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Wintry Winter Discussion 2023/24

The geps and gefs are in oddly good agreement at a little bit of a PV disturbance around D10 that at least places some pressure on the strat pv and elongates it. Probably won't be enough to split or weaken significantly but these disturbance in recent winters have led to short term blocky episodes and cold intrusions into the US.
 
The geps and gefs are in oddly good agreement at a little bit of a PV disturbance around D10 that at least places some pressure on the strat pv and elongates it. Probably won't be enough to split or weaken significantly but these disturbance in recent winters have led to short term blocky episodes and cold intrusions into the US.
It's probably just a stretch of the pv that Judah Cohen mentions often.
 
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Maybe the first handful of days but that would be about it
Yea , I can echoe you are correct as that what modeling has been saying. All consistently have painted late week 1 and week 2 as run of the mill Meh, nada burgers. week 3-4 there's been some hints we may work into better pattern and some that say we want. Really gonna depend on how the PV evolves imo. Hopefully it want get wound up tight over the NP and just stay parked there as we roll into 2024. Still have lag times after its disruption and that just kicks can further down the road.
 
Is an early SSWE on the table?
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Wasn't there someone telling us last winter it takes about 4-6 weeks for a SSWE to impact our area anyway? That would be about right
My understanding is it can sometimes be less. 2-3 weeks...so maybe January gets rocking and rolling. If it happens at all, of course.
 
My understanding is it can sometimes be less. 2-3 weeks...so maybe January gets rocking and rolling. If it happens at all, of course.
A few thoughts here...per Simon Lee's research, a -NAO is 7 times more likely to occur when the lower stratosphere (100mb) is in a weakened state.

There are multiple ways to get the Strat PV weak at 100mb. One way is to have an SSW. SSWs are designated / occur in the upper stratosphere at 10mb. So if the SSW occurs at 10mb, then downwells into the lower strat at 100mb, that would move the 100mb layer into a weakened state. The downwelling into the lower strat may take 2-3 weeks. In some cases, the downwelling associated with the SSW isn't effective, and the weakening in the lower strat is minimal.

However, if the lower strat is already in a weakend state when the SSW occurs, the downwelling is essentially instantaneous, and it simply magnifies the lower strat weakness over the next several weeks. This is the ideal evolution for those who like winter and is what occurred in the 2020-2021 winter when Texas/OK were hit hard with cold, snow, and ice.

But even without an SSW occurring, the lower stratosphere can be in a weakened state. Take the big -NAO in Dec 2010 / Jan 2011. Here we can see on the chart below the lower strat at 100mb in a weakened state in the Dec to mid-Jan timeframe (i.e. red 100mb zonal wind line on the chart), and no SSW occurred that winter. Cases of the lower strat being in a weakened state in absence of an SSW typically occur when the strat PV is getting attacked with rounds of heat flux from waves upwelling from the troposphere, but not in such a strong manner that it leads to an actual SSW.

Bottom line, the most fertile environment for high latitude blocking to occur is when the lower stratosphere is in a weakened state. An SSW isn't a must in order to have the lower strat in a weakened state, but it's one way to get there if the downwelling environment is suitable following the SSW.

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Follow the MJO
It’s not really that simple. The MJO has been in low amp for a while now and it looks like it’s headed for COD in about 10 days. Also remember that the MJO was in great phases last winter from about mid January on and things still stayed very mild.
 
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