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Thursday, January 11, 2018

Jan 16 - 18


1-16 - Had light snow and flurries yesterday from some ocean affect.  Also some flurries this morning
This is how the radar has looked for past 8 hours or so.  With some breaking off and heading over our area.
So whats happening...."clippper" system to our west was coming through when it started crawling.  It is supposed fall apart and regenerate a new low off the coast. This has caused fits with where the precip should be, particularly on the NAM.  Instead of one system to figure, it has to sense where the first storm ends, and second begins.  The precip over PA and CNY is clipper/stalled front related.  The precip to our east is new storm related.  Trend has been for the storm to pull west, but thats not reflected easily in the NAM trend below.
The other challenge has been temps.  Not aloft, 850 temps are solid for snow.  But with the LP coming further west, it brings in warmer air.  But the NAM again is all over the place.
Now temps of 32-33 can still support snow if its falling hard enough.  And in the morning hours, it should be.  Even the 925 mb temps (2500ft) are jumping around, but if they settle below 0c then I would expect snow over rain.  And in heavier bursts, would cool the entire column to freezing.


Last variable would be how warm the surface is at the beginning.  A lot of upper 30s and 40s around NYC and the island right now. Those will be hard to overcome.  But inland temps are low to mid 30s.

NWS has a pretty good map as does WFSB.  I could see NYC 2-4 with island 0-1.  NE NJ 2-4 but 4-5 NW.  CT coast 2-4 with I84 corridor 3-6.

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1-12  Pouring rain today. 58 throughout most of CT as I traveled.  Dense fog.  Snowpack almost gone at home.

Just a look at some Euro snow maps... these are 24 hr snowfalls
0z Euro

12z Euro
Euro dissolves the clipper in the 12z run and reforms a storm off the coast.  With the ULL coming down earlier and to the west, its neutral to negative and cut off.  So the new storm formed heads north, bombing it to 974 coming in over RI, which causes rain and mixing problems for areas east of Rt 8. Hence the cut off on the maps.


NAVGEM takes initial energy from the clipper with some light snow for us, then redevelops just to our east brushing us with more light snow. Navgem rule states that all other modeling should be to its west, so this is a good signal.

 NAVGEM also drops the ULL down, but doesn't cut it off anymore, keeping a positive tilt.  This is a bad sign for a storm.
UKMET has the ULL even farther west.  It keeps the clipper in tact as it goes through the area, then redevelops another storm to our south which sweeps east. 


12z ukmet 6hr precip

 JMA brings through the clipper, supper weak, but some light snow.  Then forms a storm well out to sea as the trough is positive. By the time its neutral/negative the storm is long gone.



Icon (German) model shows the clipper coming through with light accumulation, then another storm forming. 
Icon Clipper

Icon second storm
The GFS also takes the clipper through with light snow, putting it to our north.  Usually we don't get snow when they are to our north.  Then another storm develops, completely separate, off NC and goes ENE out to sea.

So the upper pattern needs to be figured out....
Gonna need more time for this one. 

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1-11  After a warm up today and Friday, cold front comes through with some possible sleet at the end of it.  Been following on Accu Forums but decided against a blog on it due to the regional nature and we are not getting much if any snow out of it.

However, a clipper and upper air disturbance will be following shortly there after.  A lot of model support this morning for this, but there is still time for this to either just not happen or go out to sea.  I don't think this can go very far west of us since its spawned offshore.

Euro right now depicts it the strongest.  Strong upper low drops down with fresh cold air, spawning a storm off the coast (remnants of a clipper).  Pay attention to the blue thickness line, indicating a mix here and rain to the east, which ultimately keeps the snow amounts down east of here.
 Seems like a rare scenario - it is.  Happens a couple times per winter, sometimes not at all. Is there other support for this? UKMET is least committal, but upper level supports.  NAVGEM rule applies as it is the furthest east. 
Icon (German)

Ukmet

Ukmet precip

GFS snow

Navgem
Snow could fall as early as late on the 16th.  If you believe the Euro, its a 24 hr snowfall.
A lot of time for changes - Upper low could be weaker, could drop further west or east. 



Thursday, December 28, 2017

Jan 4-6 timframe

1-4  evening - results
Top winds were
64mph Great Gull Island
61mph Coast Guard Academy
66mph Bayville LI
68mph Scotchtown, Orange Cnty
58mph Westchester airport
55mph JFK
52mph Bridgeport airport

Snow
CONNECTICUT

...Fairfield County...
   Stratford             13.2   308 PM  1/04  Public
   Monroe                13.0   307 PM  1/04  Public
   Newtown               12.6   600 PM  1/04  Amateur Radio
   Weston                12.5   630 PM  1/04  Trained Spotter
   Wilton                12.5   445 PM  1/04  Broadcast Media
   Norwalk               12.0   410 PM  1/04  Public
Middlesex County...
   Killingworth          13.0   700 PM  1/04  Social Media
   Haddam                10.5   515 PM  1/04  Trained Spotter
..New Haven County...
   Southbury             14.2   620 PM  1/04  Fire Dept/Rescue
   Seymour               14.1   534 PM  1/04  Trained Spotter
   Branford              13.5   700 PM  1/04  Trained Spotter
   Bethany               13.5   618 PM  1/04  Trained Spotter
.New London County...
   Ledyard Center        10.5   313 PM  1/04  Public
   Gales Ferry            9.5   657 PM  1/04  Trained Spotter
NEW JERSEY

...Bergen County...
   Cresskill              8.8   500 PM  1/04  Public
   Haworth                8.1   315 PM  1/04  Public
   Englewood              7.1   445 PM  1/04  Trained Spotter
...Essex County...
   West Orange            7.0   400 PM  1/04  Public
   West Caldwell          6.0   556 PM  1/04  Public
   Belleville             5.9   430 PM  1/04  Amateur Radio
   Newark Heights         5.0   430 PM  1/04  CoCoRaHS
   Cedar Grove            4.5   415 PM  1/04  Public
Passaic County...
   Wayne                  6.5   430 PM  1/04  Amateur Radio
   Pompton Lakes          3.0   100 PM  1/04  Emergency Manager
NEW YORK

...Bronx County...
   Bedford Park          12.3   545 PM  1/04  Public
   Morris Park           10.7   500 PM  1/04  Public
 
...Kings County...
   Flatlands             12.5   400 PM  1/04  Public
   East Flatbush         12.4   515 PM  1/04  CoCoRaHS
   Sheepshead Bay        12.0   700 PM  1/04  Trained Spotter
 
...Nassau County...
   Baldwin               15.1   245 PM  1/04  Amateur Radio
   East Hills            14.0   515 PM  1/04  Public
 New York County...
   Gramercy Park          9.8   530 PM  1/04  Public
   Central Park           9.8   700 PM  1/04  Park Conservancy 
 Putnam County...
   Mahopac                7.0   600 PM  1/04  Trained Spotter 
 Suffolk County...
   Terryville            16.4   645 PM  1/04  Trained Spotter
   1 S Bohemia           16.3   415 PM  1/04  Public
   Middle Island         16.0   435 PM  1/04  Public
   Islip Airport         15.8   700 PM  1/04  FAA Observer
.Westchester County...
   Harrison              12.5   655 PM  1/04  Public
   Yonkers               12.2   715 PM  1/04  Public
   White Plains          12.0   400 PM  1/04  Trained Spotter 
 
1-4
3pm snow on deck - ruler no longer works



1pm position - 952 or so.



11am - officially a blizzard, at least on LI. 3hrs of under .25 vis and winds over 35mph.

Some sat pics and radars










1-4  For the record, the GFS went to .8 for OXC and .59 for DXR on the 0z run.  NAM went down to .47 for DXR and  .59 for OXC.  The 0z EUro went to .73 for DXR; .78 for OXC.

1-3
All models are in (except 3knam) with a sub 960 low passing over or just se of the BM.  The east models (except navgem) have corrected west, NAM went east.  But there still is 100-200 mile spread between them all, which is in reality the usual. The debate over the last day has been the precip field and its lack of the western edge.  As discussed below, benchmark storms typically are great for NYC area, including NNJ back to the PA/NY border.  However, some runs weren't giving ANY precip for western NJ. Problem seems to have been fixed.

NAM went nuts again overnight but backed off.
GFS shifted precip west, though the low passes the same 40/69 spot every time
Ukie
Euro
All of the these look pretty good.  The RGEM however is swiftly lowering amounts for N of NYC.
Meanwhile, down south, we saw a LP form off of FL, actually two, and one that tried east of the Bahamas.  Now the situation looks like this...


It snowed in Jacksonville, Savannah and Charleston so far.

Concerns remain if that last piece of energy 1 - phases with the current ULL and strenghtens it, or slows it down; 2 - that piece misses completely, and we see if the system stacks or 3 - the piece kicks the system out to sea. I think that's was driving the NAM crazy.  6z it wanted to phase it, 12z left it alone and 18z kicked it out.

Ultimately I like 6-8 inches for eastern Fairfield county, 5-6 for western, 6-8 through central CT and 8-12 east of the river with 12-16+ in parts of eastern Mass.  The Jersey Shore looks to get into the 6-8 inch range and they have blizzard warning up, as does Long Island, which also should see 6-10"  The risk in these areas is rain, believe it or not.  NNJ is still challenging. I'm keeping it at 4-5" for now for eastern half (east of Rt 15 or I287 more south) and 2-4" for western NJ west of 287 south of Morristown or west of Rt 15.  I don't think my ideas are that different than the NWS, and I'm only at the 50% confidence level, with 25% being higher amounts and 25% being lower.  Wind will be an issue, but I think mainly in eastern sections and at the coast especially.  Cold will be the worst its been, which is already very cold.


School is already cancelled and we are in a winter storm warning.  We'll see what happens!

Wait, one more.  The 21z SREFs came back highest so far.



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1-2 evening.  GFS continues to trend west. NAM holds.



1-2 late afternoon.  NAM relaxed a little, GFS came west, which is more important.

Here's the GFS precip trend.  I'm 50/50 on the 4 inch thing.  Again thats like 50% for a 2-4"
or 50% for a 4-8".  Starting to lean, after listening to some pro's to the 4-8".  Ukie came west today as well.

1-2  Nam goes crazy.  Globals hold steady, slightly west.

GFS ensembles west by 20-50 miles last few runs.  Something to watch, though ensembles are less useful under 48hrs.

The problem remains on how the low is being generated.  The globals are sensing an upper air disturbance around the Bahamas and are placing the low there.  The typical area of cyclogenesis is along baroclinic zones - storms tend to form where the temperatures and dewpoints differences are the greatest.  The NAM forms the low and keeps it near the temperature clashes, by the coast.
 And it moves it along the coast to the Outer banks (OBX).

GFS had been forming the low east of the Bahamas.  It was coming in with three areas of convection and bumping the low from one area to another in what is known as convective feedback.
It has since solved for that and is forming the low near the coast.  However, it continues to chase the thunderstorms further away which influences the main low to be further from the temp contrasts.  You can see three areas here with the middle one having another low.


Last night the NAM and GFS got to the same place around the benchmark 40N70W.  But in different ways.  The NAM took the low up the coast, then a kicker piece of energy took the system on a hard right out to sea before the ULL captured it.  The GFS just went NE from its incorrect spot.

The NAM dropped the idea of a strong kicker this mornings 6z and 12z runs and keeps the low closer to where it should be, along the temperature contrasts.  That results in the low going to or inside the benchmark.  More snow and wind for coastal states.  The nam forecast itself is amazingly deep.  It goes by us as a 959 LP on the 12z run
but could be as low as 949mb as shown on the 6z run
The deeper the low, the more tight those isobars are, the windier it gets.  Hurricane strength winds would remain over the ocean.  These are the highest sustained winds I could find - 82mph.

Locally, the gusts would look like this.
Nam max gusts
So this could be an extreme event.  Its just that the global models are too far offshore and the WPC is still outside the benchmark with their prediction.  But many of us amateurs and  even some pro mets in the media are watching this very closely.   Last minute add - Euro moved west to just SE of the BM and has 948mb pressure.
with these winds near hurricane force.

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12k
3k
1-1 Looks like those gifs above are permanent.  Earlier nam runs.  Right now the NAM/JMA seem to have a grip on where the low will be.  UKMET/EURO/GFS still start the run too far east.  However, they all, except JMA/CMC, seem to end up in the same place, a few degrees west of the BM.  Normally this would be a good thing.  For some reason, perhaps just the trajectory of the storm, the precip is headed northeast and we are left with minimal impact in the tristate.   The exception to this right now are the SREFs. These are more bullish and trending positive for close to a foot of snow at Oxford.
CMC and JMA are also exceptions.


NAVGEM is also crossing 40N around 68W
These all give us some precip, but not like the SREF.  The latest NAM runs take the low up the immediate coast to OBX/Delmarva and hard right it out, to about the same spot as the others.  Different path, same result.  Only a few inches.  500mb shows a vort kicking it out, which wasn't on the other models until recently. 
Amazingly, the NAM keeps hitting SC with snow.


Ukie seems to start off too far east and stays too far east.
But it loses its double barrel (the interior low that the NAM has) in the 12z run, leaving any meaningful snow in SNJ and immediate MA/ME coasts.

Euro has edged back heavily over the days, but still keeps us from getting anything major

This path, just outside the BM, gives us this precip
So I'm lowering the west solution odds to 0.  Snow of 3" or more for tristate is still 40%, less than that with more snow to our east is at 60%




12-31 - some shifts east today, but NAVGEM still holding at BM.  GEFS are also holding at 66W.

 CMC came out with this crazy one.... But UKMET is east, due to dual lp structure most likely

Outside...ball 2

CMC say what?
But the euro still trending west ever so slowly


Posts
12-30  Took yesterday off and missed a crazy back and forth day with the models.   As of late afternoon, trends are back west.  Thanks to the members of the AW forums for these as I was out all day.

The Ukie came really far west with a punishing storm idea.  Trackwise, the UKMET has high verification this far out.

Which causes this precip
And runs this track



 GFS Ensembles are 50/50 for snow. This has been steady most of today.  A huge improvement over yesterday
Euro is still offshore, close enough to brush eastern parts.  This is an improvement over yesterday, but has a way to go. 


Its ensembles look good though.

which brings - wait thats the operational.  oh well, don't have it.
NAVGEM is very encouraging.  You don't usually see it this amplified or be further west than the Euro and GFS.  Typically the GFS will correct to it.
So right now, I'm 20% it goes inland and there is mixing east of NYC.  The axis of the ridge spooks me, as does the chance the mystery vort doesn't come into play.   40% that it hits somewhere within 50 miles of the benchmark, or between the BM (40N/70W) and Montauk.  If it is 50 miles east of the BM, look for light snow in west Jersey, 2-4 in NYC NJ burbs, 3-6 NYC east and 4-8 eastern CT/LI.  If its around Montauk, its probably an epic blizzard from eastern PA to RI.   40% that it misses OTS and hits Canada. 

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12-28 evening.  18z GFS backed off the idea.  NAVGEM came in a bit more west and amped, but phases too late.  EPS mean is trending well and the control is nuts.

944 LP off long island
And the 12z Euro came in with these wind gusts
109mph gusts

105mph gusts

18z GEFS still showing members in the area




12-28 - after going off the rails at 6z, the GFS came around to the Euro/CMC idea of a MAJOR storm which smacks New England.  Here is the evolution at 500mb and 850mb.  It involves an upper low coming down from Canada, shearing apart a potent southern stream storm.  Only way this can get worse is if that southern stream storm is fully absorbed.  Now being 8 days away, this is likely to change, but it does fit the pattern.


Result is this snow map

Now the EPS control has it further west with a 964LP over LI - this is a warm storm for SNE/LI
And the Euro operational looks like a combo of the 12z GFS and 0z EPS Control.