In Depth Model Discussion, Analysis and Summaries

[Methuselah]

Aye peeps, please use the winter-forecast thread for making unsubstantiated seasonal predictions... I know we all do it, but here isn't the place.

Thank you peeps...

[BLAST FROM THE PAST]

Is that a specific forecast for this winter Fred, or upcoming winters in general?

This one, early thoughts. With potential weak el nino possibly in favour too. This year has seen big amplification of the jet and its seems to be an increasing theme since -ve PDO and perturbation cycle has kicked in. I don't believe that the jet will become domniantly flat at all.

BFTP

[BLAST FROM THE PAST]

Ah, is there anything in this theory to back it up? After all this is the Tech Model thread....

One of the main theories is the pdo/perturbation cycle 'co-inciding' with an enhancemenmt of -ve NAO phases. Anyway here and now, as Stew says a period of high amplification looks like approaching and we could be in the mix of the trough section.

BFTP

[Glacier Point]

Not suprising that the models have struggled a lot this week with the nuances of our neck of the woods given the overall state of angular momentum and the GWO. Next week's trough has some support, although it's vulnerable to being eaten away at the edges and deamplification will tend to shift the mid Atlantic ridge back towards us, potentially with a closed low towards Iberia.

The real eye catching thing for me...

Upper stratospheric temperatures are at or close to record low levels over the tropics. Signs that we are seeing an enhanced Brewer Dobson Circulation this autumn perhaps (the process of transport of ozone from the tropics to the pole), potentially setting us up for greater ozone concentrations in the polar stratosphere (high latitude blocking) this winter as upwelling occurs and the air cools over the tropics. Note the difference in tropical stratospheric temperatures compared to last year.

Edited September 18, 2012 by Glacier Point

[johnholmes]

Can you give a link please Stewart to a site that shows this for previous years?

thanks

[chionomaniac]

A good spot Stewart. It appears though that the south pole is benefitting mostly from this, with a warming at the 2 hpa level between 65-90S.

http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/02mb6590.gif'>http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/02mb6590.gif

Ozone level at SP: http://www.cpc.ncep.noaa.gov/products/stratosphere/sbuv2to/gif_files/sbuv16_sh_latest.gif

Ozone level at NP: http://www.cpc.ncep.noaa.gov/products/stratosphere/sbuv2to/gif_files/sbuv16_nh_latest.gif

Hopefully our time will come!

John, link below:

http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/

[johnholmes]

thanks chio

[UV-RAY]

Not suprising that the models have struggled a lot this week with the nuances of our neck of the woods given the overall state of angular momentum and the GWO. Next week's trough has some support, although it's vulnerable to being eaten away at the edges and deamplification will tend to shift the mid Atlantic ridge back towards us, potentially with a closed low towards Iberia.

The real eye catching thing for me...

Upper stratospheric temperatures are at or close to record low levels over the tropics. Signs that we are seeing an enhanced Brewer Dobson Circulation this autumn perhaps (the process of transport of ozone from the tropics to the pole), potentially setting us up for greater ozone concentrations in the polar stratosphere (high latitude blocking) this winter as upwelling occurs and the air cools over the tropics. Note the difference in tropical stratospheric temperatures compared to last year.

Which particular mechanism is responsible for enhancing the BD circulation, are there numerous parts of a jigsaw at play or is there one in particular that will kick starts this process?

[chionomaniac]

One of the factors in enhancing the BDC is the state of the QBO realtive to the sun state.

http://www.agu.org/pubs/crossref/2010/2009JD013020.shtml

The main point is this:

However, the solar response in the middle to lower stratosphere differs significantly for the two QBO phases. During solar maxima a weaker Brewer-Dobson circulation with relative downwelling, warming, and enhanced ozone occurs in the tropical lower stratosphere during QBO east conditions, while a stronger circulation, cooling, and decreased ozone exists during QBO west conditions. The net ozone increase during QBO east is the combined result of production and advection, whereas during QBO west the effects cancel each other and result in little net ozone changes. Especially during Southern Hemisphere late winter to early spring, the solar response at polar latitudes switches sign between the two QBO phases and qualitatively confirms observations and other recent model studies

The bolded bit (by me) may be what GP has spotted.

[UV-RAY]

One of the factors in enhancing the BDC is the state of the QBO realtive to the sun state.

http://www.agu.org/pubs/crossref/2010/2009JD013020.shtml

The main point is this:

However, the solar response in the middle to lower stratosphere differs significantly for the two QBO phases. During solar maxima a weaker Brewer-Dobson circulation with relative downwelling, warming, and enhanced ozone occurs in the tropical lower stratosphere during QBO east conditions, while a stronger circulation, cooling, and decreased ozone exists during QBO west conditions. The net ozone increase during QBO east is the combined result of production and advection, whereas during QBO west the effects cancel each other and result in little net ozone changes. Especially during Southern Hemisphere late winter to early spring, the solar response at polar latitudes switches sign between the two QBO phases and qualitatively confirms observations and other recent model studies

The bolded bit (by me) may be what GP has spotted.

Thanks Chion, I thought solar activity was the main piece of the jigsaw just wasn't sure what net effect this had.

[ZONE 51]

http://wekuw.met.fu-...var=all&lng=eng

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http://wekuw.met.fu-...var=all&lng=eng

-

Couple of links.

--

Below image first posted the other day by GP and he circled the particular areas, (yellow/blue lines i have added for my own use) i find this interesting.

Edited September 21, 2012 by ElectricSnowStorm

[cooling climate]

http://wekuw.met.fu-...var=all&lng=eng

-

http://wekuw.met.fu-...var=all&lng=eng

-

Couple of links.

--

Below image first posted the other day by GP and he circled the particular areas, (yellow/blue lines i have added for my own use) i find this interesting.

I have mentioned this in other threads and is I think an important development of a

weakened polar vortex this winter because of a weaker gradient between the pole

and the equator. Add to this a - QBO in the mid stratosphere and I think this adds

up to a much better position going into winter 2012/13 than we were going into

last winter.

[lorenzo]

6 cups of coffee later and a few hours browsing, think I have just broken my brain..

Will leave this link here for those looking to have a browse.. the filters in the search function help a whole lot.

http://climatedataguide.ucar.edu/all-datasets/filter

[summer blizzard]

It looks to me that we could be in the running for a >-1 -AO value making us one of the most negative on record (2009, 2006, 2002, 1981, 1979, 1974, 1968, 1966, 1960).

Is there any significance to this or is the expectation for the pattern to default in November?

[Glacier Point]

Up until now, the reasoned idea has been that El Nino would struggle to evolve this winter. However, we might just be starting to see some atmospheric support for a borderline Nino, based within regions 4 and 3.4,

For El Nino events I will always look to the North Pacific and Atlantic for evidence of low pressure. Over the last month we've started to develop this pressure anomaly pattern. Here is the H500 anomaly pattern for the last month.

Much of the Atlantic 'low' has been sustained by tropical system Nadine stuck around the Azores for the last month. The impact on the SST has driven a notable cooling in that region which could well be sustaining a feedback loop in the atmosphere The GFS 12z ensemble mean depicts nicely a pattern which may be reinforcing feedback loops with intense upper low likely to result in further cooling, both over the Atlantic and Pacific surfaces.

SSTA profile in the Atlantic Oct 1-10:

GFS 12Z ensemble mean H5 anomaly:

We can also look at the upper U-flow profile as starting to show evidence of a sub-tropical jet and also a southward displacement of the polar jet. Pictured here is the ECM day 10 forecast showing a somewhat El Nino type flow.

Add to that a series of westerly wind bursts in the Indian Ocean which have finally managed to 'break through' and develop into the eastern Pacific with convergence zones setting up around the Dateline (increased thunderstorm activity and cloudiness).

These are all first signatures of the atmosphere beginning to lean towards an El Nino base state, albeit very weak.

Looking at the sea surface profile we see a bubble of warmer water beneath the central Equatorial Pacific. If the atmosphere 'decides' its going to go along with El Nino development, I think we have reasonable grounds for calling a weak borderline Nino which is west based.

The signiifcance going forward into the winter season is that we'll see a string of poleward fluxing AAM anomalies (mountain torques and +AAM tendency) driving wave trains into the high latitudes and the GWO orbiting towards phases 4-5-6-7-8 (as it last did in 2009). This is an ingredient of stratospheric warming and blocking development.

Incidentally, timing wise, next westerly wind pulse late November and then again mid January ..............

Edited October 15, 2012 by Glacier Point

[BLAST FROM THE PAST]

I was going to ask a question but the answer is in there Stew, it being west based. The reason being the cold pulse of water intensifying off Peru's coastline.

Interestingly the PDO looks less -ve, maybe hence why we're seeing a Nino atmospheric response?

BFTP

Edited October 15, 2012 by BLAST FROM THE PAST

[Isolated Frost]

Interesting how GLAAM seems to be heading increasingly negative as we progress through October.

Anyone for a 2-3-4 GWO progression? I think it's looking increasingly likely as we progress through November. Negative AAM anomalies departing due to torques and we see a more El-Nino pattern progressing a la GP.

MJO looks like shifting into stage 2 into 3. Interesting November composites for phase 3...

Btw I'm only learning and this is my first venture into the Tech Model thread but will hope to post more as any knowledge is gained. If anyone can direct me in the right direction for stuff about the MJO, GWO, AAM, tropical convection, that sort of stuff, that would be great! Ta.

Edited October 23, 2012 by Isolated Frost

[johnholmes]

just try Google or to start go into the Guides there is plenty in there or the Startosphereic intro by chio?

[fUnKy]

I don't suppose there is any chance of someone putting together a glossary of all of the terms used in respect to the models etc and pinning it? Terms like FI. I've looked around but can't find anything and it's a bit of a barrier to the uneducated newbie like myself.

[lorenzo]

Try Here http://forum.netweather.tv/topic/35186-acronyms-and-abbreviations/

[fUnKy]

Try Here http://forum.netweather.tv/topic/35186-acronyms-and-abbreviations/

thank you.. the Rosetta stone of netweather

[Glacier Point]

A couple of considerations to put along current modelling.

The last 30 days NH circulation shows a particular +ve height anomaly across the Northern Pacific extending from the Aleutians to Kamchatka.

In part, the near record advance in Eurasian snowcover can be seen to be influencing this. 250hPa winds over eastern Asia are displaced southward as the cold block is encountered (this is well documented by Cohen). The Asian jet is strengthened and associated with an upper low as the troughing on the poleward side of the jet extends well into the middle latitudes of the Pacific.

This leaves a relatively strong eddy to develop in the higher latitudes which is our North Pacific ridge. Even with a +AO phase, this is adopting a high latitude for this feature (one of the key reasons why the stratospheric lead is not enganging with the troposphere).

The presence of a strong +ve height anomaly teleconnects to a trough off the eastern US and consequent ridge in the North Atlantic.

With no prospect of a reversal in the upstream pattern over Asia, this looks a rock solid modelling feature, set to dominate the NH circulation. The GEFS 12z run tonight has this throughout the run.

GEFS for final weak of November has the Aleutian ridge as an extremely strong and poleward displaced. The downstream teleconnector over the North Atlantic is well modelled, and actually gains intensity in the final stages of the output. The SSTA both in the North Atlantic will reinforce this pattern.

The key question is therefore the mean state of the AO / NAO which will influence the northern extent of this very blocked pattern.

I suggest that with a strong collaboration of MJO wave, poleward +AAMr signal and succession of Wave 2 activity in the next 2 weeks, the stratospheric vortex may be on the bring of collapse 1st week December and ripe for a higher latitide block to take root in December. Whilst not totally against any Scandinavian ridge, I think the wavelengths here more favor a ridge to our W / NW.

Edited November 11, 2012 by Glacier Point

[johnholmes]

A couple of considerations to put along current modelling.

The last 30 days NH circulation shows a particular +ve height anomaly across the Northern Pacific extending from the Aleutians to Kamchatka.

In part, the near record advance in Eurasian snowcover can be seen to be influencing this. 250hPa winds over eastern Asia are displaced southward as the cold block is encountered (this is well documented by Cohen). The Asian jet is strengthened and associated with an upper low as the troughing on the poleward side of the jet extends well into the middle latitudes of the Pacific.

This leaves a relatively strong eddy to develop in the higher latitudes which is our North Pacific ridge. Even with a +AO phase, this is adopting a high latitude for this feature (one of the key reasons why the stratospheric lead is not enganging with the troposphere).

The presence of a strong +ve height anomaly teleconnects to a trough off the eastern US and consequent ridge in the North Atlantic.

With no prospect of a reversal in the upstream pattern over Asia, this looks a rock solid modelling feature, set to dominate the NH circulation. The GEFS 12z run tonight has this throughout the run.

GEFS for final weak of November has the Aleutian ridge as an extremely strong and poleward displaced. The downstream teleconnector over the North Atlantic is well modelled, and actually gains intensity in the final stages of the output. The SSTA both in the North Atlantic will reinforce this pattern.

The key question is therefore the mean state of the AO / NAO which will influence the northern extent of this very blocked pattern.

I suggest that with a strong collaboration of MJO wave, poleward +AAMr signal and succession of Wave 2 activity in the next 2 weeks, the stratospheric vortex may be on the bring of collapse 1st week December and ripe for a higher latitide block to take root in December. Whilst not totally against any Scandinavian ridge, I think the wavelengths here more favor a ridge to our W / NW.

I would agree with your view of a ridge, if and when it does occur, being nw rather than ne of the UK.

[bluearmy]

maybe we are on the cusp of one of stewart's win, win scenarios !! awaiting the naefs 12z update as the ecm 00z and 12z mean seem pretty certain of a scandi block extending nw towards svaalbard, whilst gefs builds a decent greeny block in its latter stages as per stewarts post. i guess we could build a scandi block that retrogresses to greeny across the top of the troughing to our sw becoming cut off ? that has been a scenario painted by many gefs members recent days

[shotski]

maybe we are on the cusp of one of stewart's win, win scenarios !! awaiting the naefs 12z update as the ecm 00z and 12z mean seem pretty certain of a scandi block extending nw towards svaalbard, whilst gefs builds a decent greeny block in its latter stages as per stewarts post. i guess we could build a scandi block that retrogresses to greeny across the top of the troughing to our sw becoming cut off ? that has been a scenario painted by many gefs members recent days

Hi Bluearmy

Would this not be a similar set-up to November 2010 if we ended up with a Scandi block that retrogresses to Greenland ?