March 14th-15th Possible Storm

Ok, CP had asked me earlier today about my thoughts for this weekend. I know it's quite late, that many (if not all) of you are not on here right now, but I figured I'd post this tonight anyway and you can read it in the morning. I would like to preface this brief discussion with what I mentioned a few pages back, about how we will be seeing the worst model-mayhem yet this season, since this is "prime time" for cut-off mid-level (H5) lows to start making their appearances. As I also said, all models are horrifically bad in handling the development and evolution of these mid-level lows for reasons that I do not know, and so we must not get hung up on any particular solution outside of 48 hours. Within 48 hours we should start paying attention, but even so, things are far from being set, as we have already clearly seen this season. Time for the discussion.

As many of you have probably seen, the GFS Operational runs have been insistent on a much snowier solution than the EURO Operational (both seen below using today's 12z runs, respectively).

http://images0.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_P850TS_0144.png

http://images0.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_P850TS_0144.png

Interesting to note, the EURO does not look entirely different from the GFS Op other than it is significantly faster with departing the surface high pressure over southeastern Canada as well as with the propagation of the surface low pressure to the north from the southern states, which are factors caused by differences in the H5 heights (to be discussed). There are other "cosmetic" differences between the two, such as the "cleanliness" of the transfer to the coast, which in both cases is still too late to keep anybody all snow save northern New England, but that is irrelevant at this time frame and so will be left out.

What I would like to draw attention to, though, is the direction that the surface low pressure travels from its initial stages all the way through its impacts here in 12-hour increments. First will be the GFS followed by the EURO.

GFS:

http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_P850TS_0090.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_P850TS_0102.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_P850TS_0114.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_P850TS_0126.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_P850TS_0138.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_P850TS_0150.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_P850TS_0162.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_P850TS_0174.png

EURO:

http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_P850TS_0090.png
http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_P850TS_0102.png
http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_P850TS_0114.png
http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_P850TS_0126.png
http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_P850TS_0138.png
http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_P850TS_0150.png

Look at the almost perfect south to north propagation of the system......that is a track that we don't normally see. Usually, there is some sort of west to east component to the systems, even in Apps runners or Great Lakes Cutters. Not this one. Why? I would like to now direct your attention to H5 (mid-levels, 500 mb). Remember those pesky cut-offs I discussed? Well, here comes one. The following images will be of the exact same times as those earlier, but at H5, where some of the "steering" and dynamics for surface systems come from. As you loop through the following images, please pay attention to the heights over the nation's heartland as well as the East Coast.

GFS:

http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_H500C_0090.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_H500C_0102.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_H500C_0114.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_H500C_0126.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_H500C_0138.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_H500C_0150.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_H500C_0162.png
http://images1.earthsat.com/misc/mod-images/GFS/OP/12/GFS_12_opUS_H500C_0174.png

EURO:

http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_H500C_0090.png
http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_H500C_0102.png
http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_H500C_0114.png
http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_H500C_0126.png
http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_H500C_0138.png
http://images1.earthsat.com/misc/mod-images/ECM/OP/12/ECM_12_opUS_H500C_0150.png

Do you see the differences?

The GFS actually has a pretty interesting evolution. Between hours 90-114, there is a short-wave trough that enters the western United States at the leading edge of a rapidly strengthening mid-level ridge that centers over the West Coast (possibly being aided by the MJO). By hour 114, do you notice how that ridge folds over the short-wave? That is what's known as a wave break (exactly like a wave in the ocean crashing onto the shoreline), and in this case, is an anti-cyclonic (clockwise) one. This causes the remnants of the short-wave trough to become cut-off. Between the hours of 108-114, there is another cut-off that develops over the heartland of the U.S., and by hour 120 they merge. This is why the GFS solution shows more snow. Because of this evolution, the broad cut-off low, even if only for approximately 18 hours, prevented the heights from rising too much along the East Coast. It also allowed the primary surface low that was cutting to our west to remain very, very weak via dynamics (very weak and early-to-close off H5 = very weak surface cyclone), which limited the warm-air advection out ahead of it at the lower levels of the atmosphere. The reason that the surface low is moving from south to north, is because of the wind flow, which if you imagine blows parallel to the height contours and from west to east, yield a southerly wind. As for the high over southeastern Canada, that is being produced by confluence of the northern and southern streams over that region.

The EURO, however, is quite different. Although it tinkers with the same idea, it is much slower to wave-break the western ridge, and in fact, doesn't do so until the system is more or less departing our area. The result; higher heights along the East Coast, a **more organized** cutting surface cyclone and the eastward displacement/more rapid departure of the confluence (helping to force the surface high) to the north as compared to the GFS. This allows more warmth to be drawn up ahead of it, and turn us to rain much faster.

The CMC/GEM, although not posted, is currently siding with the EURO.

As for inclusion of the ensembles, there is no DEFINITIVE way for me to comment on the details of the evolution of H5 because the spaghetti plots that I have access to do not contour the height lines that are needed for this discussion. However, basing my observations ONLY on the 850 mb temperature spaghetti plots, it would seem that each ensemble is showing strong support for its own operational model. What does this tell me? Well, it seems to me, and this is only my opinion, not fact, that the discrepancies are arising due to some sort of parameterization. Whether it has something to do with something as large-scale as, say, the Earth's momentum budget, or something as small and sub-meso-scale as a cumulus parameterization in updrafts (as was the reason why the EURO accurately predicted Sandy at the 8-day lead window while it took the GFS until lead-day 4) I cannot say; but to have such support for each separate solution leads me to believe that it is more than coincidence, because don't forget that ensembles are the same model run with slightly different initial conditions (input). The only way to know what is going to happen, unfortunately, is to play the good ol' fashioned waiting game.

My thoughts on the forecasts.....As we have seen again and again, the -EPO is unbelievably dominant with the low-level cold air, as (I think) it was Algae who pointed this out weeks ago, so the temperature profile of the GFS does not seem unreasonable at all. However, I do not really like its H5 evolution, and I feel that the EURO is more believable. The GFS is suggesting two closed mid-level (H5) cyclones within a very small horizontal scale, which is very, very rare. Although this is possible, and it has happened in the past a few times, I do not think that this will happen. It will only be one, likely forced by the wave-breaking of the western ridge. So, blend the evolution of the mid-levels from the EURO and the temperature profile of the GFS and I think that we have our solution. There are a ton of working parts to this, though; MJO feeding into the PNA and the EPO, among others, so if any single piece changes, as I'm SURE it/they will, we will see different outcomes. These are only my thoughts as of now, so take them with a salt-shaker. I stress again, when cut-off lows are involved, it is absolute HELL for forecasters lol

I hope that this makes sense to you all, and that it was somewhat decent. I apologize for it being so late, but I hope it was worth the read. Good night all!!!

Thanks RB I appreciate it. It's not as encouraging as I was hoping for this weekend but I guess we can't rule it out until we get closer to Saturday.

Update:

It looks like the EURO ensembles started changing their course overnight last night, at least with respect to the temperature profile. There is much stronger support for the GFS in that regard. With respect to the H5 evolution, that is still iffy, although it looks like there may have even some positive strides there with the ensembles as well. I cannot inspect that at this time, but if I can manage time sometime today/tonight I will.

FOR FUN PLEASE CHECK OUT THE 06Z GFS SNOWFALL MAP. INTERIOR AND ANYWHERE NORTH OF NYC SEES A GODZILLA+++

Here's a low-res image......

Make sure you are listening to Aerosmith's Dream On when viewing....

http://images0.earthsat.com/misc/mod-images/GFS/OP/06/snosums/0120/GFS_06_opUS_SF_0186.png

6z gfs...wow

Frank_Wx wrote:6z gfs...wow

Yeah man, that's what I said too hahaha H5, although still unrealistic to me, was gorgeous lmao kept heights along the East Coast very muted.....It will be interesting to see how the EURO plays this one out: Will it continue to trend toward the just-as-consistent GFS, or will it back-track and take the GFS with it? Based on H5, I still side with the latter, but honestly the way this season has gone it would not "surprise" me if the former occurred lol

The 6Z GFS for Sunday is actually a dream come true scenario for the HV and NEPA. Actually NYC and NNJ don't do bad either. I don't buy it but I can dream.

CPcantmeasuresnow wrote:The 6Z GFS for Sunday is actually a dream come true scenario for the HV and NEPA. Actually NYC and NNJ don't do bad either. I don't buy it but I can dream.

I am right there with ya CP. I am still convinced that we see it trend away from this solution, but too bad. I'd have a bonafide Roidzilla if this run verified verbatim :/

FWIW 15 of the 50 euro ensembles versus almost none at 12z yesterday show 6 or more inches of snow into my area, obviously this is a low chance but lets see what happens. With the loss of so much snow this week this storm will have to be cold, at least down here, you guys up north have many of the euro ensembles on your side 6+, I wish we could all get in on the action and its possible from what I am reading but climo suggests north areas benefit. Heres to hoping for a blitz this coming weekend! Oh and BTW OT but Frank sweet new top of page.

The GFS keeps the High overhead while the foreign models bring it off the coast of New England at an imperfect time. Big difference.

And which one is right? If I know the models this year only mother nature knows, so are we saying we won't have a clue until Thurs/Fri? I cannot believe how much snow has already melted just from yesterday.

Frank_Wx wrote:The GFS keeps the High overhead while the foreign models bring it off the coast of New England at an imperfect time. Big difference.

frank that's the key to this event. gfs has it somewhat stronger and pressing down and holding more than the other models. ncep has the ao really tanking this week so maybe gfs could be right. that's only if ncep tele conn are correct.

jmanley32 wrote:And which one is right?  If I know the models this year only mother nature knows, so are we saying we won't have a clue until Thurs/Fri?  I cannot believe how much snow has already melted just from yesterday.

There may not be any left by the time Saturday gets here.

algae888 wrote:

Frank_Wx wrote:The GFS keeps the High overhead while the foreign models bring it off the coast of New England at an imperfect time. Big difference.

frank that's the key to this event. gfs has it somewhat stronger and pressing down and holding more than the other models. ncep has the ao really tanking this week so maybe gfs could be right. that's only if ncep tele conn are correct.

The -AO/-NAO will not come until after the 20th. The threat this weekend is very much thread the needle. N&W of NYC are in much better position to see accumulating snowfall than we are at this juncture.

That would be pretty crazy to lose all the snow in one week, going to be pretty wet and muddy if so. I still have places where there is over a foot but that's in shaded areas, those huge piles though won't go away for a while. Not thinking much for this weekend if something happens its icing on the cake at this time 54 inches pretty darn good for this year considering what we thought at the g2g (that's IMBY), if the storm does come GFS route the ground may be too warm down here to even stick if its wet and bare.

12z GFS says no.

hearing the cmc is an ice storm for this weekend

cmc



actually snow to ice

mainly for n/w suburbs. big diff from gfs is precip comes in much sooner. cmc has support from other models as gfs uncharacteristically is less progressive than other global models.

cmc snow map

cmc has precip moving in around 8 to 10 pm fri night over by noon sat. most n/w locals never go above freezing. gfs start time is about 8am sat. big big differences.

lets just assume models are going to waffle on this. still 4-5 days out

if I were a betting man I wouldn't bet against the trends this last month or so. basically events have trended colder as we get closer and it seems like it just wants to snow in our area. i understand we are in march now but still early enough. why should we expect that to change?

RB , great write up !! Thanks for everything you post !