In Depth Model Discussion, Analysis and Summaries

[Gavin P]

GP, run after run after run GFS is going for high pressure to take over in early September. Any idea if its picking up on something or is it whistling in the dark?

[summer blizzard]

GP, run after run after run GFS is going for high pressure to take over in early September. Any idea if its picking up on something or is it whistling in the dark?

It only seems to happen after GFS has the current invest 95L approaching us as a ex hurricane, so i don't think it will be a permanent feature.

[Glacier Point]

Interesting little passage of weather right now. Lots of potential pitfalls for high pressure not least because the ensemble means maintain an amplifying ridge located close or just to our west out to t144 so plenty of time for events to progress. The weakness in the sub-tropical ridge in the Atlantic is also another possible pitfall.

Based on where the Global Wind Oscillation is right now, centred in phase 2-3 heading towards phase 3-4, I think the most likely evolution is for the ridge to become shifted northwards and then retrogress towads Greenland consistent with phase 4 GWO composites:

Key message: enjoy any dry and settled weather you get Sunday through Monday. The pattern continues to look unsettled.

[Gavin P]

Thanks for the update GP. :lol:

So your not buying the models high pressure heatfest for early September?

[mushymanrob]

Thanks for the update GP. :o

So your not buying the models high pressure heatfest for early September?

i dont think many of us are..... atm.... but its what the models currently are showing so are elegible to be talked about!

[Gavin P]

i dont think many of us are..... atm.... but its what the models currently are showing so are elegible to be talked about!

Er, I never said it wasn't?

[Eugene]

I don't see any heatfest on GFS 12Z and ECM 12Z for early September, you need more than just HP in September for heat.

The main three models are trending towards GP's retrogression towards greenland thoughts.

[Gavin P]

I don't see any heatfest on GFS 12Z and ECM 12Z for early September, you need more than just HP in September for heat.

Agreed. Theres no heatfest shown on any model tonight.

Also agree that the models are starting to play with GP's retrogression idea. :o

Edited August 25, 2010 by Gavin P

[Cecil Hogmanay Melchett]

Models are pretty unanimous for a spell of High pressure starting this weekend.Low pressure to the NW looks like preventing any retrogression so next week looking good.

[Gavin P]

Yes, against the odds it really does look like high pressure is going to make it next week. Will it persist for days or weeks? Or will it be quickly broken down, thats the next question?

[Cecil Hogmanay Melchett]

No offence Gavin but isn't that always the question,hehe.

Anyway i m not to confident as i have seen NWP way off the mark in the medium range before now so be interesting to see GPs take on the output at the moment.

[The PIT]

I think we're seeing a pattern change due to the Ex Hurricanes which tends too happen.

[summer blizzard]

I think we're seeing a pattern change due to the Ex Hurricanes which tends too happen.

These changes are usually temperory, however given that we have three FISH storms, we are likely looking at a warm ten day period because the Azores High won't be allowed to retrogress.

[Eugene]

Models are pretty unanimous for a spell of High pressure starting this weekend.Low pressure to the NW looks like preventing any retrogression so next week looking good.

Most models are currently showing a strong retrogressing high to our northeast, allowing LP in from the SW as i did say 4 days ago.

because the Azores High won't be allowed to retrogress

Well the models are allowing it for end of the week so not sure what you on about here maybe you are looking way ahead of that

[Snowyowl9]

5 days of HP on the 12z from monday so make the most of it.

http://www.wetterzentrale.de/pics/Rtavn1201.png

The 6z was an easterly frendly run at T192 nice one but probaly won`t happen,as the S/SE-ly looks more likely then a low.

[len]

This thread seems to be losing its special in-depth/technical nature. A lot of recent posts belong in the model thread I believe.

[Eugene]

The past few weeks developments clearly show that it's in your own interest to trust your own thoughts ahead of the models, use them for guidance yes but never be hooked in by them so much especially after 3 to 5 days, some models were going for HP domination over the UK and some very warm temps(they never really going for a heatfest to be honest) before downgrading and picking up GP's retrogression ideas though HP retrogressed more northeastwards than even he thought.

[johnholmes]

This thread seems to be losing its special in-depth/technical nature. A lot of recent posts belong in the model thread I believe.

I agree with you Len. It would be a shame if the thread became too full of model comments rather than the more in depth posts from the likes of GP and a few others.

But it is very diffcult to get the balance right, the team want to encourage others to dip in here so will be reluctant to start removing posts to other threads.

Edited September 5, 2010 by johnholmes

[Glacier Point]

The Global Wind Oscillation is on the move and NWP is starting to reflect this.

Relative angular momentum is now moving downwards, reflecting strong ocean-atmosphere forcing from La Nina and the Southern Oscillation was have tanked over the last 10 days.

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

Both mountain and frictional torques are also trending firmly negative:

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/gltauf.90day.gif

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/gltaum.90day.gif

That's a lot of removal of westerly winds / addition of easterly winds to the global dynamical system. Tendency on angular momentum is, as a result, sharply down:

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/gltend.sig.90day.gif

This has driven the GWO out of its low amplitude slumber in phase 2 towards phase 1:

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

Low level wind satellite images show a firm push of easterlies across the tropics heading towards westerly winds, collision Indonesia driving a possible bout of convergent waves triggering large scale convection.

http://cimss.ssec.wisc.edu/tropic/real-time/wavetrak/winds/wavetrkP.html

The fall in angular momentum should maintain us towards phase 1 over the next 10-14 days. This teleconnects to a ridge centred high in the Atlantic and ominpresent Pacific ridge around the Aluetians / NE Pacific.

If this comes to fruition, it will set up the rest of the Autumn with a solid mean anomalous ridge to our west and NW with trough ensconsed over Scandinavia.

[Gavin P]

Thanks GP.

So the hints the models are giving of a northerly sometime around mid to late next week teleconnects to the global situation quite nicely?

This will be a semi-permanant pattern this autumn, so perhaps the coldest autumn since 1993 coming up?

Edited September 7, 2010 by Gavin P

[BLAST FROM THE PAST]

Thanks GP.

So the hints the models are giving of a northerly sometime around mid to late next week teleconnects to the global situation quite nicely?

This will be a semi-permanant pattern this autumn, so perhaps the coldest autumn since 1993 coming up?

This autumn is set to be very 'autumnal' and cool to cold at times as per my sig and my early winter heads up. I believe GP is calling this right and coupled with the La Nina that developed as expected the set up will become entrenched.

BFTP

[Yorkshiresnows]

The Global Wind Oscillation is on the move and NWP is starting to reflect this.

Relative angular momentum is now moving downwards, reflecting strong ocean-atmosphere forcing from La Nina and the Southern Oscillation was have tanked over the last 10 days.

http://www.esrl.noaa...g1-21.90day.gif

Both mountain and frictional torques are also trending firmly negative:

http://www.esrl.noaa...ltauf.90day.gif

http://www.esrl.noaa...ltaum.90day.gif

That's a lot of removal of westerly winds / addition of easterly winds to the global dynamical system. Tendency on angular momentum is, as a result, sharply down:

http://www.esrl.noaa...d.sig.90day.gif

This has driven the GWO out of its low amplitude slumber in phase 2 towards phase 1:

http://www.esrl.noaa...gcm/gwo_40d.gif

Low level wind satellite images show a firm push of easterlies across the tropics heading towards westerly winds, collision Indonesia driving a possible bout of convergent waves triggering large scale convection.

http://cimss.ssec.wi...s/wavetrkP.html

The fall in angular momentum should maintain us towards phase 1 over the next 10-14 days. This teleconnects to a ridge centred high in the Atlantic and ominpresent Pacific ridge around the Aluetians / NE Pacific.

If this comes to fruition, it will set up the rest of the Autumn with a solid mean anomalous ridge to our west and NW with trough ensconsed over Scandinavia.

I have to Say G.P that your posts are always superb and I look forward to reading them .... and then re-reading them to see if I can fully appreciate what you are saying.

My understanding of the various teleconections is basic compared to yours (so I apologise in advance for getting things muddled), but would I be correct to sumise, that with La Nina firmly now in control and engaged with the global atmopshere / circulation .... forcing low angular momentum. That we should expect frequent bouts of Mid to high Atlantic blocking (as you have indicated in your post above) to continue throughout Autumn and possible into the early /mid parts of winter ?

Is it possible at this early stage to comment on the likelihood of developing Greenland high pressure over the extended outlook and also what impacts you feel will be felt by a possible change in the QBO possible around the mid-winter period?

Many Thanks

Y.S

[Glacier Point]

Is it possible at this early stage to comment on the likelihood of developing Greenland high pressure over the extended outlook and also what impacts you feel will be felt by a possible change in the QBO possible around the mid-winter period?

Many Thanks

Y.S

Thanks YS.

Yes, very much the ecxpectation that the low angular momentum base state, aided and abetted by the developing profile of SSTAs in the North Atlantic will lead to strong forcing for a mid Atlantic blocking ridge becoming shifted further northwards during November and December. It's also worth noting that analogues for tropical convection centred west of Indonesia (MJO phase 4-5) also support this solution.

The west QBO / solar combination will I think bring about a slow sink of the ridge to a mid latitude feature in January and February although the later we go the more vulnerable we become to a Major Mid Winter Warming of the stratosphere, much like 2008/9. Its worth pointing out the equatorial westerly winds in the stratosphere have increased and we may now be looking at values of +10 to +20 m/s this winter. This is already having an impact on stratospheric ozone concentrations and the Brewer Dobson Circulation which would appear to be weak, even at this early stage.

[johnholmes]

You are going to put this place into meltdown Stewart with posts like the last 2!

Way above me but what little I do think I understand does tend to suggest that its a cold rather than mild few months towards January. Beyond that then we know what happened with the last 'super' warming but of course other factors are different this time round.

An interesting few months again I suspect, and no doubt admin and mods are going to be kept very busy.

It really would be nice folks if we can all TRY to post our thoughts and not have quite so many side swipes at others as was quite often the case last winter.

Lets enjoy the models, what ever they bring to our own locality, be happy for those who get what they hope for, along with reading the posters like GP and a few others who post constructive views about the shorter and longer term model outputs.

sorry to go on mods-if its felt out of place or inflammatory then please delete the bits that might offend

[Guest harshwinter09]

Thanks YS.

Yes, very much the ecxpectation that the low angular momentum base state, aided and abetted by the developing profile of SSTAs in the North Atlantic will lead to strong forcing for a mid Atlantic blocking ridge becoming shifted further northwards during November and December. It's also worth noting that analogues for tropical convection centred west of Indonesia (MJO phase 4-5) also support this solution.

The west QBO / solar combination will I think bring about a slow sink of the ridge to a mid latitude feature in January and February although the later we go the more vulnerable we become to a Major Mid Winter Warming of the stratosphere, much like 2008/9. Its worth pointing out the equatorial westerly winds in the stratosphere have increased and we may now be looking at values of +10 to +20 m/s this winter. This is already having an impact on stratospheric ozone concentrations and the Brewer Dobson Circulation which would appear to be weak, even at this early stage.

Hello again GP. I do not understand your comment about the stratospheric westerly wind values being +10 to +20 values.

Can you explain this? What does it mean?

How will this have an impact on the polar vortex?

Thanks again.