December 14/15 winter storm threat

[Ginx snewx]

Well rounds 1+2 0z wise were wins, Euro should be fun, hope it stays with that 19th sig too

[CoastalWx]

Yea, I suppose The Storm of the Century would offer a good rebuttal to a rule of thumb lol

Just a bit of isentropic lift

Just popped in my head. That storm still has the greatest obs ever coming out of Logan.

[40/70 Benchmark]

Just popped in my head. That storm still has the greatest obs ever coming out of Logan.

Track that bad Larry 100 miles to the east

[powderfreak]

This would probably be pretty decent for a lot of folks...roughly 36 hour storm? 

 

 

 

 

[centralmass]

This would probably be pretty decent for a lot of folks...roughly 36 hour storm?

 

Here is an hour by hour look at that.

[powderfreak]

Here is an hour by hour look at that.

 

That would work for a very large chunk of New England...impressive.

[mahk_webstah]

HPC on board.  One of the best discussions in a while!  Triple phase.

 

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1206 AM EST WED DEC 11 2013

VALID 12Z SAT DEC 14 2013 - 12Z WED DEC 18 2013


...MAJOR WINTER STORM THIS WEEKEND FROM THE CENTRAL APPALACHIANS
TO THE NORTHEAST...
...SHARP ARCTIC OUTBREAK FOR THE UPPER MIDWEST SUNDAY AND MONDAY...

RELIED ON THE 12Z/10 ECMWF FOR THIS FORECAST PACKAGE, WHICH SHOWED
A STRONG POSITIVE CORRELATION WITH BOTH THE ECENS AND CMCE MEANS
FROM THAT DATA CYCLE, AS WELL AS THE 00Z/11 GFS. THE MOST CRITICAL
REGIONS IN TERMS OF MODEL SPREAD VIS-A-VIS SENSIBLE WEATHER
THREATS ARE THE MIDWEST AND EAST COAST, WHERE SEVERAL SHORTWAVES
ARE EXPECTED TO CONVERGE. THE DISJOINTED NATURE OF THE COMPLEX
FLOW PATTERN EVOLVING OVER THE EASTERN HALF OF THE NATION THIS
WEEKEND MAKES FORECASTING WHERE SPECIFIC HAZARDS WILL OCCUR QUITE
DICEY. THE INTEGRITY OF THE COLD AIR BANKED FROM THE GREAT LAKES
TO NEW ENGLAND IS CRUCIAL FOR PRECIPITATION TYPE. THE DUMBBELLING
OF MID-LEVEL VORTICES WILL DICTATE WHERE MOISTURE WILL CONVERGE
AND WHERE DRY SLOTS WILL BE FORCED. AT THIS POINT, THE MOST LIKELY
DETERMINISTIC OUTCOME WOULD BE FOR A TRANSFER OF SURFACE LOW
PRESSURE FROM THE OHIO VALLEY TO THE MID ATLANTIC COAST SATURDAY
NIGHT, WITH A SUBSEQUENT BOMBING OF THE ATLANTIC LOW AS AN ARCTIC
VORTEX PLUNGES INTO THE GREAT LAKES SUNDAY AND SUNDAY NIGHT. THE
PRECISE INTERACTION BETWEEN THE GREAT LAKES VORTEX AND THE NEW
ENGLAND COASTAL LOW WILL DETERMINE HOW SEVERE THE WINTER
CONDITIONS BECOME OVER THE NORTHEAST--AND HOW CLOSE SNOW AND ICE
GET TO THE MAJOR CITIES FROM WASHINGTON TO BOSTON. ANOTHER
ATLANTIC COASTAL LOW AT THE END OF PERIOD--NEXT WEDNESDAY--COULD
REINVIGORATE WINTER WEATHER FOR THE NORTHEAST METROPOLITAN
CORRIDOR.

THE ARCTIC VORTEX DROPPING INTO THE GREAT LAKES SUNDAY WILL DRAW
SOME OF THE COLDEST AIR OF THE SEASON SO FAR INTO THE UPPER
MIDWEST. PARTS OF EASTERN NORTH DAKOTA AND NORTHERN MINNESOTA MAY
NOT GET ABOVE ZERO FOR A 36-HOUR PERIOD SUNDAY AND MONDAY, WITH
MINIMUM TEMPERATURES NEARING THIRTY DEGREES BELOW NORMAL IN THAT
REGION.

OVER THE WEST, THE SPLIT IN THE WESTERLIES OFF THE PACIFIC COAST
SHOULD KEEP THE SOUTHWEST DRY AND THE NORTHWEST--ESPECIALLY ALONG
AND WEST OF THE CASCADES--UNSETTLED.

[jamesnichols1989]

Three jet streams get involved on this storm, so a triple phase is certainly possible.

[ctsnowstorm628]

Euro is way flatter...something weird is going on at 500mb there. Everything is way off.

 

High is stronger too.

[ORH_wxman]

Euro is actually colder/SE of the 12z run...that high is a beast.

[dryslot]

.50-.75" qpf

[dendrite]

Three jet streams get involved on this storm, so a triple phase is certainly possible.

lol what?

[It's Always Sunny]

Three jet streams get involved on this storm, so a triple phase is certainly possible.

Pretty sure there's just two. Polar and Subtropical.

[dendrite]

Pretty sure there's just two. Polar and Subtropical.

Triple phases are a rare thing. I save the term for storms like Mar '93.

[It's Always Sunny]

Triple phases are a rare thing. I save the term for storms like Mar '93.

Yeah I was a bit too young to remember that. You would need like a nose diving Arctic Jet to mingle with the Polar Jet. I'm coming off a mid shift so my mind can't really comprehend this phenomena right now lol.

[dendrite]

ecens get the 0.75" mean line about 1 county inland through coastal ME from Eastport down through CON-ORH-KHYPE-BDR. 0.50" wiggles around far NNE.

[dendrite]

I'm half awake and haven't looked at much yet, but the euro op/6z gfs look dynamically weaker. We get less of a front end thump and it becomes more of a prolonged -SN/OCNL SN. At least the ecens are juicier than the op. Anyways, hopefully we don't see vort swinging through weakening again as we approach T-0hr. This probably works out better for far SE folks though. I'll take the 0z GGEM though.

[mahk_webstah]

Yeah I was a bit too young to remember that. You would need like a nose diving Arctic Jet to mingle with the Polar Jet. I'm coming off a mid shift so my mind can't really comprehend this phenomena right now lol.

Well I'm not a meteorologist, nor did I stay at a Holiday Inn late night, but the HPC discussion (see above) describes an arctic shortwave diving in and causing deepening of the low when it is off the coast.

[N. OF PIKE]

Did this slow down a bit in last 36 hrs?

[Randy4Confluence]

For the newbies, and those who just don't know....think of a low pressure system as a cylinder stretching from se to nw throughout all levels of the atmosphere.....surface being lowest, and furthest se, and H7 being highest, and furthest nw....you want to be just to the nw of the entire cylinder...ie, just nw of the H7 low.

Obviously, as a major cyclone matures, the surface and H7 become vertically stacked, and it occludes, but systems at their most prolific stages are elongated se to nw throughout the atmosphere.

Thanks good stuff. So 700 lows arr higher up than 500 lows? I've always deduced,from reading posts, that 500 lows, or "Upper Level Lows" are higher but I guess not?

[SnowMan]

Thanks good stuff. So 700 lows arr higher up than 500 lows? I've always deduced,from reading posts, that 500 lows, or "Upper Level Lows" are higher but I guess not?

I believe 500 lows are higher...

[SnowGoose69]

Did this slow down a bit in last 36 hrs?

 

I did not pay much attention to timing but its entirely possible it did slightly, the models tend to be a bit too fast with systems beyond day 4 and 5, more so in summer than winter but still a bit in winter, I mentioned in the NYC thread 2 days ago that would lead to the high having more time to get in place north of us if the system ended up 24 hours later which could lead to more overrunning snows but also potentially cause the system to be more suppressed in the end and less phased.

[moneypitmike]

Pretty disappointing EC, and the 06z GFS blows--relatively speaking.  Hopefully things will revert to stronger/nw solutions.

[mahk_webstah]

I did not pay much attention to timing but its entirely possible it did slightly, the models tend to be a bit too fast with systems beyond day 4 and 5, more so in summer than winter but still a bit in winter, I mentioned in the NYC thread 2 days ago that would lead to the high having more time to get in place north of us if the system ended up 24 hours later which could lead to more overrunning snows but also potentially cause the system to be more suppressed in the end and less phased.

will be interesting to see if this is the trend.  Broadly speaking I would expect it to trend more s and e on the runs, for a day or 2 and then come back partly nw.  I thikn we often se that with model depictions in big storms...they sniff them out 6-7 days, the models waffle or trend, and then come back closer to the 6-7 day outcome.

[Randy4Confluence]

Weather Channel has me with snow showers and <1 inch on Sat....what the Sam hell?

[ice1972]

Thanks good stuff. So 700 lows arr higher up than 500 lows? I've always deduced,from reading posts, that 500 lows, or "Upper Level Lows" are higher but I guess not?

500 Upper Level

700 Mid Level

850 Low Level

925 Surface (well just off the deck - forget about how high this is)

[weathafella]

500 Upper Level

700 Mid Level

850 Low Level

925 Surface (well just off the deck - forget about how high this is)

While I'm not positive I think 700/850 are mid levels. 850 is about 5,000 feet so it would be hard for me to conjure that as low level.

Think of it this way:

300: jet stream

500: 18,000

700: 10,000

850: 5,000

925: 2,000

[CoastalWx]

Pretty disappointing EC, and the 06z GFS blows--relatively speaking. Hopefully things will revert to stronger/nw solutions.

You're fine.

[ice1972]

While I'm not positive I think 700/850 are mid levels. 850 is about 5,000 feet so it would be hard for me to conjure that as low level.

Think of it this way:

300: jet stream

500: 18,000

700: 10,000

850: 5,000

925: 2,000

Excellent....thanks....I remember the order but never knew the actual altitude....I believe the altitudes fluctuate up and down around those numbers you posted....

[CoastalWx]

Excellent....thanks....I remember the order but never knew the actual altitude....I believe the altitudes fluctuate up and down around those numbers you posted....

Yes.