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Bob Chill

December 2019 Med/Long Range Disco

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High pressure will consistently perform well this winter. That means sometime suppressive but sometimes good. We will have very few 33-35 and rain because of high being too weak.

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GFS also needs trough to get at least neutral to negative sooner for us to get in on the coastal. It's a strong storm sitting off the coast initially but precip isn't all that great because trough is still too positively titled.

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18z gfs has like 5 50/50s in 2 weeks. Lol. The one 10 days down the line pops a -nao. I'm going to start paying more attention to the 50/50 area because if LPs hanging out around there becomes a persistent feature this winter then good things will happen by default.

A 50/50 is the ultimate block for MA snow events. Has more influence on storm track than the AO or NAO. I highly recommend looping the NA or NH 18z gfs h5 and mslp anomaly panels and check it out. We can go entire years without a legit 50/50 and the gfs is throwing them out there like rice at a wedding 

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17 minutes ago, Bob Chill said:

A 50/50 is the ultimate block for MA snow events.

The 50/50 is so important for our area it is featured among DT's  checklist of MECS. 

I know he loves focusing on the QBO, but when he goes down his list of key features needed for the big ones, the 50/50 is always talked about in detail. 

The throwing rice at a wedding thing was a good one ......:lol:   I love these HH runs ! 

 

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2 minutes ago, frd said:

The 50/50 is so important for our area it is featured among DT's  checklist of MECS. 

I know he loves focusing on the QBO, but when he goes down his list of key features needed for the big ones, the 50/50 is always talked about in detail. 

The throwing rice at a wedding thing was a good one ......:lol:   I love these HH runs ! 

 

A 50-50 low really goes hand in hand with a -NAO though. Without the block, a vortex in the 50-50 region is mostly a transient feature, which is ok, but not the same as having a low trapped under a legit blocking ridge in the NA.

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29 minutes ago, Bob Chill said:

18z gfs has like 5 50/50s in 2 weeks. Lol. The one 10 days down the line pops a -nao. I'm going to start paying more attention to the 50/50 area because if LPs hanging out around there becomes a persistent feature this winter then good things will happen by default.

A 50/50 is the ultimate block for MA snow events. Has more influence on storm track than the AO or NAO. I highly recommend looping the NA or NH 18z gfs h5 and mslp anomaly panels and check it out. We can go entire years without a legit 50/50 and the gfs is throwing them out there like rice at a wedding 

There are several things I like seeing right now. The mjo being muted before it gets to the maritime continent. The sst in the north Pac. The tendency for troughs to kick out of the west quickly. But the one that I am most thrilled with is that almost every system this year is amplifying through the 50/50 space. The last few years systems would either get squashed or pull up into Quebec and the WAR would hold. This year everything else up a 50/50. Keep that up and it’s a ticking time bomb, only a matter of time before something goes off. 

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

A 50-50 low really goes hand in hand with a -NAO though. Without the block, a vortex in the 50-50 region is mostly a transient feature, which is ok, but not the same as having a low trapped under a legit blocking ridge in the NA.

It’s not as good in that they are temporary features and so the window is shorter. But if we get a year where everything wants to amplify through that domain it will create multiple opportunities to time something up. We will likely get some hits. It wouldn’t be 2010 epicness without a stout block but that tendency could be the difference between a sub par year and a pretty good one. 

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Just now, psuhoffman said:

But the one that I am most thrilled with is that almost every system this year is amplifying through the 50/50 space. The last few years systems would either get squashed or pull up into Quebec and the WAR would hold. This year everything else up a 50/50. Keep that up and it’s a ticking time bomb, only a matter of time before something goes off.

Thought I read this might be related to the SST profile up there. 

Over the summer when we had the periodic bouts of -NAO it was mentioned the cold pool was responsible. 

Do you have any thought on it  psu?   Secondary guess would be wave breaking, but not sure.  

And yeah, love seeing this.  

 

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

A 50-50 low really goes hand in hand with a -NAO though. Without the block, a vortex in the 50-50 region is mostly a transient feature, which is ok, but not the same as having a low trapped under a legit blocking ridge in the NA.

Very true, it has been so long that we have had all the players working for us in our favor. ( ie. the 50/50 or a -NAO leading to a HA event, etc. )  I miss the Big Dogs !  The atmosphere may want to cooperate this winter. 

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Just now, psuhoffman said:

Gefs starting to look like the euro heading towards mid December. 

Wish HM would pop in and chime in on that map, from a HL point of view. . I might want to guess and say it looks at 500 as a precursor pattern for further vortex weakening.  

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Just now, psuhoffman said:

It’s not as good in that they are temporary features and so the window is shorter. But if we get a year where everything wants to amplify through that domain it will create multiple opportunities to time something up. We will likely get some hits. It wouldn’t be 2010 epicness without a stout block but that tendency could be the difference between a sub par year and a pretty good one. 

Yeah that's my point- vortices rotating through the 50-50 region absent a NA block are thread the needle deals. I will take that over having higher heights in that region every time though for sure. But no way in  hell I believe that is the ultimate/ better or equivalent to having a sustained -AO/NAO.

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

A 50-50 low really goes hand in hand with a -NAO though. Without the block, a vortex in the 50-50 region is mostly a transient feature, which is ok, but not the same as having a low trapped under a legit blocking ridge in the NA.

Yep, best setup is always a -nao with a 50/50. Even in progressive flow a transient 50/50 can still help block an upstream shortwave from scooting north of us. Looking at the loops of multiple recent gfs runs there's a recurring theme of tracking pretty strong LPs through the 50/50 space. Oh please please please let this be the dominant storm track this season...

6 minutes ago, psuhoffman said:

There are several things I like seeing right now. The mjo being muted before it gets to the maritime continent. The sst in the north Pac. The tendency for troughs to kick out of the west quickly. But the one that I am most thrilled with is that almost every system this year is amplifying through the 50/50 space. The last few years systems would either get squashed or pull up into Quebec and the WAR would hold. This year everything else up a 50/50. Keep that up and it’s a ticking time bomb, only a matter of time before something goes 

Agree 100%. We're seeing a lot of features we want working in unison. Started early this month and isn't letting up. Ens agree on a +pna building during the first week of Dec. If flow remains active and doesn't dry up we'll be in the game for a warning level event and not dealing with jacked up flawed light events. 

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For the weekend system the latest Gefs is much less progressive then 12z looking at most members . Several going negative tilt and hugging the coast.  The overall h5 evolution has changed so much the past 24 hours and we have so long to go . Nothing but positive steps today .I'm pretty stoked about tracking the next several days.  Probably be late Thursday before the track is  sorted out. 

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

 But no way in  hell I believe that is the ultimate/ better or equivalent to having a sustained -AO/NAO.

I wasn't implying that a transient 50/50 is better than a -ao or nao or anything like that. I was just saying that 50/50 has the most direct impact in keeping upstream waves from cutting west of us. We get west tracks with a -ao/nao and it's nearly always because there was no 50/50 to block a storm from gaining too much latitude. Most of our big events in +ao/nao patterns are lucky timing with a 50/50 on the move. 

Another thing I've been noticing lately is wave spacing has been really favorable. Storms are getting wound up without getting beat up, sheared, or tugged around by crowded flow. 

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10 minutes ago, Bob Chill said:

Yep, best setup is always a -nao with a 50/50. Even in progressive flow a transient 50/50 can still help block an upstream shortwave from scooting north of us. Looking at the loops of multiple recent gfs runs there's a recurring theme of tracking pretty strong LPs through the 50/50 space. Oh please please please let this be the dominant storm track this season...

 

Agree with this. I probably misinterpreted your post. I thought you were suggesting a 50-50 vortex (transient or otherwise) was more important than having a -AO and or -NAO. A -NAO/50-50 combo is absolutely the ULTIMATE block imo to force a favorable storm track for MA snow events.

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While this is focused on “major snow events” in the Philly region, I found it a quick, easy read on the major factors to look for in our area (50/50, NAO, EPO, etc).  DT helped put it together based on the credits.  Some of the specifics for things that work well for them aren’t the case here but still a handy read.  You’ll notice they use images from the KU textbook.

https://www.abington.k12.pa.us/teachers/hurmms/Majorsnowstormchecklist_files/Stormchecklist.ppt

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18 minutes ago, nj2va said:

While this is focused on “major snow events” in the Philly region, I found it a quick, easy read on the major factors to look for in our area (50/50, NAO, EPO, etc).  DT helped put it together based on the credits.  Some of the specifics for things that work well for them aren’t the case here but still a handy read.  You’ll notice they use images from the KU textbook.

https://www.abington.k12.pa.us/teachers/hurmms/Majorsnowstormchecklist_files/Stormchecklist.ppt

I have seen that before. Pretty good presentation.

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1 hour ago, frd said:

Thought I read this might be related to the SST profile up there. 

Over the summer when we had the periodic bouts of -NAO it was mentioned the cold pool was responsible. 

Do you have any thought on it  psu?   Secondary guess would be wave breaking, but not sure.  

And yeah, love seeing this.  

 

I’ve always suspected the North Atlantic Tripoli sst look was more an effect than a cause. As @Bob Chill often points out a few degree difference in cold waters in the high latitudes isn’t changing the equation that much. The difference between 42 and 50 degree water is not adding as much heat and moisture to the atmosphere as a change from 78 to 86 degree water.  Imo the warmer SSTs near Greenland are from the ridging with a -NAO and the colder sst near New Foundland is from the constant parade of storms forced through that region by the NAO blocking.  Because the NAO tends to run in multi year cycles that can create the mirage of causality at times.  I do think there is a feedback cycle though that can contribute.  For instance, the colder sst profile in the 50/50 domain is often caused by storminess there, and enough storms blowing up there can help contribute to ridging into the NAO domain.  So there can be a chicken or the egg type play there.  For now I’m not going to over think it.  It’s just plain good to see lots of lows bombing into the 50/50 space.  If that continues it will up our chances significantly. 

 

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20 minutes ago, WxUSAF said:

He’s never predicted below average snowfall in the last 6 years. Very on brand. 

Even during the back to back La Niña’s when odds of climo snow are like 18% he predicted above both years!  Rotfl 

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

Agree with this. I probably misinterpreted your post. I thought you were suggesting a 50-50 vortex (transient or otherwise) was more important than having a -AO and or -NAO. A -NAO/50-50 combo is absolutely the ULTIMATE block imo to force a favorable storm track for MA snow events.

The NAO is really important for our monster storms though. In order to score the big ones we need either the 50/50 or a displaced PV under it acting like a 50/50. That is when we get really crushed.

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