In Depth Model Discussion and Summaries

[johnholmes]

the main thing shed' is that plenty of folk read it, on a quiet day 64 reads is not bad. But yes I too find it sad that objective model watching is looked upon as 'boring' by some especially in winter, but never mind, the sun is out here after a very dull and rather cool morning so all is forgiven!

[shedhead]

the main thing shed' is that plenty of folk read it, on a quiet day 64 reads is not bad. But yes I too find it sad that objective model watching is looked upon as 'boring' by some especially in winter, but never mind, the sun is out here after a very dull and rather cool morning so all is forgiven!

Don't disagree JH, of course folk read it, but because it does not fit with what they want to see very few hit the 'like' button. Had you provided charts to show a good chance of HP drifting east and bringing a significant heatwave the majority of those who read it would have 'liked' it for certain.  In my opinion the 'like' button is not there to be used just because you like the weather being talked about, it's there to show appreciation for the content and effort involved in producing it, but perhaps I'm wrong...anyhooo, rant over! 

Edited July 8, 2013 by shedhead

[Suburban Streamer]

keep up the good work John, excellent stuff

[johnholmes]

thanks for that, here is the latest one copied from the model thread, easier to find in here even in summer

latest 500mb update 9 july 2013.pdf

[chionomaniac]

Thanks JH, an excellent informative post. Sad to see so few members appreciating it, simply (in my opinion) because it shows what many don't want to see. Does make you wonder sometimes if this is a forum for genuine weather enthusiasts, or just those who simply crave bitterly cold winters and boiling hot summers.

It is of course a forum for all of those criteria, Shed ( by wanting a particular type of weather type in a season does not mean that you not geniune in your enthusiasm for weather, as you seem to suggest).

[cooling climate]

A look at how the 500mb anomaly models have changed over the last 4-5 days indicating a change for many after this week.

500mb chart changes Monday 8 july 2013.pdf

 

Another instant among many others that show you can not put to much stock in the anomaly charts.

Just like any other forecasts or charts they are not infalable but then try to second guess the weather

and state of the atmosphere will always have its pitfalls I suspect.

Edited July 14, 2013 by cooling climate

[johnholmes]

hi cc

As you probably know I did about 2 years of daily checks on them to arrive at my suggestion that on 70% of occasions 6-15 days ahead they will get the upper pattern correct. I still stand by that. You have of course highlighted one where the charts I showed are hardly what we see overhead at the moment.

There is then the much more difficult task of trying to get the bottom 18,000 feet of the atmosphere correct, the hardest part as it contains that nasty ingredient called moisture. If my memory serves me correctly some 80% of moistre (water vapour and ice) occurs below 18000ft. The clever meteorologists that chose 18000ft decades ago as the basis for trying to predict the weather 2-3 days ahead were pretty savvy folk. Mind you the next generation then went to 30,000ft where there is even less moisture but then even more trouble trying to work out the bottom 29,000 feet, hence why the 18,000 feet charts (500mb) are still used in the christmas pudding.

 

well the last two words are funny, quite why the Net Wx filter has chosen those I have no idea, I did try to say - 

m-o-d-e-r-n e-r-a !!

below is the actual 500mb chart and one can see from that, remember it will change as the GFS/Extra output updates, the trough is way west hence out summer remains intact.

http://www.netweather.tv/secure/cgi-bin/premium.pl?action=gfs;sess=45d24ed4e3635bd7395286189e088ec6

 

re the charts I will get round to maybe a weekly outlook using them again from some time in August, in here and copied into the other somewhat more hectic thread.

I will guarantee one thing, they will be produced with as little bias as I can manage and be totally objective and also honest when they go wrong as they will at times.

Edited July 14, 2013 by johnholmes

[Bristawl Si]

Don't disagree JH, of course folk read it, but because it does not fit with what they want to see very few hit the 'like' button. Had you provided charts to show a good chance of HP drifting east and bringing a significant heatwave the majority of those who read it would have 'liked' it for certain.  In my opinion the 'like' button is not there to be used just because you like the weather being talked about, it's there to show appreciation for the content and effort involved in producing it, but perhaps I'm wrong...anyhooo, rant over!

Oh dear....."significant heatwave" - erm that's what were having and have had since the early July posts.Weather modelling charts = v short shelf life.

[Sky Full]

Maybe amongst all the chat about the synoptic models it is a good idea to see what the longer term drivers are suggesting.

 

If we look at ENSO and I am not even remotely pretending I understand what effect it has on our summer weather patterns. So anyone with such knowledge please put them in-thanks.

The latest output says this

The majority of the model forecasts favour the continuation of ENSO-neutral, with most models

Predicting Niño-3.4 index values below zero (Fig. 6). A smaller number of models (mainly statistical)

predict  weak  La  Niña  conditions  (Niño-3.4  less  than  -0.5°C)  as  soon  as  the  Northern  Hemisphere

Summer. As a result, the forecast consensus indicates larger chances for La Niña relative to El Niño, but

There still remains close to a 60% or greater chance of ENSO-neutral through the Northern Hemisphere

Summer 2013 (see CPC/IRI consensus forecast

 

On to the MJO it currently is in phase 1 which equates to the 500mb pattern shown in the link below

http://www.americanwx.com/raleighwx/MJO/MJO/JunePhase1500mb.gif

In brief a block from se Iceland over the UK down across western Europe and into north Africa.

It appears to be heading towards phase 8 with reasonable amplitude which usually gives a little more credence to the forecast.

Phase 8 is in the link below and I have given both June and July as we are nearing month end.

Phase 8 in June equates to the block still there to some extent but having retreated south east with low values over the Iceland area as well as in the region of the Azores.

For July the picture is as below

http://www.americanwx.com/raleighwx/MJO/MJO/JulyPhase8500mb.gif

Again in brief with the upper ridge having regained some ground north west and also out over Scandinavia.

 

The AO is currently +ve and predicted to edge down with the NAO even more +ve and again predicted to edge down.

 

To the shorter term and the 500mb anomaly charts. All 3 have over the past 3 days suggested some kind of +ve heights, over Europe and Scandinavia with the trough being filled out as the heights rise over Europe. They are not totally alike but are along similar lines in the major pattern idea.

 

Thus the increasing tendency of the synoptic models to show more situations that are similar with surface high pressure shown over or close to the country do have some merit. Discussions as to how warm/hot etc are not for this post as it is simply to give some background to why the 4x and 2x daily synoptic charts are showing this pattern at times.

 

It is still to early to go for this set up but I would think in the 6-15 day time scale then, starting in the south (SE) a more settled pattern is going to develop and probably (60% at the moment but increasing) slowly extend further north. How far is too far ahead but much of the UK away from the far NW should see this development occurring in my view.

 

As always this carries the usual forecast health safety warning.

Copying into the model and more leisurely thread areas

 

John

John.

I always try to read your posts but don't think about 'liking' them - doesn't mean I don't like em though! IMO I don't think anyone makes more accurate or more informative contributions than you and your post from June 27 is evidence of this. Did anyone else in June forecast the present settled spell, moving slowly north, which exactly came to pass? That the conditions also brought about higher than average temperatures for 10 days could not possibly be foreseen that far ahead.

I am interested in the relationship between the jet stream at 30000 ft and weather conditions on the ground because the move away from settled heat is coinciding with the jet stream moving south of the uk again. Many are interpreting current models as introducing a period of thunderstorms and rain early next week - is the jet stream an engine of this change or just another symptom? Or is there somewhere I could find out more on this subject? SF

[johnholmes]

hi skyfull

Just noticed this as I was about to post something-give me a bit of time as I am fairly busy just now having just got back from holiday and I will try and reply to you.

the same post is also in the model thread but this is often easier to find

 

 

500mb charts-how close to the actual thur 25 july 2013.pdf

 

[johnholmes]

I am interested in the relationship between the jet stream at 30000 ft and weather conditions on the ground because the move away from settled heat is coinciding with the jet stream moving south of the uk again. Many are interpreting current models as introducing a period of thunderstorms and rain early next week - is the jet stream an engine of this change or just another symptom? Or is there somewhere I could find out more on this subject? SF 

 

the short answer is the whole atmosphere is linked so what happens with the jet and the 500mb anomaly charts is always linked. As to which comes first then it is the usual cheicken and egg really. Both happen because of the other and without each neither can occur if that makes sense.

The jet is the manifestation of the difference between hot air to its south and cold air to its north, winter and summer. It moves huge amounts of heat and moisture around the hemisphere and its opposite number does so in the southern hemisphere. They are different largely because of the topography in the two hemispheres and the amount of ocean.

The 500mb anomaly charts are a guide to what is happening  in the atmosphere. Decades ago before computers the level was called the level of non divergence, Sutcliffe theory etc, and has continued to be a useful level to indicate in the ranges 6-15 days what the overall upper air pattern is likely to be. The bottom 18,000ft of the atmosphere is hugely difficult to get a hold of in the same way. part of that is due to the great majority of the moisture in the atmosphere is in that level and that is incredibly difficult to predict be it 12 hours ahead, will it rain, when, where, will there be a thunderstorm type question, to the more general idea of where the water vapour may be in 6-15 days time and hence what will the actual weather be.

 

bit rushed but hope it helps. If I have made any errors then folk please correct any?

Edited July 25, 2013 by johnholmes

[Sky Full]

I am interested in the relationship between the jet stream at 30000 ft and weather conditions on the ground because the move away from settled heat is coinciding with the jet stream moving south of the uk again. Many are interpreting current models as introducing a period of thunderstorms and rain early next week - is the jet stream an engine of this change or just another symptom? Or is there somewhere I could find out more on this subject? SF 

 

the short answer is the whole atmosphere is linked so what happens with the jet and the 500mb anomaly charts is always linked. As to which comes first then it is the usual cheicken and egg really. Both happen because of the other and without each neither can occur if that makes sense.

The jet is the manifestation of the difference between hot air to its south and cold air to its north, winter and summer. It moves huge amounts of heat and moisture around the hemisphere and its opposite number does so in the southern hemisphere. They are different largely because of the topography in the two hemispheres and the amount of ocean.

The 500mb anomaly charts are a guide to what is happening  in the atmosphere. Decades ago before computers the level was called the level of non divergence, Sutcliffe theory etc, and has continued to be a useful level to indicate in the ranges 6-15 days what the overall upper air pattern is likely to be. The bottom 18,000ft of the atmosphere is hugely difficult to get a hold of in the same way. part of that is due to the great majority of the moisture in the atmosphere is in that level and that is incredibly difficult to predict be it 12 hours ahead, will it rain, when, where, will there be a thunderstorm type question, to the more general idea of where the water vapour may be in 6-15 days time and hence what will the actual weather be.

 

bit rushed but hope it helps. If I have made any errors then folk please correct any?

Thanks for taking the time to provide such a detailed response. If ever there could a short answer to my question, that would be it! I am beginning to understand the totally interconnected nature of all the various components of the atmosphere and that the jetstream is just one of these, albeit quite an important player and one of the tools used in forecasting. It just brings home how difficult it is to predict the workings of this chaotic system sufficiently accurately to avoid criticsism. I will continue to read your posts with great interest and read up on this some more.

[johnholmes]

Once again some folk are looking too closely at specifics at the surface way ahead.

 

That is referring back to the model thread where this is also posted.

 

Instead of that watch the two models out to T+240 and how they both shift the upper trough from a position west of the UK and pulling in air from a warm even hot source to something quite different.

See below, on the free version

http://www.netweather.tv/index.cgi?action=modelcomp;sess=

 

This ties in pretty well with the overall idea from the anomaly charts that the upper trough is going to move east. I think that the NOAA version, link below and the ECMWF-GFS link below that, will be the nearest of the 3 outputs in the 6-12 day time scale.

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

 

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

Notice also the wave length of the major troughs, roughly 70-80 degrees between the 3. A 3 trough system with this spacing is often very slow to alter significantly in terms of the major wavelength pattern.

Another factor to support this is that the MJO is in a very low orbit, forget what phase it does not matter, and the prediction I use shows no change in amplitude although the phase is indicated to change. This suggests that there is nothing in the tropical set up to make for any marked change in the disturbed temperature latitudes which is where we sit alongside much of Europe.

 

Again there seems nothing looking at the upper air charts in the Tropics/Caribbean area to suggest any major tropical storm development in the next few days.

 

Putting all this together and I would go for the upper air pattern much as NOAA 8-14 shows. Of course the weather may make a fool of me yet again but it is to me the form horse over the past few days for the early part of August possibly the first 10 days or so.

 

Dropping this into the other area, technical although the content is not really technical-just sometimes easier to find.

Edited July 30, 2013 by johnholmes

[johnholmes]

also in the model thread, some comments about the 500mb charts leading to the change from the upper air around the UK changing from ridge dominated to trough dominated.

 

500mb anomaly charts-july to august 2013 on sat 3 august.pdf

[johnholmes]

an example of good guidance from 500mb anomaly charts in the 6-10 day range

 

 

500mb correct prediction july to august 2013.pdf

[johnholmes]

the 500mb ideas for August BH weekend from about 16 August

 

 

what did the anomaly charts suggest for the August BH weekend.pdf

[Isolated Frost]

a few AO composites I've been working on, with pretty sound results

 

AO for September neutral and October neutral (mild, wet and southwesterly dominated)

Strong signal for -ve anomaly over Iceland and Greenland during November-February, especially in December-February. Much milder for NW Europe and colder for SE Europe during the winter months when AO is neutral in both September and October.

 

AO for September neutral and October positive (mixed start, cold ending from the east)

-ve heights to north and east and +ve heights for south and west to begin winter, but when rolled onto December-February, it's a strong signal for +ve heights to north and east and -ve heights for south.

 

AO for September neutral and October negative (stormy and mixed throughout, very wet)

strong consistent signal for +ve heights to the north, and then north-west and -ve heights across the UK. 

 

AO for September positive and October neutral (generally mild, very dry and high pressure dominated)

consistent signal for +ve heights across the UK, and increasingly -ve heights to the north later on in the winter. Colder for E Europe.

 

AO for September positive and October positive (extremely mild, quite wet)

+ve heights to east and -ve heights to west with Southerly flow early on, changing to more SW/W flow with increased precipitation later on.

 

AO for September positive and October negative (mixed signals, 2003/04 and 2005/06 milder, 2009/10 and 2012/13 cooler)

an anomaly. 2003's and 2005's November AOs were positive, and therefore late January and February relatively mild, whilst 2009's and 2012's November AOs were neutral, after extremely -ve October AOs, which gave exceptionally cold January/February conditions

 

AO for September negative and October neutral (cold start, drier and less cold later on)

extreme +ve anomalies to the north and west, -ve anomalies to the south-west and south, very cold early on, turning milder as +ve anomalies move south and -ve anomalies to the north appear

 

AO for September negative and October positive (only 2001/02, but similar to above, less cool and slightly milder)

very dry with +ve heights over UK early on, they transfer south later on with -ve heights to the north and a wetter, milder end to winter

 

AO for September negative and October negative

none found

 

That's part 1 of this 'experiment', part 2 will have October-November links that will give composites for December-March, I was really surprised at how consistent these composites were, and will definitely use them to make a forecast this winter

Hope this is interesting to anyone and feedback would be appreciated

Edited August 25, 2013 by Isolated Frost

[Isolated Frost]

part 2 (for December to March)

 

AO for October neutral and November neutral (very dry, increasingly mild)

+ve heights across the UK, slowly moving SE towards the start of Spring, large -ve heights to the north, dry throughout

 

AO for October neutral and November positive (similar to above, but slightly milder and wetter)

extreme +ve heights to the south and south-west of the UK and -ve heights to the north, very wet, very mild, one of the warmest possible solutions

 

AO for October neutral and November negative (colder, increasingly wetter, stormy)

strong +ve heights to north and north-east, -ve heights to south-west, increasingly -ve heights over the UK, very wet, colder to the north and north-east

 

AO for October positive and November neutral (mixed start, increasingly stormy and milder)

general southerly flow earlier on, average temperatures and rainfall, turning stormier and wetter into February and March

 

AO for October positive and November positive (colder and drier, at times much warmer, dominated by the continent)

beginning slightly subdued, +ve anomaly over UK and to north and south/east, -ve anomaly to west, SE flow, increasing E flow into January and February... curiously January 1987 and February 1991 both occurred during the 3 of the past 30 years in which October and November had a +ve AO, conductive to continental outbreaks?

 

AO for October positive and November negative (mild start, increasingly cold from the east, very dry)

begins with generally -ve heights over Europe and +ve heights over Russia, increasingly cold as -ve heights drop south and +ve heights move into the north and west, very dry and increasingly cold

 

AO for October negative and November neutral (extremely cold, deep north and east winds)

huge +ve anomaly to the north and north-west,-ve anomaly to the south, consistently cold north/east flow, very, very cold

 

AO for October negative and November positive (very dry, average to cooler)

weak -ve anomaly to the east and +ve heights surrounding it, generally dry and mixed, becoming milder and drier later on

 

AO for October negative and November negative

none found

 

I think that this is a really interesting experiment, because the consistency of the composites are very good, considering it is based on one teleconnection based on roughly 2 month lag; for coldies, the best AO pattern seems to be September -ve, October -ve and November -ve, something that has happened just once since records began in 1950, in 1968/69, for sun lovers it seems to be September +ve, October neutral and November neutral, and for storm obsessors, 3 neutrals would seem to suffice

 

again, any feedback would be great and any criticism as well

[johnholmes]

copied from the model thread

 

 

What may be in store for September 13-31 august.pdf

 

ps

Thanks for that detailed work above IF, I have no knowledge to prove or disprove your ideas but a lot of work and maybe you have something. Others with more knowledge may respond once they notice it-thanks anyway.

Edited September 6, 2013 by johnholmes

[Suburban Streamer]

thanks Isolated Frost for the above 2 posts - unfortunately i cant see any of the composites is it just me?

[summer blizzard]

 

High amplitude phase 6 forecast.

 

Anybody have the composite for September.

[johnholmes]

the latest ENSO prediction can be found here

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf

 

High amplitude phase 6 forecast.

 

Anybody have the composite for September.

phase 6 see below for September

http://www.americanwx.com/raleighwx/MJO/MJO/SeptemberPhase6500mb.gif

 

sorry for some reason it will not allow it

low heights from the pole to southern Europe over the UK and to our east and positive heights from southern Greenland down to the west of the UK towards Iberia

Edited September 5, 2013 by johnholmes

[Gael_Force]

Here is September composite for phase 6.

 

[Gael_Force]

....and for October as the lag may take us closer to that month.

 

[mushymanrob]

so if the mjo is correct, the outlook is decidedly cool