December 2017 Mid-Long Range Disco 2

[CAPE]

0z Euro op has a cold front arriving 23-24th, and verbatim Xmas day looks to be cold and dry.

[BristowWx]

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

0z Euro op has a cold front arriving 23-24th, and verbatim Xmas day looks to be cold and dry.

Just like the GFS did...They must have collaborated on that one

[CAPE]

4 minutes ago, BristowWx said:

Just like the GFS did...They must have collaborated on that one

6z GFS looks a little stormy with the cold pressing in. Verbatim would be some rain-ice-snow for Xmas.

[CAPE]

1 minute ago, losetoa6 said:

Majority of Eps members have plumes of moisture streaming up to our necks . Christmas week could be some fun tracking it appears.

Yup looks like the cold presses in just in time for Xmas, and then maybe some chances shortly thereafter.

[BristowWx]

1 minute ago, C.A.P.E. said:

6z GFS looks a little stormy with the cold pressing in. Verbatim would be some rain-ice-snow for Xmas.

If that happens I’m buying you a nice Christmas present.  

[CAPE]

Just now, BristowWx said:

If that happens I’m buying you a nice Christmas present.  

A Bourbon barrel aged Imperial stout would work  

[aldie 22]

Just now, C.A.P.E. said:

A Bourbon barrel aged Imperial stout would work  

Got whiplash yet?

[CAPE]

2 minutes ago, leesburg 04 said:

Got whiplash yet?

Return of the SER. Story at 12z.

[showmethesnow]

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

Return of the SER. Story at 12z.

I think we have seen more tracking with realistic expectations so far this year then we saw the whole of last winter. Have to love it. If the whole winter ends up being like this I can see me suffering from lack of sleep and getting far behind on projects I am in the middle of.

[SomeguyfromTakomaPark]

40 minutes ago, Neblizzard said:

If those models are right , the pattern has great overrunning potential and with the SE ridge more suppressed on this run...we would likely be on the favorable side of the gradient. So after a brief relaxation , the pattern looks to be promising right around Christmas into the new year. 

Ah I love overrunning events, really hope to get a good one this year. 

[pasnownut]

Big picture takeaway to me is that we are nowhere close to any solutions, and any warmups are likely transient.  seeing that the pre christmas trough coming back to the east when 2 days earlier it was warmish says were not close.  Im not worrying about exact placement of this and that.  Seeing the WAR losing the war is great (but mind you can lead to suppression depression)...so beat him up, but dont knock him out.

Little bit of baileys in the coffee to keep us chill as we figure this out.  (PTO day...)

Nut

 

 

[Bob Chill]

Very nice split flow look across all ens developing during the holiday week. Models are starting to pick up on the ao returning to negative to go with it. Not ready to bite with all the jumping around but at least all 3 global ens agree on the same general look. Which could be very kind to us to close out the year....

[Bob Chill]

A lot of folks already know how to look at upper level panels and identify favorable setups but I threw together some quick (and sloppy) maps to show it visually. Split flow is something we say over and over again. Why is split flow good? It allows phasing of streams over the conus. Split flow isn't always good for snow in  the eastern US because just having split flow doesn't mean we're going to have a good storm track. 

All 3 global ens are showing favorable split flow for potential eastern US impacts. One of the key ingredients for our area is confluence to the north. What is confluence? Confluence is compressed upper level flow. Convergence zone where the isobars are tightly packed act like a block. Storms can't just cut north into this and it's something that folks in the MA like to see because it greatly reduces the chances of an easy cut to our N and/or W. Our favored confluence or convergence zone is over New England or the eastern tip of Canada

 

Here's some crude maps:

 

EPS h5 anomaly plot showing the upper level streams splitting and converging in a good spot in the conus. I circled the area of confluence to our north. This is a block that will keep storms from easily gaining latitude or cutting to our west (while bringing warm air with it). For reference, 500mb plots represent the atmosphere @ approx 18k'. 

If the area in the circle was filled with higher heights or a western atlantic rige (WAR) then the pattern wouldn't look at good because a WAR greatly increases the risk of warm air intrusion or a storm track to our N-W. This upper level plot shows a lot of key ingredients to produce snowfall in our area. 

 

This is the GEFS 250mb wind plot (or jet panel) for the same period. 250mb is approx 35,000 and is an important level to watch for jet placement and steering flow aloft. 

 

The Pac jet is split due to the EPO ridge. Some energy rides over top of the epo ridge and other energy can undercut the ridge and enter the US from the SW. The split stream converges right over us and to the N. Confluence is in place to our N as well to the storm track would be favorable. 

 

Even with what looks like favorable conditions, a lot still has to break right for us to get a snowstorm. Timing and placement of energy is every bit as important as the upper level flow. Those kinds of things can't be figured out until med-short range. I will say that the last few ens runs are showing a favorable pattern for more than conversational snow in the east. Now all we have to do is hope and pray the ens guidance has it mostly right down the line. That can be a tall order. lol

[weatherCCB]

7 minutes ago, Bob Chill said:

A lot of folks already know how to look at upper level panels and identify favorable setups but I threw together some quick (and sloppy) maps to show it visually. Split flow is something we say over and over again. Why is split flow good? It allows phasing of streams over the conus. Split flow isn't always good for snow in  the eastern US because just having split flow doesn't mean we're going to have a good storm track. 

All 3 global ens are showing favorable split flow for potential eastern US impacts. One of the key ingredients for our area is confluence to the north. What is confluence? Confluence is compressed upper level flow. Convergence zone where the isobars are tightly packed act like a block. Storms can't just cut north into this and it's something that folks in the MA like to see because it greatly reduces the chances of an easy cut to our N and/or W. Our favored confluence or convergence zone is over New England or the eastern tip of Canada

 

Here's some crude maps:

 

EPS h5 anomaly plot showing the upper level streams splitting and converging in a good spot in the conus. I circled the area of confluence to our north. This is a block that will keep storms from easily gaining latitude or cutting to our west (while bringing warm air with it). For reference, 500mb plots represent the atmosphere @ approx 18k'. 

If the area in the circle was filled with higher heights or a western atlantic rige (WAR) then the pattern wouldn't look at good because a WAR greatly increases the risk of warm air intrusion or a storm track to our N-W. This upper level plot shows a lot of key ingredients to produce snowfall in our area. 

 

This is the GEFS 250mb wind plot (or jet panel) for the same period. 250mb is approx 35,000 and is an important level to watch for jet placement and steering flow aloft. 

 

The Pac jet is split due to the EPO ridge. Some energy rides over top of the epo ridge and other energy can undercut the ridge and enter the US from the SW. The split stream converges right over us and to the N. Confluence is in place to our N as well to the storm track would be favorable. 

 

Even with what looks like favorable conditions, a lot still has to break right for us to get a snowstorm. Timing and placement of energy is every bit as important as the upper level flow. Those kinds of things can't be figured out until med-short range. I will say that the last few ens runs are showing a favorable pattern for more than conversational snow in the east. Now all we have to do is hope and pray the ens guidance has it mostly right down the line. That can be a tall order. lol

Nice Post Bob. Good to see most ens. showing split flow. Much better opportunity’s for real snow.  I stil feel ok about our chance for some

early pre or post holiday love.

 

[Wonderdog]

12z run for next Saturday at 12z shows a precip shield with less of a "bow" to it. Would that be due to less influence by the SER?

[Interstate]

4 hours ago, leesburg 04 said:

Got whiplash yet?

I do

[yoda]

Christmas Eve snow is always nice

[Wonderdog]

Nice look on Christmas Eve.

[WhiteoutWX]

Just now, yoda said:

Christmas Eve snow is always nice

Yet another completely different solution. I’m getting tired of saying that lol. The slightest bit more amplification of the SE ridge and this is rain for most people. The slightest bit more amplification of the northern stream wave and this probably all gets shoved south and it’s cold and dry. Razors edge stuff.

[Bob Chill]

Just now, WhiteoutWX said:

Yet another completely different solution. I’m getting tired of saying that lol. The slightest bit more amplification of the SE ridge and this is rain for most people. The slightest bit more amplification of the northern stream wave and this probably all gets shoved south and it’s cold and dry. Razors edge stuff.

No doubt man. Sure, the panel looks nice but it's sooooo delicate that buying into it is silly. I will say that some of the better runs for that period have a cutoff in the SW instead of a trough. Which makes sense because it allows the NS to dampen the se ridge and get us on the right side. I guess I'll root for a cutoff until something more interesting comes along. lol

[Jandurin]

1 minute ago, WhiteoutWX said:

Yet another completely different solution. I’m getting tired of saying that lol. The slightest bit more amplification of the SE ridge and this is rain for most people. The slightest bit more amplification of the northern stream wave and this probably all gets shoved south and it’s cold and dry. Razors edge stuff.

What are the chances of a massive city crippling snowstorm?

[Ji]

Bob,i thought i read somewhere where you said the AO was neutral in December which kind of screws our hope for a -AO winter. But this says otherwise( i mean not amazing negative)...are you using a diffrent way to measure ?

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index.html

[Ji]

5 minutes ago, Bob Chill said:

No doubt man. Sure, the panel looks nice but it's sooooo delicate that buying into it is silly. I will say that some of the better runs for that period have a cutoff in the SW instead of a trough. Which makes sense because it allows the NS to dampen the se ridge and get us on the right side. I guess I'll root for a cutoff until something more interesting comes along. lol

then when the cutoff comes out, we get our Jan 6,2017 blizzard

[Bob Chill]

Just now, Ji said:

Bob,i thought i read somewhere where you said the AO was neutral in December which kind of screws our hope for a -AO winter. But this says otherwise...are you using a diffrent way to measure ?

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index.html

I was projecting forward with current progs and estimating the monthly mean. The AO has been verifying above the gefs mean forecast all month so my guess is that continues. Looking at the 15 day forecast is looks like the AO will average above -1.25sd so this year will fall out of the group of previous -AO Dec years. When I broke down -AO decembers, Dec reading needs to be below -1.25 to correlate with a -AO Jan. 

Don't get me wrong though. Just because the AO prob won't average -1.25 for the month, it doesn't mean that we can't have a -AO in Jan or Feb because we can. The "easy signal" isn't there this year. That's really all I was saying. 

 

[Cobalt]

Christmas day as modeled by the GFS for the past 10 runs. Glad we've gotten to a consensus 

Just kidding. This is a very tricky pattern, so the GFS being this fidgety is kind of given

[Ji]

3 minutes ago, Cobalt said:

Christmas day as modeled by the GFS for the past 10 runs. Glad we've gotten to a consensus 

Just kidding. This is a very tricky pattern, so the GFS being this fidgety is kind of given

mostly blue though

[BristowWx]

3 minutes ago, Cobalt said:

Christmas day as modeled by the GFS for the past 10 runs. Glad we've gotten to a consensus 

Just kidding. This is a very tricky pattern, so the GFS being this fidgety is kind of given

the really warm solutions seem to be less prevalent.  not saying they wont happen but Torchmas seems less likely

[psuhoffman]

12 minutes ago, Bob Chill said:

No doubt man. Sure, the panel looks nice but it's sooooo delicate that buying into it is silly. I will say that some of the better runs for that period have a cutoff in the SW instead of a trough. Which makes sense because it allows the NS to dampen the se ridge and get us on the right side. I guess I'll root for a cutoff until something more interesting comes along. lol

We were rooting for less dump into the SW and instead it trended so far in that direction it ended up better off lol. 

[yoda]

After our Christmas Eve/Christmas Day "event"... GFS is mostly dry for us the rest of the run

[BristowWx]

1 minute ago, psuhoffman said:

We were rooting for less dump into the SW and instead it trended so far in that direction it ended up better off lol. 

I thought about that last night as I was looking at the 0z op run.  I was wanting a little SER and a dash SW.  the complete push through solution is cold but that's all.  Nothing to really track or get excited about.