Do We have one More in Us?

[JC-CT]

Just remember the NAM is non-hydrostatic which means it is prone to blowing up lows and allowing it to go way west than it should. I will remind folks that the NAM brought the Feb 2013 blizzard over HYA 36-42 hrs out so it's basically useless right now.

 

Nobody here will disagree on that point. But the major changes weren't at 36-42 hours, the surface low is 100 miles west at hour 18 vs hour 24 from 12z.

[dryslot]

Just remember the NAM is non-hydrostatic which means it is prone to blowing up lows and allowing it to go way west than it should. I will remind folks that the NAM brought the Feb 2013 blizzard over HYA 36-42 hrs out so it's basically useless right now.

 

And its doing just that it way NW, Snow back past NYC

[Typhoon Tip]

Just remember the NAM is non-hydrostatic which means it is prone to blowing up lows and allowing it to go way west than it should. I will remind folks that the NAM brought the Feb 2013 blizzard over HYA 36-42 hrs out so it's basically useless right now.

[wxsniss]

not sure whether to believe this run, particularly it's evolution after 36hrs, but impacts for southeast MA / Cape look similar if not more robust than 0z Euro

[CoastalWx]

Oh and lets not forget the famous KBOX bust from the 18z NAM which blew a 6 hr forecast on 2/15.

[TalcottWx]

Double barrel low look is still there. The 12z had the western surface low in almost the same exact position as 18z, except it focused the development with the eastern low @ 12z.

[Clinch Leatherwood]

Just remember the NAM is non-hydrostatic which means it is prone to blowing up lows and allowing it to go way west than it should. I will remind folks that the NAM brought the Feb 2013 blizzard over HYA 36-42 hrs out so it's basically useless right now.

 

Pretty much though this is where it's been trending.  We just needed to get rid of the spurious stuff out east.  Well maybe not spurious but "dramatically over emphasized leading to critical model errors" ....the 12z NAM was really close.   Now we're coming into a real clear focus.

 

Look at the evolution....it's pretty much as discussed but now that stuff out to sea comes NORTH vs ENE/NE like the earlier run. NCEP stuff sucks hard.

[TalcottWx]

Ack and the cape in the CCB at hr 42 964mb

[JC-CT]

Pretty much though this is where it's been trending.  We just needed to get rid of the spurious stuff out east.  Well maybe not spurious but "dramatically over emphasized leading to critical model errors" ....the 12z NAM was really close.   Now we're coming into a real clear focus.

 

Look at the evolution....it's pretty much as discussed but now that stuff out to sea comes NORTH vs ENE/NE like the earlier run. NCEP stuff sucks hard.

 

This has definitely been the trend today, is the NAM overdone? Maybe. But it wasn't at because the NAM blew up a low. It's just the opposite, it DIDN'T blow up the low down in Florida.

[CoastalWx]

Pretty much though this is where it's been trending.  We just needed to get rid of the spurious stuff out east.  Well maybe not spurious but "dramatically over emphasized leading to critical model errors" ....the 12z NAM was really close.   Now we're coming into a real clear focus.

 

Look at the evolution....it's pretty much as discussed but now that stuff out to sea comes NORTH vs ENE/NE like the earlier run. NCEP stuff sucks hard.

 

I'm just not feeling this as a huge deal right now. Like I said, I thought the BOX map was a good guess. It's pretty cool for the time of year though.

[Clinch Leatherwood]

This has definitely been the trend today, is the NAM overdone? Maybe. But it wasn't at because the NAM blew up a low. It's just the opposite, it DIDN'T blow up the low down in Florida.

 

Just need to sit back and watch now.  That stuff offshore was the key.  It looked spurious...the 12z GFS looked like garbage look at what it did out there in developing a max aloft kind of out of the blue and detached from the main trough by a LONG way.  Bogus.

 

We will wobble between the extreme solutions and something like the GGEM, it can only get so far west as the pivot point will only allow for so much NW penetration.  But, it looks good.

[JC-CT]

Hour 15 vs 21, the low is actually 4mb weaker on 18z vs 12z.

[MarkO]

Holy Shift on the NAM @ 36 hrs!

[JC-CT]

Just need to sit back and watch now.  That stuff offshore was the key.  It looked spurious...the 12z GFS looked like garbage look at what it did out there in developing a max aloft kind of out of the blue and detached from the main trough by a LONG way.  Bogus.

 

We will wobble between the extreme solutions and something like the GGEM, it can only get so far west as the pivot point will only allow for so much NW penetration.  But, it looks good.

 

The Cape gets manhandled, like 70mph gusts on the Outer Cape.

[Clinch Leatherwood]

I'm just not feeling this as a huge deal right now. Like I said, I thought the BOX map was a good guess. It's pretty cool for the time of year though.

 

Should be historic for ACK.  Probably the outer cape.  Will have to see for the rest in terms of March events.  4-8 feels right here for the moment, if we see the RGEM and GFS pedal west then it's probably time to....wait Box has it covered already.

[TalcottWx]

Holy Shift on the NAM @ 36 hrs!

It doesn't have sizeable implications for anyone really if you aren't se ma/cape/islands. Anyone outside of the area may see more light snow on NAM versus 12z.

[SouthCoastMA]

Oh and lets not forget the famous KBOX bust from the 18z NAM which blew a 6 hr forecast on 2/15.

That's what I was referring to a couple pages back. Right on cue the 18z delivers..and will taketh away within an embarrassingly close lead time

[bboughton]

It doesn't have sizeable implications for anyone really if you aren't se ma/cape/islands. Anyone outside of the area may see more light snow on NAM versus 12z.

 

Yeah... not much change for mby

[Clinch Leatherwood]

That's what I was referring to a couple pages back. Right on cue the 18z delivers..and will taketh away within an embarrassingly close lead time

 

Yes and no, the 18z NAM isn't terribly different than the Euro.  Remember for whatever reason I've noticed the 12z pulses down, 0z pulses up on the Euro.  Been going on for most of the winter on these offshore lows.  It's still very much within the ballpark of the Euro though +/- some.

[bristolri_wx]

BOX Discussion:

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/...

HIGHLIGHTS...

* POTENTIAL BLIZZARD WITH DAMAGING WINDS POSSIBLE FOR CAPE/ISLANDS
* GUSTS OF 55-65 MPH W/LOW PROB UP TO HURRICANE FORCE CAPE/ACK
* SHARP CUTOFF IN SIGNIFICANT SNOWFALL EXPECTED NEAR I-95 CORRIDOR
* LITTLE TO NO IMPACT ACROSS INTERIOR SOUTHERN NEW ENGLAND

DETAILS...

POTENT NORTHERN STREAM ENERGY WILL BE DROPPING SOUTHEAST FROM CANADA
LATE TUESDAY. THIS WILL SPAWN A LOW PRESSURE SYSTEM OFF THE MID
ATLANTIC COAST. THE LOW PRESSURE WILL BECOME A COMPLETE BOMB AS
PRESSURE DROPS 30 MB IN JUST 12 HOURS! IN FACT...SOME OF OUR
GUIDANCE TAKES THE STORM CENTER DOWN TO 950 MB BY WEDNESDAY
AFTERNOON. GIVEN THE COLD AIRMASS IN PLACE...IF THIS STORM TRACKED
INSIDE THE BENCHMARK WE WOULD BE LOOKING AT 1 TO 2 FEET OF SNOW
ACROSS MUCH OF THE REGION. HOWEVER...THE STORM WILL BE PASSING
CLOSE TO 200 MILES SOUTHEAST OF THE BENCHMARK. THIS WILL LIMIT THE
BULK OF THE STORM/S FURY TO THE CAPE/ISLANDS...WITH SNOW/WIND THREAT
RAPIDLY DIMINISHING TO THE NORTHWEST. TIMING OF THIS LOOKS VERY
LATE TUESDAY NIGHT INTO WEDNESDAY MORNING.

THIS MAY BE A VERY SERIOUS STORM FOR THE CAPE AND ISLANDS WITH
DAMAGING WINDS ALONG WITH HEAVY SNOW/BLIZZARD CONDITIONS. THE ONE
THING WE REALLY WANT EMPHASIZE IS THE POTENTIAL FOR THESE STRONG AND
DAMAGING WINDS. TREMENDOUS PRESSURE GRADIENT WITH LOW PRESSURE NEAR
955 MB EAST OF THE BENCHMARK AND AND A 1030 MB HIGH PRESSURE SYSTEM.
WE EXPECT WIND GUSTS OF 55 TO 65 MPH...BUT A LOW PROBABILITY FOR A
FEW GUSTS TO HURRICANE FORCE ACROSS THE OUTER-CAPE/NANTUCKET. THIS
MAY RESULT IN DOWNED TREES AND POWER OUTAGES ALONG WITH NEAR ZERO
VISIBILITY IN HEAVY SNOW ALONG WITH SOME BLOWING AND DRIFTING. WILL
CONTINUE BLIZZARD WATCHES FOR 5 TO 10 INCHES OF SNOW IN THIS REGION
WITH A LOW PROBABILITY FOR A FOOT OF SNOW. DECIDED NOT TO UPGRADE
TO BLIZZARD WARNINGS YET...SINCE ITS LATE 3RD AND 4TH PERIOD. THE
GFS MODEL IS STILL NOT ONBOARD WITH THE ECMWF...KEEPING THE HEAVIEST
SNOW OUT OVER THE OCEAN SO DON/T WANT TO LOCK US INTO SOMETHING
GIVEN MODEL UNCERTAINTY.

WILL CONTINUE WINTER STORM WATCHES JUST NORTHWEST OF THE CAPE COD
CANAL...WHICH INCLUDES MOST OF SOUTHEAST MA AND FAR SOUTHEAST RI.
LOW PROBABILITY THAT WE MAY NEED TO HOIST A BLIZZARD WATCH FOR
SOUTHEAST PLYMOUTH COUNTY IF WESTERN ECMWF TRACK IS CORRECT...BUT
NOT ENOUGH SUPPORT FROM THE OTHER MODELS FOR 50 PERCENT CONFIDENCE
AT THIS POINT.

LOOKS LIKE WE WILL BE DEALING WITH A VERY SHARP CUTOFF IN THE MAIN
QPF SHIELD....SOMEWHERE NEAR THE I-95 CORRIDOR. THEREFORE...OUR
SNOW ACCUMULATION FORECAST IS QUITE LOW IN THE REGION OF BOSTON TO
PROVIDENCE. THE MODELS ARE OFTEN NOT TIGHT ENOUGH WITH THEIR QPF
GRADIENT. WILL HAVE TO SEE HOW CONVECTION OUT OVER THE OCEAN WITH
RAPIDLY BOMBING STORM PLAYS INTO THIS SCENARIO...WHICH IS VERY
DIFFICULT FOR THE MODELS TO RESOLVE. CERTAINLY NO POINT IN BEING TOO
DETAILED AT THIS POINT...SO BLENDED AGGRESSIVE ECMWF WITH THE TAMER
GFS MODEL. WE MAY EVENTUALLY NEED WINTER WEATHER ADVISORIES FOR
EASTERN MA AND INTO RHODE ISLAND...BUT GIVEN UNCERTAINTY AND BEING
LATE IN THE 3RD/4TH PERIODS PLENTY OF TIME TO RESOLVE. WE MAY ALSO
HAVE TO CONSIDER WIND ADVISORIES FOR THE BOSTON TO PROVIDENCE
CORRIDOR...BUT THAT WOULD NOT OCCUR UNTIL EARLY WED AM SO PLENTY OF
TIME TO RE-EVALUATE.

TO THE NORTHWEST OF THIS SHARP CUTOFF IN SIGNIFICANT SNOWFALL...JUST
EXPECT A COATING TO 2 INCHES MAINLY FROM THE UPPER LEVEL ENERGY.
THIS INCLUDES MUCH OF INTERIOR SOUTHERN NEW ENGLAND.

SUMMARY:

THE MAIN IMPACTS FROM THE STORM WILL BE VERY LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING. THE TUE EVENING RUSH HOUR SHOULD BE FINE...BUT
THE WED AM RUSH HOUR MAY BE VERY DIFFICULT ACROSS THE SOUTHEAST NEW
ENGLAND COAST AND PERHAPS NEARLY IMPOSSIBLE ACROSS THE CAPE/ISLANDS.
AGAIN...THE MAIN IMPACTS WILL BE ACROSS THE CAPE/ISLANDS...WHERE THE
POTENTIAL FOR A BLIZZARD WITH DAMAGING WIND GUSTS OF 55 TO 65 MPH
AND A LOW PROBABILITY FOR HURRICANE FORCE WIND GUSTS. DAMAGING WIND
GUSTS...DOWNED TREES AND POWER OUTAGES ARE THE MAIN CONCERN.
SNOWFALL AMOUNTS RAPIDLY TAPERS OFF TO THE NORTHWEST...BUT THAT
EXACT LOCATION IS UNCERTAIN. VERY LITTLE IMPACT OR SNOW IS EXPECTED
TO WHERE EVER THE SHARP QPF GRADIENT SETS UP. OUR BEST ESTIMATE FOR
THAT NOW IS NEAR THE I-95 CORRIDOR.

[dryslot]

DE Maine gets spanked

[snowdazed]

Would the consensus (taking into account that it's still 24 hours out) be that PVD gets whiffed?

[wxsniss]

Just need to sit back and watch now.  That stuff offshore was the key.  It looked spurious...the 12z GFS looked like garbage look at what it did out there in developing a max aloft kind of out of the blue and detached from the main trough by a LONG way.  Bogus.

 

We will wobble between the extreme solutions and something like the GGEM, it can only get so far west as the pivot point will only allow for so much NW penetration.  But, it looks good.

 

Exactly what I asked earlier this morning... mechanisms for that vorticity popping up out of nowhere when I'd expect it exiting the base of the trough. I agree with you, it doesn't seem right. The convection at best baroclinicity (mentioned by Box too) is fair, but unclear if that's really what's happening vs. models just running away with it. Interesting shifts for sure.

[JC-CT]

At least the NAM keeps it interesting.

 

The clown map does look a lot like the Euro from last night.

[SouthCoastMA]

Yes and no, the 18z NAM isn't terribly different than the Euro. Remember for whatever reason I've noticed the 12z pulses down, 0z pulses up on the Euro. Been going on for most of the winter on these offshore lows. It's still very much within the ballpark of the Euro though +/- some.

Of course I'm secretly hoping its right. Haven't seen the euro but if true that's a bit more credence...qpf aside.

rgem should be interesting in a bit

[CoastalWx]

Should be historic for ACK.  Probably the outer cape.  Will have to see for the rest in terms of March events.  4-8 feels right here for the moment, if we see the RGEM and GFS pedal west then it's probably time to....wait Box has it covered already.

 

I think it could be awesome for ACK and Chatham.

[bristolri_wx]

I wouldn't say a whiff in PVD just yet.  But PVD is on the edge of the precipitation cutoff for most of the modeling.  Even if it comes west, I'm guessing the most it will be is an "I-95 Special" instead of a "CC Special". 

[HoarfrostHubb]

Not for nothing, but didn't the NAM do okay in the NH/ ME event last week?

Not that I am buying the NAM's cheap wares

[EastBayWx]

I wouldn't say a whiff in PVD just yet.  But PVD is on the edge of the precipitation cutoff for most of the modeling.  Even if it comes west, I'm guessing the most it will be is an "I-95 Special" instead of a "CC Special". 

Being southeast of Providence helps marginally for us with these tight offshore lows, but New Bedford- Plymouth corridor usually is the cutoff with these Cape Cod Specials.  If I didn't work Wednesday morning, I would be going to Chatham tomorrow night for a good Snowicane chase.

[Clinch Leatherwood]

Exactly what I asked earlier this morning... mechanisms for that vorticity popping up out of nowhere when I'd expect it exiting the base of the trough. I agree with you, it doesn't seem right. The convection at best baroclinicity (mentioned by Box too) is fair, but unclear if that's really what's happening vs. models just running away with it. Interesting shifts for sure.

 

Too lazy to post the maps but you can really see where the NAM shoved everything NW into the Delmarva and that carried all the way into maine.  Makes sense, let's see what the GFS does.  Normally it's incapable of shedding the convection based stuff at this range.  It was awful by 30 hours on the earlier run.