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NYC/PHL 12/21-12/22 Threat

hazwoper

By hazwoper,
in New York City Metro

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earthlight

earthlight

Posted
Posted

It's going to be much easier to get good snows out of this system IMO just eyeballing it right now. As long as there aren't excruciating changes..the general pattern argues for some very good potential right near Christmas. Obviously the changes can happen very easy--but it's good to see this on the globals and NCEP models as well.

It's kind of something that falls into place as the Pacific ULL breaks down and is ejected east into the CONUS. The confluence shouldn't be too overbearing especially by 12/24 and onward. The Euro is actually very close to having an 18z GFS-like solution and bringing the northern stream in dramatically. Regardless it was good to see it jump towards the idea.

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BaltimoreWxGuy

BaltimoreWxGuy

Posted
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It's going to be much easier to get good snows out of this system IMO just eyeballing it right now. As long as there aren't excruciating changes..the general pattern argues for some very good potential right near Christmas. Obviously the changes can happen very easy--but it's good to see this on the globals and NCEP models as well.

It's kind of something that falls into place as the Pacific ULL breaks down and is ejected east into the CONUS. The confluence shouldn't be too overbearing especially by 12/24 and onward. The Euro is actually very close to having an 18z GFS-like solution and bringing the northern stream in dramatically. Regardless it was good to see it jump towards the idea.

The only thing I can say about this post is I 100% agree.:thumbsup:

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earthlight

earthlight

Posted
Posted

So what would be the chances of that upper level low that's rotating around that complex diving south and phasing ala GFS style?

What's more important on the Ukie is to note the bending in the H5 height lines in the northern Plains. That's indicative of a shortwave trough coming east/southeast in similar fashion to the GFS. That feature would ultimately interact with the southern stream shortwave..which looks very sharp near the TX panhandle actually.

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earthlight

earthlight

Posted
Posted

Is there a nice positive PNA out west on the Euro? It looks great on the gfs, just need the ridge axis alittle more west...The PNA signal is very encouraging

The PNA ridge is there at 174 hrs...the height's aren't dramatically impressive...but it has a huge ridge all the way into West-Central Canada.

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Yes_Probably_Maybe_No

Yes_Probably_Maybe_No

Posted
Posted

What's more important on the Ukie is to note the bending in the H5 height lines in the northern Plains. That's indicative of a shortwave trough coming east/southeast in similar fashion to the GFS. That feature would ultimately interact with the southern stream shortwave..which looks very sharp near the TX panhandle actually.

Ah yes, thanks for pointing that out.

might as well its fun

euro-5.jpg

light green .25-.5

dark green .5-.75

yes plz

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SnowGoose69

SnowGoose69

Posted
Posted

Ah...looks like a no to me

post-605-0-61737100-1292659001.gif

But then again, you guys are better at this than me.

Yeah, not even close, the trough never took on a negative tilt and despite the fact a more or less closed low developed over VA/NC in association with the surface low the main vort in Canada was unable to capture the system....3/2/09 was the successful version of the same event...up until 2-3 days before the models were depicting a very similar scenario to 2/24/89.

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tmagan

tmagan

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Yeah, not even close, the trough never took on a negative tilt and despite the fact a more or less closed low developed over VA/NC in association with the surface low the main vort in Canada was unable to capture the system....3/2/09 was the successful version of the same event...up until 2-3 days before the models were depicting a very similar scenario to 2/24/89.

Not from the atmospheric setup, just from the fact that when a setup looks good three to five days in advance, there have been forecasts hours in advance of a snowstorm (granted in another era) that have busted.

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tombo82685

tombo82685

Posted
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Not from the atmospheric setup, just from the fact that when a setup looks good three to five days in advance, there have been forecasts hours in advance of a snowstorm (granted in another era) that have busted.

as tmagan said radar picks up the virga. But yes i think it's modeled well. Here is the current radar shot compared to the nam's composite reflectivity. This is from stormvista which picks up virga to

centgrtlakes.gif

NAM_221_2010121806_F06_CREF_SURFACE.png

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earthlight

earthlight

Posted
Posted

Just finished a package for the blog tonight...read away. Night dudes.

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

Short Term

It really has been amazing to watch the guidance struggle so mightily with the pattern in the short term especially in regards to the storm system making it's way up the eastern seaboard this weekend. A lot of the struggles stem for an initially poorly sampled shortwave that was entering the southwest US, as well as initialization problems and +24 hour forecast issues with the Polar Vortex. The result was a wild spread on model guidance as recent as last night, with differences of over 350 miles in regards to positioning of the surface low pressure.

The one thing we did try to keep in mind all along is the tendency for the upper air pattern, tropical forcing timing, and ENSO state (historically within La Nina regimes) would favor a weaker southern stream shortwave. This has been precisely the case as guidance backed off considerably on it's strength. The Polar Vortex handling was a whole other juggernaut of problems--but guidance can't be expected to perform exceedingly well with exact features in regards to this type of vortex with many shortwaves embedded within it's circulation. When one considers the guidance latching on to the storm potential off the east coast as early as +160hrs, and the general resemblance of surface features now to the guidance packages then, it becomes more apparent that the guidance actually performed decently on this potential, but struggled with the fragility of the pattern thereafter.

As far as weather impacts, the guidance has settled in on a track well south and east off the coast of the Mid-Atlantic. Saturday will be a fair day, but expect cirrus to begin to build in especially in our south and east counties. Our area will be under weak and transient ridging. I liked the NAM 2m temperatures...so blended with more weight towards them yielding mid 30's highs. Saturday night will feature an increase in clouds south and east. Decided to carry 10% pops on this package on Eastern Long Island given the SREF and GEFS means both indicating low probabilities for measurable precipitation there. The general idea, though, is that impacts will be minimal.

As mentioned, this occurs for a variety of reasons, but the main factors at play here include 1) The La Nina pattern: less amplification in the southern stream is generally a good rule to follow. 2) The northern stream shortwave doesn't interact with the broad trough until the system is off the coast, not conducive for coastal storm formation and finally 3) Guidance is forecasting an area of strong confluence near or just north of our area which, even with a stronger southern stream, would create issues as far as bringing precipitation into the region. The storm track we favored was a blend of the ECMWF and SREF mean. We did keep 10% pops in the forecast for Sunday on Eastern Long Island as well.

Long Term

Aforementioned storm system is forecast to track north and east towards the North Atlantic, and then slowly retrograde west as it is captured by the Polar Vortex which phases in late in the Short Term period. The next feature of interest ejects east from the Pacific by early week, and then slides east within the fast upper level flow over the CONUS. Depending on the degree of confluence over the region; i.e how fast the upper level low moves away to the north and east, potential does exist for a light snow event mid-week as a northern stream shortwave comes through the Northern Plains and then towards the Mid-Atlantic states. With the SREF mean beginning to target some light precipitation, and the 00z NAM/UKmet a bit more amplified, introduced 20% pops for Wednesday.

Beyond this, the same general pattern continues with strong blocking in place and an active Pacific flow. Long range models (specifically now GFS and ECMWF) indicate another strong Pacific shortwave ejecting east by Day 5..and interacting with the northern stream by Day 6. The height field suggests the potential for overrunning snows into our forecast area by next weekend; coincidentally near Christmas Eve and Day. Too far out to begin guessing now--but with ensemble agreement at this range it appears the threat for snow on Christmas is at least in the picture. For now carried a cold and dry forecast through the extended with continued below normal highs and overnight lows.

JH

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Ericjcrash

Ericjcrash

Posted
Posted

Well, the echos over W. TN are moving east, so not those echos, but something like that. Keep in mind that the simulated reflectivity is never going to be 100% accurate.

yes not south.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/nam/06/images/nam_ref_012l.gif

because ^^ that looks remotely close virga or not that a simulated radar on a hi-res model 12 hours out.

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