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Potential Winter Storm March 6-7


NEG NAO

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Time is running out on this . We are now down to 5 days or 120 hours and virtually all guidance tonight from the NAVGEM to the ECM is in agreement with this being south and east. The guidance certainly has not trended good since 12 Z runs earlier in the afternoon 

If you see this on Monday, time will be running out. Not yet, however.

WX/PT

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Time is running out on this . We are now down to 5 days or 120 hours and virtually all guidance tonight from the NAVGEM to the ECM is in agreement with this being south and east. The guidance certainly has not trended good since 12 Z runs earlier in the afternoon

120 hrs out and time is running out ? Too you re last point

Thrs at 12z it was Atlanta to Raonoke bullseye

Friday at 12z it was DC a bullseye

Sat at 12z lets see

Sun at 12z let's see.

Mon at 12z let's see.

If after that it shows a shunt , then with the NAO that deeply negatitive I could believe it , but let's see the 12z and see the data absorbed from getting on the grid. And then 3 days of it in the US gets you to 48 hrs

Problem is we've been tracking it from 9 days so it feels like an eternity. It may b a shunt but at 120 hrs one would b nuts to make that call

I don't like seeing a whiff either on the euro but it's not that late yet.

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The current model runs are tracking as far south as they are due to the 400 meter block

over Canada. 

 

attachicon.gif00zeuro500mbHeightAnomalyNA048.gif

 

It's the confluence with the ULL,underneath the block, that keeps this more suppressed. The GFS, GGEM, and ECMWF were slower to lift out the ULL last night. Even with more phasing with the northern stream, the confluence still suppresses the surface low or precip shield, to our south.

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It's the confluence with the ULL,underneath the block, that keeps this more suppressed. The GFS, GGEM, and ECMWF were slower to lift out the ULL last night. Even with more phasing with the northern stream, the confluence still suppresses the surface low or precip shield, to our south.

 

That stronger block is responsible for the increased confluence as the trailing piece of the 50/50 energy 

is slower to exit east  and suppresses the storm track. it's similar in strength to the 400 meter block

on 2/6/10 that caused the confluence zone to be too far south. We always run the risk of suppression

when the storm coincides with the peak -AO dates. That's why we usually do better when the AO 

starts to recover form the low.

 

 

 

 

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That stronger block is responsible for the increased confluence as the trailing piece of the 50/50 energy 

is slower to exit east  and suppresses the storm track. it's similar in strength to the 400 meter block

on 2/6/10 that caused the confluence zone to be too far south. We always run the risk of suppression

when the storm coincides with the peak -AO dates. That's why we usually do better when the AO 

starts to recover form the low.

 

attachicon.gif500.gif

 

attachicon.gifao.sprd2.gif

It's a cut-off block, it's not really preventing the ULL from sliding out. A stronger block pressing down, actually causes the ULL split or slide further east.

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It's a cut-off block, it's not really preventing the ULL from sliding out. A stronger block pressing down, actually causes the ULL split or slide further east.

 

The strength of the block is key. The reason the NAVGEM is further north is that it has a weaker block which

doesn't trap the trailing piece of 50/50 energy underneath. The only way this will trend north the next few days

is if the models are too strong with the block and start to back off.

 

 

 

 

 

 

 

 

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The block over Canada is currently a 2 standard deviation block and forecast to exceed 3 standard deviations in coming days.

 

The Euro has a +416 meter anomaly in 48 hrs which initially forces the low to track a little too far south.

 

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The strength of the block is key. The reason the NAVGEM is further north is that it has a weaker block which

doesn't trap the trailing piece of 50/50 energy underneath. The only way this will trend north the next few days

is if the models are too strong with the block and start to back off.

 

attachicon.gifnvg10.500.114.namer.gif

 

attachicon.gifGeopotential3250032hPa32and32Temperature32at3285032hPa_North32America_120.gif

 

That is the after the storm is already on the coast. The block weakens after it starts pressing down and merging with SE ridge.

 

The block is at 552dm, when the Pacific s/w over the Upper Midwest. Same as the 0z Euro:

post-187-0-37205500-1362233730_thumb.gif

 

 

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That is the after the storm is already on the coast. The block weakens after it starts pressing down and merging with SE ridge.

 

But the initial track of the low is further south as it encounters the block as it's building down toward the GL.

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Just catching up now. The models have gone back and forth with the orientation of the block and thus the location of the associated confluence almost every run. So they can easily change back again to where they were 24 hours ago. Model consensus (or close to it) almost 5 days out really doesn't mean much considering all the factors at play.

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The strength of the block is key. The reason the NAVGEM is further north is that it has a weaker block which

doesn't trap the trailing piece of 50/50 energy underneath. The only way this will trend north the next few days

is if the models are too strong with the block and start to back off.

nvg10.500.114.namer.gif

Geopotential3250032hPa32and32Temperature32at3285032hPa_North32America_120.gif

That is the after the storm is already on the coast. The block weakens after it starts pressing down and merging with SE ridge.

The block is at 552dm, when the Pacific s/w over the Upper Midwest. Same as the 0z Euro:

post-187-0-37205500-1362233730_thumb.gif

Yeah, we need to get back to the block linking with the SE ridge, at least somewhat. I think that's doable considering how often they have wavered with the orientation of the block. I think part of the reason they are waffling with that is because they don't have a great idea as to what's happening with the northern stream energy in between our storm and our block. Subtle changes with the northern stream will make the block either link too much with the Midwest ridging (suppressive), or have it go back to linking with the SE ridge. The NAVGEM looks to link it with the SE ridge, helping heights to rise.

I think the orientation is more important than magnitude. Though, shifting the block east makes it act like a weaker block, so in that regard I guess you're weakening it's magnitude, though I don't look at it that way.

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Also, as I've said before, shifting the orientation of the block to the east not only links it to the SE ridge, but helps to move the downstream confluence further east (out of the way).

What's a tad bothersome though is that if you shift the block's orientation to the east, your cold air source is not as good, since the high pressures would bring maritime air as opposed to continental air.

But I think there are a couple of positions where we can get cold for snow and the right track. But there are also positions where we can get a further north track but have temps be an issue.

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Pretty strong consensus now that the NAO is at least 3 SD below normal , the euro actually heads it towards 4. There's pretty good consensus that a strong SLP is off HSE at 120 hrs. We happen to b in between.

So it comes down to the position of the block , if it's 150 miles north , this spins up , 150 miles south it's suppressed . In my mind that's all that's left to be sorted.

And it's going to be very easy for the models to center this a little north or a little south over the next few days. I really think I wana see this 72 hours out before I go all in .

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Also, as I've said before, shifting the orientation of the block to the east not only links it to the SE ridge, but helps to move the downstream confluence further east (out of the way).

What's a tad bothersome though is that if you shift the block's orientation to the east, your cold air source is not as good, since the high pressures would bring maritime air as opposed to continental air.

But I think there are a couple of positions where we can get cold for snow and the right track. But there are also positions where we can get a further north track but have temps be an issue.

Weren't there double barreled HPs over the Midwest in the past few runs?

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