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

[packfan98]

What’s the verification scores?


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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

 

[Brett]

Let's pull out the CRAS model for fun!

Very heavy precip there

 

[packfan98]

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.

 

[Webberweather53]

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.

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....

 

[Mitch West]

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.

What's your personal opinion on the Columbia, SC area?

 

[Mitch West]

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.

 

[Michael21]

A

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.

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.

 

[Brett]

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.

Do you see Suffolk VA possibly getting heavier snow right now it shows ligher then the coast?

 

[Wildboutsnow]

Snow flurries close to Lavonia where I am now in Bowersville Ga! Win

 

[Brett]

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.

Ok thanks.

 

[BHS1975]

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.

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


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[Mitch West]

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.

Thanks man, I'm hoping for a couple inches atleast. Given the cold ground and everything, that will cause a ton of trouble

 

[Webberweather53]

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.

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.


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.

 

[Nomanslandva]

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.

 

[Mitch West]

Here comes the NAM guys. Let's see how jacked up everyone gets off this run

 

[Mitch West]

Everyone needs to wake up! This is a big day for this storm model wise! Lol

 

[Brett]

Everyone needs to wake up! This is a big day for this storm model wise! Lol

lol I'm up, and excited

 

[Mitch West]

lol I'm up, and excited

All the guys that give us play by play of the models aren't lol

 

[RollTide18]

Here comes the chaser

 

[packfan98]

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.

The 1958 example from yesterday was great! I'm guessing something similar is on the table at least.