Model Output Discussions 12z 01/09/2016

[Ali1977]

2 minutes ago, knocker said:

I'm sorry but I completely disagree. I think you are misreading that chart at T336. Mind those charts are not very clear. Here is the 500mb contour chart for T336 which I think is the chart you chose with the wind barbs and they coming from the westerly quadrant. I will post the 500mb contour chart with anomaly (just ignore the latter) and again the upper flow will be along the contour lines.

I'm by no means as knowledgable as you and others but don't winds go clockwise round highs? And that's a huge high anomaly over the whole of Canada? 

[Frosty.]

I would take this from the Ecm 12z, there is still time for more upgrades as per Gfs 12z..it's nice to be talking about colder weather as a realistic prospect rather than a deep Fi pipe dream!

[January Snowstorm]

When you consider the ensembles and ECM are so so jury remains out for me. Yes they all go for sustained blocking but the uppers are not quite good enough.

Of course the bigger picture is still v good and intriguing.

Just remember guys we have learnt many a time that if there is even a glimmer of hope for mild it usually wins out

[Ice Day]

Another excellent set of runs today from all three major models if cold is your thing.  A very nice looking chart from the ECM at 240 to finish with

A completely blocked Atlantic again with north/north easterly incursions becoming more likely. The biggest plus for me is the consistency of keeping the Atlantic quiet allied to the disorganisation of the PV.  Let's hope the output stays this positive as we start to enter winter proper.

As Ian Drury once said, reasons to be cheerful!

[Zakos]

5 minutes ago, knocker said:

I'm sorry but I completely disagree. I think you are misreading that chart at T336. Mind those charts are not very clear. Here the 500mb contour chart for T££6 which I think is the chart you chose with the wind barbs and they coming from the westerly quadrant. I will post the 500mb contour chart with anomaly (just ignore the latter) and again the upper flow will be along the contour lines.

This chart is at 312 hours but is more clear. surely a large swath of North America is under the influence of Atlantic sourced air? 

[knocker]

10 minutes ago, Ali1977 said:

I'm by no means as knowledgable as you and others but don't winds go clockwise round highs? And that's a huge high anomaly over the whole of Canada? 

Forget about the anomaly as this has nothing to do with direction of the upper flow. It merely indicates areas which are indicating  negative or positive pressure in relation to climatology..The upper flow is always indicated by the contour charts, whatever pressure level. Much the same isobars on the surface without the friction.

Edited October 29, 2016 by knocker

[Summer Sun]

Whilst ECM might not be as good as some other runs on face value it ends with cooler / colder air filtering down

Could be worse we could have low after low coming in from the Atlantic

I'm sure for the communities flooded last year this Autumn will be very pleasing so far

Edited October 29, 2016 by Summer Sun

[weirpig]

3 minutes ago, January Snowstorm said:

When you consider the ensembles and ECM are so so jury remains out for me. Yes they all go for sustained blocking but the uppers are not quite good enough.

Of course the bigger picture is still v good and intriguing.

Just remember guys we have learnt many a time that if there is even a glimmer of hope for mild it usually wins out

Oh yes I agree. But it's November  even if it does go the way of the pear  still loads of time. If this was in the last throughs of winter I perhaps wouldn't be so relaxed 

[Ice Day]

5 minutes ago, January Snowstorm said:

When you consider the ensembles and ECM are so so jury remains out for me. Yes they all go for sustained blocking but the uppers are not quite good enough.

Of course the bigger picture is still v good and intriguing.

Just remember guys we have learnt many a time that if there is even a glimmer of hope for mild it usually wins out

Agree completely, mild is our default and always seem to scupper our hopes of sustained cold.  Surely we will throw a double 6 one of these days though?

[knocker]

1 minute ago, Zakos said:

This chart is at 312 hours but is more clear. surely a large swath of North America is under the influence of Atlantic sourced air? 

Well the surface analysis will not necessarily show the source of the air but indicate the wind patterns for that particular analysis which will vary across the whole country. In anycase you were originally talking about and showing a 500mb chart and then a  thickness, although I don't know what the latter has to do with it.

[Zakos]

12 minutes ago, knocker said:

Well the surface analysis will not necessarily show the source of the air but indicate the wind patterns for that particular analysis which will vary across the whole country. In anycase you were originally talking about and showing a 500mb chart and then a  thickness, although I don't know what the latter has to do with it.

Unless I am reading these contours incorrectly they show a low pressure system stalling against the Atlantic block, dragging Atlantic air across North America, with the contour pattern stretching from the Atlantic to Alaska

Edited October 29, 2016 by Zakos

[bobbydog]

Reading through the last couple of pages, anyone would be forgiven for thinking it was the last week of February and we were doing the usual straw clutching. It's still October! We are facing northerlies and easterlies being modelled in the next couple of weeks and people are disappointed it won't bring scenes like 1962! The strat is in tatters and we have an unprecedented  recurring blocking theme which will not give up. We might even get a proper, Victorian, christmas card style winter if we're lucky! Get a grip!

[knocker]

12 minutes ago, Zakos said:

Unless I am reading these contours incorrectly they a low pressure system stalling against the Atlantic block, with Atlantic air flooding across North America, with the contour pattern stretching from the Atlantic to Alaska

Okay let's assume you are correct as I suspect this boring everyone else but I will just add a couple of points. You originally spoke of the source of the air and posted a 500mb and anomaly chart. And as I said you need to use the contours for the upper flow. You now appeared to have switched to the surface and still talking of contours when obviously it should be isobars. And again the airflow within these systems doesn't necessarily indicate the source of the air. And in any case looking at the surface analysis in no way does it show Atlantic air flooding across N. America,

Edited October 29, 2016 by knocker

[johnholmes]

Just a brief comment, it would be a good idea if one or two of you did some reading in the Guides area. With particular reference to anomaly charts. No dig at anyone but you will get more enjoyment if you really understand what they show.

For instance the 500mb anomaly charts you often see me quote=the lines are NOT contour lines or isobars the are lines showing the degree of anomaly for that height, be it +ve or -ve. Don't be misled by what appear to be directions.

Just to complicate it there are contour lines on those charts, see below. The green lines are the contour lines and winds blow roughly along those as on a surface chart. That is clockise around a high and anticlockwise around a low. The dashed red lines are the anomaly heights and do NOT indicate anything else.

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

Please pm me if you want any help.

 

Edited October 29, 2016 by johnholmes

[feb1991blizzard]

1 minute ago, johnholmes said:

Just a brief comment, it would be a good idea if one or two of you did some reading in the Guides area. With particular reference to anomaly charts. No dig at anyone but you will get more enjoyment if you really understand what they show.

For instance the 500mb anomaly charts you often see me quote=the lines are NOT contour lines or isobars the are lines showing the degree of anomaly for that height, be it +ve or -ve. Don't be misled by what appear to be directions.

Please pm me if you want any help.

 

Yes John but the charts for that specific timeframe (312 I think it was) show higher heights North of Lower heights so roughly the flow into Canada is from the East or at least an Easterly quadrant?

[Zakos]

17 minutes ago, knocker said:

Okay let's assume you are correct as I suspect this boring everyone else but I will just add a couple of points. You originally spoke of the source of the air and posted a 500mb and anomaly chart. And as I said you need to use the contours for the upper flow. You now appeared to have switched to the surface and still talking of contours when obviously it should be isobars. And again the airflow within these systems doesn't necessarily indicate the source of the air. And in any case looking at the surface analysis in no way does it show Atlantic air flooding across N. America,

No, I didnt.

The original post you quoted was in regards to this chart, which to my mind shows Atlantic sourced air moving across North America.

Also, isobars are a form of a contour line, hence my terminology is still correct, though yes strictly they should be referred to as isobars.

Edited October 29, 2016 by Zakos

[bluearmy]

Michael ventrice mused about the potential for ex tropical depressions to get involved in the northwest Pacific days 7/10. I commented that this looked likely to head into se Asia - not sure the initial modelled storm ever verified as such but ECM and gem are both showing possible ex trop depressions becoming involved in the nw Pacific in just over a weeks tme. watch the way one of these fellows invigorates the aleutian low late in the run.   If these systems do verify and become involved in events the other side of the NH, don't underestimate what this could do for the development of the NH Dec in general. my guess would be that this type of injection of ex trop air into the Pacific side Arctic would flip the balance in favour of an even more negative AO than already seems likely for November. 

[Singularity]

When looking at the absolute temperatures in the model output, it's worth bearing in mind what the long-term averages are for the time of year; recent GFS runs have the CET region some 2*C below the LTA by the start of week 2 and that anomaly remains the same or grows even more negative by the end of the week, depending on which particular run you look at.

There's a good few weeks more seasonal cooling to be done before blocking patterns have an easier time delivering wintry weather to lower ground, particularly with the sea temperatures. I say easier because recent years have really shown us how hard it can be to get the blocks in the right place - or in the right part of the season for that matter - but this year there's no escaping the fact that we seem to have a lot more running in our favour. The predicted state of the polar vortex days 8-16 in the troposphere is extraordinary, following a similarly extraordinary setup in the stratosphere this coming week or so. Enjoy what you can of the model watching, regardless of what you actually get at the end of it - any white deposits on the ground beyond a bit of frost is going to be a bonus appetizer ahead of the main course, though as yet we can't be sure if the right ingredients for the main course have arrived in the stockroom! 

[Gael_Force]

I don't know if this helps it's the 500 mb winds over Canada and the US.

http://www.instantweathermaps.com/

 

[knocker]

9 minutes ago, Gael_Force said:

I don't know if this helps it's the 500 mb winds over Canada and the US.

http://www.instantweathermaps.com/

 

Aye GF but I've already posted this chart with wind barbs And isobars are not a form of contour lines unless you going to use very loose terminology. And I repeat Zakos that chart doesn't show that, not do the others you posted.

 

Edited October 29, 2016 by knocker

[Zakos]

I am aware that anomaly charts do not display the air current direction and therefore I was wrong to post the Anomaly chart.

 The airflow is not directly east to west as the above chart could appear to show , it was misleading of me to post that chart.

+276

+336

However, From +276 to +336, we see the colder upper air temperatures removed from the NE of North America. is this not caused by Atlantic air being dragged in from the east?

 

 

 

Edited October 29, 2016 by Zakos

[Nouska]

On 25/10/2016 at 00:15, Nouska said:

They are not as big as they might appear - at this time of year it is normally a big mass of very low heights over the polar regions.

 

Excuse me quoting myself but in view of earlier comments - a reminder about the climatology we are setting the anomalies against.

I like to use the NOAA upper air charts for purposes such as this.

Take a look at the progged day eleven upper air anomaly - when was the last time you saw something as spectacular as that in early November.

Even as dramatic as it is, it is not enough of a height differential to reverse the contours right across N America.

http://www.cpc.ncep.noaa.gov/products/predictions/short_range/tools/model_guidance.php?dayin=11

Edited October 29, 2016 by Nouska

[knocker]

23 minutes ago, Zakos said:

I am aware that anomaly charts do not display the air current direction and therefore I was wrong to post the Anomaly chart.

+276

+336

From +276 to +336, we see the colder upper air temperatures removed from the NE of North America. is this not caused by Atlantic air being dragged in from the east?

Zakos if we are back to surface charts then just ponder one thing.I  suspect you are taking a lot of notice of the low along the eastern seaboard.which has much of the NE within it's circulation. Bet where did that low and the air within originate? Down in the SW States and not the Atlantic. In any case much of the US is not within the circulation

 

 

Edited October 29, 2016 by knocker

[Summer Sun]

Precipitation over the next week remains below average week 2 may increase but the usual cautions apply at the range

Temperatures over the next week look very close to average again anything in week 2 should be taken with caution

[Zakos]

Yes that is strictly true,as the air within the low is sourced from the SW states. Still, when the low stalls against the Atlantic block it does drag Atlantic air over its northern edge across Canada. However yes to say it is altantic sourced is not strictly true.

I should have been more clear in my original post, and as you and others have pointed out, height anomaly charts are not indicative of air flow direction and therefore that chart should not have been posted. Not sure why i posted that  chart to be honest.

Edited October 29, 2016 by Zakos