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November 2012 Observations and Discussions


Snow_Miser

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I like the look of the Euro ensembles a lot. It looks like it's heavily phase 1 MJO influenced -- it moves the Aleutian Ridge to the west, which helps to form lower heights in the eastern Aleutians, helping to form a PNA ridge. I think that would coincide well with the December 5th snowstorm threat.

Also nice to see that ridging move west but not break down -- and it's trying to connect with the Atlantic ridging, which would help form a beautiful ridge bridge and lock in a cold pattern for several weeks.

Yeah you can see it on the OP as well. +PNA starts to get going nicely, and higher heights start moving west over the davis straights in the long range.

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The ensemble guidance is beginning to pick up on cold air coming from the poles as the Aleutian ridge anomaly moves east a bit and strengthens. At 144 hr the 18z GEFS display things pretty well. If things were to play out like this, we should hypothetically see a shot of cold arctic air into the Northern 1/3 of the US (and the Northeast).

f144.gif

Not surprisingly the ensembles are picking up on this and have -18 to -24 height anomalies over the Northeast US a few days later. You can also clearly see the above normal height anomalies over the higher latitudes despite the somewhat east based nao signal.

f192.gif

We'll have to see if this is how it plays out...I'd watch for the 144 hour period with the positioning and strength of the Aleutian ridge because that seems to be setting of the sequence of events that eventually leads to the cold air intrusion...and down the road blocking in the North Atlantic and storm chances.

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The ensemble guidance is beginning to pick up on cold air coming from the poles as the Aleutian ridge anomaly moves east a bit and strengthens. At 144 hr the 18z GEFS display things pretty well. If things were to play out like this, we should hypothetically see a shot of cold arctic air into the Northern 1/3 of the US (and the Northeast).

f144.gif

Not surprisingly the ensembles are picking up on this and have -18 to -24 height anomalies over the Northeast US a few days later. You can also clearly see the above normal height anomalies over the higher latitudes despite the somewhat east based nao signal.

f192.gif

We'll have to see if this is how it plays out...I'd watch for the 144 hour period with the positioning and strength of the Aleutian ridge because that seems to be setting of the sequence of events that eventually leads to the cold air intrusion...and down the road blocking in the North Atlantic and storm chances.

What a difference from last year. Incredible.You can see the splitting of the PV very clearly in those charts, and the NAO/AO ridging in between the split vortices.

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I think a GLC is the more likely scenario which will lead to a change in the overall pattern, bring down the season's first really cold air, and set us up for a more climatologically acceptable Dec. 1-8 snow event for the EC.

GFS is a GLC. This model changes its tune every 6 hours. Unbelieveable.

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I think a GLC is the more likely scenario which will lead to a change in the overall pattern, bring down the season's first really cold air, and set us up for a more climatologically acceptable Dec. 1-8 snow event for the EC.

Climo favored, yes. But the evolving block on all modelling might have a say based on timing? It would really be a special event if it happened prior to climo and expectations.

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Yes, also the PV over Northern Canada next week, favors the storm track west of us.

Yeah, the PV is dropping the PNA just a little too much at that time. We can do ok with a weaker -PNA

like we saw earlier this month, but it gets tougher as we get closer to -1.

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The Euro operational should correct on the next run or 2 for next week . The depth of the trough in the pacific and the heights of the ridge on the west coast argues for a more amplified trough in the east day 7- 10 . SO IT WIL BE COLDER IN THE EAST in this time period , if theres a storm it should not go west of the mtns . The EURO ensembles already show a stronger trough in the east than its 12 z operational .

i will stick with this , as pr 12z euro today - next weeks system goin to be hard pressed to run to the lakes in the face of a block ....

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It's way too early to tell where the storm is heading. The storm earlier this month was forecast to be further inland and we know what happened with that!

storms like to belly under blocks , not run into them .I am looking at the pattern not run to run , just what i see from here 7 days out

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EURO is cold, but the pattern is way worse, pacific is terrible. You can tell past day 10 it would torch everyone.

Why look at the op at day 10? I would look at ensembles past day 6. You will set yourself up for disaster. 12z gfs ensembles bring back a much better looking ridge into the west.

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18z GFS keeps the storm south of us, with a track right over Philly, then to Trenton, then over Long Island at 174 hrs down to 982mb, and it bombs it out between Baltimore and Long Island. Then it cotinues to deepen to 977mb in the Gulf of Maine, with us in the wrap around between 174 and 180 hrs. and 850's finally below zero. Track is much more Euro like, but much warmer than the Euro initially because it is much stronger. Now let's wait and see on future runs if it continues to get colder with the 850's. It definitely is not liking the idea of running into that block and is slowing it down and causing it to come south of us and then cut up. Would indicate the possibility of light frozen precipitation in some locations at the start, changing to rain for the majority of the storm, then changing to snow before ending on Wednesday night.

The 18Z gfs ensemble mean is southeast of the operational run and is colder. It takes the low from Mississippi to the Carolinas, then to south of Long Island at 156 hrs, then to the Benchmark at 162 hrs. It keeps the 850's below zero the entire time. Interestingly, the individual ensemble members seem to mostly either wrap up west of us, or wrap up east of us, while the operational went right in between the two.

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Yeah I can't believe the models are flipping around...

Only previous time I can recall it happening was on the morning of September 21, 1938. That morning, the 12z run of the OTS model (the GFS of its time) had the hurricane passing harmlessly well east of both Nantucket and the Benchmark. However the 12z run of the SOL model (which ran on numerical computations quite similar, though far more primitive, than the current Euro) took the hurricane directly over central Long Island...

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