In Depth Model Discussion, Analysis and Summaries

[Glacier Point]

There are definately changes afoot in the middle timeframe.

Zone's 1,2 and 3 have experienced a marked uplift in ENSO temperatures in the last week along with a subtle shift in the tropics.

It's too early to see whether this is a longer term 3 month change but will need watching over the next few weeks. What we have also seen is the SOI 90day avg hitting 20+ and the 30day avg hitting 25+

In the last decade whenever the 90day avg has gone above 20 it has always been followed by a sharp fall to at least 10, it looks like some almost in built mechanism.

My prediction is that October will be a month of variability and shifting in the longer range predictors.

Note sure I would want to place too much emphasis on the last 10 years as a reliable guide here given the potential historical significance of where the coupled ocean-atmosphere is now and the strength of the cold sub-surface anomalies in the Pacific.

All atmospheric indicators are gunning for Nina conditions. These are constructively interfering with the Pacific circulation and aiding upwelling of colder sub-surface waters in the central Pacific. There's plenty of cold water in the tank with values dipping below -4. Take a look at the sub-surface profile over the last few weeks:

I'm thinking come December after at least one further trade wind surge in the next 3-4 weeks we could see the atmospheric base state in a record low angular momentum - July and August coming very close to 2007 in terms of low angular momentum. I can easily see the sub-surface reacting and the CFS forecast for DJF is strong, potentially rivalling the winter of 1973:

Those lessening ENSO regions 1 + 2 values are probably just responding to westward pushes in cold water. Interesting the CFS goes for a further dip in these areas next Spring. The start of the Nina of 2011?

May be i am missing something here, but with us moving into la Nina and conditions ripe for a positive NAO over the next few days, will that not make the difference to the projected GWO phase.

I see the Westerlies continue well into mid October and the jet being kept South, influenced by deep low pressure towards Greenland. I can not see a sustained ridging in the Atlantic making its presence felt here in the UK or moving us moving towards phase 2 due to this.

I am not as experienced in this area as some on here, so i expect to be corrected, but i have posted this so that i can learn so when correcting please add explanation as to why this line of thinking is wrong, so i can learn from it and anyone else who needs further understanding of this subject.

It's true that a deep upper low over Iceland can sustain low heights over Greenland by lowering the tropopause and deflecting Rossby waves and continuing cooling of the stratosphere above it. However, in this instance, and I think as a template for the winter, the Pacific wavelength associated with La Nina is going to be hard to overcome in the long run, signalling a band of mid ridges arond the northern hemisphere. Continued signs that as the GWO swings back to phase 2, modelling backs off the zonal flow.

Edited September 30, 2010 by Glacier Point

[chionomaniac]

Interesting state and forecast for the MJO presently - the first time a strong amplitude wave is forecast for some time.

Currently we are in phase 3:

But with a strong phase 4 forecast by most models:

It looks like the current model output has a lot of support.

The composite analogue for MJO phase 4 in October suggests a lot of Northern blocking from Scandinavia to Greenland with a southerly tracking jet stream.

Interesting to see where we go from there onwards.

[Glacier Point]

Support also from the GWO Ed.

Curently in phase 3 and likely to persist there for the next 8-10 days. Composites for phase 3:

[BLAST FROM THE PAST]

very interesting. May I submit that the solar and lunar phasing foresaw this set up sometime ago as I alluded to in my previous signature, as also the onset of a significant La Nina. There certainly seems to be an agreeable outlook. We are in Las Nina perturbation cycle since Feb 2007 and this equates to a 'general' -ve NAO state due to the southerly shift of the jetstream. To me it seems no coincidence that the teleconnections 'agree' with the method I use. This theme is likely to continue overall for sometime to come.

Great updates guys

BFTP

Edited October 4, 2010 by BLAST FROM THE PAST

[cooling climate]

Interesting state and forecast for the MJO presently - the first time a strong amplitude wave is forecast for some time.

Currently we are in phase 3:

But with a strong phase 4 forecast by most models:

It looks like the current model output has a lot of support.

The composite analogue for MJO phase 4 in October suggests a lot of Northern blocking from Scandinavia to Greenland with a southerly tracking jet stream.

Interesting to see where we go from there onwards.

I have been following this the last few days myself along with the EWP forcasts.

Could you tell me how or where you get the composite analogues from please.

[Typhoon John]

You can get MJO composites here: http://raleighwx.easternuswx.com/MJO.html

Not sure if GWO is available like that but you can construct the composites yourself using this site: http://www.esrl.noaa.gov/psd/cgi-bin/data/composites/printpage.pl if you know which data applies.

[Glacier Point]

Just to throw this one into the mix,

September's NAO value was negative and that makes 9 months on the bounce with negative values. First time since records started in 1950 that this has been the case.

http://www.cpc.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table

[cooling climate]

I am convinced this negative phase along with the AO has a lot to do with the

very long weak solar activity we are in and would not be surprised to see the

NAO and to a lesser extent the AO continue negative through the months ahead.

Cheers for the links Jonathan F. although the MJO does not seem to work.

Now all I have to do is suss out how to use them.

Edited October 5, 2010 by cooling climate

[Typhoon John]

http://raleighwx.eas...wx.com/MJO.html this link? Works ok for me.

You need to look at what phase the MJO is in or where it is forecast to go. Like in chionomaniac's post above, the MJO is forecast to head towards phase 4 and then ultimately phase 5: http://www.cpc.ncep....EFS_membera.gif

Looking at the the composites, scroll down to the mean monthly 500mb Height Anomalies for Phases 1-8. Under phases 4 and 5 look at the charts for October, this shows the pressure anomalies that are likely to be observed under this MJO phase, at this time of year, based on data from the last 60 years. So the two charts we get are:

http://raleighwx.eas...toberPhase4.gif

http://raleighwx.eas...mbAnomalies.gif

That's pretty much in line with what we have been seeing from the models.

I think it might be the other link that wasn't working properly, try this:

http://www.esrl.noaa...ata/composites/

This is just a page that lets you interrogate the reanalysis data yourself. But you need to know what variables you're using. So if you want to plot the 500mb height anomalies based on the GWO you'd need to feed in the octobers for the years when the GWO was in the same phase as present, i.e. phase 4. http://www.esrl.noaa...gcm/gwo_40d.gif

But it's not something I use all the time, so there maybe easier ways to do it.

[cooling climate]

Jonathan F. your a diamond thank you.

[BLAST FROM THE PAST]

I am convinced this negative phase along with the AO has a lot to do with the

very long weak solar activity we are in and would not be surprised to see the

NAO and to a lesser extent the AO continue negative through the months ahead.

I partially agree with this. I believe the NAO is in general negative phase in line with the solar driven approx 36yr perturbation cycle. It changed in Feb 07 which if one remembers so the southward shift of the jetstream. I believe this -ve NAO is enhanced further by the low solar activity and likely to be re-inforced as we head into the next cycle and a true grand minima. That is 20 years away though.

BFTP

[chionomaniac]

Just to throw this one into the mix,

September's NAO value was negative and that makes 9 months on the bounce with negative values. First time since records started in 1950 that this has been the case.

http://www.cpc.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table

Just to emphasize that, look at this 500hPa anomaly chart for the last year. Quite something isn't it.

Edited October 6, 2010 by chionomaniac

[Duane S.]

Just to throw this one into the mix,

September's NAO value was negative and that makes 9 months on the bounce with negative values. First time since records started in 1950 that this has been the case.

http://www.cpc.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table

Yep, beating 1963 which finally went positive in September of that year. Even more impressive, it's now 12 consecutive months going back to October of last year that we have had a negative NAO.

Some interesting facts about the monthly NAO index (well, at least I find it interesting ). Taking each month from 1950 until now, None of the 20 highest value months in that period (1950 - Sept. 2010) fall within the past 16 years (1995 through to and including 2010), yet 10 of the 20 highest value NAO months fall within the previous 9 years! (1986-1994). Read into that what you will! A similar story occurs with the AO which shows the stark contrast between values returned in the late eighties and those that have occured in very recent times (certainly the Dec-Feb average of -3.42 will take some beating!).

This year is set to produce a remarkable -NAO by the looks of things

The last 20 years yearly (Jan-Dec) average comes in at...

1989: 0.7

1990: 0.6

1991: 0.3

1992: 0.6

1993: 0.2

1994: 0.6

1995: -0.1

1996: -0.2

1997: -0.2

1998: -0.5

1999: 0.4

2000: 0.2

2001: -0.2

2002: 0.0

2003: 0.1

2004: 0.2

2005: -0.3

2006: -0.2

2007: 0.2

2008: -0.4

2009: -0.2

2010: Currently (Jan-Sept) -1.05!! (Unlikely to finish year end that low but still odds on to end up highly negative)

The AO, as is normally the case, closely follows suit...

1989: +1.0

1990: +1.0

1991: +0.2

1992: +0.4

1993: +0.1

1994: +0.5

1995: -0.3

1996: -0.5

1997: 0.0

1998: -0.3

1999: +0.1

2000: 0.0

2001: -0.2

2002: +0.1

2003: +0.2

2004: -0.2

2005: -0.4

2006: +0.1

2007: +0.3

2008: +0.2

2009: -0.3

2010: Currently (Jan-Sept) -1.00!!

Edited October 8, 2010 by s4lancia

[MR EXTREMES]

id be more worried that the long neg nao could flip very soon to positive that would throw a spanner in the works for our winter.

[snowking]

Yep, beating 1963 which finally went positive in September of that year. Even more impressive, it's now 12 consecutive months going back to October of last year that we have had a negative NAO.

Some interesting facts about the monthly NAO index (well, at least I find it interesting ). Taking each month from 1950 until now, None of the 20 highest value months in that period (1950 - Sept. 2010) fall within the past 16 years (1995 through to and including 2010), yet 10 of the 20 highest value NAO months fall within the previous 9 years! (1986-1994). Read into that what you will! A similar story occurs with the AO which shows the stark contrast between values returned in the late eighties and those that have occured in very recent times (certainly the Dec-Feb average of -3.42 will take some beating!).

This year is set to produce a remarkable -NAO by the looks of things

The last 20 years yearly (Jan-Dec) average comes in at...

1989: 0.7

1990: 0.6

1991: 0.3

1992: 0.6

1993: 0.2

1994: 0.6

1995: -0.1

1996: -0.2

1997: -0.2

1998: -0.5

1999: 0.4

2000: 0.2

2001: -0.2

2002: 0.0

2003: 0.1

2004: 0.2

2005: -0.3

2006: -0.2

2007: 0.2

2008: -0.4

2009: -0.2

2010: Currently (Jan-Sept) -1.05!! (Unlikely to finish year end that low but still odds on to end up highly negative)

The AO, as is normally the case, closely follows suit...

1989: +1.0

1990: +1.0

1991: +0.2

1992: +0.4

1993: +0.1

1994: +0.5

1995: -0.3

1996: -0.5

1997: 0.0

1998: -0.3

1999: +0.1

2000: 0.0

2001: -0.2

2002: +0.1

2003: +0.2

2004: -0.2

2005: -0.4

2006: +0.1

2007: +0.3

2008: +0.2

2009: -0.3

2010: Currently (Jan-Sept) -1.00!!

Very interesting to highlight to those less experienced members too the significance of the 2007 values for both NAO and AO, with 2007 having been one of the poorest in recent times for the UK (well, the poorest amongst a long running spell of poor winters). Hopefully this highlights the significant role both a negative NAO and AO play in colder winters for NW Europe

SK

[weather eater]

Very interesting to highlight to those less experienced members too the significance of the 2007 values for both NAO and AO, with 2007 having been one of the poorest in recent times for the UK (well, the poorest amongst a long running spell of poor winters). Hopefully this highlights the significant role both a negative NAO and AO play in colder winters for NW Europe

SK

Those are certainly some interesting figures, if we keep with a negative NAO for the rest of the year, then this year will dwarf previous negative years.

NAO

-0.5 in 1998, currently -1.05

AO

-0.5 in 1996, currently -1.00

Those are quite astonishing figures.

[Pennine Ten Foot Drifts]

Very interesting to highlight to those less experienced members too the significance of the 2007 values for both NAO and AO, with 2007 having been one of the poorest in recent times for the UK (well, the poorest amongst a long running spell of poor winters). Hopefully this highlights the significant role both a negative NAO and AO play in colder winters for NW Europe

SK

Not sure I understand, I thought AO/NAO were simply expressions of pressure differentials, and not drivers in themselves. In other words, AO/NAO do not 'play a role' in any seasonal outcome, they are merely expressions of the pressure state in the Atlantic/North Atlantic, and of course one would expect to see negative values in a colder winter because colder winters are often characterised by blocked patterns i.e. higher than average pressure to our west/north west. In other words negative AO/NAO is merely another facet one could reasonably expect to see in colder winters, and not in any way a contributing factor to the cause of colder winters ?

[Weather-history]

Yep, beating 1963 which finally went positive in September of that year.

Looking at that list, it actually went postive in the May with +2.16

[knocker]

Those are certainly some interesting figures, if we keep with a negative NAO for the rest of the year, then this year will dwarf previous negative years.

NAO

-0.5 in 1998, currently -1.05

AO

-0.5 in 1996, currently -1.00

Those are quite astonishing figures.

It appears to have gone positive so far for Oct.

NAO +.32

AO +.25

PNA +.27

[Weather-history]

Just to throw this one into the mix,

September's NAO value was negative and that makes 9 months on the bounce with negative values. First time since records started in 1950 that this has been the case.

http://www.cpc.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table

Looking at that list

15 of the last 16 months have been -ve

25 of the last 30 months have been -ve

Since April 2008, the only +ve months have been Sep 2008, Feb 2009, Mar 2009, May 2009 and Sep 2009

[phil nw.]

Yes a remarkable series of neg.values illustrated further by looking at the Historical Graphs here,

[Duane S.]

Looking at that list, it actually went postive in the May with +2.16

Yep, you are right, I missed that. A very positive month.

[johnholmes]

below is a pdf giving my ideas on how realistic is the prediction from GFS and now ECMWF for a coldish snap in 7-10 days; largely for newcomers and trying to help them get used to the terms which many of us use in both the tecknical and model threads over the coming months.

Part 6 from 8 October 2010-lrf.pdf

the 7:30 on comment at the end should read 70% to 30% of it happening, however brief in the time period dealt with.

Edited October 8, 2010 by johnholmes

[phil nw.]

below is a pdf giving my ideas on how realistic is the prediction from GFS and now ECMWF for a coldish snap in 7-10 days; largely for newcomers and trying to help them get used to the terms which many of us use in both the tecknical and model threads over the coming months.

Part 6 from 8 October 2010-lrf.pdf

the 7:30 on comment at the end should read 70% to 30% of it happening, however brief in the time period dealt with.

Thankyou John as ever a good presentation.

Latest runs do seem to favour blocking close to our Latitude up to T240hrs.with any Colder air tending towards Scandinavia/Russia later on with the flow likely to be more from the North West for the UK.

[weather eater]

It appears to have gone positive so far for Oct.

NAO +.32

AO +.25

PNA +.27

If model runs are to be believed then that will soon change .