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White Christmas?

Latest odds and storm events for the holidays tracked

Phased Vort

November 15-16, 2018 | East Coast Snow/Ice Storm

Solstice

An open album has been created in the historical weather gallery. Anyone can submit photos there, just to look back on later!

 

Message added by Solstice

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Even better:  look at the differences between the operational and FV-3 GFS at 96 hours. Oh boy. OP first, FV-3 second.

gfs_z500_vort_us_17.png

fv3p_z500_vort_us_17.png

 

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139.track.thumb.png.b3d2572237d302aa6334aebebeef1438.png

UKM - Miller A with JAX Rule connection. 

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Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 AM EST Sun Nov 11 2018 Valid 12Z Wed Nov 14 2018 - 12Z Sun Nov 18 2018 ...

Overview and Guidance/Uncertainty Assessment...

Over the past day a lot of the guidance has been exhibiting significant changes/trends within an expected re-establishment of a western ridge-eastern trough pattern after a brief flattening of mean flow very early in the forecast period. The two primary trends of note involve greater separation and concentration of residual shortwave energy reaching the southern Plains/northern Mexico during the latter half of the short range period followed by a sharper/more amplified depiction of the rebuilding West Coast ridge and amplifying downstream trough. The combination of stronger southern tier energy and a sharper/slower trough amplifying to its northwest is significantly increasing the potential for a widespread precipitation event over the eastern states and low pressure development along the East Coast. Deeper trends with the amplifying eastern trough lead to colder temperatures over the East by next weekend. ……..

 Looking at guidance comparisons through the 12Z/18Z cycles, there was decent clustering from day 3 Wed into early day 4 Thu. After that time specifics diverged regarding the southern/eastern energy and upstream amplifying trough along with corresponding surface evolution. The scenario that seems to be in the process of being reinforced in the 00Z guidance had generally been a minority solution seen in a small percentage of ensemble members along with a run or two of the ECMWF a number of days ago. The signal started to reappear a bit yesterday and the past couple ECMWF runs plus the 12Z CMC and 18Z GFS/GEFS mean added to it. At the time of forecast preparation it appeared best for a single deterministic forecast to incorporate both operational model and ensemble mean ideas which would provide some degree of trending while awaiting agreement on the specifics.

Regarding northern U.S./southern Canada flow, GFS runs have generally been at odds with the majority cluster of guidance over the past couple days. Consensus has held fairly steady with the system forecast to track over/near the upper Great Lakes late in the week aside from perhaps some modest timing adjustments. However latest GFS runs have been straying to the north of established consensus while 24 hours ago they were accelerating ahead of consensus. At the same time earlier GFS runs had been among the most eager to bring upstream Pacific energy into the western North America ridge late in the week. More recent GFS runs are much closer to the guidance majority. Regarding the eastern Pacific trough nearing the West Coast late in the period, ensemble spread has improved out to about days 5-6 Fri-Sat. During the weekend there is a pronounced divergence of models/ensemble members regarding how much flow separation may occur and where. Preference leans toward the means late in the period given the uncertainty in specifics but with the understanding that the trough may ultimately be less phased.

Based on the combination of forecast considerations, the forecast started with a blend of 12Z operational models (more GFS/ECMWF than CMC/UKMET) early in the period and then increased 18Z GEFS/12Z ECMWF mean input so that the means comprised 70 percent of the blend by day 7 Sun. ...Weather Highlights/Threats... Very deep storm system reaching eastern Canada by early Wed may bring strong winds to parts of New England around midweek. Also expect some lingering lake effect snow on Wed, mainly over the northeastern half of the Great Lakes region.

Then during the latter half of the week guidance is showing greater potential for an area of moisture to overspread portions of the eastern U.S. in association with a mid level feature lifting out of the southern Plains and surface low pressure near the East Coast. Some wintry precipitation may be possible in western/northern portions of the moisture shield. Confidence is currently below average regarding specifics as guidance has been changing considerably over recent runs. There is somewhat better confidence in persistence of some rainfall over/near Florida until low pressure to the north pushes the trailing front eastward. Late this week into the weekend low pressure tracking near the Canadian border will bring an episode of mostly light precipitation to the Great Lakes, followed by another period of lake effect snow. Shortwave energy reaching the West Coast by early Wed will produce a brief period of rain and higher elevation snow over the Pacific Northwest and northern Rockies. Some moisture may reach the Pacific Northwest coast this weekend but it is likely that precipitation amounts will be on the light side. The midweek time frame will see the most extreme cold anomalies over the east-central U.S. with some highs 20-25F below normal and possibly cold enough for daily records. Records for morning lows appear to be somewhat less likely/widespread. There should be some moderation late in the week but the East may trend colder again next weekend with expanding coverage of highs 10-15F below normal. Western warmth will cover a decent proportion of the area from the West Coast states into the northern High Plains with some pockets of plus 10-15F anomalies for min/max readings. Rausch

 

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Not sure much is actually sleet, but here’s the ukmet total snowfall.  

6D285CF4-BEE0-434D-A8D4-B01CF33DB0C4.png

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I managed to put together a hastily assembled FB blog post about this potential.

 Wx Wiinii FB Page

 

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00Z GFS, FV3 GFS and ECMWF:

 

 

fv3p_mslp_pcpn_frzn_us_fh84-138.gif.42868581e17a08788644371e9fd3a234.gifgfs_mslp_pcpn_frzn_us_fh84-138.gif.e14d18354280715a3da0780545175551.gifgiphy.gif

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1 hour ago, UTSwiinii said:

 

Just to add some caveman art I made back on 11/8 - this general idea has been (as WPC points out) increasingly supported by various ENS model output and, now, more strongly being shown in the deterministic (operational) runs. 

f168.thumb.gif.1063088eeefc6693c0e0c05d27255d9c.gif

f192.thumb.gif.f91d193b4ae2a881146950b8c027b1f0.gif

I would think the circles and arrows really don't need explanation. 

In a subsequent post, I mentioned that sooner of later, these dual cored systems should mesh more "in concert" - with increasingly "colder" results. 

 

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1 hour ago, UTSwiinii said:

 

ECMWF EPS Ensemble Control MSLP was on point to a decent degree for many runs, so much so that I used it to give the thread credence and back up the observations I was making for the thread´s opener.

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3 minutes ago, Phased Vort said:

ECMWF EPS Ensemble Control MSLP was on point to a decent degree for many runs, so much so that I used it to give the thread credence and back up the observations I was making for the thread´s opener.

To add to this, since it goes out to 15 days, it´s very helpful.

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4 minutes ago, UTSwiinii said:

Just to add some caveman art I made back on 11/8 - this general idea has been (as WPC points out) increasingly supported by various ENS model output and, now, more strongly being shown in the deterministic (operational) runs. 

f168.thumb.gif.1063088eeefc6693c0e0c05d27255d9c.gif

f192.thumb.gif.f91d193b4ae2a881146950b8c027b1f0.gif

I would think the circles and arrows really don't need explanation. 

In a subsequent post, I mentioned that sooner of later, these dual cored systems should mesh more "in concert" - with increasingly "colder" results. 

 

Gotta love this Mr @UTSwiinii

I really enjoy how you point that out. And will be really pleased to continue to see your collaboration to this thread.

Should be thrilling coming days for this forum, as this may be as I mentioned late last night, the first more realistic shot at wintry precipitation at the coast or a few miles inland.

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1 minute ago, Phased Vort said:

To add to this, since it goes out to 15 days, it´s very helpful.

Even more so when it and the OFM ( BSR in this case) are in support. Not sure if we are in "tri-fecta" territory, but...

(off topic- the BSR sure looks like W Ridge/ E trough notion kind of locks in for a while)

 

 

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2 minutes ago, UTSwiinii said:

Even more so when it and the OFM ( BSR in this case) are in support. Not sure if we are in "tri-fecta" territory, but...

(off topic- the BSR sure looks like W Ridge/ E trough notion kind of locks in for a while)

 

 

Can´t even try to disagree here.

When I saw the BSR signal and put together the EPS Ensemble Control MSLP output from a few runs, I needed to observe the possibility.

It´s indeed neat.

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8 minutes ago, Phased Vort said:

Gotta love this Mr @UTSwiinii

I really enjoy how you point that out. And will be really pleased to continue to see your collaboration to this thread.

Should be thrilling coming days for this forum, as this may be as I mentioned late last night, the first more realistic shot at wintry precipitation at the coast or a few miles inland.

Not a problem, PV. I'm "liking" this for frozen precip to be much more widespread than previous incarnations. (not that I like frozen precip - in fact, I, somewhat, increasingly detest it with each passing year - but I digress)

6z GFS spaghetti indicates that Operational run has gathering "member" support

f120.thumb.gif.45c56cbb0c1583c4c5a578956ed619cc.gif

Not a "great" set up - very "marginal" in fact (western ridge negatively tilted and western displace - heights out front/downstream, really not robust but should "help") . Which is why all snow would still be well inland, but the wintery mix precip types very well creeping ever further east. 

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There is a lot to keep an eye on this will flip be flipping back and forth let’s just hope for a eastern shift to bring in ct mod snow ️ 

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From the 00z GEFS Ensembles available on e-WALL, these three solutions embody the type of storm I expect to occur:

1371039420_11-1100zGEFSmember3.png.b5d6b94a264632e3b15d02425f3b73f3.png581694504_11-1100zGEFSmember2.png.cd4be4e7321226b5b20933c053520ca2.png24859425_11-1100zGEFSmember1.png.47dd91ad5fe628471500577582db0ae3.png

Subtropical moisture being pulled inland (heavy rain along the coast) with the low elevation rain/snow line setting up west of the Appalachians. Good synoptic snows for most of the Great Lakes region with lake enhancement and lake effect during and after the storm, respectively. 

Edited by StL WeatherJunkie

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What are your expectations as the 12Z GFS stars, guys?

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20 minutes ago, Phased Vort said:

What are your expectations as the 12Z GFS stars, guys?

So far it looks pretty good to me.   Always seems like those systems that pop up out of nowhere only a days out out overachieve compared to those discussed for a week+ out. 

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Ehh looks just a tad too warm

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Icying should be an issue still.

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12z GFS: Energy held back more, storm comes in a good bit warmer. Still front end frozen for a lot of people, then over to white rain. We will see what the rest of the 12z suite shows. 

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2 minutes ago, TheDayAfterTommorow said:

12z GFS: Energy held back more, storm comes in a good bit warmer. Still front end frozen for a lot of people, then over to white rain. We will see what the rest of the 12z suite shows. 

Great Lakes low hurting this system 

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Too close to the coast.

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1 hour ago, StL WeatherJunkie said:

From the 00z GEFS Ensembles available on e-WALL, these three solutions embody the type of storm I expect to occur:

1371039420_11-1100zGEFSmember3.png.b5d6b94a264632e3b15d02425f3b73f3.png581694504_11-1100zGEFSmember2.png.cd4be4e7321226b5b20933c053520ca2.png24859425_11-1100zGEFSmember1.png.47dd91ad5fe628471500577582db0ae3.png

Subtropical moisture being pulled inland (heavy rain along the coast) with the low elevation rain/snow line setting up west of the Appalachians. Good synoptic snows for most of the Great Lakes region with lake enhancement and lake effect during and after the storm, respectively. 

This post foreshadowed the 12z Op run - and is very hard to argue against. " (for lack of better term) Dual cored" storm with this track will tend to be increasingly "cold" at the edges. But so long as there is a distinct inland reflection, that lessens the frozen precip potential. 

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Don't forget to take note of FV3 output, for comparison sake. (this run displays difference to the standard GFS)

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1 hour ago, Phased Vort said:

Too close to the coast.

Yes needs to shift south east 

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