2/19-2/20 Miller A Magic?

[John1122]

Euro still in high desert mode. Someone will have to blink in the next 24 hours or so. 

[Holston_River_Rambler]

6z Euro looked a little less dry, but not by much. 4 run qpf trend

[Carvers Gap]

There are two main drivers which are causing this to lose precip.  The main one is the convection along the GOA.  The other is that the system is not a Miller A.  It is a true slider now.  So, the flow doesn't back over the eastern valley as it did in earlier runs.  Very La Nina-esque pass by this system, and something we have seen during several of the last winters due to so many La Nina's.  There is a reason that climatology favors middle and western areas during Nina events - Apps runners or sliders which lose moisture as they traverse the state.  

I do wonder if we have one more card to play.  It is pretty common for modeling to under-model the qpf for a system during February.  Let's see if the trend reverses(I don't see that reversal at this time).  However, that reversal can sometimes occur as radar driven modeling adjusts during an event.  Short term modeling is so good, that almost always at least one model catches that trend.  Time will tell.  

[Holston_River_Rambler]

 

MRX notes the main mechanism for lift is being in the right entrance region of a jet and that looks pretty well set:

The lagging jet initially over Montana and Wyoming in the gif above tries to help buckle it

 

But there has to be some precipitable water/ relative humidity to lift. 

Most of our deeper, mid level moisture is west Pac moisture

 

Some gulf moisture gets involved late, and I think there is some room for the Euro to improve here, but not much. 

[Holston_River_Rambler]

1 minute ago, Carvers Gap said:

I do wonder if we have one more card to play.  It is pretty common for modeling to under-model the qpf for a system during February.

The more I looked at the 500-700mb relative humidity depicted on the Euro, I actually got a little bit more optimistic. 

 

[Carvers Gap]

1 minute ago, Holston_River_Rambler said:

 

MRX notes the main mechanism for lift is being in the right entrance region of a jet and that looks pretty well set:

The lagging jet initially over Montana and Wyoming in the gif above tries to help buckle it

 

But there has to be some precipitable water/ relative humidity to lift. 

Most of our deeper, mid level moisture is west Pac moisture

 

Some gulf moisture gets involved late, and I think there is some room for the Euro to improve here, but not much. 

And you can see why NE TN kind of backs into decent totals with that jet streak right at the end.  I do think that trailing system will be good for some.

[Carvers Gap]

And time of day along with marginal precip is usually not a great recipe for decent snow IMBY.  We need this to overpeform.  

[Holston_River_Rambler]

I think maybe if we just pretend this is and old fashioned I-40, 2-4" clipper, just forget the precip. to our south,  we might not be too far off. 

[Carvers Gap]

The 0z and 6z RGEM has bumped up totals over NE TN as it has a second round of snow w/ the NW flow event.  4-5" totals.  We'll watch it for trends.

[Carvers Gap]

With the exception of the NAM and Euro, most models over NE TN increased last night.  I do want to see some improvement from the Euro though.  The NAM....has been really bad IMBY this winter.  The RGEM has been good.  I would think maybe to half the totals of the RGEM and seems maybe right.  2-3" as Holston noted....some of that will need to fall the evening after the storm when sun angles are low.

[Holston_River_Rambler]

Just now, Carvers Gap said:

The 0z and 6z RGEM has bumped up totals over NE TN as it has a second round of snow w/ the NW flow event.  4-5" totals.  We'll watch it for trends.

RGEM really likes the upper low/ TPV swinging in. It even has some FGEN over east TN:

I wonder if that might turn into something like an arctic front with 20:1 ratios? 

[Holston_River_Rambler]

I think the hi resolution of the Euro is seeing (rightly or wrongly) more convection in the Gulf. 

 

The above is a gif of lightning flash density according to the 6z Euro. It's maxed out just south of Louisiana and the convection is parallel to the coast. The whole complex just pushes SE further into the Gulf. 

Like Carvers said I think this is kind of a watch and see radar deal now. I wish the RGEM had a similar parameter on weatherbell for comparison. 

Also, I think the convection is a nail in the coffin for anything more than a widespread 1-3" or 2-4", not necessarily a nail in the coffin for the whole event. 

 

 

[Carvers Gap]

I do wonder if the Euro is having feedback issues over the Gulf.  The RGEM is what is I am going to roll with on this one - I think.   It and the GFS have been good in the short range this winter.  They have barely budged for days.  

[Jed33]

The RGEM looks good for my area as well. Almost looks like it has an upper level low or disturbance that moves in with the arctic air after the main system passes. Those are so hard to predict until they actually occur. Hopefully it’s on to something. 

[*Flash*]

Per Bobby Boyd: “6 am 2/17. Update for snow across Middle Tennessee Tuesday night through Wednesday morning 2/18-19. I have trimmed back total snow amounts by about one inch, but mesoscale banding, if it occurs, can raise totals above what I have in some areas. I'll be watching the Geostrophic equivalent potential vorticity above the Frontogenetic layer in an attempt to predict the heavy snow bands. I expect snow to start in the Nashville area Tuesday evening and end around noon Wednesday. Snow totals in Nashville around 3 inches.”

[Holston_River_Rambler]

I liked that NAM run. It got the heavier precip further north from the Gulf:

12z.         vs          6z 

[Holston_River_Rambler]

[PowellVolz]

2 hours ago, Holston_River_Rambler said:

I think the hi resolution of the Euro is seeing (rightly or wrongly) more convection in the Gulf. 

 

The above is a gif of lightning flash density according to the 6z Euro. It's maxed out just south of Louisiana and the convection is parallel to the coast. The whole complex just pushes SE further into the Gulf. 

Like Carvers said I think this is kind of a watch and see radar deal now. I wish the RGEM had a similar parameter on weatherbell for comparison. 

Also, I think the convection is a nail in the coffin for anything more than a widespread 1-3" or 2-4", not necessarily a nail in the coffin for the whole event. 

 

 

If that convection has a (kinda) positive tilt to it, would that be better than a W to E orientation? Also the convection kinda falls apart moving east. I’m wondering if that helps us any?

[Holston_River_Rambler]

Just now, PowellVolz said:

If that convection has a (kinda) positive tilt to it, would that be better than a W to E orientation? Also the convection kinda falls apart moving east. I’m wondering if that helps us any?

Oh yeah, if we got a line of storms pumping moisture N/NE through the deep south rather than parallel to the coast that should help. 

[Holston_River_Rambler]

But it is the NAM, so let's see how the rest of the runs go this PM. 

[*Flash*]

Not disappointed in the 12z ICON and RGEM, especially for the northwestern half of TN.

[Carvers Gap]

1 hour ago, Jed33 said:

The RGEM looks good for my area as well. Almost looks like it has an upper level low or disturbance that moves in with the arctic air after the main system passes. Those are so hard to predict until they actually occur. Hopefully it’s on to something. 

That is what it is.   I think NE TN will get as much or more from it.  The 12z has the same.  Slight tick north.

[fountainguy97]

16 minutes ago, Carvers Gap said:

That is what it is.   I think NE TN will get as much or more from it.  The 12z has the same.  Slight tick north.

Yeah that's the only player we can get anything of note from at this point for E and NE regions. The initial precip shield is doomed to the transfer. Maybe a very lucky few get 1-2" Wednesday morning at best. 

[PowellVolz]

Columbia SC Met…

 

[Carvers Gap]

1 hour ago, fountainguy97 said:

Yeah that's the only player we can get anything of note from at this point for E and NE regions. The initial precip shield is doomed to the transfer. Maybe a very lucky few get 1-2" Wednesday morning at best. 

The 12z GFS is pretty healthy - bumped up totals.  Maybe we are seeing modeling see the Feb strengthening that January isn’t known for.  I am not even remotely ready to give up on system one.   I think time of day will limit system one…though north Johnson City has snow on the ground as we speak.  I think upslope areas will do better with the second system.  

[Carvers Gap]

I like watching the GFS around this time frame as it will often catch trends before other globals.  It has been pedestrian at d8+.   Once inside of d5, it has been solid.

[Daniel Boone]

Wound up with about 3/4" here overnight. Puts my Seasonal Total at 15.2".

[Daniel Boone]

4 hours ago, Holston_River_Rambler said:

I think the hi resolution of the Euro is seeing (rightly or wrongly) more convection in the Gulf. 

 

The above is a gif of lightning flash density according to the 6z Euro. It's maxed out just south of Louisiana and the convection is parallel to the coast. The whole complex just pushes SE further into the Gulf. 

Like Carvers said I think this is kind of a watch and see radar deal now. I wish the RGEM had a similar parameter on weatherbell for comparison. 

Also, I think the convection is a nail in the coffin for anything more than a widespread 1-3" or 2-4", not necessarily a nail in the coffin for the whole event. 

 

 

Any way you slice it, the Euro is having a problem with Moisture getting in the System. Could be partially ( in Layman's Terms) it seeing the Atmosphere being drained from the previous System. Convective to the South a probable reason as well.

[John1122]

It may end up entirely different because the systems were a bit different, but modeling was very far off on precip totals imby even 36 hours out for the system that just passed. I ended up with nearly 4 inches of rain, and the Euro for instance, was showing 1.5ish as of 12z Thursday.

[Daniel Boone]

15 minutes ago, John1122 said:

It may end up entirely different because the systems were a bit different, but modeling was very far off on precip totals imby even 36 hours out for the system that just passed. I ended up with nearly 4 inches of rain, and the Euro for instance, was showing 1.5ish as of 12z Thursday.

Yeah, it seems to really be doing that since the recent "upgrade".