it comes to big surface lows developing off the coast or near the coast. It's there specifically with the globals, too. The GFS is notorious for this. That being said, the GFS is still nothing like the NAM when it comes to it's height field..so we can't say that the surface correction is what's lagging. The surface low track makes sense when you watch the upper air evolution.

The NAM and the higher resolution models (save the Euro) are closing off the H5 534dm contour over Illinois or whereabouts (west of Ohio, where the GFS closes off) while most of the globals are remaining open at that time. It's a small feature, but something to consider. You can also compare the GFS and NAM height lines on the east coast to see how the NAM is backing the height field to south-north along the coast. When the PVA/WAA get going off the coast the surface low tucks northwest as the H5 energy tucks underneath.

That being said..you are 100% correct with the trending on the globals. A bunch of people are ignoring the fact that the globals (all of them... GFS, GGEM, Euro) trended deeper and further south with the shortwave over the MS Valley as it moves east. We are at a breaking point here. Any more amplified with that feature and they would all tuck the low northwest like the NAM. But the NAM can certainly fold..and I have seen it do just that before, multiple times.

[tombo82685]

Not sure how much I trust the HIRESW as they ARW NMM had 6 to 10" for CTRL Jersey at 36 for Sats event. Think 2.2 was the highest for that area. Of cousre totally different setup.

as was the nam, it was pushing almost .5 back towards phl...the globals actually had a more realistic qpf

[baroclinic_instability]

I agree with much of your post. Regarding the height field corrections and the surface lag, I have noticed this specifically this winter..but it's there almost every winter when it comes to big surface lows developing off the coast or near the coast. It's there specifically with the globals, too. The GFS is notorious for this. That being said, the GFS is still nothing like the NAM when it comes to it's height field..so we can't say that the surface correction is what's lagging. The surface low track makes sense when you watch the upper air evolution.

The NAM and the higher resolution models (save the Euro) are closing off the H5 534dm contour over Illinois or whereabouts (west of Ohio, where the GFS closes off) while most of the globals are remaining open at that time. It's a small feature, but something to consider. You can also compare the GFS and NAM height lines on the east coast to see how the NAM is backing the height field to south-north along the coast. When the PVA/WAA get going off the coast the surface low tucks northwest as the H5 energy tucks underneath.

That being said..you are 100% correct with the trending on the globals. A bunch of people are ignoring the fact that the globals (all of them... GFS, GGEM, Euro) trended deeper and further south with the shortwave over the MS Valley as it moves east. We are at a breaking point here. Any more amplified with that feature and they would all tuck the low northwest like the NAM. But the NAM can certainly fold..and I have seen it do just that before, multiple times.

Yeah I don't buy the NAM verbatim as it may be a tad too amped. But I do believe the mesoscale models have been far better with this event thus far, and the global models have been making far larger corrections with respect to the height field. The GFS/ECM show decent development off the coast, but given how fat and directed that S/W is over the coast, I find it difficult to believe there is little to no hook in the track. Given the amazingly compact nature of the low and how fast it develops in all the models, some very mesoscale forcings will be prominent in development which will both slow it down and track it NW with time. There will definitely be feedback here, and the GFS track looks flat given how quickly even it intensifies the storm. Personally I think closer to the mesoscale tracks at this point--but not quite NAM insanity. But it is a close call, 12Z tomorrow will be telling. Usually the global models don't falter this long. Also want to see the ensembles.

Even with the slight east shift on the ECM, the better upper level height field representation is good--imo at least.

[CooL]

i remember this happening with the last storm..But wouldnt the closed 500mb low over the mid atlantic pull the low more nw? gfs and euro seem to be trying to do this but it escapes east instead of getting tucked in towards long island...thanks in advance since this is my last post

[tombo82685]

Yeah I don't buy the NAM verbatim as it may be a tad too amped. But I do believe the mesoscale models have been far better with this event thus far, and the global models have been making far larger corrections with respect to the height field. The GFS/ECM show decent development off the coast, but given how fat and directed that S/W is over the coast, I find it difficult to believe there is little to no hook in the track. Given the amazingly compact nature of the low and how fast it develops in all the models, some very mesoscale forcings will be prominent in development which will both slow it down and track it NW with time. There will definitely be feedback here, and the GFS track looks flat given how quickly even it intensifies the storm. Personally I think closer to the mesoscale tracks at this point--but not quite NAM insanity. But it is a close call, 12Z tomorrow will be telling. Usually the global models don't falter this long. Also want to see the ensembles.

Even with the slight east shift on the ECM, the better upper level height field representation is good--imo at least.

yea the euro looked better with the northern stream diving in more, but the hgts on the east coast were lower compared to the 12z.. If the nam has the same solution as it does tonight tomorrow night, then i think you might have to start giving it some serious thought, if no models have trended towards it. Nam within 48s hrs is what its designed for.

[A-L-E-X]

I wouldn't discount the NAM, the models may still be trending with their surface features to match the upper levels. Like I said before, the gfs is probably the furthest east it can go. With a primary way back inland and a rising NAO, you're not going to have a secondary too far east. I'm actually thinking the NYC area will see 1"+ QPF amounts with this one or a good MECS.

Yeah, I dont get why people are upset over tonight, looks like the "floor" would be about .75 qpf, which is higher than what it was last night. We still have over 36 hours before this thing even starts!

[earthlight]

Yeah I don't buy the NAM verbatim as it may be a tad too amped. But I do believe the mesoscale models have been far better with this event thus far, and the global models have been making far larger corrections with respect to the height field. The GFS/ECM show decent development off the coast, but given how fat and directed that S/W is over the coast, I find it difficult to believe there is little to no hook in the track. Given the amazingly compact nature of the low and how fast it develops in all the models, some very mesoscale forcings will be prominent in development which will both slow it down and track it NW with time. There will definitely be feedback here, and the GFS track looks flat given how quickly even it intensifies the storm. Personally I think closer to the mesoscale tracks at this point--but not quite NAM insanity. But it is a close call, 12Z tomorrow will be telling. Usually the global models don't falter this long. Also want to see the ensembles.

Even with the slight east shift on the ECM, the better upper level height field representation is good--imo at least.

There was definitely a correction on every single one of the globals tonight when you loop through their old 12z runs and tonights 00z runs at H5. I think it's interesting that the Euro looked better with the shortwave over the OH Valley. It was digging it more, somewhere between the NAM and GFS. But it's height field on the East coast was slightly less amplified, so I knew it was going to go a tick east of it's 12z run with the CCB. I think the 00z NAM is a bit of a dream solution, not only with surface low track but with QPF. It's certainly a great case for "save this image", though..because seeing those kind of dynamics and frontogenic developments within 60 hours is very rare.

I'm also perplexed at how strongly the SREF's seem to agree with the NAM's wrapped up solution. They trended about 10m deeper with the surface low on their 21z run in comparison with their 15z run from earlier today.

[Absolute Humidity]

as was the nam, it was pushing almost .5 back towards phl...the globals actually had a more realistic qpf

Thats right, believe it was 12z NAM at 30, basically gave all a 4 to 8" event south of NYC. Not sure if the high res models will be that out to lunch with a Miller B so much with their surface low placement as bad as they were depicting QPF from the last invereted trough.

[A-L-E-X]

Yeah I don't buy the NAM verbatim as it may be a tad too amped. But I do believe the mesoscale models have been far better with this event thus far, and the global models have been making far larger corrections with respect to the height field. The GFS/ECM show decent development off the coast, but given how fat and directed that S/W is over the coast, I find it difficult to believe there is little to no hook in the track. Given the amazingly compact nature of the low and how fast it develops in all the models, some very mesoscale forcings will be prominent in development which will both slow it down and track it NW with time. There will definitely be feedback here, and the GFS track looks flat given how quickly even it intensifies the storm. Personally I think closer to the mesoscale tracks at this point--but not quite NAM insanity. But it is a close call, 12Z tomorrow will be telling. Usually the global models don't falter this long. Also want to see the ensembles.

Even with the slight east shift on the ECM, the better upper level height field representation is good--imo at least.

I remember you said to watch out for convection with the last storm, and this may be the case here also. There were tornadoes in Texas with this and thundersnow was reported in Mississippi, Alabama and Georgia. Just another thing to watch out for-- plus the fact that the winds might be amped up significantly; despite what the know-nothings who believe wind has "no impact"-- most of us know better

[tombo82685]

There was definitely a correction on every single one of the globals tonight when you loop through their old 12z runs and tonights 00z runs at H5. I think it's interesting that the Euro looked better with the shortwave over the OH Valley. It was digging it more, somewhere between the NAM and GFS. But it's height field on the East coast was slightly less amplified, so I knew it was going to go a tick east of it's 12z run with the CCB. I think the 00z NAM is a bit of a dream solution, not only with surface low track but with QPF. It's certainly a great case for "save this image", though..because seeing those kind of dynamics and frontogenic developments within 60 hours is very rare.

I'm also perplexed at how strongly the SREF's seem to agree with the NAM's wrapped up solution. They trended about 10m deeper with the surface low on their 21z run in comparison with their 15z run from earlier today.

yea i was talking to tim about this, cause we both don't think the nam is correct. The interesting thing is, usually the 21z srefs are based off 18z data. The nam at 18z looked like the gfs missed the h5 and escaped east. So you would think with that being like that the 21z srefs would of trended towards less qpf and amplification, but they didnt, they went the other way.

[A-L-E-X]

Thats right, believe it was 12z NAM at 30, basically gave all a 4 to 8" event south of NYC. Not sure if the high res models will be that out to lunch with a Miller B so much with their surface low placement as bad as they were depicting QPF from the last invereted trough.

It would have been nicer if that gulf low tracked all the way up the coast as a Miller A. Oh well.... I guess this goes to refute those who thought NYC doesnt do well in Miller B's.... we dont do as well as SNE, but most Miller B's are at least a moderate hit around here.

[baroclinic_instability]

There was definitely a correction on every single one of the globals tonight when you loop through their old 12z runs and tonights 00z runs at H5. I think it's interesting that the Euro looked better with the shortwave over the OH Valley. It was digging it more, somewhere between the NAM and GFS. But it's height field on the East coast was slightly less amplified, so I knew it was going to go a tick east of it's 12z run with the CCB. I think the 00z NAM is a bit of a dream solution, not only with surface low track but with QPF. It's certainly a great case for "save this image", though..because seeing those kind of dynamics and frontogenic developments within 60 hours is very rare.

I'm also perplexed at how strongly the SREF's seem to agree with the NAM's wrapped up solution. They trended about 10m deeper with the surface low on their 21z run in comparison with their 15z run from earlier today.

Yeah it really comes down to the way the models handle the development of the S/W and its strength as it passes through the OV. The strongest solutions have the strongest wave passing through the OV with a deeper primary, and as a result, a stronger and enhanced region of WAA off the coast with the coastal tucked in farther W. Amazing how identical NAM/GFS are at 48 except the NAM is more intense with the OV S/W with the dual lows phase shifted a tad bit farther W than the GFS.

Either way this will be a fun one to remember see how it plays out.

I remember you said to watch out for convection with the last storm, and this may be the case here also. There were tornadoes in Texas with this and thundersnow was reported in Mississippi, Alabama and Georgia. Just another thing to watch out for-- plus the fact that the winds might be amped up significantly; despite what the know-nothings who believe wind has "no impact"-- most of us know better

Here the non-hydrostatic models will have that edge. All guidance has a large regions of moist conditional instability which will hasten development if it is tapped early enough in the development cycle. Deep convection won't play the same role that the last trough did because the deepest height falls are farther inland early on with the trough traversing more W-E, but low static stability will be important.

[A-L-E-X]

Yeah it really comes down to the way the models handle the development of the S/W and its strength as it passes through the OV. The strongest solutions have the strongest wave passing through the OV with a deeper primary, and as a result, a stronger and enhanced region of WAA off the coast with the coastal tucked in farther W. Amazing how identical NAM/GFS are at 48 except the NAM is more intense with the OV S/W with the dual lows phase shifted a tad bit farther W than the GFS.

Either way this will be a fun one to remember see how it plays out.

Here the non-hydrostatic models will have that edge. All guidance has a large regions of moist conditional instability which will hasten development if it is tapped early enough in the development cycle. Deep convection won't play the same role that the last trough did because the deepest height falls are farther inland early on with the trough traversing more W-E, but low static stability will be important.

Thanks! Do you think the banding will be of the same nature as with the last storm? We had a discussion the other day about how the areas that fall between the cracks of the banding have lower snowfall totals, and how a less intense overrunning storm usually dumps a generally more consistent heavier snowfall. But if Will's March 1960 analog holds true, perhaps we could get the best of both worlds.

[nzucker]

yea i was talking to tim about this, cause we both don't think the nam is correct. The interesting thing is, usually the 21z srefs are based off 18z data. The nam at 18z looked like the gfs missed the h5 and escaped east. So you would think with that being like that the 21z srefs would of trended towards less qpf and amplification, but they didnt, they went the other way.

I don't think anyone honestly believes the NAM's QPF forecast is correct, but it may have the general idea right in tucking the low closer to the coast with H5 closing off....the H7 low also has a beautiful track just south of LI which guarantees that everyone in the metro would see fairly heavy snow, although I do think locations like JFK and the immediate Jersey shore might be dryslotted slightly as the heaviest banding occurs over SW Connecticut through Westchester into the Bronx and N NJ. GFS seems to pull the H7 low away more quickly, which would be a negative for NYC and its NW suburbs but might actually help people in Long Island. I do believe the NAM's QPF is on crack, though; there's just not much precedent for such a wide area receiving nearly 1" liquid in 6 hours, especially with the surface low only deepening to around 990mb. So far, I like a compromise between the NAM and ECM where the heaviest banding yields 12-15" snowfall with most places in the 8-12" category, perhaps 6-10" a bit further SW.

[Absolute Humidity]

It would have been nicer if that gulf low tracked all the way up the coast as a Miller A. Oh well.... I guess this goes to refute those who thought NYC doesnt do well in Miller B's.... we dont do as well as SNE, but most Miller B's are at least a moderate hit around here.

True, we do have a really good Miller B track record for MECs type snows, even Philly, as far as QPF, with all that moisture seen in the water vapor loop down south and west, could we, in fact get the NAM dream do to latient heat being a factor? Its a Miller B so its not truely tapping the gulf, still seems like the NAM should be a bit dryer despite its bomb.

[baroclinic_instability]

Yeah it really comes down to the way the models handle the development of the S/W and its strength as it passes through the OV. The strongest solutions have the strongest wave passing through the OV with a deeper primary, and as a result, a stronger and enhanced region of WAA off the coast with the coastal tucked in farther W. Amazing how identical NAM/GFS are at 48 except the NAM is more intense with the OV S/W with the dual lows phase shifted a tad bit farther W than the GFS.

Either way this will be a fun one to remember see how it plays out.

Here the non-hydrostatic models will have that edge. All guidance has a large regions of moist conditional instability which will hasten development if it is tapped early enough in the development cycle. Deep convection won't play the same role that the last trough did because the deepest height falls are farther inland early on with the trough traversing more W-E, but low static stability will be important.

Another thing I was going to say, A-L-E-X, since you are into this stuff, non-hydrostatic models are currently relegated to the mesoscale models for a reason. There probably won't be any global non-hydrostatic models anytime soon since they are far more sensitive beasts. NAM and others require less aggressive filters to preserve higher resolution features, but this of course means greater noise in the analysis. Moreover, non-hydrostatic models are very sensitive, and this shows up in the NAM with its huge differences run by run. The globals aren't supposed to do this, and one could imagine how bad and dreadful that would be if global models had the same sensitivities as mesoscale non-hydrostatic models.

[earthlight]

We should have a general idea where this is going soon, with the 03z SREFs coming out in a few minutes. Although they are not the best source, they should offer a clue since they were so amped up at 21z.

[A-L-E-X]

I don't think anyone honestly believes the NAM's QPF forecast is correct, but it may have the general idea right in tucking the low closer to the coast with H5 closing off....the H7 low also has a beautiful track just south of LI which guarantees that everyone in the metro would see fairly heavy snow, although I do think locations like JFK and the immediate Jersey shore might be dryslotted slightly as the heaviest banding occurs over SW Connecticut through Westchester into the Bronx and N NJ. GFS seems to pull the H7 low away more quickly, which would be a negative for NYC and its NW suburbs but might actually help people in Long Island. I do believe the NAM's QPF is on crack, though; there's just not much precedent for such a wide area receiving nearly 1" liquid in 6 hours, especially with the surface low only deepening to around 990mb. So far, I like a compromise between the NAM and ECM where the heaviest banding yields 12-15" snowfall with most places in the 8-12" category, perhaps 6-10" a bit further SW.

I think we need to apply the old formula of cutting the NAM qpf in half.... it seems to overdo precip as we get within this time range. Happened with the last storm too and its been a repeating pattern for several years.

[tombo82685]

here are the indiv gfs ens runs