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Wintry December 28-29th Possible Winter Storm

BHS1975 said:
Is that the highest resolution? How much does the ICON have?


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Yes the Swiss model's resolution is 9x that of our best and highest resolution 3 km HRRR (in the x-y plane you can fit 9 1km grid boxes into one 3km grid box). The German model's resolution is 13km (about an eighth of a degree) which is 4x higher than the GFS and slightly lower than the full resolution version of the ECMWF (9 km)
 
1300m said:
Euro at H5 also looked a little better. We need just a little bit more of this trend. As Webber posted earlier, if we can just get winds aloft to tap that moist air to our south it will set off significant overrunning and precipitation will blossom nicely. As bad as it looks with precipitation, it could go from zero to something much bigger with only another tick or two in the same direction at H5.

00Z:
00_Z.png


12z:
12_Z.png
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Yeah no doubt the Euro is digging this trough over the upper midwest more, if we can do this for a few more runs, it should help veer the mid-level flow from WNW to W-WSWly at least long enough to tap into the eastern pacific moisture...

ecmwf_z500_dt_noram_11.png
 
SimeonNC said:
There is one big concern, if a solution like the ICON/Swiss models ends up playing out. We're getting to the point where there would be little to no warning of that happening, multiple cities in GA and the Carolinas would have their own snow/icejams.
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Possibly. Good thing in the KCHS area, it's already being heavily montiored due to that this region is in the battlezone between some precip or possibly more already. It's places around that could be caught offguard badly now that the guard has been let down if all of the sudden, the rest of the outputs start trending towards the ICON/Swiss grids
 
BHS1975 said:
But if we get too much of a southern component wouldn’t that create a warm nose?
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Always a fine balance. That's why sig SE winterstoms are not too common. Too westerly = often too dry. Too much southerly component (SW) may mean too warm/too far NW of a track. That's why WSW if often the ticket.
 
Looks like the wave looks better on all modeling. Baby steps. The Canadian didn't look as good as others, but it was still a slight improvement.
 
The 00z cycle might possibly have a better sampling of the wave in question but probably now the most important cycle coming up whether it's game on for a wider portion of the Carolinas, GA or not
 
Stormsfury said:
The 00z cycle might possibly have a better sampling of the wave in question but probably now the most important cycle coming up whether it's game on for a wider portion of the Carolinas, GA or not
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It's hard for me to believe the 9KM Euro is totally off with it's solution, versus something like the Swiss or German modeling, but again, this is a great test for those two models.

Icon, at least, gets Wintry weather all the way back into ATL.
 
the 12Z EPS is pretty similar to the 0Z EPS/12Z Euro with only light qpf near the SE coast and hardly anything well inland. The H5 flow is still too westerly for great prospects.

Edit: To clarify, the qpf I'm referring to is only for the 12/28-9 wave.
 
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GaWx said:
Always a fine balance. That's why sig SE winterstoms are not too common. Too westerly = often too dry. Too much southerly component (SW) may mean too warm/too far NW of a track. That's why WSW if often the ticket.
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Yup, it's why we see so much cold rain, lol. So many little things need to tie together with timing. It's why stuff sneaks up so often. T
 
GaWx said:
the 12Z EPS is pretty similar to the 0Z EPS/12Z Euro with only light qpf near the SE coast and hardly anything well inland. The H5 flow is still too westerly for great prospects.
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The EPS actually took a step in the right direction and shifted the precipitation northwestward for both the 27th & 28-29th events vs the 0z suite, it's the first NW shift we've seen from the EPS in at least several days. Baby steps...
output_5nBq8L.gif
 
Webberweather53 said:
The EPS actually took a step in the right direction and shifted the precipitation northwestward for both the 27th & 28-29th events vs the 0z suite, it's the first NW shift we've seen from the EPS in at least several days. Baby steps...
View attachment 2344
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Yeah, I did see a small tick NW. To clarify, the qpf I'm referring to is only for the 12/28-9 wave. The 12Z EPS qpf for this wave is still under 0.05" more than about 50 miles inland of the Carolina coasts vs you showing both waves combined.
 
GaWx said:
Yeah, I did see a small tick NW. To clarify, the qpf I'm referring to is only for the 12/28-9 wave. The 12Z EPS qpf for this wave is still under 0.05" more than about 50 miles inland of the Carolina coasts vs you showing both waves combined.
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Well at least for now it is...
 
While we don't have grids for Central SC or ATL for the Swiss model; I'd wager a bet it's not as snowy as the upstate of SC into NC. It's likely IP/Snow mix before going over the ZR for some.
 
Catfish said:
just got a special weather statement for possible light sleet tonight north of I20 in GA
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Yeah, it's not often I get 3 different periods of rain,zr,sleet and snow over a 7 day period on my point cast, lol. Good times, if some of it happens...sans the zr, or course. T
 
FFC: .LONG TERM /Thursday through Tuesday/...
Challenging forecast through the extended with diverging model
solutions and the potential for winter precip. The morning model
runs have continued to trend slightly drier than previous for
Thursday afternoon through Friday`s freezing rain/sleet event.
Model sounding continue to show that moisture will overrun wedge
of cold air, with a deep enough cold layer near the surface to
refreeze melting hydrometeors falling through the warm nose. For
now, have generally gone with freezing rain/sleet in the south
metro area, freezing rain/rain in middle Georgia, and all rain in
the far southern CWA. The NAM run for the beginning of the
extended period continues to be the outlier solution, and at this
point, given the new consistency between the ECMWF/GFS/Canadian,
have opted to trend away from its more gloomy forecast. At this
time the only accumulations are for freezing rain, with amounts of
0.02 inches or less, and only for portions of east central and
middle Georgia where the best moisture combines with the coldest
temperatures. Confidence in amounts is low.
 
Shawn said:
Flow sucks through here. Need the wave to be a bit stronger to cause it.
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Yep, the flow is due westerly until the very last second when it flips to WSWly over the Carolinas and boom the precipitation begins to blossom, but it's a little too late for areas well inland of the coast this run.
namconus_ref_frzn_seus_43.png
 
The 500mb vort maps from the ICON show a stronger digging wave shifting the winds from NW to SW to SSW as the low forms quite close to the coast. Look for a stronger wave, and winds becoming more West South West and it's game on.

Again, I can't see how the 9KM Euro can be so far off with it's solution. Swiss & Icon, we shall see.
 
I would believe that the Icon had no chance of verifying, but it has our New Years system much more Euro like versus say, the GFS trying to break Wintry precipitation out. So I'm not quite ready to totally throw in the towel, until the ICON model starts going drier. You'd think if the ICON had some sort of bias around here, it would be doing something big with the New Years storm like this event we are tracking.
 
GaWx said:
Yeah, A few years ago I researched the H5 maps for many SE sig qpf winter events that weren't clippers. The one thing that the vast majority of them had: WSW (at least a little S of W) or SW winds at H5 over one's location. VERY few had straight W winds and almost none had WNW winds at the locations of the sig winter event. Again, I'm not talking about light precip events or clippers.
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You actually want to focus your studies on a slightly lower level in the troposphere if you're trying to capture large-scale synoptic flow and its effects on moisture transport in the SE US, because that's where the most intense latent heating, moisture advection, & WAA is occurring, and this is typically somewhere around 700 hPa... The flow is increasingly geostrophic in the mid & upper levels around and above 500 hPa and if you direct most of your attention here you'll get results which are less conclusive wrt flow orientation and QPF amounts... This upcoming storm is a great example, note the flow is southwesterly to west-southwesterly over the Carolinas Thursday night especially over southeastern NC where most of the moisture over coastal GA & SC at that time is being advected in.


namconus_z700_vort_seus_44.png


Meanwhile, 500 hPa winds are west to west-northwesterly everywhere (even earlier in the run before the precipitation arrives) which argues for little-no precipitation and this isn't the case for coastal portions of the Carolinas and GA
namconus_z500_vort_seus_44.png
 
Shawn said:
I would believe that the Icon had no chance of verifying, but it has our New Years system much more Euro like versus say, the GFS trying to break Wintry precipitation out. So I'm not quite ready to totally throw in the towel, until the ICON model starts going drier. You'd think if the ICON had some sort of bias around here, it would be doing something big with the New Years storm like this event we are tracking.
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That's a pretty good point man
 
Robert West said:
That's a pretty good point man
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And to go with that; the energy and 500mb is much better for New Years, in theory, than what we have for this potential system. You'd think if ICON was over doing the strength and consolidation of the wave, it would be overly amplified and tilt happy with New Years's wave that is much more robust.

I am still routing for the Icon, not because I want ZR, but because I want another model I can half-way trust. The GFS has been such a letdown, I literally only look at the GEFS for a good idea now.
 
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