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December 14/15 winter storm threat


Typhoon Tip

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For a few cycles now, and across multiple operational guidance types, there have been systems flagged between the 15th and 20th of the month.   This is a very early lead and thus is subject to change (duh), but the turmoil in the various operational runs as to which impulse(s) in the spatial-temporal maelstrom could be capable of bringing the winter goods, can at least in part be supported by the teleconnectors leading up through the ides of the month. 

 

It's not overwhelming as a signal, first off, but it is there nonetheless.  The PNA is currently being registered near -1.5SD at the CPC.  This is actually understandable considering there is positive correlation coefficient wrt to the EPO, which as we know has been predominantly negative in recent weeks (CDC).   The EPO is neutralizing according to the CDC, even going modestly positive by the end of week 2. What is interesting is that in that time the PNA begins to rise.  It is more impressive at the CPC, which determines the tele numbers based on mid level geoptential heights; where as the CDC utilizes low-level wind flux (anomalies).

 

post-904-0-24428800-1386544831_thumb.jpg  post-904-0-88311400-1386545083_thumb.jpg

 

 

Technique aside, you have a moderating EPO and an elevating PNA, and that is a longer term statistically supported concurrence of events.  

 

I can't type small words... not sure why... But, what all that gobble-gook means is that the general circulation may undergo some changes based on changes in the modes of the various mass fields.  The (albeit transient) "bulging" of heights over the west heading into next weekend, may be real.  That would of course impose downstream interests during a continental cold anomaly on-going at that time. 

 

Sure enough, you see the operational GGEM with a coastal;  you see the Euro with a kind of PD type system (followed by a clipper that detonates along the NE coast), and the GFS with a general mess but storminess nonetheless. 

 

By the way, there is so much cold up in Canada, that should a relaxed EPO be met with a rising PNA, I do not believe the PNA has to be substantially positive to incur wrath.  Smaller variations in the PNA can have bigger results when thermal gradients are intense.  Also, I am noticing a tendency to lower the extremeness of the "gradient pattern" we have been witnessing as this week progresses.  That does allow for impulse-centric mechanics to more effectively operate cyclogenesis.

 

As an ending thought, the 18z GFS/NAM agree on yet another ANA swath Tuesday night... mustn't forget the little critters that bite in the meantime (should they ....)

 

John 

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Loving the back-to-back whammy on the 0z Euro at 144 and 192.  Brutal cold with the 192 storm (I think that's the clipper grenade), could get some lovely snow ratios.  Fingers crossed!

 

 

It is more likely that one of those becomes the dominant player... It is actually a more proficiently phased version of the 12z guidance from yesterday.   But yeah ...overall, this is the familiar layout in my mind to what the tele's taste like heading into that period of time.  We notice the western heights rise?  And with in situ cold and available, the rather abrupt immediate downstream result of OV trough dig thus has ample baroclinicity in the ambient ... p-type/details are impossible at this range, though the GFS does look a little bit pushy. 

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Looks like a SWFE on the euro.

 

Yes ... unfortunately, none of this really speaks to p-type or the satisfaction of winter enthusiasts therein ... 

 

Having said that, an event of any kind still supported and seeing the PNA continuing to rise in pulses at both CDC/CPC is statistically correlated to eastern N/A activity as we know.   If it is any consolation for eye-sore products ... it is D6 and the Euro's latching onto this event and having it go west is a model bias that could easily correct SE in time. But ... having a front end snow thump sort of set up isn't all that bad, either.  

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Yes ... unfortunately, none of this really speaks to p-type or the satisfaction of winter enthusiasts therein ... 

 

Having said that, an event of any kind still supported and seeing the PNA continuing to rise in pulses at both CDC/CPC is statistically correlated to eastern N/A activity as we know.   If it is any consolation for eye-sore products ... it is D6 and the Euro's latching onto this event and having it go west is a model bias that could easily correct SE in time. But ... having a front end snow thump sort of set up isn't all that bad, either.  

 

Yeah it has a pretty decent front end thump...of course, exact details are meaningless at 126-132 hours out...but its the type of system that would probably be favored in this pattern given the SE ridge that doesn't give in easily. Also cannot rule out an uglier cutter either.

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Yeah it has a pretty decent front end thump...of course, exact details are meaningless at 126-132 hours out...but its the type of system that would probably be favored in this pattern given the SE ridge that doesn't give in easily. Also cannot rule out an uglier cutter either.

 

I actually think the SE ridge would tend to dismantle as the week progresses and the gradual shift in the PNA supports more of a +PNAP over mid-latitudes of N/A.  How much? Heh.  We'll see...  

 

Fwiw folks, NCEP is onto the pattern change and the eastern cyclogenesis threat.  I think the "progressive" character to the flow will dictate farther E tracks:

 

EXTENDED FORECAST DISCUSSION

NWS WEATHER PREDICTION CENTER COLLEGE PARK MD

1100 AM EST MON DEC 09 2013

VALID 12Z THU DEC 12 2013 - 12Z MON DEC 16 2013

...ACTIVE WINTER PATTERN OVERVIEW...GUIDANCE ASSESSMENT...SENSIBLE

WEATHER HIGHLIGHTS...

THE MEDIUM RANGE MODELS AND ENSEMBLES ADVERTISE A TRANSITIONAL AND

SPLIT WEATHER PATTERN GENERALLY OVER NORTH AMERICA. THIS PATTERN

IS HIGHLIGHTED BY A DEEP TROUGHS/LOWS OVER THE GULF OF AK...A

SERIES OF HARDER TO TIME AND MORE PROGRESSIVE AND WINTER WEATHER

FOCUSING SYSTEMS/LOWS BOTH DIGGING DOWNSTREAM WITHIN A NRN STREAM

INTO/ACROSS THE US NRN TIER STATES AND WITHIN AN EJECTING SRN

STREAM ACROSS THE US SRN TIER STATES...EVENTUALLY LEADING TO SERN

AND NERN COASTAL CYCLOGENESIS. THE BIGGEST WINTER THREAT SEEMS TO

BE ON THE NRN PERIPHERY OF OVERALL COMPLEX SWATHS OF QPF EXPANDING

EMPHASIS STRETCHING FROM THE CENTRAL PLAINS ENEWD TO NEW ENG DAYS

FRI-MON. MEANWHILE...UPSTREAM APPROACH OF PACIFIC ENERGIES LATER

IN THE PERIOD MAY ALSO INCREASE EMPHASIS OVER THE NWRN STATES BY

THEN. 

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I actually think the SE ridge would tend to dismantle as the week progresses and the gradual shift in the PNA supports more of a +PNAP over mid-latitudes of N/A.  How much? Heh.  We'll see...  

 

Fwiw folks, NCEP is onto the pattern change and the eastern cyclogenesis threat.  I think the "progressive" character to the flow will dictate farther E tracks:

 

EXTENDED FORECAST DISCUSSION

NWS WEATHER PREDICTION CENTER COLLEGE PARK MD

1100 AM EST MON DEC 09 2013

VALID 12Z THU DEC 12 2013 - 12Z MON DEC 16 2013

...ACTIVE WINTER PATTERN OVERVIEW...GUIDANCE ASSESSMENT...SENSIBLE

WEATHER HIGHLIGHTS...

THE MEDIUM RANGE MODELS AND ENSEMBLES ADVERTISE A TRANSITIONAL AND

SPLIT WEATHER PATTERN GENERALLY OVER NORTH AMERICA. THIS PATTERN

IS HIGHLIGHTED BY A DEEP TROUGHS/LOWS OVER THE GULF OF AK...A

SERIES OF HARDER TO TIME AND MORE PROGRESSIVE AND WINTER WEATHER

FOCUSING SYSTEMS/LOWS BOTH DIGGING DOWNSTREAM WITHIN A NRN STREAM

INTO/ACROSS THE US NRN TIER STATES AND WITHIN AN EJECTING SRN

STREAM ACROSS THE US SRN TIER STATES...EVENTUALLY LEADING TO SERN

AND NERN COASTAL CYCLOGENESIS. THE BIGGEST WINTER THREAT SEEMS TO

BE ON THE NRN PERIPHERY OF OVERALL COMPLEX SWATHS OF QPF EXPANDING

EMPHASIS STRETCHING FROM THE CENTRAL PLAINS ENEWD TO NEW ENG DAYS

FRI-MON. MEANWHILE...UPSTREAM APPROACH OF PACIFIC ENERGIES LATER

IN THE PERIOD MAY ALSO INCREASE EMPHASIS OVER THE NWRN STATES BY

THEN. 

 

 

I do agree the SE ridge is getting fought by the rising PNA in that time, but it is still pretty stout with the strong +NAO pattern. Maybe the PNA is enough to push this east into sort of a hybrid Miller B/SWFE. Often a snowy a look for us, but that type of evolution is probably abit too complicated to talk about still 5 days away.

 

The +PNA may help in lowering the chances ofa huge lakes cutter.

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That's interesting to see that subtle damming signaled ... although I am not sure what the Euro ens do for granularity at this range, typically.

It's pretty impressive for a 132hr mean. Mean QPF is warning criteria for the interior although i haven't seen the individual members to see how many cut yet.
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It's pretty impressive for a 132hr mean. Mean QPF is warning criteria for the interior although i haven't seen the individual members to see how many cut yet.

 

 

It looks like very few members are actual cutters from what I can see. The members are clustered pretty closely for a 132 hour prog.

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Yeah it has a pretty decent front end thump...of course, exact details are meaningless at 126-132 hours out...but its the type of system that would probably be favored in this pattern given the SE ridge that doesn't give in easily. Also cannot rule out an uglier cutter either.

I'd take a net gain and run at this time of year....looks beautiful tonight.

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It looks like very few members are actual cutters from what I can see. The members are clustered pretty closely for a 132 hour prog.

 

Looks like most of them are actually slightly colder than the op @850 on the spaghetti plots. Pretty good cluster like you said.  

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