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Knocker and Recretos have more or less convinced me to do with a negative AMO when thinking about winter composites... many thanks for your informative posts. I'm officially a big fan of your work  :good:

 

The jet stream behaviour this month is starting to catch my eye, with GFS in particular tending to keep it fairly weak and meandering across much of the N. Atlantic (and into Europe) for the foreseeable future. It seems to me that most of the stronger segments have tended to be very close to the SE side of Greenland... where the 'warm' Atlantic contrasts with the very cold ice sheet, and GFS suggests this continuing. ECM also has similar ideas from the looks of its 500 mb height progression.

 

Prior to the autumn getting underway, I was thinking that the region of unusually low SSTs would encourage the jet stream to develop strong segments down near the Azores (the southern reaches of the neg. anomalies), based on what happened in past years with such cold pools, but this year is showing little sign of that so far. The atmospheric temp. gradients driven by seasonal cooling in the Arctic seems to be by far the dominant player.

 

I'm not exactly surprised though, as in my investigation of winters from 1990 to 2014, only 3/4 of the years showed much of a relationship between the  SST anomalies and the jet stream, leaving plenty of room for alternative behaviour driven by other forcing.

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So, have you ever wondered how exactly would N Atlantic look like if you would pump out all the water? Well, its one big mountain range (MAR - Mid Atlantic Ridge). It gives you a feeling and a differe

Yeah, I think that's quite a disingenuous chart (no reflection on yourself , of course!).   If we look at the months used in that chart, and the 9 months leading up to them, we get the following:  

The 13 hours later this arrived..   Many thanks for your enquiry regarding North Atlantic sea surface temperatures. I have spoken to the relevant scientists within the Met Office Hadley Centre who h

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Knocker and Recretos have more or less convinced me to do with a negative AMO when thinking about winter composites... many thanks for your informative posts. I'm officially a big fan of your work  :good:

 

The jet stream behaviour this month is starting to catch my eye, with GFS in particular tending to keep it fairly weak and meandering across much of the N. Atlantic (and into Europe) for the foreseeable future. It seems to me that most of the stronger segments have tended to be very close to the SE side of Greenland... where the 'warm' Atlantic contrasts with the very cold ice sheet, and GFS suggests this continuing. ECM also has similar ideas from the looks of its 500 mb height progression.

 

Prior to the autumn getting underway, I was thinking that the region of unusually low SSTs would encourage the jet stream to develop strong segments down near the Azores (the southern reaches of the neg. anomalies), based on what happened in past years with such cold pools, but this year is showing little sign of that so far. The atmospheric temp. gradients driven by seasonal cooling in the Arctic seems to be by far the dominant player.

 

I'm not exactly surprised though, as in my investigation of winters from 1990 to 2014, only 3/4 of the years showed much of a relationship between the  SST anomalies and the jet stream, leaving plenty of room for alternative behaviour driven by other forcing.

 

I wouldn't jump ahead quite so soon. While some signs of a coming -ve AMO are evident, the surface is still very much exhibiting +ve AMO features. In fact, the last month has shown a very large increase in the AMO index, from +0.197 in August to +0.319 in September, the 15th most +ve September value in 160 years of records.

 

The pattern for the last few years has generally been for close to neutral values during winter and spring, then becoming more positive during summer, peaking in early Autumn and falling into winter again. We seem to be following that pattern so far, but maybe this winter will see things really plummet?

 

bY3fPmI.png

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US east coast sea levels as an indicator of change in Atlantic circulation patterns.

 

Paper (paywalled)    http://www.nature.com/nature/journal/v521/n7553/full/nature14491.html#access

 

Powerpoint presentation.    http://naclim.zmaw.de/fileadmin/user_upload/naclim/Archive/Dissemination/EGU-2015/McCarthy_NA_session_Mon_1145_EGU2015.pdf

 

Their research suggests a transition to -AMO is in process.

 

JsQ1S5V.png

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North Atlantic meridional overturning circulation variations from GRACE ocean bottom pressure anomalies

 

Concerns about North-Atlantic Meridional Overturning Circulation (AMOC) changes imply the need for a continuous, large-scale observation capability to detect changes on interannual to decadal time scales. Here, we present the first measurements of lower North-Atlantic-Deep-Water (LNADW) transport changes using only time-variable gravity observations from Gravity Recovery and Climate Experiment (GRACE) satellites from 2003 until now. Improved monthly gravity field retrievals allow the detection of North Atlantic interannual bottom pressure anomalies and LNADW transport estimates that are in good agreement with those from the ocean RAPID-MOCHA array. Concurrent with the observed AMOC transport anomalies from late-2009 through early-2010, GRACE measured ocean bottom pressures changes in the 3000–5000 m deep western North Atlantic on the order of 20 mm-H2O (200 Pa), implying a southward volume transport anomaly in that layer of approximately −5.5 Sv. Our results highlight the efficacy of space-gravimetry for observing AMOC variations to evaluate latitudinal coherency and long-term variability.

 

(paywalled)

 

http://onlinelibrary.wiley.com/doi/10.1002/2015GL065730/abstract

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Cheers BFTV and Nouska, this is a real puzzler but thankfully probably not a huge player in our winter patterns based on the fact that when I create composites of +ve and -ve AMO years since 1948 they turn out to be very similar, with anomalies generally pretty weak anyway.

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The latest CSFv2 seasonal SST anomaly and the fading Nino.

 

Next year looks ripe for a highly active Atlantic hurricane season, what with that SST anomaly pattern and neutral to La Nina conditions developing.

 

As for the cold pool, CFS was killing that off before the winter when I checked it out about a month ago... how things have changed!

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Isn't the increase in SST aligned with a fairly benign period of weather, hence not much agitation allowing SST to rise, but it will take a fair bit of Sun to warm that amount of water to any great depth.

Wouldn't surprise me if the cold pool came back once the Atlantic gets a bit more mixing over the next week or two...

I stand to be corrected of course!

 

Yep, cheers Nouska.  Looks like a slight extension south of the cold pool.  Read that discusion you posted, interesting stuff

 

BFTP 

 

Like I suggested the other day, Cold Pool could well come back with a bit of agitation following a relatively settled period ...

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Those CFS SST charts seem a bit ropey for higher latitudes, especially Arctic region, winter anomaly into double figures around Novaya Zemlya, just no, lol.

 

The EUROSIP group have a substantial positive anomaly for the same area.... signifying ice free in Kara/Barents?

 

IMME_tmpsfc_season3.png

 

If so, that will please the crowd looking for cold winter indicators.

 

http://onlinelibrary.wiley.com/doi/10.1002/jgrd.50584/pdf

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I thought it might be interesting to graph the Monthly Mean SST for the last few years to show the annual pattern of the cold pool surface temperature. Using the ESRL/NOAA website to generate the data for the cold pool coordinates we’ve adopted in this thread (see chart below, courtesy of BFTV), here’s the graph for 2012 to 2015.

 

As has been the case for every month so far this year, the September mean SST remains below the corresponding month from the last few years.

 

To put the graph and data into perspective: this September’s mean was 11.8C, the lowest Sept mean since 1948 (when NCEP reanalysis data starts) was 11.036C in 1992. For the cold pool be beat its all-time low SST since 1948 it needs to drop below the 7.038C that was reached in March 1994. It has already come close earlier this year, dropping to 7.083C in Feb, so my money is on it achieving an all-time low in the early months of 2016.

 

Area graphed post-20040-0-86045000-1444336079_thumb.p Monthly Mean SST graph post-20040-0-66101800-1444336103_thumb.j

 

Monthly Mean SST data  post-20040-0-55071900-1444336117_thumb.j

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I thought it might be interesting to graph the Monthly Mean SST for the last few years to show the annual pattern of the cold pool surface temperature. Using the ESRL/NOAA website to generate the data for the cold pool coordinates we’ve adopted in this thread (see chart below, courtesy of BFTV), here’s the graph for 2012 to 2015.

You're using slightly different coordinates to BFTV?

Also ideally I think it's preferable to select the 'area weight grids' option.

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What the Atlantic cold 'blob' means for the UK

 

There's a cold anomaly in the North Atlantic Ocean that has emerged recently, causing record cold temperatures from January through to August for a substantial area. It's surprising given the globe as a whole is likely to have its warmest year on record.

 

BBC Weather's John Hammond explains what's caused it and what the impacts might be for the UK.

 

http://www.bbc.co.uk/weather/features/34489981?ns_mchannel=social&ns_campaign=bbc_weather&ns_source=twitter&ns_linkname=news_central

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What the Atlantic cold 'blob' means for the UK

 

There's a cold anomaly in the North Atlantic Ocean that has emerged recently, causing record cold temperatures from January through to August for a substantial area. It's surprising given the globe as a whole is likely to have its warmest year on record.

 

BBC Weather's John Hammond explains what's caused it and what the impacts might be for the UK.

 

http://www.bbc.co.uk/weather/features/34489981?ns_mchannel=social&ns_campaign=bbc_weather&ns_source=twitter&ns_linkname=news_central

 

 

An excellent, concise summary. The Beeb at its best.

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its also a possibility with such temp contrast maybe producing deeper more active north atlantic deepressions be pretty good if this also equates to a more southerly shift in the jet stream with high lat blocking more common feature and of coarse add in the declining solar cycle brrrrrrrrrr

 

post-9143-0-34984100-1444402936_thumb.jp

post-9143-0-00165500-1444402946.gif

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Great video! It really is quite interesting to know the professionals are keeping a close eye on Atlantic SST as are we on here - some really top class posts on here. Of all the winters I've been on NW - I feel most convinced this will be the cold one. UK is certainly favoured a colder winter to a warmer one imo.

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What the Atlantic cold 'blob' means for the UK

  

BBC Weather's John Hammond explains what's caused it and what the impacts might be for the UK.

Doh, it's multidecadal

 

 

I wouldn't jump ahead quite so soon. While some signs of a coming -ve AMO are evident, the surface is still very much exhibiting +ve AMO features. In fact, the last month has shown a very large increase in the AMO index, from +0.197 in August to +0.319 in September, the 15th most +ve September value in 160 years of records.

 

The pattern for the last few years has generally been for close to neutral values during winter and spring, then becoming more positive during summer, peaking in early Autumn and falling into winter again. We seem to be following that pattern so far, but maybe this winter will see things really plummet?

 

bY3fPmI.png

Interesting the differences in values depending on the differing calculation methodology, Atlantic area used and SST dataset.

For example the NOAA ESRL trends you've posted are similar to this AMO index SST 25-60N, 7-75W minus regression on global mean temperature, as in van Oldenborgh et al 2009, based on HadSST 3.1.1.0

 

iamo_hadsst.png

 

Whereas the values have recently plummeted in this version - AMO index SST EQ-60N, 0-80W minus SST 60S-60N, as in Trenberth and Shea 2006, based on HadSST 3.1.1.0

 

iamo_hadsst_ts.png

 

Source : KNMI Climate Explorer

More details can be found here - http://climexp.knmi.nl/[email protected] noting that the observed record is too short to decide whether there is a well-defined period

 

Using NOAA/ESRL raw data from the cold pool area Blessed Weather used, undetrended anomalies from the overall mean show the characteristic imprint of the AMO similar to the last half of the second graph above with a recent plummet -

 

post-2779-0-93354700-1444412454_thumb.gi

 

The positive anomalies of the 1950s/60s lasted about 18 years, the current positive anomalies have lasted also about 18 years, maybe its time is up!

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Have the Met Office been reading this thread! :)  Joking aside, it's good to see the pro's also taking an interest in the cold pool!

 

Thank you Interitus for your comments on my graph. You are right, I was a couple of degrees out with my lat/long co-ordinates. I've also switched to using the 'area weight grids' option as you suggest. So below is the re-calculated graph.

I've re-written my summary to reflect the changes, but the headline message remains the same:

 

post-20040-0-73602300-1444421011_thumb.j

 

.........this September’s mean was 13.473C. The lowest Sept mean since 1948 (when NCEP reanalysis data starts) was 12.841C in 1992. For the cold pool be beat its all-time low SST since 1948 it needs to drop below the 8.379C that was reached in Feb 1990. It has already come close earlier this year, dropping to 8.454C in March.......

 

 

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Those CFS SST charts seem a bit ropey for higher latitudes, especially Arctic region, winter anomaly into double figures around Novaya Zemlya, just no, lol.

 

LOL Indeed Interitus.

 

Just posted this map of Arctic sea ice in the appropriate thread. Doesn't seem to tie in at the moment with the above prediction, but we all know how accurate the CFS is?

 

But thought it worth posting to show that this particular prediction  looks definatly shaky.

 

http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif

 

MIA

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