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Significant Ocean Storm March 6-8 2013 Discussion Part III


earthlight

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I've seen at least half of them produce blizzards with every single winter storm set up at some point this year. The SREF used to be a very useful tool but at this point, after having to analyze them in detail and adjust for biases of the ARW and NMM members makes them almost irrelevant. They were producing 1.5" QPF at 24 hours ahead of this system....just like the NAM.

on the plus side the SREF's were only off by about 1.47" qpf at my house....

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But like I said, the GFS is above freezing for the whole event on the soundings for BDR.

Gets close to freezing by 7am.

It's also the warmest model, EURO is plenty cold and often better with temps. no met that I've talked to thinks temps will be an issue for this, look at southeast MA, plenty of models had them raining all day, and it's ripping there. I'm more worried about QPF, and even if it's 33 or 34 for the event, without the sun, it can still accumulate no problem.

-skisheep

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on the plus side the SREF's were only off by about 1.47" qpf at my house....

 

It's very difficult as a forecaster to toss them completely, especially when they were consistent essentially from 84 hours until 12-18 hours. So my forecast 24 hours before the event weighted the Euro and NCEP models about 70/30 respectively. And even that, trying to provide a sense of normalcy with a blend, ended up busting high by about 3 inches.

 

So I think at this point it's safe to say that the NAM, SREF and high resolution models are making things more difficult for forecasters than anything else.

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John, for a good laugh, am I interpreting that to be 80mm over LI which is 3 inch qpf? again, just for a good laugh that is.

 

That's accumulated snowfall on the 12z high resolution NAM...so 8-12" for Long Island with a small area of 12+ on the North Shore.

 

In fantasy land.

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Quit a difference between the NAM and RGEM with 700mb VVs, over us late tonight. Make a difference in qpf amounts and amount boundary level cooling we see :

 

2mcxgf6.jpg

 

2ni1cpk.jpg

As always, the answer probably lies somewhere between the two, RGEM probably overreacted a bit with it's shift east, NAM is out to lunch as always. My guess is somewhere in between the two, maybe similar to the 6z RGEM, but with 40% less QPF up here, somewhere around 10-12 mm or so. NAM is about 25mm, which is insane.

-skisheep

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It's very difficult as a forecaster to toss them completely, especially when they were consistent essentially from 84 hours until 12-18 hours. So my forecast 24 hours before the event weighted the Euro and NCEP models about 70/30 respectively. And even that, trying to provide a sense of normalcy with a blend, ended up busting high by about 3 inches.

 

So I think at this point it's safe to say that the NAM, SREF and high resolution models are making things more difficult for forecasters than anything else.

 

any thoughts as to why the higher resolution models have progressively gotten worse, especially this season?

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It's crazy that only a couple hundredths of QPF have fallen over the area, given even the Euro showing over 1" QPF. 

 

The high pressure and dry air to the north was more formidable than the models thought that it would be. 

Really unlucky timing with the Peak of the -AO suppression.

 

 

 

 

 

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.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...

ALL SYNOPTIC SCALE MODELS SHOW THE UPPER LVL LOW/SHORT WAVE OVER

THE NORTHERN GREAT LAKES MVG SE AND ROTATING AROUND THE STRONGER

OFFSHORE UPPER LOW...FORMING AN INVERTED NORLUN TROUGH.

HIGH CONFIDENCE IN WIDESPREAD PRECIPITATION AMOUNTS RANGING FROM

1/4 TO 1/2 INCH LIQUID EQUIVALENTS MAINLY TONIGHT THRU FRI

MORNING AREA WIDE.

CONDITIONS ARE FAVORABLE FOR NARROW BANDING WITH ISOLATED 3/4 INCH AMOUNTS.

BASED ON A NORTH WIND TRAJECTORY OVER LAND...SFC TEMPS SHOULD DROP

A FEW DEGS LOWER AREA WIDE TONIGHT THRU FRI MORNING CAUSING AN

ACCUMULATING SNOWFALL RANGING FROM 2-4 INCHES ACROSS NYC METRO TO

4-6 INCHES ACROSS SOUTHERN CT.

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It's been flurrying here all day but they have been small flakes. All in all none of the models really handled the coastal threat well with the nam and SREFS being atrocious.

 

The key was watching the difficulty that the precip sheild had advancing north yesterday into the dry air and high pressure.

You could see that the models were overdone with the precip forecasts. Back in the old days, the forecasters had to often

rely on observations and nowcasting since the models were much less reliable. I am not sure how anyone did a successful

snowfall forecast in the 70's and 80's off the Alden Difax charts. 

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We have a short-term model battle, with RGEM/GFS shifting north on the convergence zone/trough axis and the UKMET/HRRR shifting south.  Most of the difference seems to be related not so much to how much upstream ridging there is, but instead how strong the blocking over se Canada is.  

 

Given the tenacity of the block so far and SPC mesoanalysis supporting a slightly stronger block than the GFS/RGEM suggested, I'd have to side with the slightly further south solutions.  However, there is little room for error here as a 25 mile shift in the convergence zone would take the steady snow out of SW CT/most of LI.  

 

Current 700 mb analysis showing developing convergence zone from n. of Lake Ontario to LI/CT.   Note the deep moisture cuts off sharply a little bit south of the convergence zone:

 

post-88-0-79070000-1362677677_thumb.gif

 

Another good link for detailed model analysis:

 

http://www.hpc.ncep.noaa.gov/mdd/mddoutput/

 

 

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Actually the euro is wetter that was just through 30. Through 36 everyone NYC north and east is 0.5+.0.75+ for basically all of ct except extreme SW part of the state.

That's a good sign. Hopefully as jconsor said this convergence zone can dig a little further and include more in the snow. And hopefully at night we can mitigate the warm temps somewhat. Too many hopefully's... :(

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