In Depth Model Discussion and Summaries

[johnholmes]

first class read-thanks

edited as I was suggesting what you have already done in the model thread before I dropped in there!

Edited June 4, 2014 by johnholmes

[Vorticity0123]

first class read-thanks

edited as I was suggesting what you have already done in the model thread before I dropped in there!

 

Thanks for the positive feedback! I'm really glad to hear the post is a good read  .

 

My original post was in the model output section, but as it didn't really fit in there well, I placed it in this thread, with a link in the other thread  .

Edited June 4, 2014 by Vorticity0123

[johnholmes]

link below to Met Office model predictions for the summer, June-August

http://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/gpc-outlooks/glob-seas-prob

my summary of the above would be, 500mb heights a bit above for ost with lower south of the UK, and similar with surface pressure, rainfall not far from average and temperatures more likely above than below average for most parts. Not sure if others will agree with that summary.

[Thermohaline Conveyor]

not from me, 15 days using a mix of anomaly and synoptic outputs with a check on the background signals from AO, NAO, PNA, MJO; in the spring/summer months, possibly extending it to about 3 weeks at the very most; little can be gained from looking at the 30mb chart I find?

 

I'm not a fan of looking much beyond that either.  Picking out very generic trends is possible but it becomes more and more guess work beyond T+240

[Cloud 10]

Just had a quick look back at the height anomalies for summer 2014 and i must say it doesn't look brilliant with evidence of northern blocking and lower than normal heights over much of Europe (plenty of big storms in Germany this summer) with the AO and NAO being mainly negative.

 

 

I think its fair to say the UK as a whole did pretty well and got the best

out of a pattern that could have easily tipped into the "miserable summer" category.

 

 

Thoughts now turning to the back-end of Autumn and winter as the polar vortex begins to fire up....

[damianslaw]

Oh dear 2 posts in three months - this thread appears dead in the water, only comes alive in winter...its a shame. I don't have the knowledge to post in depth accounts of likely trends etc, but it would be good if those in the know could on occasion dip in and out of this thread just so it has some action.

 

I'd be interested to hear people's views on reasoning why the last 4 weeks have delivered such quiet weather, and what are the likely trends as we head into Autumn proper. The model discussion thread is always good, but sometimes its good to escape it and read purely unbiased non-speculative posts about likely future conditions backed up by sound reasoning, with a peep into the longer term for overall trends. GP was great at this.

Edited September 18, 2014 by damianslaw

[Woollymummy]

Is it because the jetstream was split in half?

[johnholmes]

the pdf with various things about using 500mb anomaly charts along with examples

 

500mb various posts in order of posting-21 oct 2014.doc

 

 

[knocker]

the pdf with various things about using 500mb anomaly charts along with examples

 

500mb various posts in order of posting-21 oct 2014.doc

 

Cheers John, it downloaded okay after a struggle

[Vorticity0123]

the pdf with various things about using 500mb anomaly charts along with examples

 

500mb various posts in order of posting-21 oct 2014.doc

 

Great sum-up, I think it will be a help for many!

 

To give a very rough illustration, below is the anomaly chart for 6-10 days out from the forecast of yesterday 21-10-2014:

 

6-10 day 500 hPa heights and anomalies from NOAA.

 

Focus on the contour lines indicated in green. What can be seen is that over the UK, the isobars can be clearly seen pointing upward (toward the pole). This is indicated by the black extra shading pointing toward the north (poleward). The upward pointing of the isobars illustrates a ridge is likely to be present at that location at the given timeframe. As a general rule, the positioning of a ridge overhead usually results in some kind of high pressure activity and calm/settled weather. 

 

Note that in the image above, there are also positive anomalies over the UK, which mean that the height of the 500 hPa pressure level is higher than average experienced at the given date (in the 6-10 day period)

 

Furthermore, just west of Newfoundland (US), an equatorward-dip in the isobars can be seen, which indicates a trough is situated in that area. This is likely an indication of unsettled weather occurring at that location.

 

For the ones preferring a PDF-format, below is a PDF-version of the document presented by John Holmes:

 

500mb various posts in order of posting-21 oct 2014.pdf

 

Source:

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

Edited October 21, 2014 by Vorticity0123

[Nouska]

JMA now have extensive parameter, composite anomaly charts for the MJO - might be a link of interest to some.

 

http://ds.data.jma.go.jp/gmd/tcc/tcc/products/clisys/mjo/composite.html

 

Other analysis charts and monitoring indices here:-

 

http://ds.data.jma.go.jp/gmd/tcc/tcc/products/clisys/acmi.html

[lorenzo]

Hopefully this thread can spring back to life over winter as the main model output will no doubt begin gathering pace and pages day on day. Looking around this morning found a couple of interesting things.

 

First is the GWO data, although ESRL are not maintaining chart output, email sent and hope others do to, the raw data is still being delivered in the form of a text file, we can see from this the GWO phase space and also the general tendency.

 

http://www.esrl.noaa.gov/psd/map/clim/gwo.data.txt

 

Attached are a couple of composites from last year for November to look at in association with data above.

 

Also, spotted this over on Levi Cowan's tropicaltidbits site http://www.tropicaltidbits.com/analysis/analogs.html A composite analog product that creates seasonal outlook charts, whilst weighting analog years.  Great to see another new product out there, really good page. Am not just saying that due to the January chart ! It's a monster..

 

 

 

 

 

 

 

 

[bluearmy]

his november analogue doesnt look great for n america tony ! not the most auspicious start !

[johnholmes]

To stop this being 'lost' in other threads, the latest (November) Met O model output for the winter, link below

http://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/gpc-outlooks/glob-seas-prob

The 500mb anomalies are somewhat different for the 3 winter months ut the 2m temperatures continue to show average to above.

No doubt this will cause some raised eyebrows on here.

[lorenzo]

his november analogue doesnt look great for n america tony ! not the most auspicious start !

 

True! There is a the caveat on the site that the analog tool is in development, for November analogs I doubt many would feature the huge ridging out of central CONUS at present.

 

The products on this page are experimental, undergoing development and change, and unproven in the forecasting realm.

 

From Cohen's blog, 07 November update, early Wave Activity Flux via SCE and Nuri related to having some influence here and possibly throwing analogs sideways.

[chionomaniac]

John have a look at the last 6 months T2m temp 2-4 month percentile graphs ( uploaded in no particular order)

 

 

 

Notice anything?

Edited November 10, 2014 by chionomaniac

[johnholmes]

coldish waters in the north Atlantic for starters?

 

a minimum % of 60 sometimes higher for 2m T to be above normal?

 

not very good at puzzles mate, so please enlighten me, no doubt I have missed something totally obvious?

Edited November 10, 2014 by johnholmes

[chionomaniac]

Oh and here is Nov 2009 projection:

 

[chionomaniac]

coldish waters in the north Atlantic for starters?

Yes - but other than that the 2-4 timeframe is useless for determining too much with percentile graphs other than the majority of the world is warming up due to global warming!

[johnholmes]

Yes - but other than that the 2-4 timeframe is useless for determining too much with percentile graphs other than the majority of the world is warming up due to global warming!

 

 

oh you cynic!

 

Just to be clear I am not suggesting their model output is correct, simply posting what it shows. I never keep these charts so I have no idea how far out they have been over the last 5 years or so. They did of course solidly predict some weeks ahead of the Nov-Dec 2010 cold spell pretty well. Other outputs have been best thrown away. But as you are well aware from your work in winter predictions we/they know so little of how many parameters connect up. That is why, to me, the OPI is such an interesting idea, not totally new of course and has yet to be peer reviewed but interesting. I posted some time ago about lrf work, 1 month ahead in the Met O in the mid 70's. All down to the jet stream the experts there suggested-really, how things have moved on since then.No doubt what we think is a break through at the moment will look equally old hat in 40 years time. Who knows in synoptic meteorology by then main weather cebntres MIGHT even be able to predict it will be rain or snow, how much, where and when. Mind you I would suggest folk don't expect this to happen with anything like total accuracy more that maybe 36-48 hours ahead by then!

tara

Edited November 10, 2014 by johnholmes

[Cloud 10]

The new met office update for winter seems to continue the same sort of pattern that has been the theme of much of 2014,with  a trough just west of the UK giving above average temperatures.

 

Heights..  temps..

 

 

[snowking]

From Cohen's blog, 07 November update, early Wave Activity Flux via SCE and Nuri related to having some influence here and possibly throwing analogs sideways.

Figure2b.pngFigure3b.png

Interestingly though, if you take the three closest OPI years...

 

 

Not an exact match but certainly gives the right sort of idea

 

SK

[chionomaniac]

oh you cynic!

 

Just to be clear I am not suggesting their model output is correct, simply posting what it shows. I never keep these charts so I have no idea how far out they have been over the last 5 years or so. They did of course solidly predict some weeks ahead of the Nov-Dec 2010 cold spell pretty well. Other outputs have been best thrown away. But as you are well aware from your work in winter predictions we/they know so little of how many parameters connect up. That is why, to me, the OPI is such an interesting idea, not totally new of course and has yet to be peer reviewed but interesting. I posted some time ago about lrf work, 1 month ahead in the Met O in the mid 70's. All down to the jet stream the experts there suggested-really, how things have moved on since then.No doubt what we think is a break through at the moment will look equally old hat in 40 years time. Who knows in synoptic meteorology by then main weather cebntres MIGHT even be able to predict it will be rain or snow, how much, where and when. Mind you I would suggest folk don't expect this to happen with anything like total accuracy more that maybe 36-48 hours ahead by then!

tara

I'm not being cynical, John. I just think that that is the way it is.

 

The time frame used of 3 months firstly dampens down anomalies too much, and secondly, if you have factored into your model a long term warming trend, then this will overide the monthly seasonal tendencies when added cumulatively and calculated as a percentile risk.

[snowking]

I thought it may be worth dropping in a reminder of why so many of us are very optimistic for the forthcoming winter (i think it's also important to highlight that it is still Autumn - for most that leaves us still 14 days from winter, for traditionalists that could be 35 or so days).

 

So the November analogue which I produced was formed from years with the following profile:

 

< -1.5 OPI

eQBO

El Nino

 

 

As has been said several times before, the key features to pick up are the signal for the Scandi (Or Sceuro, or Scrussianâ„¢) high, and Aleutian low. These two features in particular fit with Cohen's predicted climatology following a high Snow Advance Index, and help to drive wave activity in to the stratosphere and consequently help to weaken the Polar Vortex significantly. In addition to this we can also pick up on troughing just to the West of the UK, and the amplified pattern across the pond.

 

So how do we fare with each of those features at this the half way point of the month?

 

 

Well all the key features are there, the amplified North American pattern, the troughing just to the West of the UK, and crucially the Scandi high/Aleutian low combination.

 

This all follows the ideas laid out by Cohen to a tee, and when many of us saw analogues with such climatology projected, and now having seen these ideas progress and manifest themselves, it does bring a certain level of optimism.

 

So despite all the doom and gloom at times over on the model thread, to be expected given how early some started on what I would term "silly season", there is much to be optimistic about in the longer term, with many peoples thoughts aligning around the late December/January period right now. Whilst we talk about the model thread I have seen one or two comments about how the 'Vortex is ramping up' - tropospherically speaking we will see a bit of an increase in vortex strength in the coming weeks, but not only is this to be expected prior to anticipated events during December, it's also important to apply thoughts of the vortex strength in relative terms against the backdrop of last winter. It is also important to think about the Polar Vortex in a three dimensional sense. I think people can get a little carried away with seeing Blue's and Purples on the charts north of 60N and automatically assuming the Vortex is starting to ramp up. But the vortex does not just exist at the 500mb level - it stretches all the way up in to the Stratosphere. A strong vortex is one which exhibits strong Westerlyness all the way up in to this layer of our atmosphere too, and for as long as we see activity such as this high above us:

 

 

A happy vortex it shall not make.

 

I think finally, I will leave everyone with this thought - every January following an OPI of < -1.5 has finished with a CET below the 71-00 average.

 

SK

Edited November 18, 2014 by snowking

[Bristawl Si]

Great post SK.

Loving some of the more coherent and technical posts on NW in last couple of weeks outlining thoughts for the Winter to come, by a few 'key' posters.

Before 09/10 and Nov/Dec 10, only Winter of note to kick off in earnest before Xmas, with cold and snow was 81 (imby) in my lifetime.

I've always viewed snow before Xmas as something of a bonus, for these parts.

Edited November 18, 2014 by Bristle boy