Jan 23/24 Major Coastal Storm Discussion

[Superstorm93]

The NAM has some of the most intense banding I've seen modeled since Boxing Day 

 

Now, It wont likely happen in this region, but this is still an indicator that we have a ton of mesoscale features to work out in the short range. 

 

[ag3]

Model noise? Maybe for the city

The northwest fringe of the storm has shifted nearly 100 miles since the GGEM big hits

Could be over correction. I wouldn't worry until inside of 24 hours.

[UlsterCountySnowZ]

Could be over correction. I wouldn't worry until inside of 24 hours.

I'm still not buying any solution either way till atleast 00z Friday, so much room for error on both sides and uncertainty

[gravitylover]

Hopefully this doesn't get seen as an IMBY post but as you reach into northern Westchester the ridgelines start to run N/S and with an E/NE wind direction we tend to have slightly higher snowfall totals so hopefully my southern Putnam location on the east slop of a significant hill gives me closer to a foot than six inches.  Ehh, whatever I get is good, in fact less would be ok.

[Blizzard-on-GFS]

What's the basis for your opinion?

The doubled barrel low is often dismissed but I've seen it verify quite often. The CMC IMO displays this evolution very realistically. All that convection offshore alludes to that second low forming, as the primary can't push further north past the Delmarva the second low starts to take over and robs the primary of its moisture as the precip shield elongates. We still get hit hard but we miss out the the huge amounts you'll see around DC. This storm screams mid-Atlantic special and I don't think we see amounts over 10" north of NYC. Just my thoughts at the moment. The banding potential with this storm is through the roof so mesoscale features will be critical to snow amounts; we could end up seeing a large discrepancy in accumulations with some surprise locations north and west cashing in. This double barreled low evolution makes this forecast a lot trickier than it had appeared a day ago... Still a lot of details to iron out.

[SnowGoose69]

The doubled barrel low is often dismissed but I've seen it verify quite often. The CMC IMO displays this evolution very realistically. All that convection offshore alludes to that second low forming, as the primary can't push further north past the Delmarva the second low starts to take over and robs the primary of its moisture as the precip shield elongates. We still get hit hard but we miss out the the huge amounts you'll see around DC. This storm screams mid-Atlantic special and I don't think we see amounts over 10" north of NYC. Just my thoughts at the moment. The banding potential with this storm is through the roof so mesoscale features will be critical to snow amounts; we could end up seeing a large discrepancy in accumulations with some surprise locations north and west cashing in. This double barreled low evolution makes this forecast a lot trickier than it had appeared a day ago... Still a lot of details to iron out.

I would buy the double barreled low idea more if it was occurring off the carolinas. I'm not as sure I believe it happening as far north

[snywx]

I would buy the double barreled low idea more if it was occurring off the carolinas. I'm not as sure I believe it happening as far north

 

Why? I would think the opposite. 

[SnowGoose69]

Why? I would think the opposite.

Because it can often be convectively related, it's less likely to see convection occurring that far north in these systems than say off South Carolina

[cjr231]

The doubled barrel low is often dismissed but I've seen it verify quite often. The CMC IMO displays this evolution very realistically. All that convection offshore alludes to that second low forming, as the primary can't push further north past the Delmarva the second low starts to take over and robs the primary of its moisture as the precip shield elongates. We still get hit hard but we miss out the the huge amounts you'll see around DC. This storm screams mid-Atlantic special and I don't think we see amounts over 10" north of NYC. Just my thoughts at the moment. The banding potential with this storm is through the roof so mesoscale features will be critical to snow amounts; we could end up seeing a large discrepancy in accumulations with some surprise locations north and west cashing in. This double barreled low evolution makes this forecast a lot trickier than it had appeared a day ago... Still a lot of details to iron out.

 

Great post. I hate the dismissals that it can't happen. It certainly could. The GGEM's evolution looks more realistic than the GFS's to me at this point. 

[snywx]

Because it can often be convectively related, it's less likely to see convection occurring that far north in these systems than say off South Carolina

 

Wouldn't you think it would feel the confluence more as it heads N hence why its trying to reform E? 

 

I mean you can clearly see it on the GGEM. Its getting squashed from the north so it tries to reform E twice within a 10 hr period.

[Drz1111]

Because it can often be convectively related, it's less likely to see convection occurring that far north in these systems than say off South Carolina

Right.  Don't confuse anomalies with absolute temp.  It's warmer than normal offshore but still 10-15C cooler than off Hatteras.

[SnowGoose69]

Wouldn't you think it would feel the confluence more as it heads N hence why its trying to reform E?

I mean you can clearly see it on the GGEM. Its getting squashed from the north so it tries to reform E twice within a 10 hr period.

It's certainly possible it could be doing it for that reason as well. 2/6/10 I believe went double barreled for that reason

[Ralph Wiggum]

The doubled barrel low is often dismissed but I've seen it verify quite often. The CMC IMO displays this evolution very realistically. All that convection offshore alludes to that second low forming, as the primary can't push further north past the Delmarva the second low starts to take over and robs the primary of its moisture as the precip shield elongates. We still get hit hard but we miss out the the huge amounts you'll see around DC. This storm screams mid-Atlantic special and I don't think we see amounts over 10" north of NYC. Just my thoughts at the moment. The banding potential with this storm is through the roof so mesoscale features will be critical to snow amounts; we could end up seeing a large discrepancy in accumulations with some surprise locations north and west cashing in. This double barreled low evolution makes this forecast a lot trickier than it had appeared a day ago... Still a lot of details to iron out.

I agree with you analysis 100% regarding confluence not allowing it farther north, possible dual low/relocation of center, etc. However, when guidance is showing a capture is taking place or imminent at best, a center jump of that nature doesn't jive. As I stated earlier, I think guidance will waffle with the capture vs non capture right up til the storm and we will be nowcasting this feature.

And unfortunately, this will be the difference between a 8-16" vs 12-24" storm for some.

[snywx]

It's certainly possible it could be doing it for that reason as well. 2/6/10 I believe went double barreled for that reason

 

I hate to be using the GGEM as an example but at Hr 78 you can clearly see it pump the brakes and actually start heading S before reforming to the E. Interesting, time will tell I guess

[TheManWithNoFace]

'96 had that 'lobing' feature that I mentioned. You can see it on the last few panels.

http://www.raymondcmartinjr.com/weather/1996/07-Jan-96-SeaLevelPressure.html

[Rittenhouse]

The GFS has moved south considerably over the past 36 hours. The precip maps seem overdone for our area. Upton says this in their AFD. Look at the upper air map. The low was once over the Delmarva, now it is over Cape Hatteras...on the GFS.

 

This has major bust material written all over it. There is a lot of wishful thinking going on here. This is clearly looking like a NoVa/DC storm. The Euro's accuracy rate has been higher over the past week (see Ryan Maue's tweet). The only thing we have on our side is climatology. If there's no northward shift by the 0z runs tonight, it's time to call this off for us and hope we can sneak an advisory level snowfall.

[Blizzard-on-GFS]

I agree with you analysis 100% regarding confluence not allowing it farther north, possible dual low/relocation of center, etc. However, when guidance is showing a capture is taking place or imminent at best, a center jump of that nature doesn't jive. As I stated earlier, I think guidance will waffle with the capture vs non capture right up til the storm and we will be nowcasting this feature.

And unfortunately, this will be the difference between a 8-16" vs 12-24" storm for some.

I agree with you analysis as well. I could honestly see this going either way, however I do sense that the models are starting to converge on the double low solution. Hopefully this trend will not continue.

[allgame830]

The GFS has moved south considerably over the past 36 hours. The precip maps seem overdone for our area. Upton says this in their AFD. Look at the upper air map. The low was once over the Delmarva, now it is over Cape Hatteras...on the GFS.

 

This has major bust material written all over it. There is a lot of wishful thinking going on here. This is clearly looking like a NoVa/DC storm. The Euro's accuracy rate has been higher over the past week (see Ryan Maue's tweet). The only thing we have on our side is climatology. If there's no northward shift by the 0z runs tonight, it's time to call this off for us and hope we can sneak an advisory level snowfall.

 

As it stands right now.... advisory snowfall would be at the minimum.  Even with the current depiction the GFS and GGEM still give the area 6-12 inches.  Let's see what the EURO has in store for us in a few.

[Drz1111]

The GFS has moved south considerably over the past 36 hours. The precip maps seem overdone for our area. Upton says this in their AFD. Look at the upper air map. The low was once over the Delmarva, now it is over Cape Hatteras...on the GFS.

 

This has major bust material written all over it. There is a lot of wishful thinking going on here. This is clearly looking like a NoVa/DC storm. The Euro's accuracy rate has been higher over the past week (see Ryan Maue's tweet). The only thing we have on our side is climatology. If there's no northward shift by the 0z runs tonight, it's time to call this off for us and hope we can sneak an advisory level snowfall.

Dude, that's a 100mi shift of a 500mb low from model runs 2 days apart.  That's not "considerably south", nor is it a "shift".  You're cherry picking

[Drz1111]

As it stands right now.... advisory snowfall would be at the minimum.  Even with the current depiction the GFS and GGEM still give the area 6-12 inches.  Let's see what the EURO has in store for us in a few.

 

As it stands, the GFS and GGEM give NYC 12-24".  Don't know where you're getting 6-12" from. 

[MikeS]

Dude, that's a 100mi shift of a 500mb low from model runs 2 days apart.  That's not "considerably south", nor is it a "shift".  You're cherry picking

 

Agreed.

[IsentropicLift]

Confluence is weaker on the Euro and heights are building along the coast quicker.

[Zelocita Weather]

As it stands, the GFS and GGEM give NYC 12-24".  Don't know where you're getting 6-12" from. 

 

Indeed, NAM, GFS, GGEM all 1-2' for almost all this subforum...awaiting the Euro

[IsentropicLift]

The 500mb low is also in Central MS while the 00z run had it over Eastern Louisiana. Not a big jump but a favorable shift.

[jm1220]

This will likely be a storm that goes from a foot to little within 50 miles like 2/6/10. The dry air coming in on the north side means the sharp cutoffs shown on the NAM and GGEM are likely right. Hopefully for NYC these south trends stop, since although the confluence doesn't look as strong as that was, there will be a definite heartbreak zone north of where the banding can set up.

[allgame830]

As it stands, the GFS and GGEM give NYC 12-24".  Don't know where you're getting 6-12" from. 

 

Sorry was just being conservative... I also live 20 miles directly north of NYC so I think I would fair fine as well by looking at the 12z model suite thus far.

[SnoSki14]

I see models eventually ticking further north with the precip shield starting tomorrow (maybe tonight). The confluence issue is nowhere near what Feb 2010 was.

We want the storm to stay amped up and a negative trough to really benefit and avoid a significant decline in potential snowfall totals.

[Rittenhouse]

Dude, that's a 100mi shift of a 500mb low from model runs 2 days apart.  That's not "considerably south", nor is it a "shift".  You're cherry picking

 

It's enough to hold the bulk of the precip south of us. Serious question: how far can mesoscale banding occur from the center of low pressure? Right now, pretty much all the guidance is outside the BM. If you look at the precip map, everything looks fine and dandy, but the upper air maps look very close to the Euro runs. Not sure how we're supposed to get a foot of snow if the low tracks due east of the Outer Banks.

[IsentropicLift]

The trough doesn't dig nearly as far South, this looks significantly better through 60hrs.

[IsentropicLift]

The Northeast edge of the precip shield is advancing roughly 3 hours quicker to the NE.