December 2019 Med/Long Range Disco

[BristowWx]

3 minutes ago, Bob Chill said:

As the days go by the less we know about Dec. Lol. I'm not mad at the weekly plot you posted. It's not that far from something that can work. Better than last year's no chance in hell pattern

I would not be surprised to se another drastic change in the ensembles.  I was flipping back through the last few days and it’s like seeing op run solutions 10 days out.  Glad I am not a natural gas trader. 

[WxUSAF]

10 minutes ago, Bob Chill said:

As the days go by the less we know about Dec. Lol. I'm not mad at the weekly plot you posted. It's not that far from something that can work. Better than last year's no chance in hell pattern

Ha, you’re more positive than I am about that. That weekly map looks like a sneeze away from a blowtorch. But it’s the weeklies and they’re usually awful. Like I said yesterday, a December with 1-2 accumulation events, less than 3F above normal, and no 60F around Xmas.

[CAPE]

33 minutes ago, WxUSAF said:

Ha, you’re more positive than I am about that. That weekly map looks like a sneeze away from a blowtorch. But it’s the weeklies and they’re usually awful. Like I said yesterday, a December with 1-2 accumulation events, less than 3F above normal, and no 60F around Xmas.

The weeklies are typically so ambiguous it ends up being up for interpretation. Glass half full or half empty. Certainly it could be worse, but that is not a great look imo. And yes, it's the weeklies and they really offer little value. I'll stick with the LR ens guidance and not worry about what may happen beyond that window.

[Eduardo]

7 hours ago, psuhoffman said:

As USAF said the atmosphere is behaving “like” a nino lately. But frankly the climo cycle recently has been a warm December no matter the enso state. I’m not entirely sure if the “warm nino” thing is due to enso or that we have had way more ninos lately which skews the results vs older ninos when colder December’s wasn’t as unusual. We had some pretty cold December ninos in the 1960s and 70s.  The Atlantic and Gulf SSTs have been on fire lately. Add in the lag of sst temperatures cooling and that might have as much or more to do with the prevalence of the SE ridge early in winter lately. In essence we might be losing the early 1/3 of winter due to the current warmer SST cycle there.  Only reason our mean snowfall isn’t dropping faster is we also seem to have a higher hit rate on big storms when the pattern does rarely get right.  Boom and bust cycles seems to be our normal climo now, even more than it was historically.  

 

If that is true, then what explains the spate of cold November's in recent years?

[psuhoffman]

2 minutes ago, Eduardo said:

If that is true, then what explains the spate of cold November's in recent years?

This is all speculative and I’ve not had time to research it much to verify anything, but I’ve wondered if the decrease in sea ice has encouraged ridging in those regions in November which could favor cold dumping into the conus. Also the increased baroclinicy from the increase in SSTs could cause volatility during the transition to the winter jet pattern.  But once wavelengths broaden and the pattern settles into its winter mode, and the waters finally cool and ice over, the pattern flips.  Just a thought. 

[WxUSAF]

If you want something positive to look at, select northern hemisphere MSLP anomaly on the 18z GEFS and scroll to about hr160+. Lots of red in Santa land means a -AO.

[WinterWxLuvr]

22 minutes ago, psuhoffman said:

This is all speculative and I’ve not had time to research it much to verify anything, but I’ve wondered if the decrease in sea ice has encouraged ridging in those regions in November which could favor cold dumping into the conus. Also the increased baroclinicy from the increase in SSTs could cause volatility during the transition to the winter jet pattern.  But once wavelengths broaden and the pattern settles into its winter mode, and the waters finally cool and ice over, the pattern flips.  Just a thought. 

That sounds spot on to me.

[Bob Chill]

1 hour ago, WxUSAF said:

Ha, you’re more positive than I am about that. That weekly map looks like a sneeze away from a blowtorch. But it’s the weeklies and they’re usually awful. Like I said yesterday, a December with 1-2 accumulation events, less than 3F above normal, and no 60F around Xmas.

Lol. Yea, it's tenuous depending on which way it breaks... My gut instinct is telling me that the -pna rolls forward and a -epo ridge builds. Retro the weeklies pattern and we're toast. Literally....

Eta: no sign of a se ridge popping and that's always a good thing.

[psuhoffman]

14 minutes ago, Bob Chill said:

Lol. Yea, it's tenuous depending on which way it breaks... My gut instinct is telling me that the -pna rolls forward and a -epo ridge builds. Retro the weeklies pattern and we're toast. Literally....

Eta: no sign of a se ridge popping and that's always a good thing.

Even if we don’t score early season, I want to see a generally favorable look up top continue. I doubt the pac kills us all winter. Even the last few we had favorable periods. But what we haven’t had is a cooperative look up top.  If we get a winter where the NAO and AO cooperate some of the time we probably can eek our way to climo with a variable pacific. That’s kind of how I was leaning in my WAG.  

[Blizzard of 93]

15 minutes ago, Bob Chill said:

Lol. Yea, it's tenuous depending on which way it breaks... My gut instinct is telling me that the -pna rolls forward and a -epo ridge builds. Retro the weeklies pattern and we're toast. Literally....

Eta: no sign of a se ridge popping and that's always a good thing.

It would certainly help to avoid the dreaded SE Ridge showing up.

If the pattern ends up as relatively flat, with a general west to east storm track, we could luck into a light to moderate snow event with the help of a well placed & timed High to our north. 

If the SE Ridge shows up, then we just get watch one cutter after another.

[MJO812]

Anthony Masiello‏ @antmasiello

Pretty classic -NAO sequence ahead. It's in its formative stages now.

[raindancewx]

My analogs had a -NAO in December, but its kind of wasted in the Northeast since the -NAO isn't at its peak power as a cold signal in December, while Nino 4 warmth is at its peak as a warm signal in December - they more or less battled to a draw in the Northeast in 2009 when both were extremely potent at the opposite sign (29.72C in Nino 4 Dec 2009, -1.93 NAO in Dec 2009 - both near records). There really aren't any cold Decembers in the Northeast when Nino 4 is 29.5C or warmer.

I don't think we have a -1.9 NAO in December, but we may have a 29.7C Nino 4 - it's been around 29.5C lately.  I mentioned in my outlook that with Nino 4 near record warm, my blend likely needed to be upped 2F - so I did 1953 (x2), 1983 (x2), 1992, 1995, 2009 (x3), 2018, and then added 2F. For the NE, the (weak) tendency is that each 0.1C of warming in Nino 4 in Fall (peaking in Dec) is worth about 0.15F hotter highs in December, although the relationship is curved, with the Super La Ninas also warm if Nino 4 gets toward 27.0C. I haven't looked in a little while but I think the coldest Decembers tend to be in the 27.5-28.5C range in Nino 4, and 2010, 2013, 2017 were in all in that zone.

 

 

[Ralph Wiggum]

3 hours ago, WxUSAF said:

If you want something positive to look at, select northern hemisphere MSLP anomaly on the 18z GEFS and scroll to about hr160+. Lots of red in Santa land means a -AO.

Is it correct that the AO and NAO phases are actually based on surface pressures more than 500mb/geopotential heights?

[cbmclean]

5 minutes ago, Ralph Wiggum said:

Is it correct that the AO and NAO phases are actually based on surface pressures more than 500mb/geopotential heights?

For what it is worth on the cpc page giving the NAO/AO conditions, the label says 500 mb for the NAO but 1000 mb for the AO.

.

 

[Ralph Wiggum]

5 hours ago, cbmclean said:

For what it is worth on the cpc page giving the NAO/AO conditions, the label says 500 mb for the NAO but 1000 mb for the AO.

.

"The North Atlantic Oscillation (NAO) is a weather phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level (SLP) between the Icelandic Low and the Azores High."

Source: https://www.google.com/url?sa=t&source=web&rct=j&url=https://en.m.wikipedia.org/wiki/North_Atlantic_oscillation&ved=2ahUKEwiVpf_FgfblAhWDdN8KHSCAAQAQFjAAegQIARAB&usg=AOvVaw0GhwXcCwaPNo9xghqVw1lN

Obviously I would be more inclined to side with CPC and how they determine the NAO but I found that wiki article contradictory of what the CPC uses to measure. It seems odd that two of the big oscillation patterns would be gauged on 2 different atmospheric levels....apples to apples sort of thing. 

[showmethesnow]

12 hours ago, frd said:

So much for their hot hand....................( well like they said -   need a few more runs ) 

 

 

 

And just like that it flips again. Too much variability between runs when it comes to what we are seeing in the EPO and WPO regions to take any one run with too much seriousness. Especially when just small changes can produce huge differences. 

 

[WxUSAF]

Lots of changes on the overnight GEFS run after thanksgiving. Models definitely having trouble with the Pac. But I’d certainly take what the GEFS is selling in early December.

[CAPE]

37 minutes ago, WxUSAF said:

Lots of changes on the overnight GEFS run after thanksgiving. Models definitely having trouble with the Pac. But I’d certainly take what the GEFS is selling in early December.

The 6z run looks even better than 0z. Pumps the EPO ridge and has more widespread cold over the lower 48. 

[poolz1]

Both the GEFS and the EPS pretty much agree with their own MJO forecast in the LR.  MJO on both models has been changing quite a bit over the past few days...just like the advertised H5 look over NA.  EPS likes a reemergence in phase 2 while the GEFS like phase 8/1.

SOI with another -27.36 today...same exact # as yesterday.  That doesnt happen too often..... 

[WxUSAF]

9 minutes ago, C.A.P.E. said:

The 6z run looks even better than 0z. Pumps the EPO ridge and has more widespread cold over the lower 48. 

Looks like Eps didn’t change too much. Maybe a bit larger area of high heights in the NAO domain and over the pole.

[Ralph Wiggum]

Geez, gorgeous GEFS runs at 6z and seeing some repeating themes. Noteworthy items...WAR which seems to always be a feature these days instead of locking in or feeding the SE ridge like last year appears to be more of a player in feeding the NAO ridge. Ridge N of Hawaii doesnt lock in destroying the ML Pac flow but rather appears to help pump and feed the EPO ridge down the road. AO goes bonkers negative and appears to hang in for the extended. Lower heights under the region as December approaches. CPF trying to set up. Split flow out West continues. Aleutian low does reload briefly but appears to setup again later on. There isnt anything not to like at this time tbh. I wouldnt call it a unicorn/epic or any of those terms but if verbatim is pretty much almost exactly what we would want to see moving forward. Of course some of this IS past 240 so grain of salt as always but even by day 8ish you can see the pattern reloading and key features trying ti redevelop so it may not be too far off in some of the ideas. I am especially intrigued by the base pattern that is slowly starting to show itself across all ens families. Getting there slowly but surely. Let's get thru next week because as I mentioned a few times, that seems to be the transitional week with a reloading or changing of the pattern. Want to see how we come out of that before celebrating any premature victories for the region(s).

[frd]

I enjoyed this post vey much and put more faith into it than the "weaklies"

 

 

 

 

[frd]

This is a great thread to read further. Ventrice and BammWX added comments here. 

Always so much to consider, the IOD, the standing wave, VP forecasts and the MJO progression.

 

 

[Bob Chill]

4 hours ago, WxUSAF said:

Lots of changes on the overnight GEFS run after thanksgiving. Models definitely having trouble with the Pac. But I’d certainly take what the GEFS is selling in early December.

Simplistic view would be to just watch the EPO/PNA. We're going to be fighting those teleconections for at least a week it seems. Probably longer. However, ens are certainly hinting towards a -EPO reload and the PNA trough rolling forward. If that does in fact happen then our first legit "snow window" should present itself sometime during the first 10 days of Dec. OTOH- if we keep getting teased with a +PNA/-EPO in the long range only to have a hostile pattern dominate then it could spell trouble for at least a portion of Dec even if we do have some help in the AO/NAO domains. 

As I've said multiple times... I have mixed feelings about Dec as a whole. Kicking the month off with a window where it can snow would be our first win. If the AO/NAO continue to cooperate into late Dec then it's possible to overcome a sh!tty Pac. That's way too far down the line to speculate on. Let's finish shoveling our early Dec storm before freaking out about the rest of the month. 

[OSUmetstud]

7 hours ago, Ralph Wiggum said:

"The North Atlantic Oscillation (NAO) is a weather phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level (SLP) between the Icelandic Low and the Azores High."

Source: https://www.google.com/url?sa=t&source=web&rct=j&url=https://en.m.wikipedia.org/wiki/North_Atlantic_oscillation&ved=2ahUKEwiVpf_FgfblAhWDdN8KHSCAAQAQFjAAegQIARAB&usg=AOvVaw0GhwXcCwaPNo9xghqVw1lN

Obviously I would be more inclined to side with CPC and how they determine the NAO but I found that wiki article contradictory of what the CPC uses to measure. It seems odd that two of the big oscillation patterns would be gauged on 2 different atmospheric levels....apples to apples sort of thing. 

The old NAO calculation used the SLP anomaly differential, but the new CPC one uses a 500mb height anomaly function. The AO is still calculated using SLP/1000mb heights. 

[dallen7908]

CPC outlook for Nov 26 to Dec 2 calls for above normal temperatures and precipitation for Maryland with higher than normal uncertainty (see below).  I'm curious as to why only the EPS is used in the blend. 

Is this common during uncertain periods because blends are only useful when the ensemble means are similar? 
---------------------------------------------------------
The official 8-14 day 500-hPa height blend consists of: 100% of Today's 0z
European Ensemble Mean centered on Day 11
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Below average, 2 out of 5, due to  
a relatively amplified pattern forecast over the domain, offset by significant  
differences between today's GEFS ensemble mean and the 0z ECMWF and Canadian  
ensemble means. 
 
FORECASTER: Mike C

[WinterWxLuvr]

16 minutes ago, dallen7908 said:

CPC outlook for Nov 26 to Dec 2 calls for above normal temperatures and precipitation for Maryland with higher than normal uncertainty (see below).  I'm curious as to why only the EPS is used in the blend. 

Is this common during uncertain periods because blends are only useful when the ensemble means are similar? 
---------------------------------------------------------
The official 8-14 day 500-hPa height blend consists of: 100% of Today's 0z
European Ensemble Mean centered on Day 11
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Below average, 2 out of 5, due to  
a relatively amplified pattern forecast over the domain, offset by significant  
differences between today's GEFS ensemble mean and the 0z ECMWF and Canadian  
ensemble means. 
 
FORECASTER: Mike C

Look at their confidence level.

[WxUSAF]

12z GEFS continues with poleward ridging near the west coast starting around the turn of the month. Ridging just off the coast supports a Plains centered trough, but the -NAO ridging mutes any SE ridge tendency. Still a pattern that probably doesn’t support much snow chances in early December, but one heading in a good direction. 

And LR has been volatile, so don’t get too cozy with any look. 

[psuhoffman]

There are some repetitive themes I like so far. One is that systems have amplified and traversed the 50/50 domain frequently.  Last year too often the WAR held and systems either amplified into Quebec or washed out.  It hasn’t helped us yet as you need a perfect setup this early, but if we continue to see that all winter it will pay off. 

[Rtd208]

Just an FYI DT (WxRisk) final winter outlook will be issued this Friday according to a Facebook post he made earlier.