12z ECMWF shows wintry potential

[Cheeznado]

12Z Euro ensembles coming in- large spreads develop rather soon and the Op is a huge outlier even by days 4-5, we can probably throw this run in the trash.

[PhineasC]

12Z Euro ensembles coming in- large spreads develop rather soon and the Op is a huge outlier even by days 4-5, we can probably throw this run in the trash.

How is it an outlier if there is a huge spread?

[NaoPos]

12Z Euro ensembles coming in- large spreads develop rather soon and the Op is a huge outlier even by days 4-5, we can probably throw this run in the trash.

You don't happen to work for the HPC do you?

IS it the spread between the energy splitting over the NW PAC coast? or with the phasing..

[Srain]

EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

1235 PM EST FRI DEC 31 2010

VALID 12Z MON JAN 03 2011 - 12Z FRI JAN 07 2011

PRELIMINARY UPDATE...

USED THE 00Z ECMWF TO UPDATE THE PRELIMINARY FRONTS AND PRESSURES

FOR DAYS 3 AND 4...AND THE 00Z ECENS MEAN THEREAFTER. THE MOST

CONSISTENT GUIDANCE OVER THE PAST FOUR MODEL CYCLES HAS BEEN THE

EUROPEAN CENTRE ENSEMBLE MEAN. THIS ENSEMBLE PACKAGE HAS SHOWN

LOTS OF SPREAD AMONG ITS INDIVIDUAL MEMBERS DEPICTING SHORTWAVE

DETAILS OVER THE EASTERN PACIFIC AND THE UNITED STATES EAST OF THE

ROCKIES. THE UKMET IS A DEVELOPED OUTLIER WITH THE CYCLONE IT

SPINS UP OVER THE EAST MID PERIOD...WITH THE GEM GLOBAL ON ITS OWN

WITH THE STRENGTH OF THE STORM OVER THE EASTERN PACIFIC AT THE END

OF THE FORECAST. THE DETERMINISTIC RUNS OF BOTH THE GFS AND ECMWF

HAVE BEEN JUMPY WITH THESE DETAILS...OWING TO THE PREDOMINATELY

ZONAL COMPONENT TO THE OVERALL FLOW.

FINAL...

UNFORTUNATELY...THE ADVENT OF THE 12Z GUIDANCE HAS AFFORDED NO

FURTHER CLARITY TO THE BEHAVIOR OF THE SHORTWAVES DURING THE

MEDIUM RANGE. THE GFS SHOWS AN ARCTIC HIGH DROPPING THROUGH THE

PLAINS DAY 7...WHILE THE GEM GLOBAL LOWERS PRESSURES OVER THE SAME

REGION AS A NORTHERN STREAM CYCLONE SWOOPS THROUGH THE GREAT

LAKES. THE RELIANCE ON THE ROBUST ECENS MEAN FOR MUCH OF THE

UPDATE PACKAGE SHOULD SERVE THE FINAL ISSUANCE JUST AS WELL.

CISCO

[tombo82685]

12Z Euro ensembles coming in- large spreads develop rather soon and the Op is a huge outlier even by days 4-5, we can probably throw this run in the trash.

makes sense, the euro is way faster than any other model in ejecting the energy out of the sw. Not saying its wrong, but its against other guidance right now.

[NJwinter23]

Ehh. This looks A HELL OF A LOT similar to the Dec. 19th no show storm on the 12z euro today. Why don't we give the pattern about a week more after this date

[isnice]

I don't know if the actual maps have been posted yet, but both the 12z Euro ensembles and the 12z GEFS show at least some semblance of a disturbance off the east coast between hrs 144 - 168. The next frame of the Euro ensembles shows a low in a position similar to that of the 12z GEFS at 168. The GEFS is actually quite robust with the low. A 991mb low is a pretty strong signal to see on an ensemble this far out.

[thegreatdr]

With the last system, the ECMWF was too quick more than 144 hours out, before becoming too slow around 108 hours out. Every system behaves differently within the guidance, of course.

makes sense, the euro is way faster than any other model in ejecting the energy out of the sw. Not saying its wrong, but its against other guidance right now.

[usedtobe]

How is it an outlier if there is a huge spread?

It's not anywhere near the euro ensemble mean which has a low over the great lakes at 144hr and then has something way up in New England at 168.

[atownwxwatcher]

It's not anywhere near the euro ensemble mean which has a low over the great lakes at 144hr and then has something way up in New England at 168.

Is there not a low pressure off the coast of Hatteras at 144 hrs?

Which then looks to be east of Maine at 168 hrs?

http://raleighwx.americanwx.com/models/ecmwfens/12zecmwfens850mbTSLPNA168.gif

[Quasievil]

It's not anywhere near the euro ensemble mean which has a low over the great lakes at 144hr and then has something way up in New England at 168.

Maybe it's me being retarded but how can you get that Great Lakes low with that blocking? Oh forget it... too early for this.

[mitchnick]

Is there not a low pressure off the coast of Hatteras at 144 hrs?

that is the ensemble mean, which often will show a weak surface depiction of a Low vs. operational

[atownwxwatcher]

that is the ensemble mean, which often will show a weak surface depiction of a Low vs. operational

I am very well aware that it is the ensemble means and that is what was being referenced as does not support the operational run. I would beg to differ because it there is a weak surface reflection of an area of low pressure there and then that moves to east of Maine ..there must be some ensemble members that show something similar and hence why you have the operational run...So i would say there is probably a large spread with some that support the operational run...

[Tiburon]

Maybe it's me being retarded but how can you get that Great Lakes low with that blocking? Oh forget it... too early for this.

Maybe it's me, but how do you get a snowstorm on the east coast without any indication of a cold Canadian high pressure to be found? The GFS Ensembles at least show something but where does the EC get the cold?

[Yeoman]

Maybe it's me, but how do you get a snowstorm on the east coast without any indication of a cold Canadian high pressure to be found? The GFS Ensembles at least show something but where does the EC get the cold?

You mean like last weekend?

[THEREALTOR1]

It seems like so far this season, the 2 "potential snow" systems, 12/19 & 12/26, the Euro had a good idea about the final verification from approx. Day 6 or 7 forward, until it got within a timeframe of approx. 60 - 72 hrs., then it would do a complete 180. However, as we moved closer to the timeframe from that point, it would slowly go back to its 6/7 Day timeframe verification. It's interesting, to me anyway, is this something that its going to do consistently this year, or has it simply been a coincidence thus far?

12/16 12Z - showed an HECS, when all week prior to that it showed an OTS, and ultimately on 12/19 everything was suppressed and went OTS.

12/23 12Z - showed a OTS solution after showing an HECS all week, and as we approached 12/26 it came back more to the west as it previously showed.

[usedtobe]

Is there not a low pressure off the coast of Hatteras at 144 hrs?

Which then looks to be east of Maine at 168 hrs?

http://raleighwx.ame...mbTSLPNA168.gif

On it, the main low is over the great lakes and then ends up well north off the new england coast at 168hrs. It's a far cry from the operational euro. The little spot with the L on it just off the coast may be the reflection of one member but is hardly the start of any strong low. To me, it doesn't support the operational euro but you are welcome to disagree.

[Cyclonicjunkie]

Maybe it's me, but how do you get a snowstorm on the east coast without any indication of a cold Canadian high pressure to be found?

Check 500mb

[ORH_wxman]

On it, the main low is over the great lakes and then ends up well north off the new england coast at 168hrs. It's a far cry from the operational euro. The little spot with the L on it just off the coast may be the reflection of one member but is hardly the start of any strong low. To me, it doesn't support the operational euro but you are welcome to disagree.

Yeah it looks very northern stream to me Wes. Obviously given the time frame, anything is on the table though. The EC mean at 156 hours (not seen on those maps) has the lakes low redeveloping SE of LI but primary is still pretty strong. GFS ensembles seem to support this general idea too.

But a day 6-7 system certainly has all sorts of caveats...but going by ensemble guidance on both GFS/Euro, it has a northern stream look.

[usedtobe]

Check 500mb

The euro enemble mean 500h doesn't look like the operational.

[WxLover]

How the H--- can we trust the models, when they didn't come to an agreement 18 hrs before the last Noreaster?

[Cyclonicjunkie]

The euro enemble mean 500h doesn't look like the operational.

To me they look pretty simular, of course i'm an amateur. Could you break down the major differences for me?

[baroclinic_instability]

12Z op ECM is out to lunch, and it is a massive outlier amongst all global guidance and even its own ensembles in the way it handles the cutoff low off the Pacific Coast. I would give it a very small consideration, perhaps just tossing it completely, and it really has seemingly no idea what to do with it. 0Z run had it stalling off the coast and kicking out 1-2 days later. In terms of the threat it has at 168, I wouldn't give it much credence, but there may be better threats in the longer range.

For those talking about threats in the ensembles around 168-192, there is no developing nor'easter. As with the last two storms, some interaction with a southern S/W would be needed in this configuration to develop a coastal threat, and the ensemble run supports no such feature as the 12Z ECM OP is on its own with its depiction.

[Rainshadow]

12Z op ECM is out to lunch, and it is a massive outlier amongst all global guidance and even its own ensembles in the way it handles the cutoff low off the Pacific Coast. I would give it a very small consideration, perhaps just tossing it completely, and it really has seemingly no idea what to do with it. 0Z run had it stalling off the coast and kicking out 1-2 days later. In terms of the threat it has at 168, I wouldn't give it much credence, but there may be better threats in the longer range.

For those talking about threats in the ensembles around 168-192, there is no developing nor'easter. As with the last two storms, some interaction with a southern S/W would be needed in this configuration to develop a coastal threat, and the ensemble run supports no such feature as the 12Z ECM OP is on its own with its depiction.

If you (not you specifically, I mean generically) follow the short waves, the off the swrn conus short wave lifts toward the Great Lakes, while the British Columbian closed low digs just behind it, doesn't phase, but kicks the former and then becomes the cyclogenic trigger. That seems like a very low percentage scenario to come to fruition. Like Will said with the usual day 6-7 caveat in mind, it looks more like a northern system which could dig more before all is said and done. Even though the Euro idea was correct about an east coast hit last weekend initially, it looks like the model is again falling into some kind of carolina coastal waters trap with this(too) rapid cyclogenetic/deepening solution. This kind of reminds me when the eta had similar problems during the late 90s in the same spot. Alas its still 6 or 7 days away and I've probably put both feet in my mouth at this point.

Happy New Year Everyone!

[SnowGoose69]

If you (not you specifically, I mean generically) follow the short waves, the off the swrn conus short wave lifts toward the Great Lakes, while the British Columbian closed low digs just behind it, doesn't phase, but kicks the former and then becomes the cyclogenic trigger. That seems like a very low percentage scenario to come to fruition. Like Will said with the usual day 6-7 caveat in mind, it looks more like a northern system which could dig more before all is said and done. Even though the Euro idea was correct about an east coast hit last weekend initially, it looks like the model is again falling into some kind of carolina coastal waters trap with this(too) rapid cyclogenetic/deepening solution. This kind of reminds me when the eta had similar problems during the late 90s in the same spot. Alas its still 6 or 7 days away and I've probably put both feet in my mouth at this point.

Happy New Year Everyone!

One thing is for sure, if the Euro was right it would balance out the East Coast cities snow totals in the race for first place in the 10-11 winter...DCA and BWI would come close to NYC though NYC would likely pick up something...ACY would probably be halfway to breaking the record they just broke last winter if not more than halfway to it.

[baroclinic_instability]

If you (not you specifically, I mean generically) follow the short waves, the off the swrn conus short wave lifts toward the Great Lakes, while the British Columbian closed low digs just behind it, doesn't phase, but kicks the former and then becomes the cyclogenic trigger. That seems like a very low percentage scenario to come to fruition. Like Will said with the usual day 6-7 caveat in mind, it looks more like a northern system which could dig more before all is said and done. Even though the Euro idea was correct about an east coast hit last weekend initially, it looks like the model is again falling into some kind of carolina coastal waters trap with this(too) rapid cyclogenetic/deepening solution. This kind of reminds me when the eta had similar problems during the late 90s in the same spot. Alas its still 6 or 7 days away and I've probably put both feet in my mouth at this point.

Happy New Year Everyone!

Yeah the ECM keeps the cutoff progressive off the West coast then phases it with the Pacific NW cutoff low and then ejects ahead of the northern vortex. What I was saying was the progressive cutoff solution is not supported by anything, and is not only an outlier amongst its own ensembles, it is an outlier amongst its own previous operational runs regarding the development off that SW cutoff. The 12Z ECM is likely going to be wrong within the first 72 hours so there is no reason speculating what the ECM does 168 hours out since it likely won't verify with its progressive cutoff solution. That is all I was mentioning. The combinations of that as well as what you mentioned make this a highly unlikely event.

[Ginx snewx]

Miller B developing off NJ, swinging to Gulf of Maine, on Euro Ensemble

[Avdave]

Miller B developing off NJ, swinging to Gulf of Maine, on Euro Ensemble

A little further south Steve it looks to get going and way east of the Gulf of Maine bro.

[thegreatdr]

For those interested...a couple of us on wikipedia are improving the Numerical weather prediction page at...

http://en.wikipedia.org/wiki/Numerical_weather_prediction

For reference, this edting is not being done on government time. We're adding information, as well as trying to source some of the unreferenced lines, but it's a good introduction to the guidance in general, and why many of us don't inherently trust an individual piece of deterministic guidance more than five days into the future, no matter how well/poorly it verifies at that time range. There are references to a couple useful links regarding ensemble forecasting (why it's being done at all) as well as generic information regarding the history of atmospheric modeling. If you want to help out, feel free. Just make sure to reference your additions. =)

DR

A little further south Steve it looks to get going and way east of the Gulf of Maine bro.

[Ginx snewx]

A little further south Steve it looks to get going and way east of the Gulf of Maine bro.

????

GFS loving it too