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1/12 Possible Overrunning Storm


Zelocita Weather

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On the gfs I stay mostly/all frozen even in the height of the storm.

one has to wonder about  the GFS northern stream bias coming into play here keeping it too cold when the over running precip arrives I think a compromise between the NAM and GFS is the best idea IMHO

 

http://www.tropicaltidbits.com/analysis/models/navm.html?model=gfs&region=us&pkg=mslp_pcpn_frzn&runtime=2015011012&fh=48&xpos=0&ypos=1100

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One thing to keep in mind is that it has been exceptionally cold in the region as of late. There will likely be 1" of snow still covering the ground in most places as this storm rolls in Sunday night.

 

With ground temperatures this cold and an arctic airmass which is *departing* and yet not completely gone, with a *weak* wave moving off the coast to our southeast--I think most areas in the tristate area will have significant icy conditions very late Sunday, through Monday morning. Temperatures will be very stubborn to rise. The only area I'd exclude, at this time, is southeastern sections of LI, with enough of a fetch off the relatively warm Atlantic, to keep everything liquid. The North shore, even way out east could potentially have problems early to around Monday a.m. rush hour...

 

The low level cold WILL be reluctant to leave with relatively weak WAA, and low level cold that is fairly well entrenched throughout the Northeast.

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not much QPF though....and the RGEM was dead on the other day and it's alot warmer along with the NAM.   I'm not that impressed

 

I could not surmise much from the RGEM given its at the end of its run.  The only thing I did see was that it is picking up on the mid layers being warmer than most models, it trended warmer there from its 06Z run but I thought at the surface it trended colder...here is its Ptype at 48 hours, it sees mixed precip down in Delaware, thats a giveaway it definitely hits on the idea the surface will be cold.  The reason the NAM torches everyone is it has a funky deeper surface low, so far no other model has that.  I think this may come down to a nowcasting deal for FZRA near and just north of NYC, its very tight around 34/25 or so T/Td spread when the precip moves in, if it falls as very light rain initially its possible we won't be able to wet bulb down, this is the sort of event that could depend heavily on Ptype and intensity right at commencement time, if we come down as sleet or even a sleet/snow mix and it comes down at a decent clip we are gonna dip to 29-31 and we won't budge with models showing a WSW to eventually N wind at 5 knots.  That is similar to what occurred on 11/29/95, everyone bought into the warm BL but we wet bulbed initially and then winds went north and we never recovered...had we not had mod sleet to start it may have been mostly a slop event.

 

 

gemreg12_PT.17.gif?t=1420910060

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another thing to consider is how long will clear skies or even partly cloudy skies hold on sunday night to lower temps before the clouds and precip arrive .............if you see temps at midnight lower then 26 - 27 then there is going to be a problem

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another thing to consider is how long will clear skies or even partly cloudy skies hold on sunday night to lower temps before the clouds and precip arrive .............if you see temps at midnight lower then 26 - 27 then there is going to be a problem

 

Also watch dewpoints down over the MA, the models all advect DPs to 25-27 here by daybreak Monday, they tend to overdo the moisture return at times on SW flow in the low levels in winter, so if those end up closer to 20-22 its a big difference if we are 33-35 at the start on temps.

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Kudos to Upton with the  39 and Rain was spot on as per 12z Euro  at KNYC .

Canadian has us ice the entire storm then it tries to spin up another storm on Wednesday then another later in the week - now if it was one of those snowy winters like last year we would be getting alot of snow but not this year

 

http://www.tropicaltidbits.com/analysis/models/navm.html?model=gem&region=us&pkg=mslp_pcpn_frzn&runtime=2015011012&fh=6&xpos=0&ypos=200

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Canadian has us ice the entire storm then it tries to spin up another storm on Wednesday then another later in the week - now if it was one of those snowy winters like last year we would be getting alot of snow but not this year

 

http://www.tropicaltidbits.com/analysis/models/navm.html?model=gem&region=us&pkg=mslp_pcpn_frzn&runtime=2015011012&fh=6&xpos=0&ypos=200

The GFS has that Wed SW too . That sitting there will prevent the late next week from coming .

If that`s there when it exits it will pull the trough axis east .

Always something .

 

The Euro has it too .

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The GFS has that Wed SW too . That sitting there will prevent the late next week from coming .

If that`s there when it exits it will pull the trough axis east .

Always something .

 

The Euro has it too .

exactly - I can invision most of us entering February with less then 10 inches of season total snowfall some of us under 5 - we still have to deal with the advertised January thaw

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Kudos to Upton with the 39 and Rain was spot on as per 12z Euro at KNYC .

I'm just going to use the RGEM ptype for this event and add a cool touch since it's had a slight warm bias on that this winter compared to last year where it was always dead on I just don't know what to make of the ECMWF being so warm in the BL, the NAM makes sense being warm because it has that robust surface low the European does not so that surface warmth makes no sense to me on light winds and no east wind

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I'm just going to use the RGEM ptype for this event and add a cool touch since it's had a slight warm bias on that this winter compared to last year where it was always dead on I just don't know what to make of the ECMWF being so warm in the BL, the NAM makes sense being warm because it has that robust surface low the European does not so that surface warmth makes no sense to me on light winds and no east wind

I think we have retreating HP and the S flow ahead of WAA just pushes too far north. The backside shot of cold air is 6 hours late and almost all the models but the GFS which bias is come west in the end now see it.

I think the RGEM is a great short range model. It's the only cool card left.

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The GFS bias of being too far south and east, becomes far less significant inside 48 hours. I actually strongly favor the GFS track over the other globals, particularly the way this season has gone so far  -- weaker, further south and east, strong confluence/PV influence. 

 

Based on the upper level Synoptic setup, I don't see any reason for this wave to become wrapped up and closer to the coast. This looks like a sheared out mess to me, that will remain suppressed.

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The GFS bias of being too far south and east, becomes far less significant inside 48 hours. I actually strongly favor the GFS track over the other globals, particularly the way this season has gone so far  -- weaker, further south and east, strong confluence/PV influence. 

 

Based on the upper level Synoptic setup, I don't see any reason for this wave to become wrapped up and closer to the coast. This looks like a sheared out mess to me, that will remain suppressed.

 

Here is the 18Z RGEM...too far out in its range to be taken for gospel but it shows my concerns clearly...it obviously has NYC in rain but through 18Z the FZRA line is literally just to their NW, anytime so far this winter the RGEM has shown this signature LGA and occasionally JFK have been frozen, its tended to be 20-30 miles or so too far NW with the frozen line.  The dead giveaway to this at 15Z is how the mix line is in Ocean and Monmouth county yet the 5 boroughs is rain, that never happens.  Also notice how it has PHL or TTN mostly frozen til somewhere between 18-21Z, in a non CAD situation if those stations are frozen, NYC usually is as well, especially in the absence of an east wind which we won't have in this event.

 

 

 

gemreg18_PT.16.gif?t=1420927136

 

gemreg18_PT.17.gif?t=1420927136

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No, when water freezes, the latent heat from the liquid water transitioning into a solid is released into the air. It's the same mechanism that powers hurricanes-warm ocean water transitioning into a gas. 

Actually, you have it backwards.  Hurricanes are powered by the sun providing the energy to evaporate warm ocean water, followed by that water vapor rising, cooling and releasing its latent heat, as it condenses.  Condensation and freezing both release latent heat to the atmosphere, while melting and evaporation require heat from the atmosphere (or elsewhere, like the sun).  It takes ~10 times more energy to evaporate water than it does to melt ice, because there is a far greater increase in system entropy when creating a gas vs. creating a liquid - 2nd law of thermodynamics - take a look at my other post on this. 

 

http://wxguys.ssec.wisc.edu/2012/09/03/what-is-the-source-of-energy-for-hurricanes/

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