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Mid October 2019 Bombogensis Coastal


Ginx snewx
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18 minutes ago, jbenedet said:

I do think this evolution would make a whole lot more sense, physically, if there was a tropical disturbance off the southeast coast prior to the approach of the UL trough across the Midwest. There is a weak surface trough that stalls just off  the SE coast tomorrow. Some guidance shows shower activity and clouds collocated in that region. I’ll be focusing on that area tomorrow to see if there’s any sign of tropical development...

Looks like all the models are hinting at this (though NAM is most aggressive) but the NAM goes wild with convection across the southeast late tomorrow afternoon/evening and looks like it develops some sort of sfc low which then propagates northeast and then just goes wild as it interacts with the digging trough. 

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12 minutes ago, 40/70 Benchmark said:

It definitely underperformed relative to consensus forecasts.

I, along with many others here, never expected much.

IDK wind and rain on the Cape were impressive  less than those crazy runs for sure . 50 miles off. I don't even take verbatim outputs until 18 hrs ahead.  Winter especially.  No sense getting worked up. We post maps and outputs to generate discussion. Naysayers and doomsayers fail all the time. Best to watch closely trends and of course the actual weather.  Just dismissing out of hand when viable options are on the table always strikes me as weird.  Of course the odds are they will be right but when they are not ..... stay aware

 

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In any case ... this NAM -focused speculation and analysis is intriguing, but as some of these more recent poster's are exposing/hinting toward ... there is a velocity contamination/bias in the general circulation theme that hasn't really gone away - I'm wondering if a NAM tucked in and slower deep layer evolution really fits here.

The NAM solution(s) are either A, onto some physical means to compensate for that W-E smearing of a speed rich field, or, B, is not conserving that, which is empirically and modeled to be the case by the bevy of guidance.  The Euro being perhaps mid way between the GFS and NAM is what it is ..but I see it's backing off on the intensity between 12z yesterday and 00z last night, as both unusual discontinuity for that particular guidance inside of D4.5, but also a signal that this is an unusual scenario and even the more sophisticated tools are less than ideally handling.  

The usual nature of it is that we are rich beyond the dreams of avarice with mid level mechanics, but there's really nothing but weak baroclinic gradients between BTV and Gulf Stream in the lower troposphere ( compared to typical bombogen set ups... I mean there's some, sure - ).  With all that potential and not much to drill the cyclogen down to the surface, the NAM ( and to some extent all of them ...) seem to be latching onto geese farts ( thank you Weatherwiz!) and going "butterfly effect" with them. 

The NAM's variation on this is to take either a convective fed-backed low over the deep SE, or ...if it somehow manages to evolve a hybrid TC in such short order ( dubious as an undertaking...), it uses that feature to do said drilling - which having that much DPVA and Q-G forcing ridging off the upper M/A ...it's more than happy to do so. The problem: is its surface reflection in the deep SE even real?   Good question... Now cast that - 

Personally I feel the GFS may not be a bad way to go. I'm utterly sick to the point of throwing hands at the velocity surplus at all scales and dimensions we've been plagued with during autmns and winters ... now looking back to the late 1990s and it's increasingly the base-line character of the larger planetary circulation over this side of the hemisphere ( I haven't honestly focused on SE Eurasia and/or middle latitude Asia but I suspect it's observable there...). And these system embedded in fast flow ... it just seems the NAM, perhaps for not being a Global-scaled tool and having a finite domain space... maaaybe just allows it to 'get away' with not conserving the speed overall of the flow for complicated reasons with velocity/mass and R-wave distribution..

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29 minutes ago, powderfreak said:

Crushes parts of Maine with snow... Allagash Wilderness gets caked.

Might even get some summit level snows on the cyclonic flow up this way but need another 1C to really get excited.

:lol: 18", What a long winter this is going to be with this GFS...............

image.thumb.png.683959b23c119daee42143f1673d0e6f.png

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23 minutes ago, weatherwiz said:

Looks like all the models are hinting at this (though NAM is most aggressive) but the NAM goes wild with convection across the southeast late tomorrow afternoon/evening and looks like it develops some sort of sfc low which then propagates northeast and then just goes wild as it interacts with the digging trough. 

Yeah.  I don't think the NAM/EURO super friend compromise is too far off if the ridge out west keeps building.  A minor difference in amplitude of the ridge seems to deepen the trough, as well as slows things down just enough to blow up and amplify the Atlantic ridge to it's NE.  This seems to enable the trough to go negative.  

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6 minutes ago, dryslot said:

:lol: 18", What a long winter this is going to be with this GFS...............

 

The NAM did something similar over VT.

The 12z GGEM just brought like a foot of snow to the higher peaks of the Adirondacks.

Picnic tables across the northeast are put on notice.  Could be a real summit thumper somewhere... like 6" at 4,000ft and 0" at 3,500ft ha.

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2 minutes ago, powderfreak said:

The NAM did something similar over VT.

The 12z GGEM just brought like a foot of snow to the higher peaks of the Adirondacks.

Picnic tables across the northeast are put on notice.  Could be a real summit thumper somewhere... like 6" at 4,000ft and 0" at 3,500ft ha.

Well, Its not going to be where the GFS has it here, Katahdin maybe, Not back to that NW, There's not a lot of ele in that area......................lol

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9 minutes ago, Tornadocane said:

Yeah.  I don't think the NAM/EURO super friend compromise is too far off if the ridge out west keeps building.  A minor difference in amplitude of the ridge seems to deepen the trough, as well as slows things down just enough to blow up and amplify the Atlantic ridge to it's NE.  This seems to enable the trough to go negative.  

I'm not so sure this thing will slow down enough to make that happen. The front doesn't seem to be totally parallel to the upper-flow and there really is no (strong enough) high to the east to slow the eastward progression. Everything seems to be pointing towards a rather progressive solution here...so despite good rain potential that's why I don't think we'll have to worry too much about flooding. 

Another wild card too is how does the rain/convection evolve across the southeast tomorrow. The atmosphere will be pretty juiced (pretty high PWATs) and you have the stationary front nearby so I'm sure there will be a decent slug of rain and scattered t'storms in the southeast. Just seems to me though that (at least the NAM anyways) is being a bit too sensitive with the s/w's which traverse across the southeast tomorrow. 

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25 minutes ago, powderfreak said:

12z GGEM goes over Tolland... might get some SE MA into the warm sector on the east side looking at the temps.

I'm not sure I have a problem with this ending up being a middling low that passes inland.

Perhaps folks are rusty?  - we need this seasonal "primer" to lube up the gears of obviousness again ( for when this sort of eval has got a chance to mean anything worth while haha). But all tech rhetoric aside?  There's really no cold air in place.

Cold air below 700 mb is a damming... and, it supplies a focused frontal slope around the traditional interface axis oh... circa southern NJ to ACK ... If there is a strong low level thickness packing along that land cold air to warm oceanic interface, than as the Q-G forcing encroaches from the digging trough, the excited inflow then incurs upon that elevated slope, and it makes UVM go nuts - because of the conversion of latent heat to heat of condensation adding lift...yadda yadda yadda the low at the surface tends to organize under that UVM "chimney" etc etc..

But none of that can happen here/given what's up in the models.  So, the low can move a bit more non-traditionally along an axis that is more directive of what is happening purely at mid levels -

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6 minutes ago, Typhoon Tip said:

I'm not sure I have a problem with this ending up being a middling low that passes inland.

Perhaps folks are rusty?  - we need this seasonal "primer" to lube up the gears of obviousness again ( for when this sort of eval has got a chance to mean anything worth while haha). But all tech rhetoric aside?  There's really no cold air in place.

Cold air below 700 mb is a damming... and, it supplies a focused frontal slope around the traditional interface axis oh... circa southern NJ to ACK ... If there is a strong low level thickness packing along that land cold air to warm oceanic interface, than as the Q-G forcing encroaches from the digging trough, the excited inflow then incurs upon that elevated slope, and it makes UVM go nut - because of the conversion of latent heat to heat of condensation adding lift...yadda yadda yadda the low at the surface tends to organize under that UVM "chimney" etc etc..

But none of that can happen here/given what's models.  So, the low can move a bit more none- traditionally along an axis that is more directive of what is happening purely at mid levels -

Makes a lot of sense visualizing that.  

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23 minutes ago, powderfreak said:

Makes a lot of sense visualizing that.  

Yeah and I mean it could still detonate a deep nuke but the mid levels forcing the rising motion of the air would have to be deeper in latitude and approaching more from the SW/SSW.. Therein we get into the W-E progressivity vibe in the atmosphere and this initially an open wave coming through the Lakes that deepens and 'fake' closes off but gliding over the top of the still seasonally expanded subtropical ridging exerting from S...

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