• Hello, please take a minute to check out our awesome content, contributed by the wonderful members of our community. We hope you'll add your own thoughts and opinions by making a free account!

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

Well the RGEM, looks like something tainted the data at 500mb vort. So I would wait for the 12z. Its MESSY! whole damn map shows vorticity.

EDIT: NVM.
 
Last edited:
example (junk run):

example.png
 
@Shawn, can you explain the two lows on this map. It seems like many of the models get really wonky when that surface low starts moving north. One piece hugs the coast more and moves due north, and then the other piece takes over and takes a right turn. If the piece closer to the coast becomes the dominant piece, it's game on for many more folks.
refcmp_ptype.us_ma.png
 
Looks like the 6z GEFS was the best run yet. Here are the ensemble lows. Still room to correct west I believe.
gfs-ememb_lowlocs_eus_13.png
 
National Weather Services are starting to update their beta Winter Weather Pages. Raleigh says that there's a 10% chance of getting this much snow or more. As I see things, I would give this a 20-25% of verifying.
SnowAmt90Prcntl.png
 
packfan98 said:
@Shawn, can you explain the two lows on this map. It seems like many of the models get really wonky when that surface low starts moving north. One piece hugs the coast more and moves due north, and then the other piece takes over and takes a right turn. If the piece closer to the coast becomes the dominant piece, it's game on for many more folks.
refcmp_ptype.us_ma.png
Click to expand...

The NAM has a rapid occlusion phase, although that look surprises me some.
 
packfan98 said:
National Weather Services are starting to update their beta Winter Weather Pages. Raleigh says that there's a 10% chance of getting this much snow or more. As I see things, I would give this a 20-25% of verifying.
SnowAmt90Prcntl.png
Click to expand...
It has 6-8" on high side, hope it happens!!
 
packfan98 said:
The look where a main low takes a right turn after phasing and doesn't go up the coastline looks so strange to me.
Click to expand...

It's related to the same problem I alluded to yesterday the Bets-Miller-Janic convective parameterization scheme in the 12km NAM is notorious for creating fictitious diabatically-generated low pressure centers. What's going to end up happening in all likelihood, one will takeover and as a result, this will only serve to aid w/ inland moisture transport, so we end up with an even bigger storm further west...
 
Webberweather53 said:
It's related to the same problem I alluded to yesterday the Bets-Miller-Janic convective parameterization scheme in the 12km NAM is notorious for creating fictitious diabatically-generated low pressure centers. What's going to end up happening in all likelihood, one will takeover and as a result, this will only serve to aid w/ inland moisture transport, so we end up with an even bigger storm further west...
Click to expand...
Thanks. That was what I was thinking. I was using anecdotal data and wishcasting. It's good to know there is some science to support it!
 
Webberweather53 said:
It's related to the same problem I alluded to yesterday the Bets-Miller-Janic convective parameterization scheme in the 12km NAM is notorious for creating fictitious diabatically-generated low pressure centers. What's going to end up happening in all likelihood, one will takeover and as a result, this will only serve to aid w/ inland moisture transport, so we end up with an even bigger storm further west...
Click to expand...
When do you think models will do better, 12z?
 
BHS1975 said:
What’s the verification scores?


Sent from my iPhone using Tapatalk
Click to expand...
It's experimental. Notice the bold statement. Here is some more information:

These computer forecasts are EXPERIMENTAL and are used by atmospheric scientists to assess the value of satellite observations in numerical weather prediction. Although the accuracy of these products is consistently good, forecast errors can occur due to non-receipt of data, observation errors, and computer problems. The forecasts are fully automated and are not always closely monitored by CIMSS scientists. The risk of using the CRAS to plan weather-sensitive activities falls on the user.

The purpose of the CRAS is to test the use of satellite observations in a numerical prediction model. The quality of a numerical forecast depends on having accurate observations of the environment to define the forecast model's initial state. Here is a list of the observations that are currently used in the CRAS 12-hour spin-up forecast:
3-layer precipitable water (mm) from the GOES-13/15 sounders
Cloud-top pressure (hPa) and effective cloud amount (%) from the GOES-13/15 sounders
4-layer thickness (m) from the GOES-13/15 sounders
Cloud-top pressure (hPa) from MODIS
Gridded hourly precipitation amounts from NCEP
Cloud-track and water vapor winds (m/s) from the GOES-13/15 imagers
Cloud-top pressure (hPa) and effective cloud amount (%) from the GOES-13 imager
Surface temperature (C), dew points (C) and winds (m/s)
Sea surface temperature (C) and sea ice coverage (%) from NCEP rtg analysis
 
Allan Huffman‏ @RaleighWx 5m5 minutes ago
(1) W.R.T to the upcoming Jan 3rd/4th storm. The 6z NAM is most likely too extreme. BUT, this is a case where I trust the high-res models more than the more coarse global models. We are now getting to 72 hours and in. The high-res models are more equipped to handle these types of extreme cyclogenesis events in extreme atmospheric weather setups. The waters east of Fl are very warm. There is an extreme cold air mass moving over. Potential phasing of multiple s/w's. The ingredients are there. I still favor the biggest impacts on coastal sections. But I think the I-95 corridor east over the Carolinas/Ga could see snow. And yes we could see a high impact winter storm for some. Watch the hi-res models today. The 6z RGEM also looks threatening at hour 54. Probably the 00z ECMWF is the closest to reality. But, I could see higher end version of that verifying in the end. Lets see. But coastal areas, as I have been saying, this could be your storm. I will put out a map, no later than tomorrow, but maybe before, we shall see. Today should be a very interesting day of model runs. There is even a chance of wintry precipitation as far south as SE Ga and N Fl. Yes N FL.
 
packfan98 said:
Allan Huffman‏ @RaleighWx 5m5 minutes ago
(1) W.R.T to the upcoming Jan 3rd/4th storm. The 6z NAM is most likely too extreme. BUT, this is a case where I trust the high-res models more than the more coarse global models. We are now getting to 72 hours and in. The high-res models are more equipped to handle these types of extreme cyclogenesis events in extreme atmospheric weather setups. The waters east of Fl are very warm. There is an extreme cold air mass moving over. Potential phasing of multiple s/w's. The ingredients are there. I still favor the biggest impacts on coastal sections. But I think the I-95 corridor east over the Carolinas/Ga could see snow. And yes we could see a high impact winter storm for some. Watch the hi-res models today. The 6z RGEM also looks threatening at hour 54. Probably the 00z ECMWF is the closest to reality. But, I could see higher end version of that verifying in the end. Lets see. But coastal areas, as I have been saying, this could be your storm. I will put out a map, no later than tomorrow, but maybe before, we shall see. Today should be a very interesting day of model runs. There is even a chance of wintry precipitation as far south as SE Ga and N Fl. Yes N FL.
Click to expand...

If the models keep trending west, the coastal areas will deal w/ mixing issues, I just don't see how a negatively-neutrally tilted trough over FL/GA doesn't in some way, shape, or form shift the heaviest axis of snow at least a little bit inland. In cases like Dec 1989 where the heaviest snows fell towards the beaches, the large-scale trough axis was positively tilted all the way to the coast which pushed the storm track further offshore....
 
1300m said:
I am really not sure why some are so stuck to this coastal Carolinas only idea. The H5 setup does not support this. Furthermore, from a modeling perspective, the NAM is actually pretty good with H5 interactions. During the January 2017 event it was the first one to push the warm nose further inland, but it seems no one remembers why. The reason why is it had the shortwave responsible for our storm a little stronger, and more neutral to eventually negative tilt earlier. Thus, the NAM handled the H5 evolution of the January 2017 winter storm better than any other guidance at 60 hours out, but even it trended stronger and further west with precipitation right on up until the storm. I made a forecast map of 6-10" west of a CLT to Durham line and a lot of my colleagues thought I was crazy because no guidance suggested that, but the pattern did. The pattern suggests RDU to I-95 in NC as the jackpot zone, and I'm sticking with it unless H5 starts going the other way. 6-12" is not out of reach in this corridor, and locally more could fall if the NAM continues to trend. I also believe sleet will cut down on totals east of I-95 when this is all said and done.
Click to expand...
What's your personal opinion on the Columbia, SC area?
 
The locals here in the Midlands are easing there way into talking about it now, but are basically saying there is hardly any chance for it to get to the Midlands and only be confined to the coast. Which is the usual conservative approach.
 
A
1300m said:
I am really not sure why some are so stuck to this coastal Carolinas only idea. The H5 setup does not support this. Furthermore, from a modeling perspective, the NAM is actually pretty good with H5 interactions. During the January 2017 event it was the first one to push the warm nose further inland, but it seems no one remembers why. The reason why is it had the shortwave responsible for our storm a little stronger, and more neutral to eventually negative tilt earlier. Thus, the NAM handled the H5 evolution of the January 2017 winter storm better than any other guidance at 60 hours out, but even it trended stronger and further west with precipitation right on up until the storm. I made a forecast map of 6-10" west of a CLT to Durham line and a lot of my colleagues thought I was crazy because no guidance suggested that, but the pattern did. The pattern suggests RDU to I-95 in NC as the jackpot zone, and I'm sticking with it unless H5 starts going the other way. 6-12" is not out of reach in this corridor, and locally more could fall if the NAM continues to trend. I also believe sleet will cut down on totals east of I-95 when this is all said and done.
Click to expand...

I actually see just rain for the coast.The Warm Nose will be very strong and the NAM model is showing this.It's a good possibly that could be 10 to 15 inches of snow in Raleigh to Favetteville given the setup and around 6-10 inches for areas like Columbia South Carolina,Macon Georgia,Greenville North Carolina,Virginia Beach.I also haven't ruled out of the possibly of this system developing in the Gulf. and hugging the coast.
 
Last edited:
1300m said:
I am really not sure why some are so stuck to this coastal Carolinas only idea. The H5 setup does not support this. Furthermore, from a modeling perspective, the NAM is actually pretty good with H5 interactions. During the January 2017 event it was the first one to push the warm nose further inland, but it seems no one remembers why. The reason why is it had the shortwave responsible for our storm a little stronger, and more neutral to eventually negative tilt earlier. Thus, the NAM handled the H5 evolution of the January 2017 winter storm better than any other guidance at 60 hours out, but even it trended stronger and further west with precipitation right on up until the storm. I made a forecast map of 6-10" west of a CLT to Durham line and a lot of my colleagues thought I was crazy because no guidance suggested that, but the pattern did. The pattern suggests RDU to I-95 in NC as the jackpot zone, and I'm sticking with it unless H5 starts going the other way. 6-12" is not out of reach in this corridor, and locally more could fall if the NAM continues to trend. I also believe sleet will cut down on totals east of I-95 when this is all said and done.
Click to expand...
Do you see Suffolk VA possibly getting heavier snow right now it shows ligher then the coast?
 
:DSnow flurries close to Lavonia where I am now in Bowersville Ga! Win
 
1300m said:
I think modeled amounts will go up there, but how much will depend on how far up the coast the storm can get before being shunted east.
Click to expand...

Is that’s what keeping this from a 2000 repeat by hooking east instead of continuing north?


Sent from my iPhone using Tapatalk
 
1300m said:
My opinion is that Columbia would probably be west of the jackpot zone but certainly some snow is possible. Sort of in the same boat as that CLT to GSO region in NC.
Click to expand...
Thanks man, I'm hoping for a couple inches atleast. Given the cold ground and everything, that will cause a ton of trouble
 
1300m said:
I am really not sure why some are so stuck to this coastal Carolinas only idea. The H5 setup does not support this. Furthermore, from a modeling perspective, the NAM is actually pretty good with H5 interactions. During the January 2017 event it was the first one to push the warm nose further inland, but it seems no one remembers why. The reason why is it had the shortwave responsible for our storm a little stronger, and more neutral to eventually negative tilt earlier. Thus, the NAM handled the H5 evolution of the January 2017 winter storm better than any other guidance at 60 hours out, but even it trended stronger and further west with precipitation right on up until the storm. I made a forecast map of 6-10" west of a CLT to Durham line and a lot of my colleagues thought I was crazy because no guidance suggested that, but the pattern did. The pattern suggests RDU to I-95 in NC as the jackpot zone, and I'm sticking with it unless H5 starts going the other way. 6-12" is not out of reach in this corridor, and locally more could fall if the NAM continues to trend. I also believe sleet will cut down on totals east of I-95 when this is all said and done.
Click to expand...

Exactly. Here's what the 500 mb pattern looked like for several of the events I've analyzed since 1895 which were centered over the southeastern coastal plain or the coast. Yeah umm the pattern doesn't support this.
compday.2606_a000_1500_8174_3913_67c9_e04b_7832.0.6.41.56.gif

I'm sure everyone has seen or heard of February 1914, February 1973, & December 1989 a bajillion times so I won't post those, but here are some others that maybe less familiar but were added to this composite.
February 24-25 1968 NC Snowmap.png

December 14-15 1943 NC Snowmap.png

January 29-31 1936 NC Snowmap.png
February 21-22 1936 NC Snowmap.png

February 10-12 1912 NC snowmap.png
January 12-14 1912 NC snowmap.png
February 6-8 1907 NC Snowmap.png
January 4-5 1904 NC Snowmap.png
 

Attachments

  • February 24-26 1914 NC Snowmap.png
    February 24-26 1914 NC Snowmap.png
    37.2 KB · Views: 26
I remember a storm in 98 (pretty sure that is the year) that the afternoon forecasts came out and mine was rain to snow with 1 to 2 feet expected that night. Coastal storm. I have no idea what the pattern was but the forecast busted badly. It did start as rain. It did go to snow for about an hour then back to rain by 9 pm. We were supposed to be jackpotted with lighter amounts into WVA. In hind sight, I am guessing something phased or it went way more neg tilt but the rain snow line pushed all the way to the Ohio border and we ended up with soaking rain. I know modeling has come a long way but this is another example of how things can change up until the last minute.
 
Here comes the NAM guys. Let's see how jacked up everyone gets off this run
 
1300m said:
Very, very good analysis. I'd ask you to do the same for the modeled pattern but I know you already showed a couple of examples, and it fits with the thinking. I really think if guidance doesn't pick up on some big slowdown with the trailing wave on the 12z runs this will just continue to shift towards this more inland idea with time.
Click to expand...
The 1958 example from yesterday was great! I'm guessing something similar is on the table at least.
 
You must log in or register to reply here.
Back
Top