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President's Day Weekend 2015 Storm Potential 2/14-2/15


bluewave

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I will post this 1 last time . Yes the mean is N of KNYC  , but the spread is to the south which means that the model is likely to correct there  .

So watch and see how this probably corrects south and fall in line with the Euro and GGEM . sref_namer_066_500_vort_ht.gif

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I will post this 1 last time . Yes the mean is N of KNYC  , but the spread is to the south which means that the model is likely to correct there  .

So watch and see how this probably corrects south and fall in line with the Euro and GGEM . 

 

When I hear mean I think of average, which would mean the consensus is north over the ensembles.  But yet your saying the spread is south...are different members weighted differently, otherwise that doesn't make sense (this is the computer scientist in me talking), I'm still a WX newb

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When I hear mean I think of average, which would mean the consensus is north over the ensembles. But yet your saying the spread is south...are different members weighted differently, otherwise that doesn't make sense (this is the computer scientist in me talking), I'm still a WX newb

Yes the mean is the average per say, however, members really far off can skew it. For example if you wanted the mean of 1,2,3,4, 100; the 100 would significantly skew the mean, yet the spread would be favoring to the 1,2,3,4.

Edit : So what he is saying is that the majority of the ensembles are towards the south, but the mean is being skewed by a couple of Northern members.

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Yes the mean is the average per say, however, members really far off can skew it. For example if you wanted the mean is 1,2,3,4, 100; the 100 would significantly skew the mean, yet the spread would be favoring to the 1,2,3,4.

Edit : So what he is saying is that the majority of the ensembles are towards the south, but the mean is being skewed by a couple of Northern members.

 

Understood, then would it be safe to say that the northern models are either weighted more heavily, or that they are radically north....is there anyway to view the individual members that make up the ensembles, I think it would be interesting from a math / comp sci standpoint to see how they derive a final solution

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Yes the mean is the average per say, however, members really far off can skew it. For example if you wanted the mean of 1,2,3,4, 100; the 100 would significantly skew the mean, yet the spread would be favoring to the 1,2,3,4.

Edit : So what he is saying is that the majority of the ensembles are towards the south, but the mean is being skewed by a couple of Northern members.

so they are both right. thanks 

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Understood, then would it be safe to say that the northern models are either weighted more heavily, or that they are radically north....is there anyway to view the individual members that make up the ensembles, I think it would be interesting from a math / comp sci standpoint to see how they derive a final solution

http://mp1.met.psu.edu/~fxg1/ewallsref.html
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When I hear mean I think of average, which would mean the consensus is north over the ensembles. But yet your saying the spread is south...are different members weighted differently, otherwise that doesn't make sense (this is the computer scientist in me talking), I'm still a WX newb

the "spread" is more like the median, in that more members have it south of that position but there are likely some outliers skewing the mean north.
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500 millibar lows typically follow the greatest positive vorticity advection. On the 18 z NAM at hour 60 you clearly see the greatest vorticity advection south of NYC. I would have to believe that the 500 millibar low based on what is shown will end up south of NYC.

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500 millibar lows typically follow the greatest positive vorticity advection. On the 18 z NAM at hour 60 you clearly see the greatest vorticity advection south of NYC. I would have to believe that the 500 millibar low based on what is shown will end up south of NYC.

and so long as that 500 MB is south of us we are looking good for at least a burst of heavy snow correct? Most importantly there seem to be some positive trends with slight shifts SW to the SLP on all major models ( at the very least nothing has shifted North)

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and so long as that 500 MB is south of us we are looking good for at least a burst of heavy snow correct? Most importantly there seem to be some positive trends with slight shifts SW to the SLP on all major models ( at the very least nothing has shifted North)

There are some positive trends today, and yes if the 500 mb low is south then the surface low will be slightly further southwest allowing the surface low to get better organized to give us a shot of some mod/heavy snow.

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Since he had Long Island raining during the clipper ( there was 1 to 2 ) and the one that followed early Feb where he declared Long Island was rain for 85 % of the storm I had 8 for KNYC and 6 to 9 fell , its up to you who you believe .

I don't care who's right on this, but you've had your busts as well. You were trying to talk everyone off the ledge by the "blizzard" because we had the Euro And were sure it would be right.
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Hah yeah I feel like we've been down this road before, eh? I'm thinking 2-4" for most of us, 4-8" eastern LI, 10-15" Boston area and 24"+ for parts of coastal Maine

That's reasonable but it'll be interesting if a subltle southward trend at 500mb will translate to something slightly better.
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That's reasonable but it'll be interesting if a subltle southward trend at 500mb will translate to something slightly better.

It's possible, but at this point no model is putting out snowfall amounts that are wildly different and higher than that, so no reason to go higher. I think we've walked ourself right into the wall of disappointment by banking on things changing and the hope that if "this" does "that", then it'd be more snow, when in reality if "that" does "this", it would lead to even less snow than the lower end of many forecasts.....that is the reason why many situations (such as the one occurring right now) turns from a modeled light snowfall into the thinking that it could be much more (if things change for the better), but ultimately can end up changing for the worst and be less than even the light snowfall originally modeled. Funny how many of the complaints are in regards to the models being wrong and busting, and while clearly they are wrong many times, especially the further out in time you go, if we were to take a combination of the models especially when they form a consensus, they would not be really that bad when it comes to what we see in terms of snowfall accumulations. It is when we step in and decide "wait, this model is doing this wrong.....so this should mean much more snow with high ratios, etc etc.....so the 2-4 it shows is wrong and should be 4-8" that we end up ultimately disappointed (and blame the models anyway)
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It's possible, but at this point no model is putting out snowfall amounts that are wildly different and higher than that, so no reason to go higher. I think we've walked ourself right into the wall of disappointment by banking on things changing and the hope that if "this" does "that", then it'd be more snow, when in reality if "that" does "this", it would lead to even less snow than the lower end of many forecasts.....that is the reason why many situations (such as the one occurring right now) turns from a modeled light snowfall into the thinking that it could be much more (if things change for the better), but ultimately can end up changing for the worst and be less than even the light snowfall originally modeled

Euro EPS mean is in the 2-3" NNJ into metro NYC/WLI (at 10:1 ratio, you pick your own) 2 of the 51 member are near or just over 6" for CPK and there are about 13 with 1-2".  Still think a 1-3" or 2-4" fcst is way to go right now.  Mean SLP does have suggestion of weak norlun across L.I. into NYC.

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