0Z Guidance Discussion 12/15/2010

[NYCvort]

I’m not sure about this, but it looks to me like an important feature to watch is the s/w over WI at 72 hr. The 00Z/15 GFS, 12Z/14 GGEM, and 12Z/14 EC show this feature much stronger than the 12Z/14 GFS. That stronger s/w seems to be preventing the height rises from developing ahead of the PV anomaly that baroclinic_instability was talking about. Please correct me if I’m wrong.

[SBUWX23]

The comparisons synoptically to last Dec 19-20 blizzard dont work here. One big thing with that storm that I have researched was that the low bombed within a jet couplet. There was STJ of 150 kts plus over the SE and and 150 or kt jet over the NE and Canadian Maritimes. The low bombed in the left exit region of the STJ and the right entrance of the northern stream.

[Ed Lizard]

'Weenie' comes to mind, but how well are upper features sampled over Siberia?

NWS OKX snip from earlier...

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...

FOR FRI NIGHT INTO SAT EVENING...FAIR WX...WITH CONFLUENT

QUASI-ZONAL FLOW ALOFT TO THE SOUTH OF A RETROGRADING POLAR VORTEX

OVER SE CANADA SETTING UP A NARROW SFC HIGH PRESSURE RIDGE.

FOR LATE SAT NIGHT INTO MON...THE RETROGRADING POLAR VORTEX OVER SE

CANADA WILL BACK THE FLOW ALOFT TO SW ALONG THE EAST COAST...

ALLOWING A DIGGING SHORTWAVE TO INDUCE SFC CYCLOGENESIS IN THE

NORTHERN GULF OF MEXICO OR OFF THE SOUTHEAST COAST SAT INTO SAT

NIGHT...AND THEN TRACK NE. EXACT SFC LOW TRACK...INTENSITY AND

POTENTIAL IMPACTS TO THE AREA ARE STILL UNCERTAIN...AND DEPEND ON

HOW MUCH THE LARGE SCALE FLOW BACKS SW ALOFT AND/OR THE STRENGTH OF

THE VORT...STILL SOMEWHERE OVER EASTERN SIBERIA...AS IT DROPS INTO

THE LONGWAVE TROUGH. A WEAKER VORT AND/OR LESS RETROGRESSION AS PER

THE 12Z ECWMF WOULD STEER ANY DEVELOPING LOW FARTHER OFFSHORE...WITH

A NEAR MISS OR GLANCING BLOW. A STRONGER VORT AND/OR MORE

RETROGRESSION AS PER THE 12Z GFS/GEFS MEAN WOULD ALLOW FOR MORE

AMPLIFICATION... AND A POTENTIALLY SIGNIFICANT SNOWSTORM. MOST OTHER

MODEL GUIDANCE SITS SOMEWHERE BETWEEN THESE TWO CAMPS...WITH MANY

GGEM ENSEMBLE MEMBERS AND THE UKMET ALSO SHOWING AN INTENSIFYING

COASTAL LOW...FAR ENOUGH EAST TO MINIMIZE LOCAL IMPACTS. WITH A

SNOWFALL EVENT AT LEAST WITHIN THE ENVELOPE OF POSSIBLE SOLUTIONS...

IT IS PRUDENT TO INCREASE POP FOR THIS TIME FRAME TO CHANCE.

[yoda]

00z GGEM looks okay for those in VA... maybe up to PHL at 132... but it scoots ENE brushing SNE at 144 it appears

http://www.weatheroffice.gc.ca/data/model_forecast/colour_images/00_054_G1_north@america@zoomout_I_4PAN_CLASSIC@012_132.jpg

http://www.weatheroffice.gc.ca/data/model_forecast/colour_images/00_054_G1_north@america@zoomout_I_4PAN_CLASSIC@012_144.jpg

[baroclinic_instability]

I’m not sure about this, but it looks to me like an important feature to watch is the s/w over WI at 72 hr. The 00Z/15 GFS, 12Z/14 GGEM, and 12Z/14 EC show this feature much stronger than the 12Z/14 GFS. That stronger s/w seems to be preventing the height rises from developing ahead of the PV anomaly that baroclinic_instability was talking about. Please correct me if I’m wrong.

The orientation of the northern stream "messy" vortex plays a big part since the southern stream anomaly needs to phase, but it has to be at the exact right time or the necessary height rises ahead of the developing coastal won't develop. So yeah you are right.

[CheesyPoofs]

00z GGEM looks okay for those in VA... maybe up to PHL at 132... but it scoots ENE brushing SNE at 144 it appears

http://www.weatherof...SIC@012_132.jpg

http://www.weatherof...SIC@012_144.jpg

That is yesterday's run..132 hours would be 12z Monday, not Sunday.

[Kmlwx]

00z GGEM looks okay for those in VA... maybe up to PHL at 132... but it scoots ENE brushing SNE at 144 it appears

http://www.weatherof...SIC@012_132.jpg

http://www.weatherof...SIC@012_144.jpg

Waiting on the Euro now! I haven't written the threat off by any means but I sure do think if by tomorrow 12z we are locking into this solution it may be close.

[Atlas]

Thats old GGEM

[psuhoffman]

This is still 100 hours away... not sure I can agree with this. Is it a long shot, yes, but like you I always thought this particular threat was a long shot. I am not feeling like it is now virtually hopeless right now though, I still think its a long shot but not significantly more so then I did when the GFS alone was showing a storm. Perhaps because I consider the GFS to be complete garbage when it has no support from the euro or any other model for that matter. In that regard, losing the GFS did nothing to my gut feelings on this storm threat. You're statement regarding the time reference has me confused though. Being a veteran snow weenie in the mid atlantic and northeast I can remember way too many significant storms that shifted in a major way inside 48 hours to even blink at 100 hours.

Just to back this up and just from memory after a long day

100 hours before all 4 significant snows from the 1996 winter at IAD the forecast was for the storm to miss, one of them was never forecast...11 news the night before called for nothing, we woke up to 8-12"

1999 we got a 6-10" storm in March that was forecast to be 1" the night before.

I wont even begin to go into January 2000

100 hours before PDII models were all over, they went from being rain to suppressed south then finally latched on around 36 hours out

The significant snowstorm in December 2003 was not picked up until 24 hours before the event

The early March 4-8" storm in 2004 was not forecast correctly on models until 48 hours

Feb 2006 blizzard wasnt picked up until 48 hours

All 3 KU storms last year were not forecast correctly on models until inside 72 hours

I would have a harder time thinking of a significant 6" plus snowfall where it was shown correctly on models 100 hours out

Your other points are all valid but I strongly disagree about your idea that we are getting too close to the event for things to shift radically.

PS: I still remember sitting in the weather center at PSU Hazleton in 2000 pointing out to the resident meteorologist at the time how the radar and WV loop along with the pressure drops were ominous and not behaving according to progs and he was so dismissive about it. I will never make the mistake of taking my eye off the ball.

I was giving about a 15-20% chance 2-3 days ago when all guidance suggested it. Now I would give it less than 10% for a good hit across the area. They are right, getting close enough where probs are going down with each run and it is becoming less of an overreaction.

[ravensrule]

According to Midlo the GGEM came west but not enough for DC

[Baroclinic Zone]

According to Midlo the GGEM came west but not enough for DC

It did. The 12z GGEM was waaaaay OTS.

[Ian]

if i still lived in nw ct i'd be off a building already with the change from 18z to 0z on the gfs

[baroclinic_instability]

This is still 100 hours away... not sure I can agree with this. Is it a long shot, yes, but like you I always thought this particular threat was a long shot. I am not feeling like it is now virtually hopeless right now though, I still think its a long shot but not significantly more so then I did when the GFS alone was showing a storm. Perhaps because I consider the GFS to be complete garbage when it has no support from the GFSor any other model for that matter. In that regard, losing the euro did nothing to my gut feelings on this storm threat. You're statement regarding the time reference has me confused though. Being a veteran snow weenie in the mid atlantic and northeast I can remember way too many significant storms that shifted in a major way inside 48 hours to even blink at 100 hours.

Just to back this up and just from memory after a long day

100 hours before all 4 significant snows from the 1996 winter at IAD the forecast was for the storm to miss, one of them was never forecast...11 news the night before called for nothing, we woke up to 8-12"

1999 we got a 6-10" storm in March that was forecast to be 1" the night before.

I wont even begin to go into January 2000

100 hours before PDII models were all over, they went from being rain to suppressed south then finally latched on around 36 hours out

The significant snowstorm in December 2003 was not picked up until 24 hours before the event

The early March 4-8" storm in 2004 was not forecast correctly on models until 48 hours

Feb 2006 blizzard wasnt picked up until 48 hours

All 3 KU storms last year were not forecast correctly on models until inside 72 hours

I would have a harder time thinking of a significant 6" plus snowfall where it was shown correctly on models 100 hours out

Your other points are all valid but I strongly disagree about your idea that we are getting too close to the event for things to shift radically.

PS: I still remember sitting in the weather center at PSU Hazleton pointing out to the resident meteorologist at the time how the radar and WV loop along with the pressure drops were ominous and not behaving according to progs and he was so dismissive about it. I will never make the mistake of taking my eye off the ball.

I think we actually agree in a sense. Even when guidance was in alignment, I was going with a low probability because there needs to be a tri-phase, and the second phase has to be at the EXACT right time or self-development won't happen and this storm will be either way OTS or a near miss. I am not writing it off yet and I only went from 15-20% chance to 10% or less.

[Ian]

the 2 big storms last yr were well forecast i thought... the second (feb 5-6) especially. there was a trend back nw into the shorter range but the signs were much more clear cut.

[Guest someguy]

It did. The 12z GGEM was waaaaay OTS.

buries east va the new 0z dec 15 ggem does

[Southland Wx]

Euro is lethal, but i remember several discussions with similar model scenarios last winter that trended differently inside 120 hours. This isn't a done deal for anyone yet, and I think everyone really needs to wait for this shortwave to get over land tomorrow evening before anyone goes jumping off buildings. Rest of the 00Z tonight and 12Z runs tomorrow take or leave. 00Z runs tomorrow night are going to be absolutely critical to what comes of this storm, as they'll be the first with land obs from the southern s/w. At least that's my $0.02.

[psuhoffman]

I think we actually agree in a sense. Even when guidance was in alignment, I was going with a low probability because there needs to be a tri-phase, and the second phase has to be at the EXACT right time or self-development won't happen and this storm will be either way OTS or a near miss. I am not writing it off yet and I only went from 15-20% chance to 10% or less.

Probably true, I just corrected all the typo's in my post, god I am tired....

I will check the euro in the morning but I still have some hope just not much.

[psuhoffman]

the 2 big storms last yr were well forecast i thought... the second (feb 5-6) especially. there was a trend back nw into the shorter range but the signs were much more clear cut.

last year was more clear because models were playing into their typical bias more and the setup was a lot easier to diagnose. This is a long shot because of the phasing and timing needed. Last year at 100 hours though the models were a miss for both storms for DC though...and then did their normal north shift around 72 hours. My area up here did not really get into the snow on progs until 36 hours before the events. For DC it was closer to 60-72 hours. This time we need perfect timing so its a long shot but to say the models can not shift radically inside 100 hours is flawed IMHO.

[Ian]

last year was more clear because models were playing into their typical bias more and the setup was a lot easier to diagnose. This is a long shot because of the phasing and timing needed. Last year at 100 hours though the models were a miss for both storms for DC though...and then did their normal north shift around 72 hours. My area up here did not really get into the snow on progs until 36 hours before the events. For DC it was closer to 60-72 hours. This time we need perfect timing so its a long shot but to say the models can not shift radically inside 100 hours is flawed IMHO.

well they can shift radically within 6 hours so i'd assume several big shifts could still happen. problem seems to be they are all going east and lining up a bit better. not to say that can't change but we'd want some better signs soon.

[psuhoffman]

well they can shift radically within 6 hours so i'd assume several big shifts could still happen. problem seems to be they are all going east and lining up a bit better. not to say that can't change but we'd want some better signs soon.

very very true...just remember last year at 100 hours out we were talking about how the PV over northern new england had to shift west and allow a peice to drop in and phase or it would shunt the storm out to sea. Of course we know how that ended... the other players are all way different this time...but that one factor is similar, if the PV over Quebec shifts west a little faster and allows the trough to go negative tilt earlier this could end up in our favor.

[ORH_wxman]

well they can shift radically within 6 hours so i'd assume several big shifts could still happen. problem seems to be they are all going east and lining up a bit better. not to say that can't change but we'd want some better signs soon.

We can point out all the times the models have trended east only to come back all we want...I know I already did in the NE subforum....but we have to remember there's a ton of times too that they trended east only to stay there or go even further east too....we just dont remember those because we gave up once it became obvious at 72 or 96h out.

Selective memory can play tricks on our minds too much sometimes. This might be one of those times where it comes back west but nobody can prove it will with any good evidence. We just have to wait and see if the models trend better with the main features....this has too many moving parts for someone to say "this is definitely hitting us, the models are screwing X up"...its not just one feature, the multiple moving parts makes us a bit more at the mercy of the models than we already normally are. They can figure these out quicker than we can.

In an obvious stable setup with only one shortwave and no block and a raging pac jet, we can say stuff like "this has nothing to stop it from coming north....it probably will"....like in most Nina southwest flow events....but this is way beyond that type of analysis.

[Guest someguy]

this is classic weenie BS and excuse making filled with poor reasoning and weenie thinking

This is still 100 hours away... not sure I can agree with this. Is it a long shot, yes, but like you I always thought this particular threat was a long shot. I am not feeling like it is now virtually hopeless right now though, I still think its a long shot but not significantly more so then I did when the GFS alone was showing a storm. Perhaps because I consider the GFS to be complete garbage when it has no support from the euro or any other model for that matter. In that regard, losing the GFS did nothing to my gut feelings on this storm threat. You're statement regarding the time reference has me confused though. Being a veteran snow weenie in the mid atlantic and northeast I can remember way too many significant storms that shifted in a major way inside 48 hours to even blink at 100 hours.

you are totally missing the point...

MODEL A says out to sea...

Model B say Out to sea

Model C out to sea...

Model E says HECS.

then Model E says Out to sea.

Yet NOW you think it doesnt matter b/c you happened to not like Model E ?

Just to back this up and just from memory after a long day

100 hours before all 4 significant snows from the 1996 winter at IAD the forecast was for the storm to miss, one of them was never forecast...11 news the night before called for nothing, we woke up to 8-12"

this crap. I was NWS in VA and this is BS.

1999 we got a 6-10" storm in March that was forecast to be 1" the night before.

I wont even begin to go into January 2000

AH the oldie but goodie...Just like Jan 2000!!!!

100 hours before PDII models were all over, they went from being rain to suppressed south then finally latched on around 36 hours out

BS the euro nailed that 7 days out and never once varied

The significant snowstorm in December 2003 was not picked up until 24 hours before the event.

AGAIN more BS ... the forecast is NOT the issue... the Models showed the event .. the Euro did very well the GFS sucked until 72 hrs out

The early March 4-8" storm in 2004 was not forecast correctly on models until 48 hours

wrong

Feb 2006 blizzard wasnt picked up until 48 hours

total BS

All 3 KU storms last year were not forecast correctly on models until inside 72 hours

do you really think anyone believes this crap?

I would have a harder time thinking of a significant 6" plus snowfall where it was shown correctly on models 100 hours out

this is classic weenie.... that isnt the point.

FORECAST is not the same thing as Model.

NO forecast 100 hrs ever nails ANYTHING... You are intentionally building a strawman

[weatherweather]

whats goin on with the ggem at 144?

[baroclinic_instability]

very very true...just remember last year at 100 hours out we were talking about how the PV over northern new england had to shift west and allow a peice to drop in and phase or it would shunt the storm out to sea. Of course we know how that ended... the other players are all way different this time...but that one factor is similar, if the PV over Quebec shifts west a little faster and allows the trough to go negative tilt earlier this could end up in our favor.

Check my thoughts in the "WOOF" thread. I agree with you and suggest (although low probability) that models may flip-flop back/forth until the event and may not latch on to a solution. Very low chance but it could happen.

[Amped]

Not enough Amplification out west and no high over New England makes this storm Hail Mary at best

[SnowGoose69]

The normally progressive NOGAPS continues to be not that progressive being just outside the benchmark while the normally west/warm GEM is well suppressed

[pojrzsho]

buries east va the new 0z dec 15 ggem does

what hour is ggem in?....anyone?

[nzucker]

Since this is the 0Z thread for CONUS, parts of CA/OR mountains are going to be clobbered with heavy rains/snow with potential flooding in this pattern.

What's going on with the band of absurdly heavy precipitation over the Sierra Nevada? I assume it's WAA combined with upslope flow from the big upper low sitting off the California coast, but that seems like a mighty amount of precipitation and reaching rather far south for a La Niña winter. I've always wanted to be out there for one of the classic Pacific storms since the Sierra has a habit of getting nailed with massive amounts of snow whenever such a set-up materializes. Great skiing to be had for sure.

Not enough Amplification out west and no high over New England makes this storm Hail Mary at best

We never have a +PNA for this storm...I thought the block and potent southern stream shortwave was going to be enough to overcome the mediocre Pacific, but it's looking not to cut it at this point...the disturbance is pretty flat instead of amplifying down the backside of a PNA ridge.

[SnowGoose69]

what hour is ggem in?....anyone?

The GEM came west from 12Z but thats like saying the U.S. economy is going to improve...there was really nowhere else for the GEM to go but west given its 12Z run was so insanely far east....had the GEM come as far or west of the 00Z GFS it would be significant but overall the 00Z GEM run was meaningless unless it came way way west...it basically made its statement at 12Z that this was a non-event in its "mind"

[pojrzsho]

The GEM came west from 12Z but thats like saying the U.S. economy is going to improve...there was really nowhere else for the GEM to go but west given its 12Z run was so insanely far east....had the GEM come as far or west of the 00Z GFS it would be significant but overall the 00Z GEM run was meaningless unless it came way way west...it basically made its statement at 12Z that this was a non-event in its "mind"

thank you