The PHL/NYC Medium Range Thread - Part 2

[am19psu]

Just getting it up and running.

Isotherm, do you still have the post from Eastern with your winter forecast? I'd like to review the solar forcing stuff that you posted with your forecast.

[tornadojay]

AN EXTREMELY ANOMALOUS STRONG NEGATIVE NAO PATTERN IS LIKELY TO

CONTINUE FOR ABOUT THE NEXT 10 DAYS. AS FAR AS THE NEXT 7 ARE

CONCERNED...THE TWO STRONG POSITIVE ANOMALY CENTERS OVER THE WRN

ALEUTIANS AND ICELAND WILL BE WELL ON THEIR WAY TOWARDS MERGING

INTO ONE GIANT POSITIVE ANOMALY OVER THE DAVIS STRAIT BY THE END

OF NEXT WEEK. SOME 3-5 STANDARD DEVIATION ANOMALIES ARE INDICATED

WITH BOTH OF THOSE POSITIVE HEIGHT ANOMALY CENTERS. S OF THE

BLOCKING POSITIVE ANOMALIES ..A TROF RIDGE TROF PATTERN FROM THE

140W TO 70W WILL PREVAIL WITH A SLOWLY FLATTENING RIDGE OVER THE

SWRN CONUS.

SOME MODERATE TO HEAVY QPF EXPECTED IN THE E COAST STATES SUN.

AFTER AN ARCTIC FROPA...

VERY STRONG NNW FLOW BEHIND A DEEP SLOWLY PROGRESSIVE TROF ALONG

THE E COAST WILL BRING ARCTIC AIR FROM CENTRAL CANADA WELL S INTO

THE ERN CONUS...CAUSING LOCALLY VERY HEAVY LAKE EFFECT SNOWFALL

AND DAMAGING FREEZING MINIMUM TEMPS INTO THE CITRUS BELT IN FL.

THE HEAVIEST PCPN IS LIKELY TO FALL AS RAIN IN THE WARM MOIST

CONVEYOR BELT JUST AHEAD OF THE ARCTIC COLD FRONT IN NEW ENG. BUT

RAPID COOLING BEHIND THE FRONT WILL CHANGE RA TO SN IN THE

CATSKILLS AND ADIRONDACKS WITH HEAVY ACCUMULATIONS IN THOSE

AREAS....IN ADDITION TO THE HEAVY TOTALS IN FAVORED AREAS TO THE

LEE OF THE LAKES.

12Z DETERMINISTIC MODELS: THE 12Z/09 UKMET IS ON THE S SIDE OF THE

SOLUTION ENVELOPE AND THE GFS CONTINUES ON THE FAST/NERN SIDE. THE

CANADIAN IS IN BETWEEN THESE TWO EXTREMES AND SEEMS A GOOD

COMPROMISE. IT IS A GOOD FIT TO PRELIM CONTINUITY AS IT TRACKS A

LOW ACROSS THE NERN CONUS/SE CANADA SUN-TUE DAYS 3-5. THE 12Z/09

GFS IS A FAST OUTLIER AND BECOMES ABOUT HALF A DAY TOO FAST WITH

THE POSITION OF THE NERN CONUS/SE CANADIAN SURFACE LOW DAYS 3-5.

THEREFORE...WE PREFER A SOLUTION SHOWING THE MID LVL LOW CROSSING

THE NE CONUS S OF THE THE GFS/GEFS MEAN. TELECONNECTIONS ON THE

STRONG RIDGE BUILDING OVER GREENLAND ALSO FAVOR A MORE SUPPRESSED

TRACK. THE 12Z ECMWF STARTS OUT IN THE MIDDLE OF THE PACK WITH THE

ERN SYS DAYS 3 BUT SLIPS VERY SLIGHTLY TO THE S OF THE 12Z MODEL

CLUSTER CONSENSUS DAYS 6 AND BEYOND.

FINAL PROGS KEPT THE SAME 12Z/08 AND 00Z/09 DETERMINISTIC

ECMWF/12Z/08 ECENS BLEND AS THE PRELIMS. THE LATEST 00Z/09 ECMWF

ENSEMBLE MEAN SHOWS VERY GOOD CONTINUITY FROM ITS PREVIOUS 12Z

MEAN. THE NEW ENSEMBLE SPAGHETTI PLOTS SHOW THE COMMON BIAS OF THE

GFS MODEL BEING TOO PROGRESSIVE WITH AN AMPLIFYING SHORTWAVE

TROF...AND SUPPORT OUR CHOICE OF A ECMWF/ECENS BASED BLEND FOR THE

PRELIM FORECASTS.

PACIFIC NW WILL STAY UNDER THE GUN AS FREQUENT SHORTWAVES AND

ONSHORE FLOW BRING ALMOST DAILY PCPN...SN AT HIGHER ELEVATIONS .

THE PCPN WILL WORK ITS WAY S INT NRN CA BY THE MIDDLE OF NEXT

WEEK. AS THE DRY SWRN RIDGE FLATTENS OUT CONFIDENCE LEVEL

DECREASES IN HANDLING SHORT WAVE TRAFFIC COMING INTN THE W COAST

OF THE CONUS.

FLOOD

[Isotherm]

Just getting it up and running.

Isotherm, do you still have the post from Eastern with your winter forecast? I'd like to review the solar forcing stuff that you posted with your forecast.

Am19psu,

Here's the repost of it on this board

http://www.americanwx.com/bb/index.php?/topic/390-my-winter-outlook-2010-11/

Unfortunately we can't access the old board anymore with the great solar discussion going on.

[Isotherm]

Here's my post from the old thread wrt Dec 13th event and the better pattern beyond.

The December 13th-14th system should set-up a more conducive pattern for snow, and here's why:

1) First off, although the NAO is technically negative, this is another situation where the orientation of the block is more important than the modality of the index. East based -NAO's are generally no good w/ a strong La Nina and poor nroth pacific signal. SE ridging comes into play, and thus the short wave is allowed to cut inland/through the Lakes.

Here's the H5 appearance for early next week:

Resized to 75% (was 1373 x 738) - Click image to enlarge

After this system bombs out, it will form a new 50-50 low in SE Canada which aids in pulling the -NAO orientation further west. So in effect, although the Dec 13th event is a lost cause for I-95, it'll play a significant role in turning the regime to a more favorable one.

Note the H5 set-up for next Thursday:

Resized to 75% (was 1373 x 738) - Click image to enlarge

-NAO west, complete with a 50-50 low, tanking AO, and also an improving PNA. All these factors mean incoming short waves will be forced to track underneatht he blocking feature, thus a better shot at wintry precip for our neck of the woods. The GFS is already hinting at overrunning, W-E propagating, gradient type systems beginning late next week through the holiday period.

Hold onto your hats as I think the first real shot at accum snow may arrive after the 13th event.

[JBG]

Not that it can't happen, just the chances are lower as you stated. Weather & Forecasting October 2003 paper about it, its not just about NYC & PHL its a general lower incidence of KU type storms in La Nina winters. The last time PHL had a > 10" single snowfall event in a mdt/stg la nina winter was December 1909. Admittedly January 2000 came close.

March 1956?

[phlwx]

March 1956?

8.7" @ PHL.

[SnowGoose69]

Here's my post from the old thread wrt Dec 13th event and the better pattern beyond.

The December 13th-14th system should set-up a more conducive pattern for snow, and here's why:

1) First off, although the NAO is technically negative, this is another situation where the orientation of the block is more important than the modality of the index. East based -NAO's are generally no good w/ a strong La Nina and poor nroth pacific signal. SE ridging comes into play, and thus the short wave is allowed to cut inland/through the Lakes.

Here's the H5 appearance for early next week:

Resized to 75% (was 1373 x 738) - Click image to enlarge

After this system bombs out, it will form a new 50-50 low in SE Canada which aids in pulling the -NAO orientation further west. So in effect, although the Dec 13th event is a lost cause for I-95, it'll play a significant role in turning the regime to a more favorable one.

Note the H5 set-up for next Thursday:

Resized to 75% (was 1373 x 738) - Click image to enlarge

-NAO west, complete with a 50-50 low, tanking AO, and also an improving PNA. All these factors mean incoming short waves will be forced to track underneatht he blocking feature, thus a better shot at wintry precip for our neck of the woods. The GFS is already hinting at overrunning, W-E propagating, gradient type systems beginning late next week through the holiday period.

Hold onto your hats as I think the first real shot at accum snow may arrive after the 13th event.

That setup could be a bit too good though...if we had that for this upcoming storm it woul obviously not cut into the lakes but instead go due east and likely off the northern MA coast somewhere...the problem is it would probably be unable to really re-develop and run up the coast either with that massive vortex.

[Kaner587]

That setup could be a bit too good though...if we had that for this upcoming storm it woul obviously not cut into the lakes but instead go due east and likely off the northern MA coast somewhere...the problem is it would probably be unable to really re-develop and run up the coast either with that massive vortex.

exactly...as it looks like what the 18z GFS is gonna show. We really "can't buy a bucket" (as the announcer in NBA Jam would say) but one thing is for sure, we are going to rack up massive negative temp departures extending most likely past mid month, and while the pattern is likely to moderate it looks like we could be in for one of our coldest months relative to average since the summer (or lack there-of) of 2009

[earthlight]

18z GFS is showing the potential well in the medium range with the big 50/50 type low setting up and the energy ejecting out of the southwest US and a snowstorm off the coast at 240 hr. One thing is for sure, the NAO block that develops in that range is really just riduclous.

[Dark Energy]

18z GFS is showing the potential well in the medium range with the big 50/50 type low setting up and the energy ejecting out of the southwest US and a snowstorm off the coast at 240 hr. One thing is for sure, the NAO block that develops in that range is really just riduclous.

nice double omega blocks right there. Yea, the -NAO is quite sick. Even when it gets broken down, it just seems to come right back.

[Kaner587]

nice double omega blocks right there. Yea, the -NAO is quite sick. Even when it gets broken down, it just seems to come right back.

If this becomes the seasonal trend,which so far it seems like its heading that way, then I think we'll get ours as soon (if?) as the pacific cooperates

[earthlight]

It's a long ways out into fantasy land, but you can use this image from the 18z GFS (which later produces a snowstorm off the coast), to illustrate what the presence of blocking can do for you. The -NAO finally winds up helping us on this run despite the still pretty crappy Pacific. The shortwave in the southwest US which was driven there by the consistently active Pacific Jet ejects northeast, towards the impressive confluence over the Northeast and what you get is a rather favorable return with a gradient pattern set up well from West to East across the CONUS. We will have to wait and see if this potential will be realized..

http://www.meteo.psu.edu/~gadomski/AVN_18z/f180.gif

[Dark Energy]

If this becomes the seasonal trend,which so far it seems like its heading that way, then I think we'll get ours as soon (if?) as the pacific cooperates

I;m interested in DT's info that the la nina is weakening. If that trend continues, whoa. We all may be in for a surprise.

[Analog96]

I;m interested in DT's info that the la nina is weakening. If that trend continues, whoa. We all may be in for a surprise.

If that trend continues, get ready for an historic winter for both snow and cold, and I'm not exaggerating.

[Analog96]

By the way, I saw something today I've never seen before this early.

A local park's lake is completely frozen. It's thin ice, but it covers the entire lake.

[earthlight]

If that trend continues, get ready for an historic winter for both snow and cold, and I'm not exaggerating.

I don't know..the tropical forcing just isn't in a favorable state. The La Nina weakening slightly right now isn't going to have a dramatic effect on the pattern through the rest of the winter...we need a more dramatic drop-off if you're looking for historic cold and snow. The Pacific is still in shambles.

[Kaner587]

I;m interested in DT's info that the la nina is weakening. If that trend continues, whoa. We all may be in for a surprise.

agreed...for now I'll be happy with early season cold but its definitely prudent to keep an eye on the status of the nina esp if our NAO and AO want to continually be negative. Obviously if the nina collapses it'll most likely be a later in the season manifestation but I guess we'll just have to watch and wait patiently

[Dark Energy]

If that trend continues, get ready for an historic winter for both snow and cold, and I'm not exaggerating.

Idk if i'd go there just yet. BUT, if the trend continues, it seems like all the winter outlooks may be fooked to some degree. I just can't believe the -NAO is so bullish for this long. It is keeping up a good fight.

[Analog96]

I don't know..the tropical forcing just isn't in a favorable state. The La Nina weakening slightly right now isn't going to have a dramatic effect on the pattern through the rest of the winter...we need a more dramatic drop-off if you're looking for historic cold and snow. The Pacific is still in shambles.

And just like everybody is saying, the Pacific matters less as you head into the heart of winter. Plus, if La Nina weakens, the Pacific will improve.

[Analog96]

Idk if i'd go there just yet. BUT, if the trend continues, it seems like all the winter outlooks may be fooked to some degree. I just can't believe the -NAO is so bullish for this long. It is keeping up a good fight.

Makes you wonder if it will stay negative. I'm not saying as negative as it is now, but average negative. It shows no sign of going positive for any length of time.

[earthlight]

It's funny, though, because the more I re-analyze last winter, the more I realize how incredible it really was. The blocking was literally historic in every sense of the word. The orientation of this shortwave is unfavorable initially (this is the Feb 10 storm system). Look at the ridging flying up along the east coast. Then, the block flex's it's muscles and the entire shortwave is compressed south over DC. A real textbook guideline on how blocking works with shortwaves in the Central US that aren't digging deep enough initially.

http://www.meteo.psu.edu/~gadomski/NARR/2010/021000.png

http://www.meteo.psu.edu/~gadomski/NARR/2010/021021.png

[Dark Energy]

By the way, I saw something today I've never seen before this early.

A local park's lake is completely frozen. It's thin ice, but it covers the entire lake.

ditto on this. I have lakes here that are frozen over too. It has been cold, but it surprised me since it wasn't like that not too long ago.

[Dark Energy]

Makes you wonder if it will stay negative. I'm not saying as negative as it is now, but average negative. It shows no sign of going positive for any length of time.

as I said in a prev post. Yea, it gets knocked down and then comes right back. I know from the KU book that a lot of our bigger storms actually come when the NAO is transitioning from negative to a little less negative. Perhaps we should look for the times this happens, since it has so far, for something to pop. It's all about timing tho.

[earthlight]

I know from the KU book that a lot of our bigger storms actually come when the NAO is transitioning from negative to a little less negative. Perhaps we should look for the times this happens, since it has so far, for something to pop. It's all about timing tho.

Well that's more of the Archambault type event..in the current height patterns it would actually be pretty tough to get an Archambault to produce snow here...it could happen, but I am more inclined to believe we will do well with a consistently average negative NAO that is west based. For this upcoming storm..check out the North Atlantic pattern...absolutely dreadful. If we were to get snow from this system it would literally be a gift from the heavens.

[Dark Energy]

Well that's more of the Archambault type event..in the current height patterns it would actually be pretty tough to get an Archambault to produce snow here...it could happen, but I am more inclined to believe we will do well with a consistently average negative NAO that is west based. For this upcoming storm..check out the North Atlantic pattern...absolutely dreadful. If we were to get snow from this system it would literally be a gift from the heavens.

they key there is west based -nao. I love the Archambault events tho. They are

[earthlight]

they key there is west based -nao. I love the Archambault events tho. They are

Yeah they can be really spectacular when timed well. As far as the west based -NAO, check out how much the 12z GEFS means retrograded the heights...I think that's pretty west based, no?

http://www.meteo.psu.edu/~gadomski/ENSHGTAVGNH_12z/f228.gif

[Chris L]

its more of a problem with the Pacific and the Ridge axis out west. A better pacific will help our chances at getting a significant snowstorm ten fold; if we can get a decent PNA spike; then we can get something nice and get rid of the Gulf of Alaska Low, and develop a EPO Ridge.

It is harder to do because the MJO forecasting is not ideal right now. The block is quite a sight to see this early in winter for sure.

But timing as we all seen before with February 2006 in a Nina pattern can do its goods.

Although we would not see those insane QPF maps from last year due to Nino pattern; but the trade off is; we will be significantly colder in a Nina pattern, I would think.

[Dark Energy]

Yeah they can be really spectacular when timed well. As far as the west based -NAO, check out how much the 12z GEFS means retrograded the heights...I think that's pretty west based, no?

http://www.meteo.psu...NH_12z/f228.gif

jesus. before i clicked the link i figured the greenland block would meet up with the block over the pacific. indeed it looks like it will or *may.

[earthlight]

Also, the ensembles are forecasting another AO nose dive, sound familiar (hint, see last winter)..some of the ensembles have the AO below -4. Certainly going to be an interesting batting between the -NAO and -PNA pattern.

[Chris L]

they key there is west based -nao. I love the Archambault events tho. They are

February 2006 was a good example.