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Wednesday, December 3, 2014

Dec 8-11

12-13  Results:  Heavy rain 2+ inches tuesday, drizzle tues night, light snow, snizzle and snow showers on and off from Wednesnday noon through last night (fri nite).  Euro and UKMET were closest, though not exact.  SLP tracked up to Cape Cod, not over NYC/CT per Euro/UKMET. But at least they had it close to the coast and caught by the upper low.  GFS caught on, but later, though its runs within 48 hrs had the slp positioned better.  


Going to award this one to the Ukmet.  Euro had it figured out too, but kept trying to get fancy with it, doing loops, multiple lows, etc.  Ukmet had it right along the coast, caught around NYC and then out.  GFS clueless again until 2 days before.  CMC had the 500mb low too far south and rotated the slp into NC when Euro/Ukie had it positioned correctly, so far.  JMA took benchmark on 12-5. 

Today was interesting in that the daytime high was 28, with winds NE to ENE all day, flurries in New Haven and Newtown and light snow over LI and SNJ.  As I write this tonite at 9:30, temp still 28 with DP of 20 and winds ENE (here and airport).   I wouldn't be surprised by freezing rain over night.  Precip is approaching Cape May now. HRRR is about 3 hours behind on the radar and it has radar returns here at 4am, but based on current timing, 1am seems right.  It also has temps rising above freezing here around 10z, which based on the wind direction does not make sense. There is still a strong high, winds from the N so not sure why the surface temps rise during the night.  850's yes, but there should be strong damming at the surface.  This could lead to freezing rain.  HRRR times the arrival of precip at the same time of the temp >32.  850s forecast >0c at 12z.  925s at 3z.  That makes more sense based on the ESE wind at that level.

 So what should happen is that the Poconos, Catskills, Berks, Greens and Whites get dumped.  What's been lost is the low hanging around.  We'll have to wait and see if that happens.  If it does, we may see some back end snow showers by Wed morn. Parts of Litchfield, Sussex, Dutchess, Orange may see 1-3/2-4, but stress may. 

Sadly, I'll be traveling on 12-9 so won't get to enjoy tracking this one during the event. 

12 -07 - summary. Euro's gone loopy, see below.

UKMET has the slp off NC, Off NJ to Boston, back to over DXR and then out to the NE.  Too close to shore for snow for us, but nice further west. Cavaet that with I don't know the upper air parameters for the UKMET, just slp and 500mb heights.
CMC looks to drive the slp due north up the coast, never having it caught by the 500mb low. Its low passes just east of NYC and just east of DXR.  It brings another low into main from the Atlantic on thurs. It is also too close for any serious snow for areas from west of the immediate path eastward.

0z gfs snow map hr 108
6z GFS is similar to Euro up to Wed, except further east.  It reforms the lp further east of NC, brings it up to 40N at 71W on 0z Wed.  The ULL is over VA at that time. 12z Wed the slp is over SE Mass, the ULL has caught it and by 18z the slp is over RI, at 996mb and stacked with ULL.  From there it moves NNE occluding over Maine on Thurs Night/Friday.  0z is similar, but further west with the ULL closer to DXR and the SLP centered over Eastern CT. 0z surface temps 1-2 above 0c through the event.  850's mostly above.  6z run has warmer surface temps, cooler 850's but still looks mostly rain with a few inches of snow wed night.  Just to our N&W, its a different with 12-18 inches. 

Euro snow 0z 12-7 run at 108 hrs

12-7  0Z Euro puts out one of the strangest winter runs I've seen in the nearly 10 years of watching winter storms.  I tried to video this - watch as the front comes through today, a piece is left behind and as the next UL system comes in forms a 014 LP off SC/NC, sends that LP up to  a 1002 lp off DE by 18z Tue.  All is normal so far.  The white lines indicate the upper level heights.  You can see the upper level low coming in at 18z Tues, slp (surface low) is off ACY at 0z on Wed.  At 6z the surface low is 998 mb and still off ACY. The upper low is approaching the Baltimore area.  Its hr 84, where a second 1004 slp forms out at sea in response to the ULL, that is crazy.  The original slp starts moving WSW toward the ULL over Baltimore. By 0z on Thursday the original slp is stacked with the ULL,  the second slp is heading around the ULL and deepens to 996.  Its actually going to cross the Benchmark (40/70) from the SE.  The ULL drifts north and almost captures the now 992-994 slp hitting LI and ACK.  Instead of continuing on its NW course, it then heads SW as its captured by the ULL which is now stacked with the second SLP just south of Long Island.  A move west over NYC in the next frame 18z thurs, when the storm occludes.  By 18z Friday,  the slp and ull are still over NJ. By Sat the slp is gone, but the ULL remains over VA and ANOTHER 1010mb slp forms east over the Atlantic.  That moves west toward the ULL,  so that by Sunday there is a 1004 slp off the coast of SC, with the ULL over SC.  They stack on 0z Monday as the slp drops to 1000.   This time there is no occlusion as the ULL/slp moves slowly NE  passing 40N at 64W, still stacked and at 998mb.  And thats the last frame.  10 days of one ULL and the three slps it spawns.

Well, the video didn't turn out that well, but you can see the white lines of the Upper level low and how it behaves - all other models have it moving NE once it stacks over us. 

12-6  Not much change from yesterday, still looking at a lot of rain in our area. There is a cooling trend, but the storm needs to hang up south of Montauk to bring snow to the tristate.  Right now, longitude is crucial as the 850 line looks n-s. Areas west, wet snow.  East, rain. 

Euro keeps the low off NJ in the 12z run.  850's cool from a max of 6.9 to 4.  Whats different from yesterday is its a little east, but there's a second system forming in the ocean that rounds the UL and hits Maine on Thurs.  About 2" qpf as rain, then snow showers thurs and fri.  Ensemble mean though still has storm east of our longitude, and cold enough for snow.  But the ens trend is west.  And the ensemble control is where the operational is.  I'd look for Euro to move a little more east in the operational, and a little more west on the mean ens but don't think it will be enough to blast us with snow.  West of the hudson, different story.
Warm and West Euro operational

Colder and more east ensemble mean
UKMET has shifted slightly east in its 12z run over the 0z run.  Just from the Del river to NJ coast.  Still mostly rain

JMA still has a classic noreaster track.  Its 850's and 925 temps are favorable for snow west of Waterbury
Loading Maps...

NAM is also on board, granted through 84 hrs. It allows for the temps to crash once the UL and surface are stacked.  Giving far N&W suburbs a chance of white. 
Loading Maps...

CMC  - 0z run looked like Euro/UKIE and yesterday.  12z run loses the phase of the UL low and surface low.  Instead it still forms a strong low and brings it past Montauk at 996 mb.  If the UL were there, it would be snow, but it keeps on going and rain is ended by Tuesday evening. CMC is also pretty warm, so its all rain.  It doesn't stack until its over Nova Scotia

CMC Tues morn

That leaves the GFS.  Its kinda out on its own, none of the four model runs look the same.  Some stack the low over us, some not until NH, one doesn't even close off the low.  They are all east of the Euro, but bring only a mix of rain/snow. The 18z run closes the UL right over us, but the surface low to the east, with the 540 thickness showing snow, but the 850 showing rain. Then there is the snow map!

GFS 4panel 12z Wed

GFS 18z snow map

                                  sfc c      850 c                                                                      qpf          snow
TUE 06Z 09-DEC   0.7    -3.5     130    6979    05010     SN    0.01    0.00    
TUE 12Z 09-DEC   1.7     0.4     131    5118    04010     ZR    0.03    0.03    
TUE 18Z 09-DEC   3.2     1.2     131    5543    02013     RA    0.18    0.03    
WED 00Z 10-DEC   2.5     2.0     131    5448    35015     RA    0.34    0.03    
WED 06Z 10-DEC   2.4    -0.9     131    3522    32018     RA    0.42    0.23    
WED 12Z 10-DEC   2.0    -2.1     130    2109    31015     RA    0.61    0.73    
WED 18Z 10-DEC   1.4    -2.3     130    1359    32013     SN    0.41    1.05    
THU 00Z 11-DEC   0.4    -1.6     130     615    31014     SN    0.04    1.05    
THU 06Z 11-DEC  -0.4    -0.9     130     438    31012     SN    0.06    1.08 

Euro/UKMET east, UL and surface stack over NYC.
GFS - east. runs all over with UL/surface relationship.  18z run gives us a foot
JMA - east. looks classic, cold for snow
CMC - middle looks classic, too warm.
Hate to say this, but its going to be a mixed bag.  Keep monitoring trends


Euro quasi trop systems

 12-5  Prolonged storm event, despite pos nao. 

Euro becomes more believable.  Instead of taking the LP from OK to PA then driving it SE and having it loop back NW, the LP shears out and is mostly absorbed by this semi tropical system in the atlantic near 60/30.  Front pushes down behind that, along with a strong upper level low.  NEW low forms off NC coast and travels north in a more traditional manner. The lows become stacked, and believe it or not, drag that first low back into the new system (which is still an odd solution).  Actually, the frame below is after the low hits LI and goes SW into the UL. 

Stacked lows at 500 and surface

 All of this results in 2+ inches of rain for most of CT.  It gets more interesting west of the Hudson and in VT/NH. But the 850's are really close for West CT.  West of the Hudson is a mix, north of Mass there are some spots of 24+" .

 However, the ensembles have the low located closer to the BM rather than over NJ, which would cream most of the area. 500mb and 850 temps
Euro ens dream storm

UKMET looks similar to Euro, perhaps a little east, 50 miles or so. Its 12z run is similar.
UKMET hr 120 (it stacks shortly after)
CMC hangs onto the Euro original idea of rotating whats left of the original LP back west into NC then strengthening in response to the 500mb energy and moving it up through Delaware Bay, then NNE over DXR. Rain.

JMA looks like its the more traditional LP off NC to BM.  It cuts off the UL, but just off the NJ coast.  850's are really close

 DGEX from hr 84 brings the low straight up the coast with rain mostly east of the hudson and south of NY/NJ border.  Nothing but rain in East PA/NJ or New England.

NAVGEM cuts the UL off to our north.  Then has another UL form over FL/GA.  It blows the front through, then eddies some of the energy off the coast and brings it back up into the cut off to our north.  At  hr108 its moisture is east of the Hudson, the 850 line is at the CT/NY border, so perhaps Putnam/Dutchess see some snow for an hour or two.

GFS still doesnt buy it, mainly that the UL is going so far south.  The 12z idea was a surface LP coming through the lakes with the UL cutting off over Lake Erie or so on Tuesday.  As that UL deepens, it brings up surface energy from the Atlantic over us.  It never really deepens past 1000mb and it meanders in S Canada for several days.  There's not much precip in it for us, and its a little too warm.

18z GFS run seems to be slightly more like the Euro, but the UL cuts off too late and is not far enough south to give us snow.    And by the time the LP at off the coast deepens its near Maine. Good run for VT though.
Problem is that the GFS ens look very similar to the Euro ens - which is a very strong signal. That's spread to the north/north east.

0z Nam for 12-6 shows the Euro/CMC/Ukmet idea so far.  Its trough is strongly negative, but there is a lot going on at the 500mb level so I can't predict where it cuts off. 
 Summary:  JMA, Euro ens and GFS ens are aligned for a great snowstorm.  GFS operational is alone in its placement of ULL.  UKMET/Euro/CMC are bringing storm right along the coast or just inland for mostly if not all rain for most of the area. 

12-4  Euro changes a little.  12z run takes a low over OK on 12-5 through OH Valley on 12-6, then ESE over the OBX on Sunday.  Sometimes you see storms coming up the Apps and reforming off OBX to the ESE, but this doesn't seem to be the case.  This one looks like its shunted SE by a cold front clearing our area Sunday morning.  By Monday its still weak and spinning offshore NC at 34/72.   Interestingly the 0 line at 850 stops advancing south and decouples from the LP.   Then late Monday, the storm picks up some UL energy coming around the trough, the trough goes negative and the meandering low is comes back north.  As it comes north, it goes from a 1012 low  off NC at 0z Tues to 1000mb south of central LI by 12z Tues (see instant wx map below).  Then to a 992 low by 18z Tuesday sucking in the 850 line.  Then 988 over the Cape.  For areas north of the LI sound:  Mod snow starting late monday night, tues morn.  The next 6 hrs is a toss up - 850 line squiggles everywhere.  But by 18z tuesday western CT, western Mass, eastern NY, including the city and NE NJ are getting plastered with snow.   Temps are so marginal, only at the 850 level, that its again difficult to see where its snow vs sleet v freezing rain.  This mornings run, and yesterday had colder surface temps, leading to my concern about freezing rain (zr), but they are just above 0c this afternoon (I don't trust Euro surface temps during precip events). Euro snow map is fun too...don't trust it yet.   Euro ens control is east of the operational, still brings some snow (3-6), and is colder.
ECMWF Mean Sea Level Pressure Map Unavailable
euro snow dream

Canadian is similar to the Euro, except it brings the low as far south as SC latitude, then back  NNW over the OBX to the Chesapeake, right up NJ and spins it over NYC before bumping it back SE, then E then NE. It looks like all rain.

12z GFS says the storm over OK friday just moves on through the OH Valley until PA, when it broadens and looks more like a frontal passage for us.  The associated moisture gets as far as 64W before it turns around and heads N, then NE crossing 70W at 36N.   We get nothing.

UKIE bombs us - such a decieving hr 120 and then bam! We are under a 524 upper low stacked over a surface low.  I have not idea how cold it is, nor can I even see the pressure as the lines are too closely packed (means lots of wind).

DGEX has a more traditional storm forming over OBX and moving east of the BM.  Not a bad looking solution, though its showing us being too warm to snow.


GFS 120

Euro has interesting feature - Saturday morning  a warm front pushes over us, with a cold front following on Sunday morning.  Then on Sunday morning, a SW in Missouri on Saturday, forms a lp off NC/VA. That LP just lingers, spinning out moisture and doing all sorts of funky things with the 850 line (see below).  925 and 700 mb layers are cold enough for snow, but the 850 is very random.  It then moves north to south of LI, then NE over the CC canal.   But thats not all...  the stronger shortwave which  causes this odd behavior is over MN on Monday, MO on Tues and GA/SC on Wed when it spawns a second low which grazes us but smacks SE Mass.  CMC shows the first low, but dismisses it, focusing on the second low which it drives NW into Del. Bay. UKMET puts a 1040 high over Maine and has the cutoff low at hr 144 centered over TN
12z GFS has a low forming out to sea at hr 144 and doesnt have the strong UL as the CMC/UJIE and EUro have.  DGEX has the first storm like the Euro, but no second one and no strong UL. 

 These are the temps at various levels through the period at DXR.  Pretty cold surface temps but then there is that warm up at 850 on Monday evening. 
                             12Z DEC03
PRESSURE LEVELS  SFC  1000   925   850   700   600   500   400   300   200      
MON 12Z 08-DEC   -3    -4    -5     0    -4   -10   -19   -31   -48   -58       
MON 18Z 08-DEC   -3    -4    -5     0    -3    -9   -19   -31   -46   -58       
TUE 00Z 09-DEC    1     1    -1     4    -3    -9   -19   -32   -46   -57       
TUE 06Z 09-DEC   -1    -1    -2     4    -4   -11   -20   -33   -44   -54       
TUE 12Z 09-DEC   -1    -1    -3    -2    -5   -11   -22   -35   -45   -53       
TUE 18Z 09-DEC    1     1    -5    -4    -7   -15   -27   -36   -45   -51       
WED 00Z 10-DEC   -2     1    -4    -5    -8   -16   -26   -38   -47   -52       
WED 06Z 10-DEC   -5    -3    -6    -5    -8   -14   -25   -38   -49   -52       
WED 12Z 10-DEC   -6    -5    -5    -5    -8   -14   -25   -36   -51   -52       
WED 18Z 10-DEC   -1    -1    -7    -6    -8   -14   -25   -38   -53   -50       
THU 00Z 11-DEC   -2    -2    -7    -9    -9   -15   -25   -37   -53   -49       
THU 06Z 11-DEC   -6    -4    -8    -8   -10   -14   -24   -37   -52   -50       
THU 12Z 11-DEC   -6    -4    -8    -7    -8   -15   -24   -37   -52   -51       
THU 18Z 11-DEC    0     0    -6    -3    -6   -14   -25   -38   -49   -53 
Numbers with precip
                 sfc     850                            qpf
SUN 12Z 07-DEC   2.1     1.9    1027      72      72    0.18     565     544    
SUN 18Z 07-DEC   2.1     0.6    1029      41      39    0.03     565     542    
MON 00Z 08-DEC   0.1    -0.7    1030      48      57    0.01     565     541    
MON 06Z 08-DEC  -1.8     0.1    1027      59     100    0.05     563     541    
MON 12Z 08-DEC  -2.9     0.0    1023      82      97    0.25     560     542    
MON 18Z 08-DEC  -3.3    -0.3    1015      85      97    0.46     555     543    
TUE 00Z 09-DEC   0.6     3.7    1008      86      62    0.10     553     546    
TUE 06Z 09-DEC  -1.1     3.5    1005      88      73    0.06     547     543    
TUE 12Z 09-DEC  -1.5    -1.9    1006      86      69    0.03     545     540    
Lastly, GFS from 12z
SUN 12Z 07-DEC  -2.3     0.0    1032      74       6    0.00     564     539    
SUN 18Z 07-DEC   1.6    -1.2    1035      51      14    0.00     566     538    
MON 00Z 08-DEC  -1.7    -1.8    1038      68      26    0.00     568     539    
MON 06Z 08-DEC  -2.1    -1.8    1038      61      29    0.00     569     539    
MON 12Z 08-DEC  -2.2    -0.4    1038      73      20    0.00     568     538    
MON 18Z 08-DEC   2.8    -0.9    1033      77      12    0.00     564     538    
TUE 00Z 09-DEC   3.1    -3.4    1029      93      11    0.02     561     538    
TUE 06Z 09-DEC   4.2     0.6    1020      96      67    0.01     555     539    
TUE 12Z 09-DEC   4.4     1.1    1013      99      98    0.19     550     539    
TUE 18Z 09-DEC   6.1    -3.3    1010      76      28    0.02     542     535     

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