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January 12-14, 2019 Storm Discussion STORM MODE


WxUSAF

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3 minutes ago, psuhoffman said:

It was an absolutely awful run if we were holding out hope for more then a very low end event from the WAA.  That system crashing into CA is a big problem...it undercuts the western ridge and links up with the elongating/compressing trough and helps to flatten it even more which pretty much kills any chance for the coastal to amplify.  

That's a bingo. Anything north of DCA right now is looking pretty bleak. The early QPF is a write off and the main body of the 'storm' is compressed south.

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4 minutes ago, Wonderdog said:

I have the feeling I won't be using the , well you know....

 

I suppose not if you believe the GFS depiction at h5.  not ready to write it off just yet when there are other solutions on the table.  I guess if the Euro looks similar then I guess it was not meant to be this go around. 

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1 hour ago, psuhoffman said:

A southern system moving west to east that transfers from the TN valley to the coast is not a miller b.  I have seen that classified as an a/b hybrid since there is a fairly significant transfer and redevelopment involved but it's not the same category as a northern stream system diving in and then transferring energy to a developing coastal with little STJ involvement.   The hybrid types are actually some of our biggest snowstorms while the true northern stream miller b's are mostly a disaster scenario for anyone southwest of the Philly area.

I am not even sure I agree with some of the "hybrid" categorization.  Yea there is a jump and redevelopment of the surface system but that is really just mostly a function of the southern wave taking enough of a northerly track initially that it ends up running into the Apps and enough resistance to force a jump.  When the storm tracks along the gulf coast it can turn the corner unimpeded and you get some jump often...from southern GA to the SC/NC coast often...as it approaches the coastal baroclinic zone and leaps...but it's not as noticeable as the transfer from TN to the NC coast and without mountains there to interfere the redevelopment isn't as extreme.  

But its not the same interaction really as the pure miller b and often doesn't involve as complicated a phasing scenario.  Also...it usually is only an issue when the system is weak.  Yea when the initial TN valley system is falling apart and washing out it creates the illusion that we have the same problem as with a miller b where the coastal can form too late...but that is simply because the initial system was weakening and would have weakened and the precip would have been shredded by the mountains and done little for us even without the coastal development.  If you get a healthy amplifying system up into TN that then jumps to the coast...that is the setup for some of our biggest snowstorms (assuming there is a cold high in place).  We get the initial WAA thump, then with a healthy system transferring we will also get into the CCB of the developing coastal.  Or sometimes, like the January 2004 system, the coastal will get crushed by the flow and miss...but we still got 5-8" around here from the initial wave to our west so no one cared much.  The issue here is that the system is being compressed and washing out NOT the transfer and redevelopment.  

Answers;

I did not and do not consider this a true miller B, but it has similar evolution. Call it what you will. Hybrid makes sense to me. There is a transfer. That is my problem as we live in the jip zone  

In this setup flow is progressive and not buckled enough for enough time for transfer to work back here. I don’t care about NJ.  

NS energy is shredding primary and that is and will likely be the death of this up here. 

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40 minutes ago, Bob Chill said:

We all need to drink Molson and support the CMC. 

gem_apcpn_neus_19.png

I am more of a franziskaner fan myself but if that is the best run sure.   What I am about to say only pertains to the MD northern tier peeps but even on the CMC I don't like that NW to SE trajectory to the precip, really shows how the shred factory is winning out here.  That bothers me wrt getting a north adjustment later.  When we see that kind of trajectory, those are the storms that have tended NOT to adjust north at the end.  Think...Feb 5 2010, the first wave from March 2013 (yea I know it was rain in DC but up here I was counting on a north bump to the heavy precip and it didnt happen), both March 2014 storms... when you see that kind of thing often we fail to see any improvement at the end because the system is weakening and in that case the confluence to the north wins the fight.  With an amplifying system usually it's the opposite.

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Personally us northerners i think will get into some decent ratios and some at least decent banding as the first wave moves in. Pretty decent vort is gonna pass and there is plenty of lift. Coastal would be a bonus but i think we have to bank on a decent lead wave. Temps at the surface and aloft are plenty cold.

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15 minutes ago, pasnownut said:

Answers;

I did not and do not consider this a true miller B, but it has similar evolution. Call it what you will. Hybrid makes sense to me. There is a transfer. That is my problem as we live in the jip zone  

In this setup flow is progressive and not buckled enough for enough time for transfer to work back here. I don’t care about NJ.  

NS energy is shredding primary and that is and will likely be the death of this up here. 

Our problem isnt the transfer its that the initial system is washing out long before it gets here and the coastal is weak and blocked from gaining latitude and with no upper level support due to a compressing de amplifying flow.  Most of our best snowstorms take a track up into the TN valley then "jump" to the coast.  If the whole system was amplifying and not shearing out it wouldn't be a problem.  

Even if there was no coastal at all the result would be the same...some light snow from the frontrunning WAA wave then nothing.  But there HAS to be a jump with any storm that tracks west then is forced under a high...it isn't going to track right over the mountains and through the CAD.  But those are actually our best storms, so long as the flow isnt hostile like this.  

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Things are starting to unravel a bit. Low end is now a possible shut out because .1-.2 on globals can actually mean nothing on the ground — dry mid levels, shadowing off blue ridge, etc) if were expecting 2-3” as the coastal is pulling away... tell me how many times that’s worked out. 1-2” would be a BIG win at this point imo 

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4 minutes ago, WxUSAF said:

To slightly polish the turd that is the 12z GFS, during the WAA snows, the DGZ is quite deep and there is some weak/modest lift within it.  Ratios should be a bit better than 10:1 if this were to verify.  

gfs_2019011012_fh60_sounding_39.28N_76_83W.thumb.png.c406d9c0568d862ef16bfc30854eded8.png

At this point my hope is that the Waa can juice up some to get a wide spread 2 to 4 / 3 to 5 inch event. With good ratios I think it's definitely possible.

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1 minute ago, WxUSAF said:

To slightly polish the turd that is the 12z GFS, during the WAA snows, the DGZ is quite deep and there is some weak/modest lift within it.  Ratios should be a bit better than 10:1 if this were to verify.  

gfs_2019011012_fh60_sounding_39.28N_76_83W.thumb.png.c406d9c0568d862ef16bfc30854eded8.png

That is a good look. However I’m now concerned about spacing and timing of the transition of the slp. The moisture that is coming over the blue ridege is light as depicted. I’ve seen models overestimate the ability of that moisture transport to overcome that natural barrier. I was relying on the coastal transitioning quickly and taking a slight jog up the coast as it exits. Without that scenario we’re relying on our first 1-3” inches of snow to come by way of the front end crossing the blue ridge. Then a late coastal addition of another 1-2”. I just see way too many ways to fail on this one. My main point is I don’t like how we are positioned in the transitional zone of the handoff to the coastal. 

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Just now, Maestrobjwa said:

Pardon the amateur question, but what exactly is the WAA again? (and the DGZ?)

WAA is Warm Air Advection.  Warm air riding into colder air.  

DGZ is Dendritic Growth Zone.  If you look at the left side of the image above you will see two dashed red lines and yellow horizontal bars.  The bar represent rising air and you want to see the best rising air concentrated within the zone of the clouds where snow crystals form.  The longer and deeper you can sustain that, the better the snow accumulations will be.

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Just a small reminder that about 2-3 days ago we all thought this would be a weak (cold) strung out event with modest totals. Everyone loved that idea. Now a lot of people hate it. lol. Nearly every single storm will have "max potential" runs in the mid range. If you toss them 100% of the time you will be right 80% (or more) of the time. We're still on track for the original idea of a cold strung out light event. Is it really that bad? (don't answer Ji)

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Just now, Bob Chill said:

Just a small reminder that about 2-3 days ago we all thought this would be a weak (cold) strung out event with modest totals. Everyone loved that idea. Now a lot of people hate it. lol. Nearly every single storm will have "max potential" runs in the mid range. If you toss them 100% of the time you will be right 80% (or more) of the time. We're still on track for the original idea of a cold strung out light event. Is it really that bad? (don't answer Ji)

So at this point you see very little evidence that has us whiff completely north of EZF?  Like the WAA dries up/ blows by with little impact and coastal rides OTS.  I know nothing is guaranteed but of the things that concern you... is this one?

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3 minutes ago, Bob Chill said:

Just a small reminder that about 2-3 days ago we all thought this would be a weak (cold) strung out event with modest totals. Everyone loved that idea. Now a lot of people hate it. lol. Nearly every single storm will have "max potential" runs in the mid range. If you toss them 100% of the time you will be right 80% (or more) of the time. We're still on track for the original idea of a cold strung out light event. Is it really that bad? (don't answer Ji)

Exactly.  If you were firmly on the 2-4" train (which I was), then nothing has really changed.  Just bounced around that value.  It's going to be a really pretty wintry-feel weekend.  Looking forward to it.  

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2 minutes ago, Maestrobjwa said:

Pardon the amateur question, but what exactly is the WAA again? (and the DGZ?)

Very quick rundown of the common acronyms we use all the time. This should help anyone who is afraid to ask but wants to know. 

WAA: warm air advection precip happens on front side of approaching low pressure. Look at mid level 850 wind panels and it makes sense. Winds are always southerly but most commonly southwesterly. Hence the name "warm air" because it's coming from the south. 

CCB: cold conveyor belt. This is on the backside of low pressure. Usually cold/dry/fluffy snow. Again, look at the the mid level 850 wind panels. During CCB mid level winds will be out of the north/northeast/northwest. This draws down colder air and is also where our highest ration snow comes from.

DGZ: is the level of the atmosphere where snowflakes are produced. Sometimes this can suck and we get sand/needles/dust and other times it can be beautiful big fluffy dendrites. This is also a complicated topic so I'm not going to even remotely explain why some storms are good and others bad. 

 

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4 minutes ago, Bob Chill said:

Just a small reminder that about 2-3 days ago we all thought this would be a weak (cold) strung out event with modest totals. Everyone loved that idea. Now a lot of people hate it. lol. Nearly every single storm will have "max potential" runs in the mid range. If you toss them 100% of the time you will be right 80% (or more) of the time. We're still on track for the original idea of a cold strung out light event. Is it really that bad? (don't answer Ji)

I think the worry is that we are moving away from a light event and towards a whiff.  That’s not the model consensus but after the last few winters peioke are scared!

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5 minutes ago, Bob Chill said:

Just a small reminder that about 2-3 days ago we all thought this would be a weak (cold) strung out event with modest totals. Everyone loved that idea. Now a lot of people hate it. lol. Nearly every single storm will have "max potential" runs in the mid range. If you toss them 100% of the time you will be right 80% (or more) of the time. We're still on track for the original idea of a cold strung out light event. Is it really that bad? (don't answer Ji)

2 to 4 would be a huge win.  That being said I dont think many of us see that.

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