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Medium Range-Long Range thread


NaoPos

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The + PNA may be transient, but the -NAO seems to be at least partially be manifested from the blizzard and reinforced by the recent NATL bomb. The weeklies did have a -NAO FWIW, but they also have been too aggressive in the past with that. Whether they are right for the wrong reason, I don't know.  It's rather chaotic when looking at the global pattern and it's almost like wavelengths are starting to say I don't give a crap what composites say, as they begin to shorten perhaps? 

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Any thoughts about the early March potential?

 

1. Our cold air source will continue to modify and grow more and more stale with time.

2. The blocking initially is legit but turns more into "retreated polar heights" type of response the deeper we move into March. This is like December all over again, in what it means for our sensible weather.

3. Once the KW-IO response is complete, I expect the Southeast Ridge to grow in earnest.

Early March will be on the line between the old regime and developing new one. I could see a couple of "Feb 25, 2007" like front-end potentials into early March with possibly an interior wet snow, before it becomes too warm, in early March.

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Kelvin Waves are faster and shallower than the MJO but occasionally can overlap in things like power spectrum etc. (they also both are easterly waves while things like RWs propagate toward the west). But they both operate similarly in what to look for on a map during enhanced phases (low level convergence / upper level divergence / convection). Currently there is a KW about to enter the IO from Africa. There is also a coherent MJO signal in the eastern IO. Active MJO waves will tend to excite and slow down an oncoming KW, esp. in the IO. This KW will affect Mid Latitude circulation, similiarly to the MJO, through outflow wind / latent heat release and residual tropical cyclonic anomalies (time scale just may be briefer than a typical MJO).

Since the IO will become excited by this over the next week, the Mid Latitude circulation may appear more like a hybrid (phase 3-4 type of look) before possibly settling comfortably into the phase 4-5 look in March.

On Mike's site, you want to go to the diagrams that plot KW waves (dashed blue or black lines for CCKW) to see how they propagate and interact with the MJO. You can also use his filter VP maps to see each type of wave.

For example, here is just h2 VP anomalies for KW, only, showing the African wave and leading W PAC wave:

http://www.atmos.albany.edu/student/ventrice/real_time/timeLon/vp.filt.anom.90.5S-5N.png

Here is how the total VP picture is broken down by each wave (third image is KW):

http://www.atmos.albany.edu/student/ventrice/real_time/maps/waves/global/28.gif

You should give this a read too, if you have the time:

http://www.atmos.albany.edu/facstaff/roundy/kelvinmod.pdf

Thanks for the info HM. I will try and comprehend it when i have a clear head.

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1. Our cold air source will continue to modify and grow more and more stale with time.

2. The blocking initially is legit but turns more into "retreated polar heights" type of response the deeper we move into March. This is like December all over again, in what it means for our sensible weather.

3. Once the KW-IO response is complete, I expect the Southeast Ridge to grow in earnest.

Early March will be on the line between the old regime and developing new one. I could see a couple of "Feb 25, 2007" like front-end potentials into early March with possibly an interior wet snow, before it becomes too warm, in early March.

We agree completely. Not sure how you did it, other than you being you, but great job nailing this -NAO period.

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We agree completely. Not sure how you did it, other than you being you, but great job nailing this -NAO period.

 

I vehemently agree.  Great outlook by HM. 

 

I know I have way too much :wub: for the NAEFS week2, but they never really got on the early Morch train.  Great discussion in here, when the cobwebs from these mids end and I'm back on planet Earth, I have to go back and go through it. 

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Thanks for the info HM. I will try and comprehend it when i have a clear head.

 

It's never as bad as you think it is at first and I'm sure Mike will make more sense later.

 

We agree completely. Not sure how you did it, other than you being you, but great job nailing this -NAO period.

 

haha thanks man. For our winter fans, I'm hoping we can get a few front-end shots before this all gets eradicated. It is amazing how every time we get a -NAO response this year, the Pacific decides to take a crap on us. lol

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Some leftover strato garbage and srn stream bombs pumping heat into the NATL certainly have helped.

Oh yeah. I see how it played it now. But I definitely didn't back two weeks ago (or even a week ago), and HM was chirping as early as January about it not being a typical transition into a P3-P4-P5 +NAO regime.

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So I'm guessing that the active kelvin waves can make the MJO suffer from index number problems?  (Like -NAO sometimes not really being a true-NAO)?  As Tombo asked is there any threshold where Houston we have a problem?  Again I just gleaning from other posts, but it sure reads like the Euro weeklies have not had a good winter (not that the CFS2 has either).

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Oh yeah. I see how it played it now. But I definitely didn't back two weeks ago (or even a week ago), and HM was chirping as early as January about it not being a typical transition into a P3-P4-P5 +NAO regime.

 

I missed those posts....I'll have to go back and look. HM, what was your rationale if you don't mind. 

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I feel the same way.  Doesn't it stink when the weather gets in the way of the weather.   ;)

 

This was my go to thread when the weather sucked up until 2 weeks ago..lol. A great learning tool for someone trying to pick up some long range prowness. Mike, Adam, and HM were dishing out good stuff.

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I never said they were snow. But it is pretty awesome when you have an active southern stream how it just keeps popping out storms.

/

I know. Just keeping the mood light and friendly in here. But it is nice to see an active STJ. Maybe some type of magic can happen.

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I certainly share the sentiments with scott that this has been a great go-to haven when trying to sort out the at times confusing and often muddled tropical signals this winter.. It has NOT been an easy winter to say the least.

 

It has been frustrating to see the few -NAO developments this winter occur as the Pacific is taking a dump on us. But what immediately jumped out at me when catching up after the long weekend was the +PNA development on the guidance by ~day 8, hooking up with the -NAO anomaly through the 11-15 day/first week in March. Havent heard much chatter about this feature on the guidance today. I'm struggling to figure out why it develops and even more so why it would sustain itself like the data implies. If the mixed kelvin wave/mjo signal that has been sorted out today propogates as many are suggesting into early March, then I would think that does not support this PNA scenario. Maybe I'm missing something here?
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I certainly share the sentiments with scott that this has been a great go-to haven when trying to sort out the at times confusing and often muddled tropical signals this winter.. It has NOT been an easy winter to say the least.
 
It has been frustrating to see the few -NAO developments this winter occur as the Pacific is taking a dump on us. But what immediately jumped out at me when catching up after the long weekend was the +PNA development on the guidance by ~day 8, hooking up with the -NAO anomaly through the 11-15 day/first week in March. Havent heard much chatter about this feature on the guidance today. I'm struggling to figure out why it develops and even more so why it would sustain itself like the data implies. If the mixed kelvin wave/mjo signal that has been sorted out today propogates as many are suggesting into early March, then I would think that does not support this PNA scenario. Maybe I'm missing something here?

 

Chris,

 

In actuality, the GEFS PNA skill scores have been higher than the NAO for the same time periods, so in theory the +PNA solution "should" have a greater chance of verifying than the -NAO.  The EPO is also outlooked to be positive (dont know its skill score), so there is a mixed message out there. But, just looking at the blocky 500mb flow, its going to be tough for lows to "cut" the next couple of weeks.

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But the problem I have is that all guidance shows this. It would have to be a total fail of guidance to lose this strong signal within 7-8 days. SOmething is clearly allowing for this to happen..maybe leftover junk in the west pac or something..I really don't know. I guess what I could see is a quicker demise to the +PNA...I mentioned it being possibly transient yesterday. It is perplexing, but tough to ignore right now.

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