Historic Height Anomalies Shown

[FoothillsNC]

I've never seen this extreme level since I've been following these indices, so thought it would be good to take note of. HPC also mentioned the 850 anamolies over the Midatlantic to Southeast are progged to be over 6 SD below normal Mon/Tue Dec 13/14. Will be interesting to see to watch how this unfolds, and what happens to any southern ejections later next week.

Day 8-10:

Day 6:

Day 10:

[Brian]

I've never seen this extreme level since I've been following these indices, so thought it would be good to take note of. HPC also mentioned the 850 anamolies over the Midatlantic to Southeast are progged to be over 6 SD below normal Mon/Tue Dec 13/14. Will be interesting to see to watch how this unfolds, and what happens to any southern ejections later next week.

Day 8-10:

Day 6:

Day 10:

For us non Meteos, what does this mean please?? Thanks

[FoothillsNC]

For us non Meteos, what does this mean please?? Thanks

Means the high latitude blocking is to the extreme, or forecast to head to the extreme. I was wondering if anyone else has seen higher blocking than whats progged. I never have. The red closed circles over southern Greenland are what we're looking at. Its the reason that the ECMWF and GFS are forecasting the extreme cold wave in the Southeast next week.

[Brian]

Awesome, thanks for the explanation,,,,I just looked at my iphone wather icon, and it has 23 and 10 for Atlanta on Monday/night???

[BNAwx]

This may not be the place for this discussion but I wonder what the main factors are that are pushing the NAO to such extreme negative levels? I'm sure there are many opinions but to see it this extreme makes you scratch your head a little.

[SeanVA]

All those forcasts that had low negative-positive NAO/AO aren't looking too good.

[WXinCanton]

This may not be the place for this discussion but I wonder what the main factors are that are pushing the NAO to such extreme negative levels? I'm sure there are many opinions but to see it this extreme makes you scratch your head a little.

Solar cycle? Solar activity has been pretty low, and I have seen some people linking that with NAO. Robert would know more than me on this, but solar cycle 24 is actually on a Dalton like cycle so far. Maybe even slightly below.

[CAD_Wedge_NC]

This may not be the place for this discussion but I wonder what the main factors are that are pushing the NAO to such extreme negative levels? I'm sure there are many opinions but to see it this extreme makes you scratch your head a little.

I believe it is a combination of low solar activity and the multi-year -NAO cycle we seem to be heading into.

[FoothillsNC]

I don't know enough on the Dalton cycles tolink it , but most likely everything is linked, which is pretty much like nature anyway to be tied with something else. I'm sure a big player is the SST anomalies, which is related to the land-ocean cycle, sea currents, trade winds, prevaling westerlies, storm tracks/ ridge/trough pressure patterns and is the function, or the functioner of any of the these (chicken-egg theory). So I'm not sure why the strong block, but if the warm waters there aren't the cause, they will enhance it most likely, and we're in a longer term cycle of -NAO anyway. CPC has a study on it, I'll hunt the link.

[Carvers Gap]

So, what does that mean the weather is like in Greenland?

[Itunis]

So, what does that mean the weather is like in Greenland?

http://www.wunderground.com/global/stations/04221.html

69 degrees north and they're getting a cold rain...

[Carvers Gap]

http://www.wundergro...ions/04221.html

69 degrees north and they're getting a cold rain...

I bet someone up there is saying, " #!@* that southeast ridge!"

[Stormsfury]

Even in the January 1985 arctic outbreak, it was the sheer strength of the polar vortex vs the blocking high (which at the apex of the Cold outbreak in the East) was rolling over and retrograding back into Canada and eventually merged with ridging in the west creating a +PNA a few days later, but the pattern broke down shortly afterwards. As the Greenland High (which by the way was only around 560 dm) was rolling over and retrograding, it forced the massive PV southward into the Eastern US which at times dropped below 470 DM and the shear magnitude of the PV dumped the motherload of arctic into the US.

The EC progs are phenomenal. The 3 day average 8 to 10 from Plymouth is 583 DM!!!!!!!!!!!!!! The average basically has the look of cold air flood gates are open for business, even with the 500mb much higher in heights than the JAN 85 PV (somewhere around 510DM vs the 470 DM in JAN 1985)

[FoothillsNC]

Even in the January 1985 arctic outbreak, it was the sheer strength of the polar vortex vs the blocking high (which at the apex of the Cold outbreak in the East) was rolling over and retrograding back into Canada and eventually merged with ridging in the west creating a +PNA a few days later, but the pattern broke down shortly afterwards. As the Greenland High (which by the way was only around 560 dm) was rolling over and retrograding, it forced the massive PV southward into the Eastern US which at times dropped below 470 DM and the shear magnitude of the PV dumped the motherload of arctic into the US.

The EC progs are phenomenal. The 3 day average 8 to 10 from Plymouth is 583 DM!!!!!!!!!!!!!! The average basically has the look of cold air flood gates are open for business, even with the 500mb much higher in heights than the JAN 85 PV (somewhere around 510DM vs the 470 DM in JAN 1985)

thanks for the input Fury. When is the last time blocking of this strength occurred?

[Stormsfury]

thanks for the input Fury. When is the last time blocking of this strength occurred?

I honestly can't recall without going into some detailed research.

Actually Jan 8th 1977 582 DM East Based and it ended up retrograding to create the strong AO blocking episode that occurred in JAN 1977 particularly for the 2nd half of that month

http://vortex.plymou...yy=&mm=&dd=&hh=

[DixieBlizzard]

I honestly can't recall without going into some detailed research.

Actually Jan 8th 1977 582 DM East Based and it ended up retrograding to create the strong AO blocking episode that occurred in JAN 1977 particularly for the 2nd half of that month

http://vortex.plymou...yy=&mm=&dd=&hh=

Good stuff SF, thanks!!!!

[UpStateCAD]

I honestly can't recall without going into some detailed research.

Actually Jan 8th 1977 582 DM East Based and it ended up retrograding to create the strong AO blocking episode that occurred in JAN 1977 particularly for the 2nd half of that month

http://vortex.plymou...yy=&mm=&dd=&hh=

YIKES. Boy I remeber the '77 cold. I was in HS at the time living in WV on the Ohio River. The river froze completely over. Barge traffic was very difficult. Schools closed for a weeks at a time. High's were in the low sigle digits. COLD STUFF.

[pcbjr]

Looks like some of the models are backing off of any real cold down this way after about the 22nd. Thoughts, given the scope of this thread?

Thanks in advance!

[jburns]

The river froze completely over. Barge traffic was very difficult.

Clearest cause and effect statement I have ever seen.