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Looking towards the beginning of December


CoastalWx

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Truncation sucks. The 12z GFS weakens most of the North Pacific low anomalies after 192h and then we rapidly transform the pattern. Seems sketchy... not saying the general idea is wrong (perhaps there will be more resistence with the GOA low) but it seems awfully funny.

It looks like at least the GOA low begins to be disturbed between 180 and 192, before truncation. Of course after truncation, this is simply accelerated, and within 24 hours there's a full-blown ridge where there once was quite a stable vortex lol.

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It looks like at least the GOA low begins to be disturbed between 180 and 192, before truncation. Of course after truncation, this is simply accelerated, and within 24 hours there's a full-blown ridge where there once was quite a stable vortex lol.

And this whole situation with 12/5-9 is just ridiculous. The origin of the s/w is from a PV lobe into the NW Ter/Yukon which drop down the backside of the GOA low. Then these cross the Pac NW / Rockies before emerging into the Plains. There still is a hint of a Greenland Ridge (not a big factor), too, while this is happening.

Yikes...

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And this whole situation with 12/5-9 is just ridiculous. The origin of the s/w is from a PV lobe into the NW Ter/Yukon which drop down the backside of the GOA low. Then these cross the Pac NW / Rockies before emerging into the Plains. There still is a hint of a Greenland Ridge (not a big factor), too, while this is happening.

Yikes...

u think that might dig a bit farther than the models currently suggest? I haven't seen too much more than a fropa on the gfs and the ec. Maybe some limited les on the backside but it doesn't look classic with the cold being not overly deep.

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Both the GFS and the Euro have the idea of the PV splitting off near the Korean Peninsula around day 6. This should be the impetus for the retrogression of the Aleutian ridge back into eastern Siberia. Over the course of Dec. it wouldn't surprise me to see a similar situation play out once or twice more, backing that sucker further and further. At that point the countdown is on for the cross-polar flow. I'm thinking another 30-40 days and in the meantime I'm considering wintry stuff almost bonus.

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u think that might dig a bit farther than the models currently suggest? I haven't seen too much more than a fropa on the gfs and the ec. Maybe some limited les on the backside but it doesn't look classic with the cold being not overly deep.

I'm not sure which way it will trend but the origin of it and well forecasted PNA spike behind it could certainly allow for some splitting. I could see this trend into a 2 wave ordeal where the secondary low is more wintry. But the retreated westerlies are going to be a hindrance.

Both the GFS and the Euro have the idea of the PV splitting off near the Korean Peninsula around day 6. This should be the impetus for the retrogression of the Aleutian ridge back into eastern Siberia. Over the course of Dec. it wouldn't surprise me to see a similar situation play out once or twice more, backing that sucker further and further. At that point the countdown is on for the cross-polar flow. I'm thinking another 30-40 days and in the meantime I'm considering wintry stuff almost bonus.

Good post; I agree. The motherload / retrogression will happen and it will hit the W-C States first but the GFS may be rushing it a bit.

Yeah they do, not strong...but it's enough to help us out. It a weekly avg so perhaps it fluctuates.

I agree about it fluctuating. These brief PNA spikes / cold shots will have the potential to deliver a wintry threat.

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And this whole situation with 12/5-9 is just ridiculous. The origin of the s/w is from a PV lobe into the NW Ter/Yukon which drop down the backside of the GOA low. Then these cross the Pac NW / Rockies before emerging into the Plains. There still is a hint of a Greenland Ridge (not a big factor), too, while this is happening.

Yikes...

yeah, the amount of spread that evolves with that s/w in the GFS ensemble is telling. Also the Greenland ridge looks like the result of periodic amplification of a N Atlantic ridge, which is always loads of fun to try timing lol

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yeah, the amount of spread that evolves with that s/w in the GFS ensemble is telling. Also the Greenland ridge looks like the result of periodic amplification of a N Atlantic ridge, which is always loads of fun to try timing lol

One of the runs..GFS or GEFS over the last 24 hours did try to do a second low on the fropa as it passed through the northeast.

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yeah, the amount of spread that evolves with that s/w in the GFS ensemble is telling. Also the Greenland ridge looks like the result of periodic amplification of a N Atlantic ridge, which is always loads of fun to try timing lol

While the AAM tendency has been negative, the strong East Asian Jet continues across the Subtropics. You can see in the FT fields the beginnings of some added westerly momentum in the Mid Latitudes even though the MT dropping off a cliff and negative tendency from the EAJ. But there are already signs of that shifting today in the AAM tendency across the Mid Latitudes.

The westerlies may retract in early December but they will contain breaking waves downstream of the North Pacific Low. The state of the AAM backs up the modeling. This will complicate the situation further because where exactly these waves break will determine how much digging, splitting and influence from the -AO they experience.

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Yep, another reason to understand how this is NOT like last year.

But...people only care about their snow here.

I can't post it now but if you plot upper level tropospheric height anomalies for the last 2 to 4 weeks for the NH and compare to 2011, it is basically opposite each other.

This year the mid-winter will actually deliver this time to North America and not leave us out while the rest of the world goes into the freezer.

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I can't post it now but if you plot upper level tropospheric height anomalies for the last 2 to 4 weeks for the NH and compare to 2011, it is basically opposite each other.

This year the mid-winter will actually deliver this time to North America and not leave us out while the rest of the world goes into the freezer.

Beginning now and running out to 240 hours there is a top down integrated warm anomaly over northern Asia and Siberia area, collocated nicely with multi-run, multi-model depiction of positive geopotential anomaly in the underpinning middle to upper tropospheric heights.

I don't believe the magnitude of the EPO is handled particularly well as this is an onset transition to a new phase. (I don't have access to the ECM version of these teleconnectors).

Also, I think there is some correlative to a +PNA erupting by mid December as Bopha continues to intensify and is progged by numerous ensemble members to recurve - we're getting to the height of the correlation for western Pac tropical forcing. Meanwhile, the WPO is still tanked and every day I look at it, the extended range, it tries to elevate only to correct downward upon ensuing runs at the CDC. There was as of Monday's CPC MJO discussion a westward propagating K-wave in the subtropical WP, and this is intrigue for those possibly looking for a link between sub-tropical forcing and EPO when time lag is applied. It seems the conducive region for TC genesis succeeding, then if outside influence allow for recurve there may be a conditional correlation there, but that's supposition.

The -WPO is correlated to the AB phase of the North Pacific and the last 10 days or so we've seen the correlation break down. These relationships between the teleconnectors are obviously not 1::1 etc..etc...but imo there are compensating forces perhaps damping, thus masking the observance of the preferred state. I believe there is a growing possibility that "whip-lashing" in the slosh back may take place when said Siberian top-down forcing may combine with recurve flux, together overcoming the damp and a rather abrupt transmit of a powerful enforcing lock that takes place between these statistical packages (the physical layout of that being a strong NE Pac ridge that compresses the native troughing into the +PNA positon of NE of HA). But more than a +PNA, I think it could be an impressive NE Pac feature that engulfs portions of western Canada and severally drills a deep layer NNW flow into the CONUS; perhaps occasionally linked up with an EPO -related cross polar flow.

I see this happening Dec 10 onward - and of course others may have their reasons; probable that they are all interrelated to pick your method. I don't get to spend as much time on the boards as like at Eastern so I'm not sure what everyone's thinking is

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