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Mid to Long Range Discussion ~ 2023


buckeyefan1
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8 minutes ago, TARHEELPROGRAMMER88 said:

Who wants to bet against the Euro? Temps on CMC and Euro do not support snow. 

The Euro is a much weaker/less dynamic system. If it is correct about the strength of the system, then absolutely. but if the GFS played out as depicted, central NC would be snow. I guess the problem we run into, is somewhere in between probably wouldn't cut it, at least east of 85.

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Quit focusing so much on surface depictions right now. ULL snow is a top down process. Anybody who has experienced it knows how fast the surface temps can drop as long as it's cranking. This event will be entirely predicated on the track/tilt/strength of the  ULL. That has improved on basically all guidance since yesterday. The question is will it trend far enough to matter. 

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Alright, at the risk of being shredded by posters of the forum, I will speak my peace in regards to temps: Modeled BL temps do not matter in this setup. There is is no cold air source (we know) and if this system wasn’t there it’s likely in the 50’s. But that’s the beauty of cool pool ULL- they do not rely on CAA for snow. It’s a top down “cold manufacturing” process. If you don’t get dynamic cooling from heavy rates, no snow. What we’re looking for in this setup is going to be a system going negative tilt, rapid deepening of the surface low, and a sharp area of convergence on the back side leading to enhanced rates. These systems are extremely track-dependent and will not be a synoptic event for the area, but they can be significant over producers and have led to some great systems in the past for those under “the band.” Happy tracking 

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2 hours ago, NorthHillsWx said:

I’ll say this- if the only storm this year is someone from the forum outside the mountains getting nuked in a narrow band by an anomalous upper level bowling ball low in an otherwise abysmal pattern with absolutely no cold air source even remotely available nearby with zero Atlantic blocking and sandwiched between two spring like warmups, it would just be so fitting

 Zero Atlantic blocking wouldn't be unusual for a big RDU snow. Here is the NAO for the 23 Raleigh 6"+ SN/IP storms since 1950. (I'm calling neutral NAO to be from +0.25 to -0.25):


-1/19/1955: -NAO

- 12/11/1958: neutral NAO

- 3/2-3/1960: neutral NAO

- 3/9/1960: neutral NAO

- 2/26/1963: neutral NAO

- 1/25-7/1966: -NAO

- 2/9/1967: +NAO (+0.5)(9.1")

- 3/1/1969: -NAO

- 1/7-8/1973: -NAO

- 2/18-9/1979: neutral NAO

- 3/1-2/1980: +NAO (+0.4)(11.1")

- 1/13-14/1982: neutral NAO

- 3/24/1983: neutral NAO

- 2/6/1984: +NAO (+1.1)(6.9")

- 1/7-8/1988: +NAO (+0.5)(7.3")

- 2/17-8/1989: +NAO (+1.7 )(6.2")

- 1/24-5/2000: -NAO

- 1/2-3/2002: -NAO

- 2/26-7/2004: -NAO

- 12/25-6/2010: -NAO

- 2/24-6/2015: +NAO (+1.0)(6.5")

- 1/17-8/2018: +NAO (+1.2)(6.1")

- 12/9-10/2018: +NAO (+0.9)(8.9")


Tally:

-NAO: 8

Neutral NAO: 7

+NAO: 8


 Moreover, note that RDU had 5 big snows, including the last 3, with an NAO much more positive (see bolded five NAOs of +0.9 to +1.7) than the +0.6 that is being predicted by the GEFS for 2/12. So, RDU hasn't had a 6"+ snow with NAO under +0.9 since 12/25-6/2010! Furthermore, the other 3 +NAO 6"+ snows were only barely lower (+0.4 to +0.5).

 By the way, the big SE bowling ball snow (RDU got 3.2", ATL got 4") of 3/1-2/2009 had a +1.0 NAO along with AO of +2.1 and PNA of -0.4. So, 3/2009 had a strong +NAO/+AO!
 

 The GEFS is forecasting for 2/12/23 an NAO of +0.6, AO of +2.0, and PNA of +0.1. If there were a strong -PNA being forecasted, then I'd have much more doubt. But a neutral PNA doesn't at all hamper the odds. The MJO was on 3/1-2/2009 in phase 4 and is predicted to be in phase 5 or 6 on 2/12/23. 

 I'm not predicting either yes or no for a 2/12/23 RDU snow. It may end up too warm as we all know. I'm just saying that the progged indices on their own, especially NAO, are not at all a hampering factor per history, especially recent.
----------------------------------

NAO daily data:

https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.nao.cdas.z500.19500101_current.csv
 

RDU data:

https://www.weather.gov/wrh/Climate?wfo=rah

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1 minute ago, eyewall said:

Honestly this is probably the closest we have been to something real all winter. Hopefully we can reel it in. That ULL position will mean everything.

First time all winter we've seen positive trends at this timeframe. This has pretty much been the range when long range threats have went sour so far.

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Euro at 500 mb was a SIGNIFICANT improvement. EPS and GEFS both ticked way up in favor of something in the forum. Dare I say 12z was an excellent trend ACROSS guidance as we break into medium range inside 120 hours. Still absolutely not even close to a lock or even consensus but we’re inside 120 hours and we’re still tracking with positive trends! 

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KGSP AFD for the weekend

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 215 pm EST Tuesday: Considerable uncertainty remains over the
handling of the upstream trough axis crossing the Mid-Mississippi
River Valley Friday night. The 12Z GFS continues to feature a 500 mb
low center cutting off and migrating over the Deep South on
Saturday. The GEFS spread is quite large, however, and the NAM/CMC
feature either a more northerly track of the low or an open wave.
Until recently, the ECMWF runs have had a much more progressive,
positive tilt, open wave moving through the Appalachians. Recent ECM
trends, however, have been slightly toward the deeper and more
dynamic operational GFS, and this has some implications for wintry
weather potential over our area this weekend. For now, the forecast
has been nudged slightly wetter through the Saturday night/Sunday
morning period. This keeps mountain northwest flow snow showers
solidly in the forecast Friday night through Saturday night, but
also creates low end potential for a wintry mix east of the
mountains through Sunday morning. Confidence remains very low on
this and ensemble mean solutions still do not support much of any
accumulating snow east of the mountains over the weekend.
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It’s February 7 and we do not have a single storm thread for the season, not even a fail (no a thread about the 3 day cold outbreak and severe threads don’t count) That’s pathetic even for our low standards! This is the first mid range threat of the season. I say wait past 0z and if it’s still there someone (not me) start one tomorrow. That way we can say we killed at least one storm this year with a thread 

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From NWS RAH longer forecast...

Models have trended significantly slower with the trough, with a closed low even
developing and tracking to our south, helping a surface low deepen
off the NC coast. This would result in a wetter solution for our
region than previously thought, so bumped up POPs to chance during
this period. Northerly flow around the low and a weak high over New
England may result in temperatures cold enough for some snow or
mixed rain/snow. The 12z GFS is especially aggressive with depicting
this potential, but even the 12z ECMWF trended more in this
direction. Model soundings appear it would be more of question of
rain vs snow instead of ice. Almost half of 12z GEFS at least have
some measurable snow in some part of central NC, with less CMC
ensembles and only a small percentage of ECMWF ensembles showing it.
Uncertainty this far out is quite high, and would like to see more
consistency in the models. Even still, the latest model trends at
least justified introducing a chance of rain or snow in most places
Saturday night. Because of the uncertainty in the overall setup this
weekend, confidence in temperatures this weekend is low, but for now
forecast highs are slightly below normal.
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6 minutes ago, TARHEELPROGRAMMER88 said:

GFS further amped and west. Like a bad horror movie that keeps repeating. Ohio by Wed night? Any takers?

Nope. That bad trended way North and West. I was already on the fringe.   It’s been that kind of year. Maybe it’s too amped. 

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1676300400-0mYOXw3Oo3A.png

18z looks more like the 0z from last night. (Edit: oops, meant 06z from this morning) ULL takes more of a north easterly track than the 12z, focusing the heavier snow in the mtns and foothills from NGA/upstate SC up through the mid-Atlantic. Was actually a hair weaker with the surface low than 12z. Still a great signal and too small a change to be focused on at this range on a global model. Just shows how important the track of that ULL will be for individual backyards if we manage to reel this threat in. ULL's can produce big winners and big losers with very little margin between.

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I can tell y’all this is going to go back and forth every run until the event begins and ULL tracks are notoriously hard to pin down at range but we just need to keep the general idea alive the next couple days before we even remotely press the cancel button on this one. 18z looks fine to me at this range

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