December 8-10 Storm Discussion

[Carvers Gap]

At 84, the slp over the NC/SC coast is a few mb lower and the storm is tighter.  This helped to strengthen the defamation bands over the regions specified above.  It gains a little more latitude before going OTS than 0z.  That made a ton of difference.  That is a trend to watch.  

[TellicoWx]

Basically it looks like it's the NAM/GFS vs Euro/FV3 As far as how the 850 vort unfolds. NAM/GFS (west/less influence on coastal) Euro/FV3 (east/holds coastal and tries to turn it somewhat). CMC is kinda in the middle.

[Carvers Gap]

1 minute ago, John1122 said:

The Euro doesn't see as much downsloping for the NE so that's good. The gradient over Knox is the gradient that is over my area on the CMC. Right now it's the FV3/Euro vs the rest regarding snow in Knoxville.

The FV3/CMC/Euro have a pretty tight grouping on this run.  I am even worried about the gradient even here.  I was glad to see the Euro back some snow into KY vs remove it. As for downsloping, maybe the American suite is correct.   Not sure.  Seems a bit overdone, but I have seen it happen and it is crap city when it does.  With about 48 hours to go, seems like the operational are narrowing down solutions but some wiggle room over TN.  

[John1122]

WPC noted the GFS stays open with the wave, the Euro closes it off at points. That effects the timing and turn of the system.

[TellicoWx]

Considering the NAM is still in voodoo land at that range, its hard to put it into a camp. 

[Carvers Gap]

1 minute ago, John1122 said:

WPC noted the GFS stays open with the wave, the Euro closes it off at points. That effects the timing and turn of the system.

And that plays to the bias of each model.  GFS has a tendency not to wrap-up enough and Euro can be a bit too amped at times.  Not sure if that is the case this close to the event....so maybe blend the GFS and Euro?

[TellicoWx]

2 minutes ago, John1122 said:

WPC noted the GFS stays open with the wave, the Euro closes it off at points. That effects the timing and turn of the system.

Someone posted in the MA forum that the s/w is stronger currently vs what was modeled a little bit ago.

[Carvers Gap]

Wonder if any of our mets have anything to add?  This is all hobby knowledge from me and freely admit my understanding is a bit faulty at times. Hope they get a chance to jump in the discussion today.

[Carvers Gap]

1 minute ago, TellicoWx said:

Someone posted in the MA forum that the s/w is stronger currently vs what was modeled a little bit ago.

And it reminds me as we get closer, all of those features and mechanisms that create this storm will have better and better sampling/data with each run.  Good catch.

[Carvers Gap]

10 minutes ago, TellicoWx said:

Basically it looks like it's the NAM/GFS vs Euro/FV3 As far as how the 850 vort unfolds. NAM/GFS (west/less influence on coastal) Euro/FV3 (east/holds coastal and tries to turn it somewhat). CMC is kinda in the middle.

GFS did to look overly bad.  Don't forget to add the UKMET and CMC to the Euro/FV3.  Though the storm totals vary...they are very similar runs right now.  

[TellicoWx]

1 minute ago, Carvers Gap said:

GFS did to look overly bad.  Don't forget to add the UKMET and CMC to the Euro/FV3.  Though the storm totals vary...they are very similar runs right now.  

Wish had a lot better access to HiRes maps of the UKie. I plotted the vort for learning purposes, and you can see tell the GFS/NAM are a lot weaker and NW when the absorp into the coastal. Euro/FV3 still have it wrapped up as it's going thru GA.

[ShawnEastTN]

I know its not a much used/referenced model especially at the end of its run but the RGEM has pretty good feature placement at the end of its run.  I love the RGEM in the short range, and while its not without its faults it has had some uncanny verifications at times in previous winters.

[TellicoWx]

1 minute ago, ShawnEastTN said:

I know its not a much used/referenced model especially at the end of its run but the RGEM has pretty good feature placement at the end of its run.  I love the RGEM in the short range, and while its not without its faults it has had some uncanny verifications at times in previous winters.

It can be very useful to check for trends in the s/w as it comes ashore

[John1122]

The Euro is slightly more progressive than it was before because there is a ridge just NE of Puerto Rico that has grown slightly stronger over the last 2 days on modeling. That bumps the 50/50 low that had been in place a little more ENE and allows the system to slide out faster. It also pushes a little more towards the GOM and makes the trough there less sharp/flatter.

[Stovepipe]

Thanks to everyone that has been posting model run updates as well as great discussion!  I've been too busy lately to get in the trenches, y'all rock.

Can anyone share some of that sweet sweet Euro text data by chance?  Curious about temps at TYS.  It's at least looking like, if we don't get stickage here, I'll only have to drive a short ways towards TRI to play in the good stuff.

[John1122]

Sleet map from the Euro. Keep in mind that an inch of sleet steals about 3.3 inches of snow.

[Mr Bob]

The map production is an interesting thing to me....we are using stormvista here and it does a good job of keeping all the major cities out of the main accumulation....I agree with Stovepipe that the text sounding would probably give the best idea but obviously not promoting violating T&C of anyone's pay per view weather site.... 

[TellicoWx]

7 minutes ago, Stovepipe said:

Thanks to everyone that has been posting model run updates as well as great discussion!  I've been too busy lately to get in the trenches, y'all rock.

Can anyone share some of that sweet sweet Euro text data by chance?  Curious about temps at TYS.  It's at least looking like, if we don't get stickage here, I'll only have to drive a short ways towards TRI to play in the good stuff.

Don't have the text data, but on the maps at hr 78/84 when the accumulation happens 850T is +1/-2 and 925T is -1/-2, with a 2m of 34 at TYS.

[John1122]

4 minutes ago, Mr Bob said:

The map production is an interesting thing to me....we are using stormvista here and it does a good job of keeping all the major cities out of the main accumulation....I agree with Stovepipe that the text sounding would probably give the best idea but obviously not promoting violating T&C of anyone's pay per view weather site.... 

 

The maps are all over twitter, often posted by the people who run the sites themselves. So I vote it's a-ok... I have noticed the Vista maps are way less frozen than others I see for the Euro.

[Mr Bob]

Just now, John1122 said:

 

The maps are all over twitter, often posted by the people who run the sites themselves. So I vote it's a-ok... I have noticed the Vista maps are way less frozen than others I see for the Euro.

This was not a don't post maps thing...The resolution and the differences in how they come out on the map was my only point as well as a plug for text soundings....

[John1122]

I don't really get one aspect of the forecast being discussed by the WPC for our region. Says all snow very likely in the mountains but freezing rain in the lower elevations. I'm confused by how that happens since freezing rain is a product of warmer air at higher elevations. Most commonly around 3000-5000 feet. I guess there's a very thin later of above freezing air in the atmosphere below 3000 but above the surface? 

[John1122]

2 minutes ago, Mr Bob said:

This was not a don't post maps thing...The resolution and the differences in how they come out on the map was my only point as well as a plug for text soundings....

I was being sarcastic myself and took yours into account! It just doesn't translate as well via post.

[TellicoWx]

4 minutes ago, John1122 said:

I don't really get one aspect of the forecast being discussed by the WPC for our region. Says all snow very likely in the mountains but freezing rain in the lower elevations. I'm confused by how that happens since freezing rain is a product of warmer air at higher elevations. Most commonly around 3000-5000 feet. I guess there's a very thin later of above freezing air in the atmosphere below 3000 but above the surface? 

All the column profiles I've looked at have a sleet look to them due to a slightly warm nose in the 850 lvl, not sure where they are seeing frz rain. Surface temps are above freezing too.

[Math/Met]

57 minutes ago, John1122 said:

The Euro doesn't see as much downsloping for the NE so that's good. 

Things could change with the orientation at 850mb, but I’m leaning towards the Euro in terms of the amount of downslope over NE areas.  Usually the Euro does a good job of showing 925mb wind acceleration through the French Broad valley in NC during a downslope situation.  I don’t see much of that with this system looking at hour 72. The 925mb flow isn’t cross barrier for most of the region.  The ESE winds at 850mb would still be a factor but less compared to what the GFS shows.  Small changes could make a big difference in how significant the downslope is, so it’s something to watch for sure.

[TellicoWx]

12z EPS mean...lowered some, especially middle and west TN

[PowellVolz]

Don't have the text data, but on the maps at hr 78/84 when the accumulation happens 850T is +1/-2 and 925T is -1/-2, with a 2m of 34 at TYS.

With the 850’s that close could heavy rates make it come down? Or is that already invested into the equation?


.

[ShawnEastTN]

18Z NAM out to 19, High is a mb lower but is also a tad further south by about 100 miles or so from its previous run.

[Knoxtron]

WOMP WOMP (kinda) on 15 UTC SREF Plumes for TYS south

 

TYS

 

CHA

 

TRI

[tnweathernut]

I am never falling for any SREF love again.  Been burned too many times.  I am sure it's useful for something (other than getting hopes up), but refuse to use it as a tool in my toolbox.  lol

[PowellVolz]

WOMP WOMP (kinda) on 15 UTC SREF Plumes for TYS south

 

TYS

 

CHA

 

TRI

Knox came down a little

 

 

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