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Model Output Discussion 29th December - Into mid-Winter.


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Certainly some cautious cause for optimism for second half of January, yes we've seen the positive signals from ops and ens for early Jan in late December and got burnt on New Year's Eve, but this time there is growing support from various signals for changes in the status quo of the upper flow. Here's why:

The stratosphere is looking interesting in the medium range, with a decrease in zonal flow evident at 10 hPa as has already been posted, and check out the 12z EC stratosphere z500 at 10 hPa:

strat_240.png

the GEFS and EPS are indicating an eastward propagation of an increasingly active MJO wave into phase 8, GEFS is perhaps being too hasty, hence the amplification over the N Atlantic from day 10/11, whereas the EPS is slower and perhaps why we aren't seeing such amplification yet.

NCPE_phase_21m_full.gifECMF_phase_MANOM_51m_full.gif

AO trending negative in the means on GEFS, also NAO trending neutral to slightly -ve. EPS trending AO slightly -ve, NAO neutral.

AO.pngNAO.png

So those nice looking charts from GFS post day 10 do have some backing from the oscillations, but maybe too quick IMO in bringing in the amplification. Patience required, despite patience wearing thin!

 

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Nick F I am struggling to visualise this comment

However, the NOAA CPC 8-14 day indicates support for the 12z GFS, with a flow more N/NE than NW with perhaps the Euro trough eventually cutting off from the upper westerlies.

Where are the N-NE'ly showing on the NOAA charts please? 

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2 minutes ago, johnholmes said:

Nick F I am struggling to visualise this comment

However, the NOAA CPC 8-14 day indicates support for the 12z GFS, with a flow more N/NE than NW with perhaps the Euro trough eventually cutting off from the upper westerlies.

Where are the N-NE'ly showing on the NOAA charts please? 

Via the anomolies john - we had this discussion on here wi knocker at some point over the sou'easter in December and I recall it happened as per the anomolies rather than th upper flow

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3 minutes ago, bluearmy said:

Via the anomolies john - we had this discussion on here wi knocker at some point over the sou'easter in December and I recall it happened as per the anomolies rather than th upper flow

I cannot see a flow being N-NE when the anomalies, at 500mb, show a flow over the UK from somewhere N of W with a fairly large +ve anomaly in the Atlantic. that is hardly likely, in my view, to give the flow shown at 240h on the 12z GFS?

Or am I missing something?

 

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5 minutes ago, johnholmes said:

Nick F I am struggling to visualise this comment

However, the NOAA CPC 8-14 day indicates support for the 12z GFS, with a flow more N/NE than NW with perhaps the Euro trough eventually cutting off from the upper westerlies.

Where are the N-NE'ly showing on the NOAA charts please? 

The N/NEly flow comment was based on the anomaly contour John, OK perhaps a bit optimistic for a NE flow, but the anomalies in my eyes indicate a flow from the N rather NW over the UK. Of course they are a mean anomaly so are a rough guide.to potential mean flow in that period

814day.03_1.gif

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1 minute ago, johnholmes said:

I cannot see a flow being N-NE when the anomalies, at 500mb, show a flow over the UK from somewhere N of W with a fairly large +ve anomaly in the Atlantic. that is hardly likely, in my view, to give the flow shown at 240h on the 12z GFS?

Or am I missing something?

 

Well if you are I'm missing it as well.

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3 minutes ago, Nick F said:

The N/NEly flow comment was based on the anomaly contour John, OK perhaps a bit optimistic for a NE flow, but the anomalies in my eyes indicate a flow from the N rather NW over the UK. Of course they are a mean anomaly so are a rough guide.to potential mean flow in that period

814day.03_1.gif

Sorry Nick I'm not following this. How can you deduce streamlines from the anomalies which are not actually features at the surface or 500mb. Genuinely puzzled here.? Surely you have to take the flow from the contour lines?

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1 minute ago, Nick F said:

The N/NEly flow comment was based on the anomaly contour John, OK perhaps a bit optimistic for a NE flow, but the anomalies in my eyes indicate a flow from the N rather NW over the UK. Of course they are a mean anomaly so are a rough guide.to potential mean flow in that period

814day.03_1.gif

I think you are taking it too far to make that assumption Nick but that is just my opinion.

Are you drawing suggested isobars or contours and where are they from. They 'appear' to be on the anomaly lines, -ve and +ve?

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1 minute ago, johnholmes said:

I think you are taking it too far to make that assumption Nick but that is just my opinion.

Are you drawing suggested isobars or contours and where are they from. They 'appear' to be on the anomaly lines, -ve and +ve?

Are we confusing upper flow and potential surface flow here?

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Dreaded shortwave energy in the Atlantic showing up which is stopping the Euro slug high from edging nw. Yet another complication, we might get away with it if these track over the top of the high eastwards and theres a clearance upstream but really not needed at this point.

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1 minute ago, nick sussex said:

Dreaded shortwave energy in the Atlantic showing up which is stopping the Euro slug high from edging nw. Yet another complication, we might get away with it if these track over the top of the high eastwards and theres a clearance upstream but really not needed at this point.

It's not like we haven't seen it very recently nick!  Not exactly the same evolution but quite similar results with the surface ridge pushed back east i to  w Europe 

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1 minute ago, Man With Beard said:

Are we confusing upper flow and potential surface flow here?

 

4 minutes ago, Man With Beard said:

Are we confusing upper flow and potential surface flow here?

Whose we? :)

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9 minutes ago, knocker said:

Sorry Nick I'm not following this. How can you deduce streamlines from the anomalies which are not actually features at the surface or 500mb. Genuinely puzzled here.? Surely you have to take the flow from the contour lines?

Dont you recall this debate with me in December knocks? It does take a small leap of faith in the anomolies being accurate in representing where the surface features will lie.   

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12 minutes ago, knocker said:

Sorry Nick I'm not following this. How can you deduce streamlines from the anomalies which are not actually features at the surface or 500mb. Genuinely puzzled here.? Surely you have to take the flow from the contour lines?

 

10 minutes ago, johnholmes said:

I think you are taking it too far to make that assumption Nick but that is just my opinion.

Are you drawing suggested isobars or contours and where are they from. They 'appear' to be on the anomaly lines, -ve and +ve?

Ok, I'm not going to argue as I'm probably being too verbatim re: the anomaly contours, so accept that the flow is probably NWly based on the 500mb contours alone.

But back to my original comment, doesn't that the -ve anomaly over Europe and +ve height anomaly over N Atlantic and far south of Greenlalnd suggests something similar to 12z GFS op than 12 EC det?

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Just now, bluearmy said:

It's not like we haven't seen it very recently nick!  Not exactly the same evolution but quite similar results with the surface ridge pushed back east i to  w Europe

This is exactly why I won't believe that slug is gone until its in the more reliable timeframe. The ensembles are always slow to pick up shortwave energy. The GFS 18hrs might avoid disaster because it doesn't phase the one further upstream but if it did it would be curtains. For this reason I'm not buying any definite low heights over southern Europe until its within T144hrs.

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I am not able to chat about this at the moment but will try and explain what the 500mb anoaly charts actually show in more detail tomorrow. Just briefly now

1) The predicted contour flow ( On NOAA charts these are show in green). You could somewhat not exactly say they are isobars at 500mb

2) The dotted blue and red lines on NOAA charts are -ve and +ve height anomalies for the areas marked. Nothing to do with any surface flow.

 

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1 minute ago, johnholmes said:

I am not able to chat about this at the moment but will try and explain what the 500mb anoaly charts actually show. Just briefly now

1) The predicted contour flow ( On NOAA charts these are show in green). You could somewhat not exactly say they are isobars at 500mb

2) The dotted blue and red lines on NOAA charts are -ve and +ve height anomalies for the areas marked. Nothing to do with any surface flow.

 

But you could try to guess surface flow possibilities based on the 500mb lines, which is what I think Nick is doing?

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