Weekend Threat 12/14-12/15

[Superstorm93]

Players still haven't taken the field yet...

 

Everyone needs to take a deep breathe here. 

 

 

[Zir0b]

Look at these surface temps at the height when the 850`s are plus 3 , This is a major ICE storm for some .

If you live on the south facing shore of Long Island your probably in trouble but for a lot of people on this board , this

not a nasty set up

 

yeah, I think as long as the low is  offshore there is going to be an ice threat perhaps to the city away from the UHI and immediate south or east facing coastlines 

[donsutherland1]

With respect to the NAM and GFS (12z guidance), both models are far apart. Below is a chart that shows a key 500 mb difference and then the key difference at the surface.

 

 

The NAM has a lot more energy that leads to the development of a closed low in the Deep South. That solution mitigates the ability of a primary low to quickly warm the mid-levels of the atmosphere. In contrast, the GFS lacks such a closed low. As a result, the weak primary low it shows pushing into eastern Ohio/western Pennsylvania rapidly warmes the mid-levels of the atmosphere. Secondary development occurs too late to prevent that dramatic warming of the mid-levels of the atmosphere or to bring precipitation back to accumulating snow.

 

 

The end result on the GFS is a period of snow followed by sleet/freezing rain and then rain in the NYC metro area (a more prolonged period of freezing rain in NYC's suburbs). The NAM ends at 84 hours, but would possibly translate into greater qpf and a snowier outcome than the GFS (perhaps something closer to what the 0z ECMWF had suggested in terms of snowfall).

[NEG NAO]

With respect to the NAM and GFS (12z guidance), both models are far apart. Below is a chart that shows a key 500 mb difference and then the key difference at the surface.

 

 

The NAM has a lot more energy that leads to the development of a closed low in the Deep South. That solution mitigates the ability of a primary low to quickly warm the mid-levels of the atmosphere. In contrast, the GFS lacks such a closed low. As a result, the weak primary low it shows pushing into eastern Ohio/western Pennsylvania rapidly warmes the mid-levels of the atmosphere. Secondary development occurs too late to prevent that dramatic warming of the mid-levels of the atmosphere or to bring precipitation back to accumulating snow.

 

 

The end result on the GFS is a period of snow followed by sleet/freezing rain and then rain in the NYC metro area (a more prolonged period of freezing rain in NYC's suburbs). The NAM ends at 84 hours, but would possibly translate into greater qpf and a snowier outcome than the GFS (perhaps something closer to what the 0z ECMWF had suggested in terms of snowfall).

so now the BIG questions are: 

 

1. Does the GFS trend toward the Euro solution ?

 

2. Does the Euro trend toward the GFS solution ?

 

3. Do they meet somewhere in the middle ?

 

Which one do you choose ?

[jm1220]

With respect to the NAM and GFS (12z guidance), both models are far apart. Below is a chart that shows a key 500 mb difference and then the key difference at the surface.

 

 

The NAM has a lot more energy that leads to the development of a closed low in the Deep South. That solution mitigates the ability of a primary low to quickly warm the mid-levels of the atmosphere. In contrast, the GFS lacks such a closed low. As a result, the weak primary low it shows pushing into eastern Ohio/western Pennsylvania rapidly warmes the mid-levels of the atmosphere. Secondary development occurs too late to prevent that dramatic warming of the mid-levels of the atmosphere or to bring precipitation back to accumulating snow.

 

 

The end result on the GFS is a period of snow followed by sleet/freezing rain and then rain in the NYC metro area (a more prolonged period of freezing rain in NYC's suburbs). The NAM ends at 84 hours, but would possibly translate into greater qpf and a snowier outcome than the GFS (perhaps something closer to what the 0z ECMWF had suggested in terms of snowfall).

Thanks a lot, Don and great analysis as always. The NAM looked to warm the surface up too quickly at the end of its run-when it gets past 60 hours it's usually for entertainment purposes only. It would likely be several inches of snow for everyone verbatim.

[REDMK6GLI]

With respect to the NAM and GFS (12z guidance), both models are far apart. Below is a chart that shows a key 500 mb difference and then the key difference at the surface.

The NAM has a lot more energy that leads to the development of a closed low in the Deep South. That solution mitigates the ability of a primary low to quickly warm the mid-levels of the atmosphere. In contrast, the GFS lacks such a closed low. As a result, the weak primary low it shows pushing into eastern Ohio/western Pennsylvania rapidly warmes the mid-levels of the atmosphere. Secondary development occurs too late to prevent that dramatic warming of the mid-levels of the atmosphere or to bring precipitation back to accumulating snow.

The end result on the GFS is a period of snow followed by sleet/freezing rain and then rain in the NYC metro area (a more prolonged period of freezing rain in NYC's suburbs). The NAM ends at 84 hours, but would possibly translate into greater qpf and a snowier outcome than the GFS (perhaps something closer to what the 0z ECMWF had suggested in terms of snowfall).

This is going to be fun today when the 12z euro finally starts running. My main harbinger if you will is the cold air and high pressure for the weekend. The location of that is going to be very important for both the primary and secondary development in my opinion. Judging by todays runs so far models have trended colder ( degrees varying ) and euro being the coldest/snowiest solution out of the bunch. Trends for a colder solution are apparent we just got to wait till i'd say 0z suite and 06z/12z suite tommorow for more definitive answers as far as what were looking at.

[IsentropicLift]

Sounds like they are thinking warning criteria event.

 

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NEW YORK NY
1004 AM EST WED DEC 11 2013

CTZ005>012-NJZ002-004-006-103>108-NYZ067>075-078>081-176>179-121515-
NORTHERN FAIRFIELD-NORTHERN NEW HAVEN-NORTHERN MIDDLESEX-
NORTHERN NEW LONDON-SOUTHERN FAIRFIELD-SOUTHERN NEW HAVEN-
SOUTHERN MIDDLESEX-SOUTHERN NEW LONDON-WESTERN PASSAIC-
EASTERN PASSAIC-HUDSON-WESTERN BERGEN-EASTERN BERGEN-WESTERN ESSEX-
EASTERN ESSEX-WESTERN UNION-EASTERN UNION-ORANGE-PUTNAM-ROCKLAND-
NORTHERN WESTCHESTER-SOUTHERN WESTCHESTER-NEW YORK (MANHATTAN)-BRONX-
RICHMOND (STATEN ISLAND)-KINGS (BROOKLYN)-NORTHWESTERN SUFFOLK-
NORTHEASTERN SUFFOLK-SOUTHWESTERN SUFFOLK-SOUTHEASTERN SUFFOLK-
NORTHERN QUEENS-NORTHERN NASSAU-SOUTHERN QUEENS-SOUTHERN NASSAU-
1004 AM EST WED DEC 11 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHERN
CONNECTICUT...NORTHEAST NEW JERSEY AND SOUTHEAST NEW YORK.

.DAY ONE...TODAY AND TONIGHT.

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

THERE IS THE POTENTIAL FOR A SIGNIFICANT WINTER STORM FROM LATE
SATURDAY THROUGH SUNDAY. AT THIS TIME THE BEST CHANCE FOR A
SIGNIFICANT ACCUMULATION OF SNOW IS ACROSS NORTHERN INTERIOR
PORTIONS OF THE TRI-STATE...WITH A WINTRY MIX MORE LIKELY AT
COASTAL AREAS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

&&

THIS HAZARDOUS WEATHER OUTLOOK PROVIDES A SUMMARY OF POTENTIAL
WIDESPREAD HAZARDOUS WEATHER EVENTS THAT MAY REACH NWS WARNING
CRITERIA. MOST LONG FUSED NWS WATCHES...WARNINGS AND ADVISORIES IN
EFFECT ARE HIGHLIGHTED.

PLEASE REFER TO THE LATEST NWS FORECASTS FOR WEATHER NOT MEETING NWS
WARNING CRITERIA.

$$

 

[MJO812]

12z GGEM is a close call for the coast but just to the northwest of the city, a nice snowfall occurs.

 

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

[IsentropicLift]

[NycStormChaser]

What are the winds forecasted to be? Working on a boat always sucks during these storms in NY harbor

[IsentropicLift]

12z GGEM is a close call for the coast but just to the northwest of the city, a nice snowfall occurs.

 

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

That shows 12 hours straight of moderate snow or better but it was severely overdone with Mondays system at this range.

[PB GFI]

I pulled this off New England thread , if u wana see how close gthe surface is . its 31- 34 on a line from N/S border  of Long Island down through CNJ , Its  28 -31 once on the other side of the river . Not the final result , but the set up should give forecasters headaches

[Stormlover74]

What are the winds forecasted to be? Working on a boat always sucks during these storms in NY harbor

Way too early to tell

[dbc]

With respect to the NAM and GFS (12z guidance), both models are far apart. Below is a chart that shows a key 500 mb difference and then the key difference at the surface.

 

 

The NAM has a lot more energy that leads to the development of a closed low in the Deep South. That solution mitigates the ability of a primary low to quickly warm the mid-levels of the atmosphere. In contrast, the GFS lacks such a closed low. As a result, the weak primary low it shows pushing into eastern Ohio/western Pennsylvania rapidly warmes the mid-levels of the atmosphere. Secondary development occurs too late to prevent that dramatic warming of the mid-levels of the atmosphere or to bring precipitation back to accumulating snow.

 

 

The end result on the GFS is a period of snow followed by sleet/freezing rain and then rain in the NYC metro area (a more prolonged period of freezing rain in NYC's suburbs). The NAM ends at 84 hours, but would possibly translate into greater qpf and a snowier outcome than the GFS (perhaps something closer to what the 0z ECMWF had suggested in terms of snowfall).

 

 

so now the BIG questions are: 

 

1. Does the GFS trend toward the Euro solution ?

 

2. Does the Euro trend toward the GFS solution ?

 

3. Do they meet somewhere in the middle ?

 

Which one do you choose ?

Hard to say. You need to account for known biases too. The GFS has been observed to overdo primary lows countless times in setups like this. The way I determine if the GFS makes sense is based on analysis of what type of confluence is the primary driving into. If the confluence showing up on the GFS appears to be as strong as other modeling not showing a primary bulldozing the same strength of confluence you have to raise a red flag on the GFS simply due to it's known bias. The GFS also has a bias of pushing coastals too far south and east at times so that would also come into play in this situation as well.

[WeatherFox]

so now the BIG questions are: 

 

1. Does the GFS trend toward the Euro solution ?

 

2. Does the Euro trend toward the GFS solution ?

 

3. Do they meet somewhere in the middle ?

 

Which one do you choose ?

Mets & pros lean heavily to the Euro based on past results and known biases.

[kpantz]

GEM would be a moderate snow for the interior. Trying to sum up the individual QPF maps gives me something like ,3-.5", so maybe not quite warning criteria.  Seems to fit the idea of a respectable early season snowfall to the north and west of the mixing line.

[IsentropicLift]

12z GFS bufkit numbers

 

KMMU - SN-1.7" ZR-0.18"

KLGA - SN-0.0" ZR-0.0"

KISP - SN-0.2" ZR-0.0"

KHPN - SN-2.7" ZR-0.15"

KSWF - SN-3.4" ZR-0.05"

[Zir0b]

GGEM seems like a quick thump of snow for most

 

 

 

[SnowGoose69]

12z GFS bufkit numbers

 

KMMU - SN-1.7" ZR-0.18"

KLGA - SN-0.0" ZR-0.0"

KISP - SN-0.2" ZR-0.0"

KHPN - SN-2.7" ZR-0.15"

KSWF - SN-3.4" ZR-0.05"

That does not seem right, I'm getting 2.2 inches at LGA on BUFKIT

[IsentropicLift]

That does not seem right, I'm getting 2.2 inches at LGA on BUFKIT

This is what I use

 

http://www.meteor.iastate.edu/~ckarsten/cobb/cobb.php?model=gfs&site=klga

[IsentropicLift]

The features are in a good spot, we just need more robust development of the secondary low like the NAM and Euro show.

 

[kpantz]

That does not seem right, I'm getting 2.2 inches at LGA on BUFKIT

Same as you.

[IsentropicLift]

Subtle variances in the handling of jet interactions is playing havoc with the deteministic coherence to put it nicely ... Basically, the GFS ...as of 06z, decides to back off the "digginess" of the N-stream, as the TV S-stream S/W skirts by underneath.  The somewhat better N-stream digging of previous runs caused the whole scale flow to "tilt" more meridian-like along the EC, and that foisted the S-stream S/W more normal to the thermal fields/BL cold ...inducing better/stronger cyclogenesis.   

 

The 00z Euro appears to have a slightly more sheared out system for different reason altogether, regarding an overall weaker appeal with the Pacific intermediate stream wind max.   (I think that is also what confused some folks into thinking triple phase earlier in this thread?)  Anyway, that piece of wind dynamics phased in with the S-stream S/W more proficiently in the previous runs, and therefore when the total of it all turned the corner you had more energy aloft coming to the party (so to speak...)

 

Actually, now that I checked again, the 06z and 12z oper. GFS also has slightly less intermediate stream relay off the Pac (if the N-stream concerns were not enough...).

 

Ugh.  Oy vay.  What a big flappin' cluster this whole thing is turning into.   

[bluewave]

Very had to avoid a mixed precip event here with the +AO spiking above +4.

It creates enough of a SE ridge for WAA at 850-950 mb.

 

[Ralph Wiggum]

The features are in a good spot, we just need more robust development of the secondary low like the NAM and Euro show.

 

850 low in ov and hp 300 miles too far north are good spots? Seriously?

[IsentropicLift]

850 low in ov and hp 300 miles too far north are good spots? Seriously?

The 850 low in the OV isn't a problem at all. And really 300 miles too far north? You must be joking

[REDMK6GLI]

850 low in ov and hp 300 miles too far north are good spots? Seriously?

Think the better term is overall its headed in the "right" direction. Whether or not it will be good enough for a signifigant storm for even the coast is yet to be determined. The players are not in ideal positions.... Yet

[Ralph Wiggum]

850 low in ov and hp 300 miles too far north are good spots? Seriously?

The 850 low in the OV isn't a problem at all. And really 300 miles too far north? You must be joking

For my area I should have clarified

[Ralph Wiggum]

850 low in ov and hp 300 miles too far north are good spots? Seriously?

The 850 low in the OV isn't a problem at all. And really 300 miles too far north? You must be joking

And an 850 low travelling to your west is a real and true problem

[IsentropicLift]

For my area I should have clarified

Is it the greatest setup of all time? By no means but it's enough to get the job done.