Model tweets

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In relation to above, unsurprising that Jason Furtado refers to the NPO as he has published some interesting papers related to it eg. Linkages between the North Pacific Oscillation and central tropical Pacific SSTs at low frequencies - http://ifurtado.org/wp-content/uploads/Publications/FurtadoDiLorenzoAndersonSchneider2012.pdf

Nice collection of papers on his site http://ifurtado.org/ the Pacific Decadal Precession concept in A decadal precession of atmospheric pressures over the North Pacific is particularly interesting.

Anyway another tweet on this subject -

Like the anomaly charts, would be handy to find them on the CPC site

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On 4/12/2018 at 13:08, knocker said:

 

Was going to post a v-wind anomaly Hovmoller chart to illustrate this, but that tweet is conveniently in response to this -

 

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Edited May 7, 2018 by knocker

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Edited May 9, 2018 by knocker

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Edited May 16, 2018 by knocker

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[Singularity]

Interesting from CFSv2 as the pattern is pretty much a variation of that seen in recent weeks; the jet bifurcates west of the UK, but both arms track further south than has been the case of late.

What's notable about this is the displacement of the Azores High northeast from its usual position. This increases the chances of staying dry as and when the ridge eases off a bit before reloading from the west.

The 'pebble in a stream' pattern can produce the longest runs of dry weather in the UK. In the summer, homegrown heat can become substantial with time provided the HP circulation is not too strong (because if it is, it periodically brings in fresher Atlantic air).

Here's the wider view. It's good that this is the ensemble mean and not a single deterministic run; too often I've seen charts shared which are instead the latter, giving them far less credibility than advertised.

The model has had a generally positive tendency as far as our weather patterns May-July this year are concerned, though with a few notable wobbles from time to time. It did well with May (even showing the focus of HP to the N and NE of the UK) so that's encouraging as far as July 2018 goes.

[knocker]

20 hours ago, Singularity said:

Interesting from CFSv2 as the pattern is pretty much a variation of that seen in recent weeks; the jet bifurcates west of the UK, but both arms track further south than has been the case of late.

What's notable about this is the displacement of the Azores High northeast from its usual position. This increases the chances of staying dry as and when the ridge eases off a bit before reloading from the west.

The 'pebble in a stream' pattern can produce the longest runs of dry weather in the UK. In the summer, homegrown heat can become substantial with time provided the HP circulation is not too strong (because if it is, it periodically brings in fresher Atlantic air).

Here's the wider view. It's good that this is the ensemble mean and not a single deterministic run; too often I've seen charts shared which are instead the latter, giving them far less credibility than advertised.

The model has had a generally positive tendency as far as our weather patterns May-July this year are concerned, though with a few notable wobbles from time to time. It did well with May (even showing the focus of HP to the N and NE of the UK) so that's encouraging as far as July 2018 goes.

I'm sorry but I'm not sure what you are illustrating with the 700mb anomaly chart. It's a very rough chart but as far as can see it shows a general westerly flow over the UK where the pressure is higher when measured against the climatological average but with the Azores in it's usual position to the south west. It's very broad brush but to me that would indicate a tendency towards a N/S split and a not particularly unusual scenario  Am I missing something?

Edited June 7, 2018 by knocker

[Singularity]

6 hours ago, knocker said:

I'm sorry but I'm not sure what you are illustrating with the 700mb anomaly chart. It's a very rough chart but as far as can see it shows a general westerly flow over the UK where the pressure is higher when measured against the climatological average but with the Azores in it's usual position to the south west. It's very broad brush but to me that would indicate a tendency towards a N/S split and a not particularly unusual scenario  Am I missing something?

It's a mean across a whole month so those flow lines smooth out the interchanging of individual ridges within.

This is why I prefer to use the anomalies alongside a consideration of what the long-term average is. In July, the average is more often settled than not in the south, and near 50/50 settled/unsettled in the north, so with the positive anomaly of 8-16 dam or so, the implications is for almost entirely settled in the south and often settled in the north.

True that the Tweet above is perhaps a bit too broad in what it suggests; only the S half of the UK would be seeing a noteworthy month (at least in terms of few wet days) from that exact anomaly chart.

[knocker]

23 hours ago, Singularity said:

It's a mean across a whole month so those flow lines smooth out the interchanging of individual ridges within.

This is why I prefer to use the anomalies alongside a consideration of what the long-term average is. In July, the average is more often settled than not in the south, and near 50/50 settled/unsettled in the north, so with the positive anomaly of 8-16 dam or so, the implications is for almost entirely settled in the south and often settled in the north.

True that the Tweet above is perhaps a bit too broad in what it suggests; only the S half of the UK would be seeing a noteworthy month (at least in terms of few wet days) from that exact anomaly chart.

Yes I accept that but you also said:

Quote

What's notable about this is the displacement of the Azores High northeast from its usual position.

And that chart does not show that which is why I was puzzled

Edited June 8, 2018 by knocker

[Singularity]

On 08/06/2018 at 13:52, knocker said:

Yes I accept that but you also said:

And that chart does not show that which is why I was puzzled

Ah I see, on reflection I understand that what I should have put was 'the more frequent than usual displacement northeast of the Azores High implied by the anomaly pattern'.

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Edited June 14, 2018 by knocker

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Edited June 19, 2018 by knocker

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Edited June 20, 2018 by knocker

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[Singularity]

6 hours ago, knocker said:

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The demise of the La Nina standing wave is what the likes of me and Tamara have been waiting for with baited breath since summer came into the debatable range.

Suffice to say, this is the best news so far this season with respect to fine weather prospects during the heart of summer 2018.

It's not a guarantee of course; variations on shorter timescales can still throw spanners at the works. Hopefully they will miss!

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Edited June 28, 2018 by knocker

[knocker]

This paper might be of interest to some

P. J. Klotzbach, S. Abhik, H. H. Hendon, M. M. Bell, C. Lucas, A. Marshall, and E. C. J. Oliver: On the emerging relationship between the stratospheric quasi-biennial oscillation and the Madden-Julian oscillation. Manuscript submitted to Scientific Reports in June 2018.

 

Edited June 28, 2018 by knocker