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December and a Hint of January Pattern Discussion


Bob Chill

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Canadian predicts nao to move extremely pos: http://twitter.com/RyanMaue/status/407020172096991232/photo/1

That would kinda suck, but then we have had a -NAO that doesnt perform at all (see last winter). When cold is on our side of the globe and we have a decent west based -NAO, its just so much easier to get snow chances in the MA. Especially if our friend the 50/50 vortex shows up. The cold stays locked in, and if the PNA cooperates, trough position/orientation is usually ideal. The reality is we may not see that this winter, but at least this pattern has been able to deliver cold thus far. There is at least some potential, and we didnt have much of that last year.

 

FWIW, GFS and GEFS forecasts imply neutral to perhaps slightly negative NAO week 2 of December.

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Looks like one helluva ICE storm on the 12z GFS Day 7-8...850 temps soar, but HP keeps the low levels frigid. 

 

Its an interesting forecast,  the ridge in off the west coast is far enough west that there is room for even more troffing in the west than the GFS indicates at around 144 to 156 hours.  There are some 06Z GEFS members that have that idea.  Both the GFS and last nights euro have a monster shortwave diving southward across canada.  How that monster interacts with the shortwave energy coming out of the southwest will determine whether we have a really flat wave like the GFS,  a low towards the Great Lakes like last night's euro or something in between like the euro ens mean.  My gut feeling is the in between idea has more traction which would offer a possible snow or ice to rain solution for dc and possible snow to ice solution for points west but right now it's still too early to get into specifics as the operational euro could be right though even it has us in some winter weather prior to the low going towards the lakes. 

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Late sun through Mon is about a good an overunning setup you can ask for all things considered. The 9th remains a solid window of op.

Agreed and you can see the GFS started to show what the Euro showed last night..CAD sig.  Let's hope it sticks around the closer in we get to this.   But I'm on board.  WD index is high.

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Agreed and you can see the GFS started to show what the Euro showed last night..CAD sig. Let's hope it sticks around the closer in we get to this. But I'm on board. WD index is high.

Op run at 8 days disclaimer of course but you can't ask for a better surface hp placement and boundary alignment. Now the euro and gfs both show a decent chance with different solutions. So if you take the blend you get 1/1=1 decent chance at something.

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Agreed and you can see the GFS started to show what the Euro showed last night..CAD sig. Let's hope it sticks around the closer in we get to this. But I'm on board. WD index is high.

Seems pretty much in line with what the gfs has been showing for a while. Looks very much in line with what it showed at 0z. I like how it's been abundant in its ensembles too.

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There looks to be another overrunning chance earlier than that -- Days 5 to 6 -- but that is rain.  I assume that is what lays down  the boundaries for our later chances?

yep....in the old days :oldman: , it was common to have the first bout of precip come through as rain with the trailing slp that dragged the boundary to our south with our wintry chances increasing with round 2, or 3 if there was one

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Is that a splitting of the PV I also see at the end of the run?

Not sure. I don't know the classic evolution of that pattern.

My guess is the gfs is doing the showing signs thing and in reality if a block happens it will be delayed. If stable ridging does poke into gl with stable ridging poleward in ak then it could lock in cold on our side and buckle the flow. Total wag speculation but if anything like that we're to happen then the last week or so of the month could be fun.

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I think it's gonna take one hell of a fetch to get any moisture into the arctic air for much snow or ice, so I'm expecting more of a virgageddon type event to play out.  Maybe some freezing drizzle, etc.  But there is always a fine line when timing the precipitation with an arctic frontal passage.  As Wes pointed out these are the types of setups that typically trend colder and drier as we get closer to verification time, and I'm leaning that direction.  I believe this will be more of a dry than wet event for the immediate metro area.  Points south may see a solid snow/ice storm. Virgageddon!

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I think it's gonna take one hell of a fetch to get any moisture into the arctic air for much snow or ice, so I'm expecting more of a virgageddon type event to play out. Maybe some freezing drizzle, etc. But there is always a fine line when timing the precipitation with an arctic frontal passage. As Wes pointed out these are the types of setups that typically trend colder and drier as we get closer to verification time, and I'm leaning that direction. I believe this will be more of a dry than wet event for the immediate metro area. Points south may see a solid snow/ice storm. Virgageddon!

Your first and last sentence are completely at odds with each other. Might want to rethink the whole argument.

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I think it's gonna take one hell of a fetch to get any moisture into the arctic air for much snow or ice, so I'm expecting more of a virgageddon type event to play out.  Maybe some freezing drizzle, etc.  But there is always a fine line when timing the precipitation with an arctic frontal passage.  As Wes pointed out these are the types of setups that typically trend colder and drier as we get closer to verification time, and I'm leaning that direction.  I believe this will be more of a dry than wet event for the immediate metro area.  Points south may see a solid snow/ice storm. Virgageddon!

 

 

My comment was only if the wave was weak with the vort to our north.    With a strong vort, that's not always true but then the wave might go north of us. 

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I think it's gonna take one hell of a fetch to get any moisture into the arctic air for much snow or ice, so I'm expecting more of a virgageddon type event to play out.  Maybe some freezing drizzle, etc.  But there is always a fine line when timing the precipitation with an arctic frontal passage.  As Wes pointed out these are the types of setups that typically trend colder and drier as we get closer to verification time, and I'm leaning that direction.  I believe this will be more of a dry than wet event for the immediate metro area.  Points south may see a solid snow/ice storm. Virgageddon!

Not sure how you can be expecting a virga fest on a potential event that is 8 days out. So many details yet to be resolved and there are a variety of outcomes possible. I will say that a freezing drizzle event its probably the least likely.

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My comment was only if the wave was weak with the vort to our north.    With a strong vort, that's not always true but then the wave might go north of us. 

Which is why typically we are cold and dry (weak vort slides south of the deep cold air) or warm and wet, the strong vort moves the arctic boundary north of us.  I'm leaning toward cold and dry at the surface with plenty of virga on radar.

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Not sure how you can be expecting a virga fest on a potential event that is 8 days out. So many details yet to be resolved and there are a variety of outcomes possible. I will say that a freezing drizzle event its probably the least likely.

I agree, at this time range it's hard to be definitive about anything.

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