Potential Winter Storm March 6-7

[CooL]

^ you mind posting it?

It's already posted. The pieces are there in the northern stream

[Kaner587]

I remember that vividly and alluded to that event yesterday. I definitely recall that PV sitting north of Maine suppressing the storm south...until some of the model runs started magically splitting the pseudo 50/50 low into two pieces like Moses split the red seas...this looks like a different set-up though

Yes there was an elongated PV east to west which split around 18z 12/18/09 (thank you re-analysis maps) and allowed for amplification. Completely different set-up for sure but interesting corollary to this event

[Absolute Humidity]

I remember that vividly and alluded to that event yesterday. I definitely recall that PV sitting north of Maine suppressing the storm south...until some of the model runs started magically splitting the pseudo 50/50 low into two pieces like Moses split the red seas...this looks like a different set-up though 

Looking at H5 its almost as if the mid Atlantic ULL and the west NY vort fujiwhara a bit.

[jm1220]

There is a 45-50 kt wind contour over the S fork of LI at 84hr. That's a NNE wind; due N or NNW further west along the coast, going down to NJ and the Delmarva. The duration of ENE-NE winds over coastal areas is less on this run due to the increased northerly movement of the storm, so coastal flooding issues would probably be less than on previous runs. 

 

Amazing to see the models diverge again at this stage. 

That's key-the sooner we can get it to a northerly or NE wind, the better it is for coastal flooding prospects. A strong east wind for multiple tide cycles would be horrendous. Hopefully we see other models tonight continue the trend-I'm perfectly cool with a blizzard on offshore winds.

[SnoSki14]

Just once it would be nice to have nearly full consensus between the models under 3 days.

[Blizzardo]

Ya'll know the gfs did this because I said it was game over after the euro today.. right? LOL

[sferic]

Do you think by tomorrow evening with the ooz runs we will have our answer for NYC and vicinity?

[Zir0b]

GGEM looks like a scraper...not much different at the surface from it's 12z run 

[jm1220]

Just once it would be nice to have nearly full consensus between the models under 3 days.

The Euro was still quite far south at 12z. I would want to see a notable shift north in order to mark the GFS tonight as being anything more than a fluke. Remember how awful it did with the 2/8 storm-it's had far from a stellar record this winter.

[SnoSki14]

Seems like the issue lies in getting a better precip field and overcoming the confluence rather than a major shift in the location if the low.

[Weathergun]

I think that is MORE than somewhat more north.. the 12z ukie below... 0z Ukie shows the northern stream pulling it back further north as well as aligning a classic negative tilt look...but not quite to GFS level but a step towards it for sure 

 

 

It's difficult to compare slp, with the UKMET in 24hr intervals, beyond 72hr. But what's most interesting is the piece of ULL breaking off and interacting with the southern low.

[Zir0b]

It's difficult to compare slp, with the UKMET in 24hr intervals. But what's most interesting is the piece of ULL breaking off and interacting with the southern low.

yeah that was a significant change...surface not nearly as notable

[jm1220]

Seems like the issue lies in getting a better precip field and overcoming the confluence rather than a major shift in the location if the low.

The block has to move enough out of the way. If it doesn't it doesn't matter how nice the low and precip field look. The low will be shunted straight east and precip will get eaten up by dry air where the confluence is dominant. It was the worst of the lessons we learned on 2/6/10.

[SnoSki14]

It's difficult to compare slp, with the UKMET in 24hr intervals, beyond 72hr. But what's most interesting is the piece of ULL breaking off and interacting with the southern low.

The models may be playing catchup if the gfs has the right idea then especially at the surface.

[Dsnowx53]

I'm hoping that the Ukie trending towards showing a northern stream and an almost phase means that the Euro will at least have a semblance of northern stream interaction. 

[Dsnowx53]

But isn't that the fun part? In the summer, when we're on here tracking a 40dbz garden variety thunderstorm that has a severe thunderstorm warning on it, won't you wish we were doing this instead?

 

I think the most intriguing part about this entire setup is how the guidance is handling the three features which are on the board (all somehow, magically within the northeast us grid frame on ewall) after 48 hours. If you check out the image below,  the GFS initially looks like it will whiff to the south and east. The entire flow is oriented that way from the get go as the ULL comes out of the Plains and dives south and east underneath the fast flow to the north and blocking. However, some crazy interactions occur aloft that I think most people are missing. These will determine where the storm tracks and where the precipitation field ends up. The two very important features are

 

1) The ULL to the northeast of the main shortwave in the Northwest Atlantic. This feature is crucial for more than one reason as it not only acts as a confluent provider early on, but then it actually begins to interact with the shrotwave over the Mid-Atlantic. Look below and watch the feature highlighted. At first it is situated over the Northwest Atlantic and elongates to move over New England. As our shortwave shifts through the Mid-Atlantic, it actually retrogrades west and interacts with the northern periphery of the shortwave to the south. This is very important as it allows for a very brief but incredibly essential height rise along the coast.

 

As a result of this the precipitation shield can expand to the north and west instead of continuing to be shunted off to our south and east. The surface low can eventually slowly travel north and east along a very narrow highway as that feature moves out of the way back to the west over Western New England. The eventual track of this feature will not only determine the track but also the best jet dynamics and whether or not they will allow precipitation to expand into our area. The NAM has this aligned very poorly and the precip shield never has a chance.

 

2) The northern stream feature dropping in from Southeast Canada. Every run of the GFS has trended farther south and east with this feature with more interaction since last night at 00z. This is arguably more important for New England as it eventually phases in and kicks off new development. This is why you're seeing a secondary QPF max develop eventually over New England on the GFS. It also helps the height field orient in a better manner for us on the tail end of the CCB influence on the GFS.

 

But this is all fun and games for now. Until we see shifts from the more reliable guidance (who am I kidding, the Euro and its ensembles), I think we'll have to take these developments as interesting but not "mother of god" status. The NCEP models have not only had a history of shenanigans in this time frame, but have had a specific history with bringing surface lows and precipitation shields too far north and west. And although every storm system is different, this would be an ideal situation for them to play into that bias.

 

We will see.

 

gfs_march4.png

 

 

Excellent post, John. Hopefully the Euro trends towards showing some sort of northern stream interaction, considering the Ukie almost pulled it off. That's more important than what's going on at the surface. And cool that we now have two northern stream features at play.

 

If we can get both to phase, and the 2nd one coming down earlier, we'd get the high QPF totals that the Boston area has. 

 

I'm not too optimistic regarding the Euro, but I do have hope. I definitely don't expect it to show a GFS type solution, but a moderate graze with the northern stream actually present would be enough to color me quite interested. 

[jm1220]

The models may be playing catchup if the gfs has the right idea then especially at the surface.

Just looked at the soundings and honestly they're not that impressive for many of us near the coast, well inland looks better. 950mb and below looks torched for a lot of the event with not that good a precip rate. The dynamics look like they temporarily die out for us and re-develop up towards Boston and SNE (how fitting for this winter). We need dynamics and strong lift to have a real shot at good accumulations. Light or moderate precip would result in mostly slop that may not even accumulate if it's in the daytime. But getting the main precip shield up here would be a big first step.

[Absolute Humidity]

FWIW and it ain't much, CRAS has CCB to our NW with a coastal hugger.

[Dsnowx53]

Just looked at the soundings and honestly they're not that impressive for many of us near the coast, well inland looks better. 950mb and below looks torched for a lot of the event with not that good a precip rate. The dynamics look like they temporarily die out for us and re-develop up towards Boston and SNE (how fitting for this winter). We need dynamics and strong lift to have a real shot at good accumulations. Light or moderate precip would result in mostly slop that may not even accumulate if it's in the daytime. But getting the main precip shield up here would be a big first step.

 

 

Having it occur at night would help tremendously. Hopefully it's simply the GFS not having the resolution to resolve evaporational cooling at the BL. It'll be nice to not have a primary low problem this time around. 

[Kaner587]

According to Philly thread ggem gets 0.75 line to about SI and south shore of LI

[Zir0b]

Just looked at the soundings and honestly they're not that impressive for many of us near the coast, well inland looks better. 950mb and below looks torched for a lot of the event with not that good a precip rate. The dynamics look like they temporarily die out for us and re-develop up towards Boston and SNE (how fitting for this winter). We need dynamics and strong lift to have a real shot at good accumulations. Light or moderate precip would result in mostly slop that may not even accumulate if it's in the daytime. But getting the main precip shield up here would be a big first step.

GFS Snow map posted by Ekster in the NE forum shows 10-12" for you 

http://www.americanwx.com/bb/index.php/topic/39469-early-march-threats-mar-1st-8th-period/page-43#entry2176589

[SnoSki14]

I would bite and have more faith if it wasn't March honestly, we've gotten pretty screwed in March.

And just because we are in a blocking pattern that doesn't mean we will see snow. The BL temps will def be a problem with lighter precip.

[MJO812]

According to Philly thread ggem gets 0.75 line to about SI and south shore of LI

 

That's an old version

[Kaner587]

GEFS looks similar to op through 72

[Dsnowx53]

According to Philly thread ggem gets 0.75 line to about SI and south shore of LI

 

 

I don't have a precip total map, but looking at it aloft; it DOES try to retrograde some piece of vorticty from the departing ULL into our storm, but it's not as well defined as on the GFS. Additionally, that 2nd shortwave does try to dive down, but it doesn't quite fully phase, so it can't turn up the coast. 

[Zir0b]

That's an old version

Yeah, last night's 0z run. Tonight's GGEM looks nothing like that

[SACRUS]

ggem pcp is north from 12z (change date to 4th) but not like the gfs

 

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

[Kaner587]

GEFS agrees with op. 1-1.25in qpf for much of the area. 1.25 line runs from Philly to Trenton to SI and skirts along the south shore of LI

[MJO812]

0z GEFS is lovely

 

Over 1 QPF for NYC on the GEFS.

[David-LI]

0z GEFS is lovely

 

Over 1 QPF for NYC on the GEFS.

as rain or snow?