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Late February will be rocking. February Long range Discussion thread


Ji
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11 minutes ago, Stormchaserchuck1 said:

There are signs of a -NAO/-AO developing in the first week of March on LR models, with a +120dm anomaly over the arctic circle at 384hr on the 18z GEFS. I think initially we will even out the cold signal with -PNA/+EPO-even, but watch to around March 7/8-18 for a possible window,bridge between the Pacific/Atlantic. (10mb warmings don't always downwell to -NAO+time, but about 70% of the time they do.) 

70% of the time…it works every time 

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13 minutes ago, BristowWx said:

70% of the time…it works every time 

I'm doing more research on this "when the NAO/AO go negative in the first week of March, the PNA and EPO will flux (- and +)". On 3-1, where the current D15 ensemble mean model shows a +300dm -PNA (strong signal), in the last 3 years we had a strong PNA signal on this date 3/3 times (0/7 years previous). 

-minus 2022

+plus 2021

+plus 2020

This is what they looked like 3.9-12

compday.SmfgOgc7lH.gif.e255d852a828c33d02ca39f8656c2b37.gif

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Is that actually happening now?

It appears it’s happening. The problem is, we have no clue how it’ll impact us, and models will likely be even more volatile than usual as they try to figure it out over the next week or so. Have a feeling models are going to be all over the place. Hopefully this SWW does what we need it to and doesn’t fail in disrupting the PV.
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28 minutes ago, jayyy said:


It appears it’s happening. The problem is, we have no clue how it’ll impact us, and models will likely be even more volatile than usual as they try to figure it out over the next week or so. Have a feeling models are going to be all over the place. Hopefully this SWW does what we need it to and doesn’t fail in disrupting the PV.

So I gather that SSW effects (and the timing of them) widely vary and are usually difficult to predict?

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9 minutes ago, Heisy said:


Yea seeing first legit signal for NAO. Might have to endure -PNA for a bit… hopefully not rest of season….


.

a -PNA isn’t nearly as much of an annoyance in March due to shorter wavelengths. a -PNA/-NAO late in the year can be quite good as long as the PNA isn’t like -5 sigma 

the -PNA would provide lots of shortwaves and the -NAO would provide a 50/50 that would keep things from cutting. they can be pretty great if you do get that semipermanent 50/50

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10 minutes ago, brooklynwx99 said:

a -PNA isn’t nearly as much of an annoyance in March due to shorter wavelengths. a -PNA/-NAO late in the year can be quite good as long as the PNA isn’t like -5 sigma 

the -PNA would provide lots of shortwaves and the -NAO would provide a 50/50 that would keep things from cutting. they can be pretty great if you do get that semipermanent 50/50

Dr. Amy Butler had a good thread on Twitter yesterday about late SSWs and the MJO phase when they occur. Long story short, this current setup and SSW is conducive to producing a durable -NAO in a couple/few weeks.

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4 minutes ago, WxUSAF said:

Dr. Amy Butler had a good thread on Twitter yesterday about late SSWs and the MJO phase when they occur. Long story short, this current setup and SSW is conducive to producing a durable -NAO in a couple/few weeks.

yeah, not gonna lie, I’m getting cautiously optimistic. I want to see the -NAO at within 10 days, first of all, but I think the first 20 days of March could be quite fun before climo becomes problematic

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it seems like the clipper midweek next week may provide the first wave break that leads to blocking later on in the run. this is something that we want to monitor... if this continues to trend stronger or even remain the same, it will make it much easier for a -NAO to form

the 12z GFS looks to be doing the same FWIW

gfs-deterministic-nhemi-z500_anom-1676354400-1676916000-1677175200-20-1.thumb.gif.2fb5e5f22198da74ff5871a1ec463560.gif

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