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Winter 2014-2015 Pattern Discussion Thread III


BIG FROSTY

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The 15 day EPS mean snowfall run is nasty for the east, all the way down to N-GA/SC.  2-6" across most of NC.  The control run is just ridiculous has like 20" of snow across TN/NC days 9-15.  Has 6-8 all the way down to central GA/SC.  Looks like southern slider after southern slider.

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The 15 day EPS mean snowfall run is nasty for the east, all the way down to N-GA/SC. 2-6" across most of NC. The control run is just ridiculous has like 20" of snow across TN/NC days 9-15. Has 6-8 all the way down to central GA/SC. Looks like southern slider after southern slider.

Where do you get your snowfall maps?

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Sure thing... I should mention aside from the Equatorial VP research (-VP 30-60E), the relationships I pointed out a week or so ago between MJO Phase 7 in January & a relatively higher frequency of winter storms here in NC held up nicely for the winter weather event we had last night & this morning across central-eastern NC.

NC-winter-storms-1979-present-and-MJO.pn

 

 

last.90d.noENSO.RMMPhase.png

 

Webber,

 

Very nice couple of posts. I actually understand and much appreciate your explanation!

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(An amateur description of phenomena here, but it is only a few sentences so i think it at least is comprehensible)

I've been busy so I may have missed the occurrence systems bringing large snow accumulations in the midwest or northeast so far this winter.

If there really haven't been many of these strong winter systems yet, I think either the later half of this winter is going to be very noteworthy somewhere in the country, or, the spring/early summer pattern with very large convective regions from last year may happen again.

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Dollar bills. Don't think you can find them on the web for free, unless someone posts them. You have to get them from pay sites. Maybe Pack will be kind and draw us some maps later. :)

That would be nice. I'm interested in what site he uses.

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If that trough goes a little more neutral/negative this is going to be HECS as depicted on the GFS. It's a shame it's 200 hours away and not 75.  :weep:

 

Really loving the Greenland ridging the GFS is trending to.  The 18z show a solid ridge over Greenland by the mid range. This will keep the cold air in place by the time this potential storm pops over the GOM.  Negative NAO we miss you.

 

yrN6Hue.gif

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EURO has picked up on our 1/23 storm I see. Suprised this wasn't talked about a bit more although that pesky lakes low probably ruins this run. I think we may be on to something here. Looks pretty cold to me.

Don't sweat the lakes low. It's not a typical lakes low with low pressure fields acting like a warm vaccum and suck the track to the west. The lakes low in this setup is in response to the big closed upper level low over the lakes (pv). This feature acts like a block and not a vacuum. If the pv was up by hudson and the low was present it would be the typical lakes low screw job. The pattern looks really good for no cut.

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If that trough goes a little more neutral/negative this is going to be HECS as depicted on the GFS. It's a shame it's 200 hours away and not 75.  :weep:

 

Heck.  I'd take it inside 120, which is where I'll start to become a believer if euro and gfs still have it Sunday.

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MJO about to hit phase 7,good sign.Builds the ridge in the west.

 

Another good sign lately is the forecasted weakened PV getting pushed off the pole /Greenland area and shoved into Russia,allowing higher heights possibly.The forecast for the AO to go negative has a chance this time I think.

 

I actually feel a little more optimistic this evening,carry on.

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Webber,

 

Very nice couple of posts. I actually understand and much appreciate your explanation!

Thanks.

 

It appears the pattern will soon be hitting the reset button as the MJO finally leaves the Pacific in about a week or so. The latest MJO pulse in phase 5 & 6 did set a few daily records for amplitude for this time in the year (as I discussed/explained several days ago, the majority of the extreme MJO events tend to occur in the transition period between the Asian & Australian monsoons, especially in March). IMO, this upcoming progression progression in the Pacific is acting in a very predictable manner and the models at least in this region of the extra tropics, appear to have the correct general idea on how this will unfold. The most notable feature of course is the profound shift in enhanced tropical convection... The subtropical ridge over the North Pacific right now is quite strong and is displaced further north. This makes sense given that as the air tends to expand in the upper levels in response to latent heating overhead of the MJO's active cell, this causes air pressures to rise in the immediate surrounding region, specifically in the subtropics. The larger height gradient that results to the north of the energized subtropical ridge"squeezes" the flow, causing in this case, the Pacific jet to zonally expand & strengthen. The zonal expansion & intensification of the Pacific jet hence forces an eastward shift in its left exit region, thus the semi-permanent Aleutian Low also grows stronger and digs further east. This is the intraseasonal pattern we have now

gfs-ens_z500a5d_nhem_1.png

& the setup leading to this point is consistent w/ this orbital illustration of the atmospheric response to the MJO (I'm referring to the extratropical cyclonic anomalies, most noteworthy over the North Pacific during the Pacific MJO phases 6-8, but they actually manifest themselves (or start to appear) northwest of where the MJO regenerates in the Western Indian Ocean after naturally decaying over the central pacific, (i.e. North Africa). This approximation of the cyclonic anomaly propagation is represented by the black arrow w/ red numbers signifying their location as a function MJO phase, notice how it is in compliance w/ Allan Huffman's 500mb MJO winter composites...

Low-500mb-Heights-Global-Progression-and

MJO-Phase-1-8-500mb-AmplitudeAll-1024x27

Once the MJO reaches the eastern hemisphere, we'll really start to see the heights spike over Alaska & the EPO will fall... However, it's the nature of these strong Alaskan blocks to be relatively transient features, and the Pacific Jet loves to undercut them, thus robust Alaskan highs generally retrograde westward with time, causing the WPO to usually crash after we observe a large downturn in the EPO, and even so, there will come a point beyond that where anomalous troughing makes a return to the Aleutians. Given this information, the GFS ensembles appear correct overall...

gfs-ens_z500a5d_nhem_2.pnggfs-ens_z500a5d_nhem_3.png

 

Until then, this 500mb look is beautiful for overrunning/Miller B type storms, and they will remain the primary mode of wintry wx until the Atlantic decides to cooperate...

N-hem-500mb-NC-Miller-BCAD-Events.jpg

Idealistically, the sequence of the North Pacific pattern is as follows, Potent Aleutian Low (where we're at now)-> Pacific MJO amplitude weakens -> Subtropical Ridge falters -> flow within the Pacific Jet underneath the Aleutian Low dwindles -> Aleutian Low retrogrades & begins to be replaced by ridging near the West Coast of North America -> Continued Jet retraction leads to restoration of the +PDO base state w/ a residual trough hanging on within the cold tongue associated w/ the PDO & West Coast ridging continues to balloon west-northwestward into Alaska & the North Pacific (-EPO) -> Ridging continues to progress westward (transitioning to -WPO) -> Pacific Jet begins to undercut the retrograding N Pac ridge-> Anomalous ridging continues to retrograde westward, reaching the North Asian & arctic sectors, -> Split flow set-up fades completely and the Pacific Jet begins to return to "normal" into one unified stream-> Aleutian Low becomes restored,-> Aleutian Low intensifies-> Potent Aleutian Low (I think you see where I'm going w/ this...) 

 

On another note, I would someday also like to find the precise lag that exists between the -EPO & -WPO, & it's taking me a while to analyze the daily EPO/WPO raw data...

Daily EPO index (1948-Present)

ftp://ftp.cdc.noaa.gov/Public/gbates/teleconn/epo.reanalysis.t10trunc.1948-present.txt

 

Daily WPO index (1948-Present)

ftp://ftp.cdc.noaa.gov/Public/gbates/teleconn/wpo.reanalysis.t10trunc.1948-present.txt

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Don't sweat the lakes low. It's not a typical lakes low with low pressure fields acting like a warm vaccum and suck the track to the west. The lakes low in this setup is in response to the big closed upper level low over the lakes (pv). This feature acts like a block and not a vacuum. If the pv was up by hudson and the low was present it would be the typical lakes low screw job. The pattern looks really good for no cut.

Thanks Bob. I thought the run was rather cold for having one of those.

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