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Pattern December, Make analogs relevant again

EPS control drops the hammer w/ vengeance with the next cold shot that comes after this storm in the medium range that hits the NE US. Widespread teens and lower 20s all the way down to southern GA and AL and sub zero temps in the mountains. If only...
eps_t2min_c_nc_54.png
eps_t850a_c_conus_51.png
 
Only 300 hours away!:(
One day the models are going to get one right! :(
 
On this date in 1971, a cut-off upper level low and attendant, weak surface cyclone over the northern Gulf coast produced a very large early season snowstorm in much of west-central NC with as much as 21" of snow reported at Lake Toxaway in Transylvania County. The following set of images include a snowfall accumulation map as well as analyses from the high resolution ECMWF 20th Century Reanalysis dataset (ERA-20C).

December 3-4 1971 NC Snowmap.png


15z December 3 1971 700 hPa specific humidity (shaded), MSLP (contours), and fronts
15z December 3 1971 700 hPa Specific Humidity, MSLP, and Fronts.png


0z December 4 1971 500 hPa vorticity (shaded), geopotential height (contours), and wind (wind barbs)
0z December 4 1971 ERA-20C 500 hpa heights, wind, and vort.jpg


12z December 3 1971 2 PVU (Dynamic Tropopause) potential temperature (shaded; contoured every 10K), and wind (wind barbs)
12z December 3 1971 ERA-20C 2PVu Potential Temp & Wind.jpg
 
Thought not quite a major per my criteria, this was a pretty big deal for ATL-AHN, GA, where they got 1-3" of SN/IP along with ZR with a high liquid equiv of over 1"! Temp's were marginal which I think prevented much greater accumulations
 
Webberweather53 said:
It's too bad this is out at day 10, but this is a great overall look for us to score a few days later w/ a nice snow cover to our N and NW, s/w slowly emerging out of the SW US and northern Mexico and a clipper coming in unusually far to the south & west over the Dakotas and Nebraska... This is starting to get into that general timeframe when I think we could legitimately get a storm in this pattern. Whatever we see next weekend w/ the coastal low is a bonus
View attachment 1729
View attachment 1730
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I fell victim to getting too excited too early for next week's system despite climatology, lack of snow cover to our north and the NW trend, I'm guilty of not listening lol. But it's probably for the best that this system next week can lay down a decent snow pack to set the stage for what's next and that look on the euro certainly could be what's next, I still like where we are headed.
 
Usmeagle2005 said:
This crazy, just out of this world pattern and I’m only seeing maybe low to mid 40’s for highs at its worst, am I missing something?
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No, the models for the most part aren't plunging the cold deep down into the SE (at least not yet). Rather, the SE is near the bottom of intense cold to the north, which could pay off at some point with a winter storm traveling along the boundary if it can tap into the lower level cold air via CAD assuming WSW upper flow/upper trough axis near the MS River or a little further west..
 
The model predictions for the AO remain in the tank through mid month. This means a solidly -AO for 12/1-15 that is projected to be between -1.5 and -2.0, which would mean at least a 90 percentile high -AO going back to 1950.

Analogs for similar 12/1-15 AO's going back to 1950 with similar ENSO (centered on weak La Nina) suggest that 12/16-31's AO will likely be at least down to -1.5 and quite possibly down to -2.0 or lower as the 3 best ENSO/AO analogs of 1995 (-2.8), 2000 (-3.7), and 2005 (-2.3) suggest. The #1 analog when considering QBO, ENSO, and -AO of late Nov and early Dec. is 2000 and it had AO of -3.7 during 12/16-31, 3rd most negative AO to the -4.9 of 2009 and the -3.9 of 2010. That would favor a continuation of solid cold dominating the E US through the end of the month.

As we move forward to January, the same analogs still strongly favor a -AO (near the -0.75 to -1.0 range vs the longterm Jan average of -0.4) but not as negative as the very negative Dec. Looking further ahead to Feb, analogs are more mixed with only a slight -AO or near the longterm average for Feb., which is -0.4
 
GaWx said:
Thought not quite a major per my criteria, this was a pretty big deal for ATL-AHN, GA, where they got 1-3" of SN/IP along with ZR with a high liquid equiv of over 1"! Temp's were marginal which I think prevented much greater accumulations
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Yeah it was a pretty substantial event for areas along and north of I-20 in GA and SC, likely produced some significant ZR down to Columbia. Snow changed to sleet and then freezing rain in RDU, areas towards Charlotte and points west w/ higher snow totals stayed all snow longer but probably mixed w/ sleet near the end.
 
GaWx said:
No, the models for the most part aren't plunging the cold deep down into the SE (at least not yet). Rather, the SE is near the bottom of intense cold to the north, which could pay off at some point with a winter storm traveling along the boundary if it can tap into the lower level cold air via CAD assuming WSW upper flow/upper trough axis near the MS River or a little further west..
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So may be a blessing.
 
As was true w/ the 12z ECMWF, finally seeing a halfway decent looking overall pattern for an overrunning event here in the southern tier by day 10 on the GFS w/ a big vortex over SE Canada, solid snowpack in the northern tier, and shortwave digging into the southwestern US and Baja California
gfs_z500_vort_namer_42.png
 
Webberweather53 said:
As was true w/ the 12z ECMWF, finally seeing a halfway decent looking overall pattern for an overrunning event here in the southern tier by day 10 on the GFS w/ a big vortex over SE Canada, solid snowpack in the northern tier, and shortwave digging into the southwestern US and Baja California
View attachment 1746
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Yep. I thought it looked similar to the Euro day 10.


Sent from my iPhone using Tapatalk
 
Brent said:
Nice torch on the beyond 300 hour gfs lol
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Don't know whether it's gonna torch @ 300; heck, don't even know if it's gonna actually get cool next week for 3 or 4 days (hasn't that been the mantra since a week before Thanksgiving (?)); but one thing I do know is that in the deep SE, 8 out of 10 times, if it gets real cold early, that's it (will preach this gospel forever) ... so if we wait until 12/22 or so, fine ... now back to the cave ... o_O
 
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