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Coldtober model and pattern disco


Damage In Tolland
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The euro ensembles look like a mild period after next week but then reload on the cold pattern. Right around Halloween. We'll have to see if the timing changes or if the pattern doesn't materialize, but that could be a good pattern going into early November for an early season event. 

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28 minutes ago, dendrite said:

It's cute how the title and subtitle of this thread magically changed with the phase change to a -DIT.

Yeah, but what’s not quite as cute are all the hotel guests up here that are freezing their azzes off in drafty rooms after the resorts were informed that they wouldn’t be uninstalling A/C units until November.  They really should know better.

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25 minutes ago, ORH_wxman said:

The euro ensembles look like a mild period after next week but then reload on the cold pattern. Right around Halloween. We'll have to see if the timing changes or if the pattern doesn't materialize, but that could be a good pattern going into early November for an early season event. 

How mild does it look? 

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Intense cold floods in overnight Wednesday, night ...  Thursday a.m. dawns head scratching extreme ..relative to present calendar climo.  And it's not radiational, either.  

-8 to -12 C at 850 mb level with 30 mph gusting prior to Halloween is disturbing ... if perhaps not getting the notice it should because we are jaded by extreme-saturation. 

hm .. Euro not as intense as the NAM  ... at the warm end of that, but... either solution are disturbingly early for that sort of depth -

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21 minutes ago, USCAPEWEATHERAF said:

12z GFS shows a really high amplitude arctic shortwave jet system entering the Great Lakes around hour 100-108 out could be enough to spawn its own nor'easter.

What do you mean could?  It does become a coastal storm, just not where you want it to.  Best forcing/dynamics are well N up by NS.

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3 hours ago, HoarfrostHubb said:

First freeze for many incoming.  End of the growing season

I agree.  I touched 32° the other day but this looks like a freeze.

I'm not sure what BOX with this PnC forecast for my location:

Quote

Thursday Sunny, with a high near 42. Northwest wind 9 to 14 mph, with gusts as high as 25 mph.
Thursday Night Mostly clear, with a low around 30. Northwest wind 5 to 8 mph becoming calm after midnight.

With clear skies and calm winds, I'd expect more than a 12° drop in temps come morning.  Am I missing something?

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Just now, MetHerb said:

I agree.  I touched 32° the other day but this looks like a freeze.

I'm not sure what BOX with this PnC forecast for my location:


Thursday Sunny, with a high near 42. Northwest wind 9 to 14 mph, with gusts as high as 25 mph.
Thursday Night Mostly clear, with a low around 30. Northwest wind 5 to 8 mph becoming calm after midnight.

With clear skies and calm winds, I'd expect more than a 12° drop in temps come morning.  Am I missing something?

This air mass coming in is deep, with thicknesses plumbing to an unusually deep sub 525 dam in dale - which for mid October is pushing extremeness.

That said... yeah, it's possible the wind doesn't actually go calm?  The high is slipping SW of us ...different than retreating NE... that may cause the wind to bend back SW, thus keeping the low levels quasi-better mixing with dry warm advection kicking in over night.... Where it does go "calm" would be restricted to decoupling in favored geographies in the deep interior, but most don't..  The wind just starts veering NW --> WNW toward dark --> WSW by 1am Friday morning at 10 kt wooshes... --> SW at dawn on Friday.  Meanwhile, the overnight low temperatures nadir near 11:50 to 1:38 ...after which, steady and/or slowly rises. In fact, just looking at that Euro's 12z run, it does show the thickness plume bodily moving away with a diffuse warm boundary moving quickly through 12z Friday.  Heh...could be a spectacular day despite.  

 

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14 minutes ago, Typhoon Tip said:

This air mass coming in is deep, with thicknesses plumbing to an unusually deep sub 525 dam in dale - which for mid October is pushing extremeness.

That said... yeah, it's possible the wind doesn't actually go calm?  The high is slipping SW of us ...different than retreating NE... that may cause the wind to bend back SW, thus keeping the low levels quasi-better mixing with dry warm advection kicking in over night.... Where it does go "calm" would be restricted to decoupling in favored geographies in the deep interior, but most don't..  The wind just starts veering NW --> WNW toward dark --> WSW by 1am Friday morning at 10 kt wooshes... --> SW at dawn on Friday.  Meanwhile, the overnight low temperatures nadir near 11:50 to 1:38 ...after which, steady and/or slowly rises. In fact, just looking at that Euro's 12z run, it does show the thickness plume bodily moving away with a diffuse warm boundary moving quickly through 12z Friday.  Heh...could be a spectacular day despite.  

 

Yeah, I could see temps bottoming out in the "middle" of the night and going steady.  I'm just thinking a 15-20° drop is more likely.  I realize I'm only talking a few degrees at the low end but I think 12 is a little too conservative all things considered.  You'll get a few degrees drop with sunset and with Dp's in the 20's it would be easy to drop a few more as the wind goes calm before bottoming out.

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Well anywho... 

I agree with the general theme/interest scope for wintry expression - anomalously so ... but to what degree, who knows - during the end days of October through early to mid November. 

The reason(s) for suspecting that ...isn't really even discernible in the operation versions yet. 

The mean is heavily clustered around a tandem dive in the AO/NAO ... It is hard to know which is dominant in that relationship, as they only partially over-lap domain space. In fact, the NAO is deeper in the mean SD ...so it may in fact be the NAO "pulling" the AO down.  Either way, multi-day cycles have persisted with -SD values exceeding anything we have seen since last late February and Early March. 

Caveat emptor:  ...west vs east based, should this blocking episode succeed?   don't know - 

Last February was balmy ... culminating in a bewildering week of warmth mid to 2/3rds of the way through the month.  The warmth breaks/displaces away, and ten days later, the NAO tanks. I am not sure that "relay" is in fact unrelated as it is noted the WAA terminating at high latitudes/altitudes often mark the onset of blocking regimes ... We are passing out of a similar eastern N/A ridge over the last week, while these NAO teleconnector at both the CDC and CPC showing a similar corrective behavior.  

The other aspect is that the lead phases of the PNA and EPO support cold loading on our side of the hemisphere ... and this at large scales also may parlay at cold delivery/efficiency. It strikes me actually as a bit of a redux to 2011 ...which I don't mean to say that's destined to repeat, but a similar enhancing probability for cold and enhancing QPF is acceptable.   

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