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Wednesday, April 4, 2018

Come on.....its gotta end!

4/5  Big shift south overnight on NAM and NAVGEM - caving to GFS and Euro?  So what happened?  Last three runs of nam at surface, 500mb and the precip.

12z nam 24 hr precip trend
as is snow

4/4 update

18z GFS ensemble showing north trend with precip.


Several possibilities coming ahead.

First, Friday morning should see some snow.  Should be light and turn to rain.  850 temps support snow the entire event, all models, but surface temps do not.  Should be very light:
Euro qpf from 12z run

FRI 06Z 06-APR  -2.6    -9.1    1021      67      15    0.00     537     520    
FRI 12Z 06-APR   0.2    -7.7    1020      61     100    0.00     539     523    
FRI 18Z 06-APR   3.3    -1.4    1012      84      83    0.07     543     533 
GFS qpf 12z run
FRI 12Z 06-APR   1.9    -7.7    1018      52      98    0.00     537     523    
FRI 18Z 06-APR   7.4    -3.1    1010      71      69    0.09     541     533 
NAM qpf 18z run
FRI  8A 06-APR   0.3    -7.3    1018      64      88    0.00     537     523    
FRI  2P 06-APR   8.4    -2.0    1006      71      54    0.17     539     533    
FRI  8P 06-APR   9.6    -0.3    1007      50      82    0.00     545     539     

Then, we deal with Saturday.
NAVGEM rule is in effect - when the NAVGEM is the slowest and furthest NW model, then something is wrong.

And confusing things more is the NAM which is the earliest and furthest north.  I've come to respect 
the NAM lately even when it does wacky things

So it just dumps over 6" per below for DXR -

NAM printout
SAT  8A 07-APR  -1.2    -3.5    1008      92      97    0.16     547     540    
SAT  2P 07-APR  -1.1    -8.2    1007      89      98    0.58     542     537    
SAT  8P 07-APR   0.4    -8.5    1008      64      27    0.02     539     533 
And over a foot in other places
GFS and Euro focus further south...which in previous storms this year end up going north.

 Which brings us back to the NAVGEM rule - its likely these snow areas shift north. 
At least its the weekend and during the day.

Saturday, March 31, 2018

April 2

4-2   Started snowing 4am or so.  The 11th cancelation of school this year.

3-31  Looks like another one.  2-6 inches for Mason Dixon line through CT.  Exactly who gets the most is trending.  Timing looks conducive for accumulation as it begins pre dawn. in CT and earlier elsewhere.


GFS North
NAM North

Thursday, March 15, 2018

March 20-24 - last ones?

3-22 results

Some theories as to why this busted so bad, so far.

First, there were too many competing lows.  Sucked the warmth, fuel, etc out of the atmosphere.  The upper low should have fired that up, but with no energy available at the surface, no temp contrast, there was not a lot to work with.

Second, nothing predicted that it would stall for ten hours.

Third, I was looking at radar depictions, which were accurate on the models.  However, the snow that was involved was minimal.

Lastly, its likely NJ, LI, NY all are pounded by this overnight.  Not sure we get more than 3" now here.  But its performing well elsewhere. Double digit snow so far from MD, PA, NJ and LI.  

3-21 morning radar - shows heavy but not translating to inch/hr



The low is jumpy on the 18z nam.  Wondering if chasing convection.

3-20 Continue watching trends. 0z NAM giveth, 6z NAM taketh.

NWS forecast this morning was mind blowing
Most guidance remains a 6-8" storm.  I made a crude map last night for the first time ever.


Trends trends trends.
of course the 18z gfs breaks the trend.

Latest NAM
12z GFS
3k nam

Meanwhile, we've gone under a winter storm watch with the below currently forecast

The Upper Level Low circled over SE Canada is what will dictate if we get precip.  Even the latest NAM takes the storm to our south and doesn't develop it much, due to the influence of that ULL.  IF that ULL moves out and the two other circled areas phase (past hr 84) then game on for a strong noreaster.  If the ULL stays, then it goes south.  If the ULL moves  out but the pieces remain separate, there would be some snow from CT to DE, perhaps VA.

Still a lot of disagreement in the gfs ensembles

3/15  Strong signals that something will happen next week, just exactly what is tbd.  All models have something moving through, but is it over us, south of us and out to sea?  Here's the NAVGEM from 12z today.  Typically the NAVGEM is east or southeast of where the storm ends up. We use it as a guide to compare with other more dynamic models, so when the other models are south or east of the NAVGEM there is confusion.  NAVGEM rarely gives a storm 3 days of life.

Meanwhile the 12z GFS output this snow map with a similar setup as NAVGEM
Canadian more south for now
JMA has great position