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Wintry January 3rd-6th, 2018 Winter Storm The ARCC/Xtreme Weather Special

From met Chris Simmons on Facebook. I'll take it.

FB_IMG_1514868813591.jpg
 
As Jon correctly pointed out on twitter, losing the phase w/ the northern stream wave actually makes this event look more like Jan 2000, and the more it leaves our main s/w alone, the better...
 
NCSNOW said:
Trailer wave is almost gonna come in over the stovepipe unless it's moving east. Interested to see any vort over GL and if it messes with trailer tommorow like 0z nam.
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12z NAM at hour 15 looks almost exactly like what the current upper level atmosphere over the CONUS looks like. NAM has the trailing wave move southeastward though.
 
Webberweather53 said:
As Jon correctly pointed out on twitter, losing the phase w/ the northern stream wave actually makes this event look more like Jan 2000, and the more it leaves our main s/w alone, the better...
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Can you go into further detail, I’m trying to learn how things interact at H5 better, it’s my weakness esp vort charts which isn’t good because it’s the blueprint for everything that happens below.
 
when someone says, 'vortmax', my brain just feels like someone flushed it down the toilet..
 
EastAtlwx said:
Can you go into further detail, I’m trying to learn how things interact at H5 better, it’s my weakness esp vort charts which isn’t good because it’s the blueprint for everything that happens below.
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Essentially what's happening is the northern stream disturbance effectively acts to "kick" our southern stream wave faster out to the east despite the fact that they partially phase. As the northern stream backs off more, this allows our main s/w to consolidate more effectively and cut-off from the main streamflow. I mean if you really think about it how many times do we look to shortwaves on the west coast (like last week for ex) wanting a wave to dig and get out and separate itself from the main streamflow. Similarly here, the longer this wave is left alone, the more apt it is to slow down and not get "kicked" by the northern stream wave, and thus it has more space to amplify, and tilt which will ultimately result in a January 2000 solution if the models keep trending towards a slower northern stream wave. I can't believe I was so oblivious to this earlier...
 
Webberweather53 said:
Essentially what's happening is the northern stream disturbance effectively acts to "kick" our southern stream wave faster out to the east despite the fact that they partially phase. As the northern stream backs off more, this allows our main s/w to consolidate more effectively and cut-off from the main streamflow. I mean if you really think about it how many times do we look to shortwaves on the west coast (like last week for ex) wanting a wave to dig and get out and separate itself from the main streamflow. Similarly here, the longer this wave is left alone, the more apt it is to slow down and not get "kicked" by the northern stream wave, and thus it has more space to amplify, and tilt which will ultimately result in a January 2000 solution if the models keep trending towards a slower northern stream wave. I can't believe I was so oblivious to this earlier haha....
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Would this just be WRT QPF over North Carolina.. how does this effect areas further inland like the midlands of sc towards Augusta.? Would we want this lead wave further west as possible and how much significant change can we get at this lead time?
 
EastAtlwx said:
Would this just be WRT QPF over North Carolina.. how does this effect areas further inland like the midlands of sc towards Augusta.?
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Areas west of I-77 and NW of I-85 in NC probably not a whole lot given they're pretty far outside the legitimate margin of error here, however if the wave continues to amplify and tilt negative the low pressure center will intensify more quickly because the trough is able extract more momentum from the mid-latitude jet and mutually amplify the antecedent low-level vortex. The large diabatic heating contribution w/ this storm could partially or even completely mask the impacts wrt longwave trough orientation on surface low & precipitation track/distribution esp if only relatively subtle changes are observed aloft...
 
Webberweather53 said:
Areas west of I-77 and NW of I-85 in NC probably not a whole lot given they're pretty far outside the legitimate margin of error here, however if the wave continues to amplify and tilt negative the low pressure center will intensify more quickly because the trough is able extract more momentum from the mid-latitude jet and mutually amplify the antecedent low-level vortex. The large diabatic heating contribution w/ this storm could partially or even completely mask the impacts wrt longwave trough orientation on surface low & precipitation track/distribution esp if only relatively subtle changes are observed aloft...
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So are we wanting to see a trend away from a phase now, in order to get the lead wave out front to amplify and tilt faster? Trends tonight seemed to slow the NS energy a good bit. Even the nam backed off
 
I wonder what it’s picking up across north east ga? Or was that today’s dusting?


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From NWS Mobile

SHORT TERM /Tuesday night Through Thursday night/...The cold
surface ridge of high pressure to our north will continue to
slowly sink southward to the coast by noon Wednesday. The cold and
dry airmass will remain entrenched across the central gulf coast
region with much below normal temperatures continuing into Tuesday
night. An interesting upper level shortwave feature embedded in
the longwave trough will approach the region from the northwest
Tuesday evening, and pass quickly over the forecast area late
Tuesday night into Wednesday morning. This will bring some mid and
high level clouds above 8500 feet to the area Tuesday night along
with mid layer lifting. A very dry airmass will remain below 8500
feet, but if the snow falling in the saturated layer aloft
survives it`s journey through the dry layer to the surface we
could see a few flurries across portions of the forecast area.
Will leave mention of flurries out for now pending better high-
resolution model data on future runs.
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Preface: This is based mainly for GA/SC. I don't know much about NC, the OBX areas, how lows effect the area, etc.

Just did research into January 24-26, 2000. Long story short, here is what I learned.

- I was directed to use things like the ECMWF Ensembles to make smart forecasting choices (and not wishcasting or "what if" scenarios) in response to low locations and intensity as they were able to hint at the possibility of the storm in reanalysis and real time, removing what was seen as vital sounding data, along with other stuff that I don't totally understand, lol.

- Learned that moisture processes were wonky and forecast incorrectly.
- Convection munked with the modeling.
- The initial low started to form on the GA & SC border. This system is far from that.

- Used the above knowledge, and found out there is nothing here that suggests that the we are going to be "surprised" by a snowfall like the NAM was showing earlier in the Central Midlands of South Carolina. With that said; the chances of the images below being incorrect with low center placement this close in the forecast period, is virtually nil'.

I would like to note, this could be an entirely different ballgame, if the low pressure center was forecast by some members to be much closer to the coast, or even over land. It would be useful to consider it as some kind of "hint" that some members are seeing something radically different. With that said, here is the 00z ECMWF Ensemble low placement from 42 hours & 48 hours. Notice the cluster, and even the most Western members are still clustered far from the coast by hour 48.

eps_01.png

epos_02.png


Now, in regards to coastal sections of South Carolina & Georgia, the control run has a nice thump of Wintry weather around Charleston. The mean is not horrible, either to see some snow falling before the low pressure pulls Northeast.

eps_mean.png


eps_control.png
 
Yeah this ain’t nowhere near January 2000. Why was it even brought up in the first place?


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BHS1975 said:
Yeah this ain’t nowhere near January 2000. Why was it even brought up in the first place.


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500MB was not far off when we thought modeling was going to continue to show crazy solutions that the NAM had, before it went back east with as of 00z. 250mb winds weren't too terribly off either, and how the s/w dropped straight down into the SE United States. There were and are still many similar features at 500mb. Some of it was wish casting, and some of it was legit. It's just hard to discern the two.
 
And just to make me look stupid, here comes the 06z NAM with more snowfall/Wintry weather in Southern GA so far. The Low basically hugging the Southern FL coast.

SMH
 
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