In Depth Model Discussion, Analysis and Summaries

[BrickFielder]

Looks like the stratosphere might be developing in a way which could favour a colder period in the UK, with the dislodged vortex (currently towards us) splitting.

This gives the uk a tendency towards higher pressure.

What this will mean is that the models will become a bit more unreliable outside of the 5 day period.

In contrast though the GWO did an about turn on the 25th of Jan and went into a higher angular momentum orbit in stage 5.

GWO

Eventually this must come crashing down through stages 6,7 and 8 though with the SOI in the negative area and an MJO event stagnant and building in the western pacific we wait to see what happens.

MJO

[Glacier Point]

First good indication of propagation from the upper layers.

Heat flux at 60N shows negative values -10 km/s:

http://acdb-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/vtn_150_2009.pdf

Zonal wind anomalies to -20 m/s permeating down to 300 hPa:

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_UGRD_ANOM_JFM_NH_2010.gif

These are very good for blocking structures to form at 60N.

Relative angular momentum leaving out the QBO signal has gone off the scale thanks to growing momentum in the tropics:

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/glaam.sig1-21.90day.gif

The GWO has responded with a high amplitude phase 5 orbit (signal blocking to our north):

http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

Both frictional and mountain torques are positive. There is some scope for the Asian Mountain Torque to deliver the icing on the cake here and shoot tendency in relative angular momentum to an extreme value. That will prolong the duration in phase 5.

So definate support for cold, indeed very cold. The positioning of the high is still open to doubt beyond day 5 but looking very positive for the third cold wave of the winter.

Finally, another positive, stratospheric ozone concentrations are huge across large parts of the northern hemisphere mid and high latitudes. They are also falling across the tropics once more, similar to mid December:

http://www.cpc.ncep.noaa.gov/products/stratosphere/sbuv2to/gif_files/sbuv17_ll_latest.gif

[lorenzo]

T+12 days since the last major input from MJO and a shift in pattern from the January lull(mild).

I reckon that's a usable timeframe for transport of Indian Ocean convection to Upper to Lower + 3 days for models to factor.

From what you have written GP, would really like to know more about GWO and how the angular momentum contributes to the mid-range forecasts, are there relativities based on stage which are then adjusted via torque factors?

If you were to review this winter synoptic - which would you qualify as the most consistent signal for cold?

[Glacier Point]

T+12 days since the last major input from MJO and a shift in pattern from the January lull(mild).

I reckon that's a usable timeframe for transport of Indian Ocean convection to Upper to Lower + 3 days for models to factor.

From what you have written GP, would really like to know more about GWO and how the angular momentum contributes to the mid-range forecasts, are there relativities based on stage which are then adjusted via torque factors?

If you were to review this winter synoptic - which would you qualify as the most consistent signal for cold?

More reading on the mechanism here..

http://www.esrl.noaa.gov/psd/map/clim/wb08_revised_final.pdf

Without doubt, the most consistent signal for cold (and also warm in summer) is a sudden surge in angular momentum. This product hasn't updated yet but the last few days will also feature a similar and greater increase:

http://www.esrl.noaa.gov/psd/map/images/aam/glaam.gif

Moving to the longer term discussion in front of us....

Zonal wind forecasts clearly demonstrate why for the next 7 days we are going to srtruggle to get the core of the high pressure above 60N. Note the residual west flow over the Arctic, slight negative anomaly over 60N and strong -ve zonal wind flow centred 20 hPa.

The positioning of the high is about right I think on model solutions out to days 5-7, and is in line with GWO composites for phases 5-6.

As stated previously, I think the key to unlocking the next evolution is the downwelling of those east zonal wind anomalies between 60N and 80N. The dates posted - mid month onwards continue to look the most reasonable and safest progression, between 21 and 28 days.

Assuming we see some propagation, the latitudinal positioning of the high will shift poleward. GWO progression will likely be heading towards phases 6-7-0:

http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

Looking at composites for phases 7/8 allowing for months with -AO suggests the following pattern:

This is in reasonable agreement with the longwave solution put up by GFS / GEM ensemble mean heigt anomalies. The evolution may take some time though, and a continual failure of the models has been to rush this. The key features are obviously the blocking to the north, an increasing precipitation signal as pressure drops from the SW and also that trough persisting over Scandinavia. That looks cold and also unsettled. Interesting.

[chionomaniac]

Thanks for the update, GP.

Do you think that we need a push from the upper layers of the stratosphere to help propagate those middle strat negative anomalies? I thought last year that this may be important but this year I am more inclined to believe that how receptive the state of the troposphere is, will be the crucial factor to allowing the propagation through.

MMW still on track for next Tuesday.

c

[lorenzo]

Thanks for the reply, got some reading to do now - excellent stuff.

[lorenzo]

http://www.cpc.noaa....y/610day.03.gif

Can anyone interpret the main features of this chart for me?

Edited February 7, 2010 by lorenzo

[johnholmes]

http://www.cpc.noaa....y/610day.03.gif

Can anyone interpret the main features of this chart for me?

it shows the main 500mb forecast flow for the dates shown, they are the green lines. The red dotted lines show where +ve anomalies of 500mb height are expected and the blue ones the -ve areas.

is that any help?

Edited February 7, 2010 by johnholmes

[cooling climate]

I hope its all right to post this in here as it gives a great insight as to the drivers behind

the very cold northern hemisphere pattern setting up again.

This is American Met Larry Cosgrove lattest weather America newsletter.

http://www.examiner.com/x-3775-Houston-Weather-Examiner~y2010m2d6-WEATHERAmerica-Newsletter-Saturday-February-6-2010-at-600-PM-CT

If it is wrong to post this please remove.

[lorenzo]

it shows the main 500mb forecast flow for the dates shown, they are the green lines. The red dotted lines show where +ve anomalies of 500mb height are expected and the blue ones the -ve areas.

is that any help?

Top Class, Thank You.

I think this is a good chart for indicating the potential for blocking to our NW - am sure Chiono or GP will factor in the other elements in bringing the w/c 15/02 into perspective.

[Glacier Point]

Looking at angular momentum plots a case may be made which disagrees with the longer term model guidance for heights to fall across the North Atlantic. That would call into question the speed of any potential attempted moderation of cold surface temperatures shortly to be embedded across NW Europe.

Tendency in relative angular momentum is well, well above average and a clear indicator that El Nino has successfully drawn the cooperation of the coupled ocean-atmosphere loop.

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/glaam.sig1-21.90day.gif

Anomalous westerly zonal wind anomalies are showing up in both hemispheres across the tropics and sub-tropics fully cranking up the sub-tropical jet streams.

The Global Wind Oscillation is in phase 5 / 6 transition at high amplitude reflecting the surge in angular momentum:

http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

Frictional torques are still positive whilst mountain torques are neutral. In all probability, there will be another increase in mountain torque over the next 5-7 days which should drive the GWO back into phase 5, further adding momentum. This increases the chances of us remaining in phase 5-6 type orbit for a little while yet. The basic gist of this is that perhaps modelling is being progressive whilst the complex fluxing and eddy transport will be regressive with the pattern. I think a case could be made over the last 10 days of the models rushing evolutions. I've been looking at a couple of historical analogues and 1978 is cropping up on a routine basis. Feb 1978 saw the GWO meandering around phases 5-6-7 for the majority of the month - the net result was pressure being high over southern Greenland, the Hudsons and the North Atlantic.

All of this means that pressure may well be higher to our west and north west for a longer period than currently modelled and the trough to our east also being stronger than modelled. The effects of a reversal in polar westerlies looks like occuring around day 8 in the lower troposphere which would tend to draw the ridge out to our west further north. So whereas some longer range models suggest an attack from the SW winning at least for southern Britain, I'm not so covinced it will that quick as the trough to our east may well be stiffer than anticipated. Interestingly, tonight's ECM extended range ensembles are just hinting at backing off an Atlantic SW attack and cooling back down again.

[bluearmy]

to add to that, i've noticed that both of todays NAEFS take the temps back down again at the end of the run with signs of pressure rising again to the northwest. a question i asked this morning - could we see a complete rerun (in broad terms) of the dec/jan cycle ??

[Duane S.]

Looking at angular momentum plots a case may be made which disagrees with the longer term model guidance for heights to fall across the North Atlantic. That would call into question the speed of any potential attempted moderation of cold surface temperatures shortly to be embedded across NW Europe.

Tendency in relative angular momentum is well, well above average and a clear indicator that El Nino has successfully drawn the cooperation of the coupled ocean-atmosphere loop.

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/glaam.sig1-21.90day.gif

Anomalous westerly zonal wind anomalies are showing up in both hemispheres across the tropics and sub-tropics fully cranking up the sub-tropical jet streams.

The Global Wind Oscillation is in phase 5 / 6 transition at high amplitude reflecting the surge in angular momentum:

http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

Frictional torques are still positive whilst mountain torques are neutral. In all probability, there will be another increase in mountain torque over the next 5-7 days which should drive the GWO back into phase 5, further adding momentum. This increases the chances of us remaining in phase 5-6 type orbit for a little while yet. The basic gist of this is that perhaps modelling is being progressive whilst the complex fluxing and eddy transport will be regressive with the pattern. I think a case could be made over the last 10 days of the models rushing evolutions. I've been looking at a couple of historical analogues and 1978 is cropping up on a routine basis. Feb 1978 saw the GWO meandering around phases 5-6-7 for the majority of the month - the net result was pressure being high over southern Greenland, the Hudsons and the North Atlantic.

All of this means that pressure may well be higher to our west and north west for a longer period than currently modelled and the trough to our east also being stronger than modelled. The effects of a reversal in polar westerlies looks like occuring around day 8 in the lower troposphere which would tend to draw the ridge out to our west further north. So whereas some longer range models suggest an attack from the SW winning at least for southern Britain, I'm not so covinced it will that quick as the trough to our east may well be stiffer than anticipated. Interestingly, tonight's ECM extended range ensembles are just hinting at backing off an Atlantic SW attack and cooling back down again.

Great post again, very interestings thoughts ref feb 1978 analogue, I would certainly take that! One question for you. The Equatorial dateline convection causing the MJO to hang around in phase 7 (and now 8 ) for so long and looks to be in these phases for a while is pretty unusual is it not? This may be a daft question but is this as a result of the El Nino?

Edited February 8, 2010 by s4lancia

[mountain shadow]

This mornings 6Z backs up GP's thoughts to the letter.

[mcweather]

Great post again, very interestings thoughts ref feb 1978 analogue, I would certainly take that! One question for you. The Equatorial dateline convection causing the MJO to hang around in phase 7 (and now 8 ) for so long and looks to be in these phases for a while is pretty unusual is it not? This may be a daft question but is this as a result of the El Nino?

Me too S4L Feb 1978 bring it on.

[WINTRY WALES]

Me too S4L Feb 1978 bring it on.

What was the outcome of Feb 78 guys??

Guessing a snowy spell but for which parts of the UK?

Cheers

WW

Edited February 9, 2010 by WINTRY WALES

[mcweather]

What was the outcome of Feb 78 guys??

Guessing a snowy spell but for which parts of the UK?

Cheers

WW

18/19th Feb 1978 Worst blizzard of the century in Devon and Dorset 15-30 foot drifts common place in exposed rural areas. Major towns like Weymouth and Dorchester completely cut offor a couple of days and rural areas for up to ten days.

Heavy snow also on 15th and 16th feb in south west.

North east England also hit by heavy snowfall as was south Wales

[full_frontal_occlusion]

Hello peeps,

Originally posted on the general model thread but I guess better suited to be answered here. Going to stick my neck out and probably get it shot off however the resident teleconnection and GWO experts may like to comment on the current set of data wrt AAM, Mountain torques and flux convergence wrt next weeks synoptics currently showing n the models:

1) Relative AAM seems to have peaked although still very +ve:

2) Mountain torques have dropped to zero or are now -ve:

3) Frictional torque has gone -ve:

The torques generating the high AAM and hence reverse zonal winds would therefore suggest the westward retrogression of that low pressure system should soon be arrested. That bodes well for the models to begin picking up on a a more favourable South Easterly track?:

4) NAO indexes still show -ve deviation but is that not a function of the ensemble members which perhaps have not picked up on the AAM developments?

A better indicator is the copuling between the MJO and the NAO:

5) MJO is phase 8 transition to phase 1 imminent:

and could move to phase 3/4 within 7 - 10 days with it coupling to the NAO which should show signs of a returning to a less -ve index according to the current crop of mixed ensembles.

This is just my amateur interpretation but to me heralds a pattern change where the reverse zonal winds influence is diminished and we start to see more of an Atlantic feel once again but perhaps some fun times during the transition period starting wrt to that progged low next week, tantalising us with various trajectories depending on which model one cares to view.

Would welcome your expert comments.

Thanks.

ffO

Edited February 11, 2010 by full_frontal_occlusion

[lorenzo]

Quality post - well laid out.

MJO interests me as back to phase 1. Have a look at,and factor in, the Stratospheric analysis from Chiono and then you've got a good feel for where March is going.

[full_frontal_occlusion]

Interesting new developments showing up.

Mountain torques are on the up, MJO flipped back into phase 8 after briefly intruding into phase 1 with frictional torques looking like going +ve shortly.

So the reverse zonals at this time look rather indeterminate one way or the other.

This is still in accordance with GP's observation that ocean/atmosphere coupling is consistent and locked in with the El Nino (or could that be the effect of a Kelvin wave?).

With that forcing symmetry established, one assumes that the current patterns in our locale look locked for the forseeable. However there's the little issue of the MMW to factor downstream.

ffO.

Edited February 13, 2010 by full_frontal_occlusion

[lorenzo]

GP,

Any thoughts on the teleconnections for impact over the next 8-10 days.

MJO seems to have remained indecisive static and AM falling, NAO and AO heading neutral.

[full_frontal_occlusion]

GP,

Any thoughts on the teleconnections for impact over the next 8-10 days.

MJO seems to have remained indecisive static and AM falling, NAO and AO heading neutral.

Hi Lorenzo, yes it woud be good to get GP's thoughts on this. John Holmes wrote an excellent blog entry from first principles which is hard to argue with.

I'm assuming all of your obeservations are based on ensemble forecasts given the MJO space you attached?

Reading from the actuals one could get a different interpretation: mountain and frictional torques are toying with the idea or have weakly returned +ve again. AAM rate of change has decayed but still remains significantly +ve. The highly -ve AO (-5 SD) shows no signs of abating. NAO remains significantly -ve at around -4/5 and anti-correlating +ve PNA at this time is around +1 SD.

SST's north and north eastwards of Panama in the Mexican Gulf, around the Florida peninsula as far out as the central North Atlantic belt are all below long term average. Whereas in contrast, SST's into the Norwegian Sea and into the far North Atlantic are anomalously +ve.

Closer to our shores, Atlantic attacks would need destabilising the standing Rossby wave with subsequent shortwave propagation. In that respect the ENSO ocean/atmosphere coupling needs to be weakened.

I may be reading too much into it but there is evidence of Pacific warming in the ocean immediately west of the central Americas which could possibly herald a weakening of the ENSO signal but at this time, that's pure conjecture on my part.

In any case the coupled energy and inertia dictates a significant lag (several weeks) before effects are felt downstream but that process may already be underway.

The difficulty in extrapolation of the teleconnection indexes is a function of the time integral over which the first order EOF is calculated. i.e. no different to any other statistical average only that the harmonic in question is more difficult to extract (needs the eigenvectors in the co-variance matrix algebra set) and is always a post event analysis.

In that respect, teleconnection indexes extrapolated from ensembles which are themselves dependent on the skill of NWP ocean/atmosphere coupling models are a bit like a circular reinforced argument in justifying each other to lead us up the garden path.

ffO.

Edited February 15, 2010 by full_frontal_occlusion

[len]

Looking at other possible teleconnections..............

I don’t know what effect reduced Albedo will have now, but snow cover looks pretty phenomenal

http://www.rap.ucar.edu/weather/surface/snowNESDISnh.gif

This is confirmed by the snow cover anomalies.

A very, very rare sight, that I’ve not seen before since watching these anomaly charts. They have always been red-dominated

http://climate.rutgers.edu/snowcover/chart_daily.php?ui_year=2010&ui_day=43&ui_set=2

Will this delay spring?

Will it help to put cold in the right location for UK?

Or is the Stratosphere the sole Puppeteer, with the surface playing little part?

On the other hand, the sun has really decided to finally wake up with a real burst. Solar flux nearly went off the scale

http://www.solen.info/solar/

Perhaps this will mean the Jet Stream will track further North in the medium to long term? Or can it even boot up the Atlantic quickly?

Any experts care to comment?

[lorenzo]

FFO - thanks for the reply - first time I had really thought to have a look through the Ensembles for MJO - I guess they are on the fringes of experimentation.

Interestingly the verification plots are way off point - so not sure really what to make of them. MJO FI ?!

The CPC should release their weekly update on ENSO today at some point, last update was +ve but weakening conditions remaining into summer. Possibly a revision up and coming?

Still perfectly poised in a land of confusion.

[Glacier Point]

The current and projected hemispheric pattern is very conistent with a mature Nino. A west-based -NAO is classic February Nino and the -ve zonal wind anomaly persistent throughout the troposphere and middle stratosphere is enhancing this as far as I can see.

The GWO has swung back to phase 5 as momentum flux in the last few days has arrested the decline in angular momentum. There are continuing additions of mean west zonal winds across 30-40N despite some eastward tendency over the tropics in the last few days. Both this and tropical convection still entrenched in the central / eastern Pacific are very convincing of an El Nino which has managed to draw the co-operation of the ocean-atmosphere coupling.

So where does this take us in the next 15 days ? Based upon historical analogues (mainly 1950s and 1970s), and the MJO forecast which continues to meander around phases 7/8 for the next 15 days, probably little change with the colder air continuing to flirt with a proportion of the UK and milder air attempting to work in from the south-west. It's worth noting that the ensemble mean height anomaly forecasts have put up a significant -ve height anomaly over the Azores. Potentially very unsettled for the UK if it weren't for the jet running along a southward dispalced storm track across France and Spain - so every prospect the main intertia will be to the south of the UK.

Towards the end of the month seasonal wavelength changes should, all other things being equal, result in a mean ridge starting to feature more towards Iceland as well as western Greenland. That would imply a trend towards more below average and unsettled conditions into March. The trough and cold persisting over Scandinavia though so cold air never far away but the UK remaining on the periphery of the milder / colder air.

As far as longer term (seasonal) factors, I think there is a strong steer from the ocean.

Edited February 15, 2010 by Glacier Point