NYC/PHL December 24-27 Potential - Part 2

[BaltimoreWxGuy]

HPC going with EURO as they should

...SHORTWAVE SWINGING INTO THE SOUTHWEST DAY 1...

PRELIMINARY PREFERENCE: 00Z/22 ECMWF

THE NAM TIMING OF THIS WAVE IS CLOSE TO THE ECMWF...WITH SLIGHTLY

LESS AMPLITUDE BY THE TIME IT REACHES LOUISIANA BY THE END OF THE

PERIOD. THE GFS AND GEM GLOBAL BEGIN TO PULL AHEAD OF THE NAM AND

ECMWF LATE DAY 3 ALONG THE GULF COAST...WITH THE GFS SHOWING LESS

AMPLITUDE LIKE THE NAM. THE UKMET CONTINUES TO BE ON THE

SLOW...SUPPRESSED SIDE OF THE GUIDANCE...A BIAS OF THE MODEL.

THERE HAS BEEN A LOT OF TRENDING WITH THE SHORTWAVE OVER THE PAST

SEVERAL MODEL CYCLES...WITH THE EXCEPTION OF THE ECMWF. THE ECMWF

HAS BEEN CONSISTENT FOR THREE RUNS IN A ROW...AND WAS ALSO THE

FIRST MODEL TO BREAK TOWARD A SLOWER...MORE SUPPRESSED SOLUTION.

WILL CONTINUE TO RELY ON IT.

[HSNN4]

Feb 1978 sure started late and caused a disaster on the roads. The same was the case with Feb 1983. Jan 1996 and PD2 started "on time" but it took 4 hours for the snow to move up from the south shore of LI to the north shore.

And you dont have to even look that far back-- 12/19/09 last year also started late-- but made up for in the wee hours of the morning lol (ugh, I hate late night snows-- I want it in the daylight hours!)

One case study I remember for the 1983 storm was Snow reported at Trenton KTTN at 9am and it took almost to 2 pm for the snow to reach th Newark area, 1983 one of had more impressive starts as far as accumulation rates as the storm wasted no time in 1 to 2 inch hourly accumulation rates and the snow came on in heavy sheets right from the get go, as a child it was a very impressive storm to me with 21 inches of snow measured at this station by storms end.

[Neblizzard]

ECM looks to have a cutter in the long-range with a huge arctic front behind it and the coldest air of the season about to arrive. Massive block over Siberia as the -NAO rebuilds first into Iceland, then Greenland. We also have a +PNA/-EPO style block developing by Day 10. ECM looks to be hinting at a cold start to January after a very brief moderation of the temperature pattern.

If that occurs and persists well into January, that will be a crippling defeat for the La Nina.

[earthlight]

If the Euro is going down with this storm, it's going down hard. That much we can say right now. Still...lets all continue to consider that the storm system is 120 hours away. The pieces will be better sampled by tomorrow at 00z, but even then...they track slowly across the CONUS and there are lots of interactions ongoing.

I'm urging everybody not to get too latched on to these solutions. Someone coughing near the MS River could mess up this phase.

[RutgersWx92]

you're a met major and you cant tell from the euro images that there's no way in hell there will be mixing with that track?

lol I'm only a freshman, and I suspected that there would be a lower chance of mixing with the further south track but I just wanted to be sure. Plus it does look like surface temps might be an issue in a few coastal locations taking the Euro run verbatim:

ACY: 1.83 but ground temps are around 34-36* for most of the event...

SBY: 2.14 but similar problem, 2m temps are +3.4 for the height of the event

more inland locations are fine and H8 temps are 3-4 below along the coast but the euro depicts ground temp problems with the east wind off the ocean.

Please I am not saying this is true, just giving model output.

[A-L-E-X]

I was in 4th grade it and was my first year on Long Island when I saw that storm, and even at that tender age, I was amazed. I mean, we had prolific thundersnows and I think the entire storm was heavy snow from beginning to end. It started here around lunch time and we got out of school early (it was a friday and midwinter break followed so no snow days) but I remember, even back then, we were waiting for the snow to come up from DC all morning.

The great thing about such an expansive storm like that is you get to see all the major cities fall down like dominoes one at a time as the huge wall of white slowly crawls north, knowing youll be immersed in it for hours upon hours.

[A-L-E-X]

If that occurs and persists well into January, that will be a crippling defeat for the La Nina.

Don is already going for a more blocky Jan and is becoming increasingly bullish on an explosive March. We might have a 2000-01 type La Nina pattern to this winter.... let's just hope this storm works out like the Millenium storm did (lets just share the wealth this time ) and we get in March what March 2001 was "supposed to be."

[tombo82685]

gfs indiv ens runs...looks like 2 big hits, with a couple close calls

[A-L-E-X]

Euro QPF for BOS is 2 inches plus (according to main thread), so I guess this thing isnt as supressed as some thought it was on the model.

[bass28]

not sure to think of the sref''s at 87?

[earthlight]

I just finished the forecast package for the blog. I've pasted the part most of you are probably interested in.

http://www.nymetrowx.blogspot.com/

Long Term

Incredibly convoluted and anomalous pattern is forecast to develop in this time period, and we will do our best to highlight the most recent developments along with our concerns.

The 00z NAM initialized a very strong shortwave trough, associated with the remnants of a Pacific ULL, about 250 miles off the coast of California. This shortwave is forecast to move rapidly east over the next 24 hours, reaching the coast of California by 00z Thursday. The strong pacific jet and fast and progressive flow across the CONUS will then force this shortwave eastward. Most forecast guidance was split as to what happened thereafter, until tonight. Previous runs of the GFS and GEFS means took this shortwave east very rapidly, bringing the shortwave east of the Texas Panhandle by 06z Friday. The ECMWF, NAM, and CMC were much slower and more amplified with this shortwave, owing to the stronger ridging across the Central Plains and building ridge over the West Coast. This solution is now favored as the GFS has trended about 6 to 10 hours slower with the shortwave on it's latest 00z/22 run.

This results in most guidance agreeing on a strong shortwave, out of the southern jet stream, over the Texas Panhandle or Oklahoma at 12z Friday. The other main players on the field seem to be relatively well modeled, with some differences still existing as the model guidance diverges. By 12z Friday, with the shortwave in TX/OK as previously noted, a relatively high amplitude ridge will be building on the West coast of the CONUS with the ridge axis through the Western Rockies into West-Central Montana. Meanwhile, northern stream energy is modeled to be diving southward from Central Canada through the International Border and into the Dakotas and Northern Plains. Confluent flow over the Northeast US is expected to be lifting north/northeast as the upper level low moves out of the Northwest Atlantic. This upper level low will swing north, towards and through the 50/50 lat/lon position, driving lowering heights through Central Canada and southward.

The result, as advertised on guidance for the past few days and now especially tonight, is the potential for a major jet stream phase. The GFS misses the phase, sending the surface low from the Southeast States off the coast of the Carolinas and then out to sea. A closer look at it's H5 depiction reveals its issue; where the GFS is sending the initial shortwave that was over TX/OK too far south and east--resulting in deamplifying trough heights and a missed phase. The CMC has trended east from it's 12z solution, but is still enthused with the phase idea. In fact, although precipitation is slightly too far east to majorly impact the area, the model closes off at H5 south of Long Island, and brings a 970mb surface low directly over the 40/70 benchmark. The most interesting model so far is definitely the ECMWF, which has consistently brought the surface low very close to the coast--close enough for major weather impacts in our area. In fact, tonights 00z/22 ECMWF phases in the Polar Vortex, and traverses the surface low from 986mb off of OBX, to 972mb northeast of Ocean City, Maryland.

The result of all of this has been tremendous uncertainty. The ECMWF definitely seems to be a far northwest outlier at this point--but it has been consistent. In any other year or pattern, we would probably be including most of the ECMWF output in our package. That being said, despite the pattern amplitude, the pattern's progressive nature suggests we not jump too early on such a solution given the lack of other global support at this point. On the contrary, the GFS and GEFS mean seem way too flat and fast--so we did not include much of them into our package either. Instead, we took a blend of the GGEM and ECMWF from 12z..which brings 40-50% PoP to the coastal areas, and 30-40% PoP to inland areas at this time. Too early to guess on precipitation types or amounts, but we are not expecting precipitation type problems given our preferred forecast track. The heaviest QPF is currently forecast to be in the southeast fringes of our area..tapering off as one goes further north and west.

Obviously, with the uncertainty advertised, things could change considerably. This has the potential to be a high impact storm system. Current timing favored for impact is Sunday afternoon..through Sunday Night..and into the first half of Monday. As mentioned..we are taking the middle ground of model guidance at this point. It's still entirely possible that we see at trend towards either of the most extremely solutions, which would obviously have significant sensible weather impacts on our area. So stay tuned. Kept slight chance of PoP in through Tuesday to account for guidance indicating residual low level moisture as the surface low tracks away from the area. Temperatures through the period should continue running below normal.

[Rtd208]

Nice write up and reasonable at this point.

I just finished the forecast package for the blog. I've pasted the part most of you are probably interested in.

http://www.nymetrowx.blogspot.com/

Long Term

[tombo82685]

according to cheeznado, the euro ens are much less impressive than the 0z op. The ens would bring precip moderte precip to coastal sections.

[tmagan]

according to cheeznado, the euro ens are much less impressive than the 0z op. The ens would bring precip to mainly coastal sections.

So its basically the Euro Op. versus the world. I think I know which direction this is heading.

[A-L-E-X]

So its basically the Euro Op. versus the world. I think I know which direction this is heading.

On the bright side, we should be good for at least a few inches no matter what...

[tmagan]

On the bright side, we should be good for at least a few inches no matter what...

I'm not even sure of that.

[tombo82685]

I'm not even sure of that.

its still 5 days away, relax. If it misses it misses, nothing we can do about it.

[Rtd208]

Thank you! some of these posts are getting ridiculous.

its still 5 days away, relax. If it misses it misses, nothing we can do about it.

[earthlight]

its still 5 days away, relax. If it misses it misses, nothing we can do about it.

[earthlight]

06z NAM looks good compared to the 00z GFS. The northern stream is much more involved and the shortwave is slower.

[tombo82685]

through 54 hrs on the nam, its continuing to trend towards the euro. Its closer to tcutting off the h5 over tx as the euro did.

[CooL]

06z NAM looks good compared to the 00z GFS. The northern stream is much more involved and the shortwave is slower.

Closed off vort in TX panhandle, digging more and way south...

[earthlight]

Also looks weaker with confluence, stronger with the shortwave. Ridge axis is further west and more amplified. So we're getting there.

[earthlight]

through 54 hrs on the nam, its continuing to trend towards the euro. Its closer to tcutting off the h5 over tx as the euro did.

The big thing is the northern stream now. We've got a developing consensus that this shortwave is going to track much slower than the GFS was indicating. Now we need the northern stream involvement. Compared to it's 00z run, and the 00z GFS, the NAM has more northern stream involvement.

Keep in mind that the northern stream energy is very poorly sampled at the moment. Long way to go.

[tombo82685]

The big thing is the northern stream now. We've got a developing consensus that this shortwave is going to track much slower than the GFS was indicating. Now we need the northern stream involvement. Compared to it's 00z run, and the 00z GFS, the NAM has more northern stream involvement.

Keep in mind that the northern stream energy is very poorly sampled at the moment. Long way to go.

is the northern stream disturbance the little indent in what looks to alberta at hr 54 h5?

[Dsnowx53]

its still 5 days away, relax. If it misses it misses, nothing we can do about it.

God damnit, I was thinking about going to northern Canada, and coughing southward to help the northern stream energy dive southward. Oh well.

[tombo82685]

cut off closed low now at h5 where the 0z didnt have this feature.

[tmagan]

By the way the new HPC prelim discussion is out.

[tombo82685]

God damnit, I was thinking about going to northern Canada, and coughing southward to help the northern stream energy dive southward. Oh well.

i would just rent a plane and stall it over the air in northern canada, that should blow her pretty far south and fast.

[Dsnowx53]

i would just rent a plane and stall it over the air in northern canada, that should blow her pretty far south and fast.

Hahaha, very true...especially considering coughing at the surface won't do squat; you need to have the push southward in the upper-levels. Planes generally fly near 200mb, so that could help to enhance a jet-streak.