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Winter Forecast 2006/07


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Good Evening All-

IF the attachments are NOT working then review the full forecast here- ADMIN CAN YOU HELP?

http://www.netweather.tv/forum/index.php?s...pid=845271&

Well this is only the third seasonal forecast me & the second Winter one-

Prior to this I have a thread running for Preliminary thoughts which can be located here-:

http://theweatheroutlook.com/twocommunity/...ShowThread.aspx

This was started on 10/10/06-

Also Should anyone wish to browse through last years information the following are available from these current links:

Original Winter Forecast 2005/2006:

http://www.netweather.tv/forum/index.php?s...=26623&st=0 (Read only)

Forecast varification Post:

http://www.netweather.tv/forum/index.php?s...c=28522&hl= ( Read only)

Winter Ode

http://www.netweather.tv/forum/index.php?s...c=33180&hl= available to post in......

What has become apparent across the last 12 Months is the fact that the general consensus of people involved on the weather forums do not subscribe to the theories or decisions behind seasonal LRF's -

Is there a method behind the madness...??? Well maybe-..

There is 2 things I wish to concentrate on for this LRF, these are:

1) Actual forecast : Obviously this is going to be a post covering the seasonal period December, January & Feb- to which I will abbrieviate D,J,F-

Unlike last year though I will not be doing a Monthly CET figure just an estimated range-

I will be however offering a seasonal CET in terms of actual value against the 70/01 norm -

The 'measures' will be around temperature, precipitation & key here the third & the most important- Pressure anomalies within the Window covering Europe & Greenland-

The pressure anomaly will be there as an end product of ALL teleconnections & considered Winter drivers applied to what I think will be NET result for Winter-

This also then omits the issue of 'False' positives arising after a forecast has been issued- Having a pressure anomaly can clearly demonstrate where the author sees the anomalies for that period-

2) What tends to be skipped over the most in ANY winter forecast I have read is the thinking behind the decisions made- this then allows some forecasters to manipulate their forecasts with a hindcast- trying to show that there thinking was inline with what actually happened-

This forecast comprises as much as about methodology as it does raw data & forecast-

However....,

Before Any forecast can be issued We first have to consider the implications of Global warming to our Climate, this is a very 'topical' subject with most parties at the moment & whether we like it or not it has to be addressed-

There are SO many illustrations of the overall warming that to deny it would be foolish- here below are a couple of images that really drive home the warming trend being observed-

global-blended-temp-pg.gif

As you can see the comparison between Global & regional change appears to be linear & correlated 1 on 1-

So before discussing the forecast I Present a side topic away from MY thoughts around this Winter using Persistence and extrapolation of data to forecast a mild Winter not just for this year, but for years to come- ...

The case for Warming & the mild UK Winter-

My thoughts around GW linking in with Northwestern Europe's Synoptics-

-I really need to be as clear as possible for this especially to people who believe that GW=Perminent winter UK Warming...

The overall global climate has changed - The warmth is continual at a steady rate, however what hasnt been addressed is that of the potential 'Spin off effects' that its induced on hemispheric flow patterns in the mid & Northern Lattitudes Especially when we apply that to Europe-

What's apparent to me is that the 'boom' in global temperatures has co-incided with the exact time that NW Europe was MOST likely to experience milder Winters-

This was/is due to Sunspot activity at its highest, Stratospheric temps being coldest (Driving the polar vortex) & a Positive NAO & AO phase-

Over the last few Winters these levers have started to fall into back towards negative/weakened phases & as a result the 'trend' towards colder Winter months has possibly re-started-

Also the Propensity of Northern & North eastern blocking has been on the increase-probably down to the natural cycles & possibly through the Global warming induced changes like cloud fraction in the artic-

Remember we dont actually have ANY solid information regarding Global Warming & European Synoptics until we have passes through an entire phase of the teleconnection oscillations-

If you link the Change in blocking conditions & weakened jet stream in with surface changes for the UK you would infer that a change to a more continental climate is inevitable, this is becoming more apparent in Summer already-

I will try to be as neutral as possibly in terms of presenting a case for a mild winter -

I am going to provide some data on why Octobers & Novembers are warming at a particularly high rate & how this leads into Winter-

( this is inline with the thought around a more continental UK Climate )

The data for these 2 months has been quite alarming for the last 5 years-

Here is the 850 Mb Temp anomaly for Oct /Nov 2000-2005

This is the 500Mb data for the same period-

This is the observed surface temp anomaly for the same periods-

From this we can deduce a couple of simple things-

Due to the High pressure anomaly over Central Europe -supported by the Low heights to the west the Available air mass on tap is going to be a more 'continental type'- Obviosuly warmer -especially Oct, & Nov often Drier although wit the precipitation aspect its pretty much depends on how close the low heights are to the UK-

Also of importance is the fact that the depth of any developing seasonal cold over Northern climbs like Greenland is significantly warmer that the long term mean-

If we look at the Artic Ice anomaly trend around Late September & October for 2004-

& the overall trend-

Further modifying any polar bursts upwards against the mean- this is without considering the net effects on the Air mass from the SST's-.....

It is of my opinion that out of all the months going forward late September, October & early November stand the best chance of observing a CET thats Significantly above the long term Mean-

The Northern Air Mass problem is a direct result of the Ice pack reduction anomaly around the pole which is most significant around late September & Early Oct- & the blocking change I feel is 'based' around the weakened & displaced jet stream-

The thought process around the Northern ice cover anomaly holds true as we move into as late as December-

This is again inline with the Artic icecover recovering to long term mean-

Remember there will be a time lag- & looking at the last few years data- Late November has been the time where the recovery seems to catch up to the norm-

Here shown below are the 2000-2005 850 Mb Anomalies from October through January- where finally the +VE anomalies dissipate back down to the mean-

(Im using just 5 years data as this really illustrates the upward trend)

OCT-

NOV-

DEC-

JAN-

This then presents us with a problem with recording a below average month in November & December- Effectivly if the Air masses to the North are well in excess of 2C above the mean- then the observed frequency of weather from that zone needs to increase to at least record an 'average month'-

However looking at the Pressure pattern anomalies for Nov & Dec for the last 5 years here-

Not much joy there-

Or even with December as a single month-

Hum a bit better there but not a great deal.........

So using the last 5 years climatology We already have a forecast of A VERY large anomaly of warmth to the North in Sep/Oct & part of Nov, Also due to the pressure profiles over Europe for those months & leading into December its quite 'probable' that the overall CET will be above the norm-

December sees some sort of Pressure correction- probably because of the seasonal feedback change & the differential of Air mass anomaly returning to the Norm-

However this wouldnt be enough to correct the 'overall warming'-

As for January & Febuary the pressure profiles we have the

500 Mb Anomlies-

850Mb Anomalies

So whilst the general pattern has shifted a little the air mass modification still overwhelms the increased frequency in polar flows to the Uk-

To add to the mire we have a prescribed theory to the correlation between May-Sep SST's across the NW Atlantic & the resulting NAO phase in the Winter-

The thought process adopted by the Met office & other Professional forecasters is that a 'Warm' pool off the coast of Newfoundland correlates to a 'positive' phase of the NAO in the Winter-

NB This Summer we generally had this pattern-

See that warm anomaly exactly where the Winter cold lovers dont want it-

In Summary then- for Winter from the Persistence & climatology forecast perspective

November- 1.5 degress or above the Normal ~ 8C & 8.5C also Above Ave PPN-

December- 1 to 1.5 degrees above Normal ~ 5.6 & 6.1C Ave PPN

January- 1 degree above Normal ~ 5.2C Drier than ave-

Febuary- 0.5 to 1C Above Normal ~ 4.7C Drier than Ave-

Fortunatly this is NOT my forecast for this Winter...........

we are still in the Window for potential disparities between linear Global Warming & local conditions/ local climate changing-

Steve Murrs Official Winter Forecast 2006/07-

Working in Conjunction with Matt Hugo:

Ive Left it Very late this year to enter into the mele of Winter forecasts that occur around about the end of October/Early November-

I think Crucially this has been a good decision, this is because early teleconnection indicators at the standpoint of November 01 looked increasingly favourable for a solid Winter pattern developing Early, We had a NAO that was trending heavily negative, minor warming events in the stratosphere & NH snowcover that after week 39 ranked into the top 10 of measured data-

Coupled with this the global AAM Anomaly ( Angular Momentum) for the year- ( This measures the strength & location of the jet) showing a weak & Southerly locale-

The cause for optimism was certainly there-

However since then ALL the pre-season data has been over-run by a Southern Stream thats really sprung into life-This is inline with a classic Moderate (Peak) El Nino- & Intense Westerly QBO bouncing back from the record negativity of last year-

Here demonstrated by the most up to date Global AAM Anomaly we can see how Active the jet has been at Southern Lattitudes-

The active Southern Arm of the jet has been evident for the last 4/5 weeks & has maintained a Southerly track across the Atlantic, However once reaching 15W has always surged polewards-

As a result the formation of a High Pressure to the SE, & an abundence of Depressions running NE along that track has been well observed-

We have seen some fast developing Shortwaves where the polar front has been pulled way South in the Mid atlantic creating very Steep thermal gradients over warmer waters than usual-

With a jet diving South in the atlantic then recurving back North over 15 W the resultant situation has left the polar vortex in limbo Just east of Iceland & The Shortwaves Swinging Anticlockwise under the base-

The NAO has swung back to Neutral & has almost peaked in Positive values- ( remember Neutral is +1 to -1)

Until we see a significant Pattern Changer this will be the standard fair into the early & mid stages of December-

A Pattern Changer Will be a Storm System or a SIGNIFICANT High Pressure System that develops & Changes the Amplitude of the jet stream out the conventional flow that its in ( IE CURRENT ZONAL) & Re-Shape the flow into a 'New consistent Pattern-'

Archembault Storms that Run Inland Over America & towards the continental interior of Canada encouraging height rises over Greenland, like this-

http://www.wetterzentrale.de/archive/ra/20...00120051122.gif

theres our Inland Runner over the states-

http://www.wetterzentrale.de/archive/ra/20...00120051123.gif

Encouraging Height rises over Greenland-

http://www.wetterzentrale.de/archive/ra/20...00120051124.gif

Pattern Change Complete-

http://www.wetterzentrale.de/archive/ra/20...00120051125.gif

Another example- Close to the current Pattern-

http://www.wetterzentrale.de/archive/ra/20...00120060217.gif

Vortex to the NW

http://www.wetterzentrale.de/archive/ra/20...00120060218.gif

System running up the coast of the US-

http://www.wetterzentrale.de/archive/ra/20...00120060219.gif

Which Becomes part of the Overall Polar Vortex-

http://www.wetterzentrale.de/archive/ra/20...00120060220.gif

Height rises Surging North-

Eventually leading to this-

http://www.wetterzentrale.de/archive/ra/20...00120060226.gif

&

http://www.wetterzentrale.de/archive/ra/20...0120060228.gif-

There are other examples of 'Pattern Changers' that do see High pressures Developing Over Scandi or a Push west out of Siberia - However I think its a little early to be discussing these on the 1st of December-

Anyway the Key to the Phase change LATE December will be the Coming of the Storm over the States & the Subsequent Height rises to the North West Over Greenland-. ...

But enough about 'just' December We need to 'STILL' examine what the Teleconnections & their Feedbacks are pointing towards in the form of a 'Seasonal' Overview-

The Artic Oscillation (AO)-

This is the 'basic' overview of the AO-

The Arctic Oscillation refers to opposing atmospheric pressure patterns in northern middle and high latitudes.

The oscillation exhibits a "negative phase" with relatively high pressure over the polar region and low pressure at midlatitudes (about 45 degrees North), and a "positive phase" in which the pattern is reversed. In the positive phase, higher pressure at midlatitudes drives ocean storms farther north, and changes in the circulation pattern bring wetter weather to Alaska, Scotland and Scandinavia, as well as drier conditions to the western United States and the Mediterranean. In the positive phase, frigid winter air does not extend as far into the middle of North America as it would during the negative phase of the oscillation. This keeps much of the United States east of the Rocky Mountains warmer than normal, but leaves Greenland and Newfoundland colder than usual. Weather patterns in the negative phase are in general "opposite" to those of the positive phase, as illustrated below.

( Top is the Positive AO & The bottom is the Negative AO-)

Over most of the past century, the Arctic Oscillation alternated between its positive and negative phases. Starting in the 1970s, however, the oscillation has tended to stay in the positive phase, causing lower than normal arctic air pressure and higher than normal temperatures in much of the United States and northern Eurasia.....

again Another example of the AO's 500 Mb pattern behaviour-

NEG AO-

Jan 1977

POS

Jan 1989

It was originally thought that the AO was a Bi product of NAO, however recent studies have led us to believe that the relashonship works the other way & the NAO is a manifestation of the AO-

The driver or the AO ( remember the AO is only a measure) is the jet stream location & its intensity-

To arrive at a negative state of the AO ( which is VERY desirable for Winter) the condition of the jet stream needs to be as Surpressed as it can be, the reason for this is pretty straight forward-

There are generally 2 Caveats that need to be satisfied for High lattitude blocking:

1) The Circumploar Vortex ( Often Shortened to the Polar vortex) needs to be as weak as possible- (remember the vortex is directly correlated to the Intensity of the Jet stream-)

2) The energy from the jet is passed through the southern arm ( Subtropical jet) rather than through an intense Northern Arm-

So whats the Driver/s of theses- ??

I originally thought (as I think many still do) that the strength & location of the Jet Stream was linked to the thermal Gradients across the Land & Seas masses-

Well, I still believe that there is causation from this element however its not the marker to be used for OVERALL jet LOCATION throughout the Winter Months-

I would currently give 6 parameters that have a direct feed into the AO phase ( Remember thats Forcings South form the Polar Cell Or North from the ferrell Cell)

REMEMBER LOOKING AT THE REANALYSIS OF DECEMBERS V EXPECTED DECEMBER PATTERN THE QBO RELASHONSHIP COULD OVERWHELM THE MODERATE ENSO SIGNAL FOR NW EUROPE-

1) Strength of the polar vortex relating to the temperature of the stratosphere, ( Polar Cell)

2) QBO (Effecting the Ferrell Cell)

3) El Nino Intensity (Effecting the ferrell cell)

4) Northern Hemisphere Cryosphere ( Effecting the Polar Cell)

5) Artic Cloud ( Polar Cell)

6) Solar Minimum ( Effecting The polar Cell)

So First Up-

1)The polar vortex is a persistent large-scale cyclonic circulation pattern in the middle and upper troposphere and the stratosphere, centered generally in the polar regions of each hemisphere. In the Arctic, the vortex is asymmetric and typically features a trough (an elongated area of low pressure) over eastern North America. It is important to note that the polar vortex is not a surface pattern. It tends to be well expressed at upper levels of the atmosphere (that is, above about five kilometers).

The strength of the polar vortex has a direct impact on the strength of the prevailing Westerlies across the oceans-

The stronger the vortex the Tighter the ribbon of westerlies circulating the Northern Hemisphere, also the faster it is the farther north this ribbon is pulled towards the pole-

There is a NOTABLE correlation between Intense Polar vortex & Mild Winters observed in lattitudes around 50/60N-

This is because the cities in these locations will be sitting on the northern side of the polar front-

In the 90's there was a notable absence of Cold incursions through increased jet stream activity driven on by a 'Stimulated vortex'-

Co-incidentally there was a string of colder Winters in the 80's because the vortex was weakened-

So what can we expect this Winter from the Polar vortex-

Well being a stratospheric phenomenon we need to observe the state of the Stratosphere with respect to its temperature-

The rule of thumb to abide by is the COLDER the stratosphere the Faster the vortex & vice-versa....

Now this is where it gets interesting-

The 90's has already been mentioned & was punctuated by a COLD stratosphere-

The cause of this put down to increased emissions of C02- So you would expect this trend to increase in tandem with the Co2 Emissons-

However this isnt the case, infact since 200o we havent observed cooling, but major warming events-

Its at this point the most up to date information regarding the Stratosphere needs to be examined & for this we use the NOAA Site from this link-

http://www.cpc.ncep.noaa.gov/products/stra...ere/strat-trop/

Selecting either the Current 3 Month T anomaly or the Whole year-

The Current data as of November 26th is-

Note the recent Cooling that has influenced the Nortehrn hemisphere polar Vortex- This tends to propergate downwards & eventually manifest itself in a Faster Flatter jet across the NH-

Even if the flow is slightly furtehr South than usual the absence of High Lattitude Blocking will ensure the cold is bottled up 'MOSTLY' over the pole-

If you actually take time to Study the Graph there is an ~ 21 day Propergation time between Cooling/Warming event & developing flow Pattern-

On a brighter side to seeing this initial Cooling nearly ALL warming events come POST XMAS....

2) The QBO-

You would think a Wind blowing at high altitude in the equatorial regions would have much of an effect on flow patterns to the North, but how wrong can we be -

The Phase of the QBO ( Whether that be Easterly or Westerly) Directly effects the Transportation of Air Masses between the tropics & poles-

The +VE QBO Phase (WESTERLY) exhibits Colder Air in the Upper Layers of the Pole & The -VE ( EASTERLY) Tends to be the opposite- with warmer air at the Pole-

( Remember the Warmer the pole the SLOWER THE VORTEX)

The Paper by Thompson,Balwin & Wallace Explains the relashonship here:

http://www.atmos.colostate.edu/ao/Thompson...dwinWallace.pdf

Before I move into the data for QBO I thought I would add the re-analysis data for DECEMEBERS in Westerly QBO's that CLOSELY resemble this years current figures-

RING ANY BELLS FOR THE OPENING PATTERN OF DEC 2006...?????

Moving On-

Here below is the data for the QBO- As you can see the switch between Westerly & Easterly Phases are Pretty Uniform & Luckily enough the Westerly Phase Longivity is Shorter than the easterly Phase-

On Inspection of the Paper & Historical data analysis indicates that the polar Vortex is Weakened in Easterly QBO Winters-

However the reality of this being observed in terms of the AO & NH Pressure Patterns doesnt seem very Strongly correlated-

Here Is the Winter Pressure anomalies with the Strongest easterly QBO Winters-

Off the 30 Winter Months Only 18 Months were Observed Neutral To Negative AO- Not really conclusive-

More Interestingly though was the Pressure patterns observed in the Westerly QBO Years-

Also more striking was the fact that again 18 of the months were Neutral to Negative-

I Guess I Would have to investigate the Thompson,Balwin & Wallace Paper further to see if Easterly QBO Months developed more NEGATIVE AO Phases ( below -1) Rather than Neutral to Negative-

Anyway the point here is not Whos wrong or right, but the Actual Preferred pattern for NW Europe in Either an Easterly or Westerly QBO, Well Surprisingly to me the Westerly QBO phase does favour blocking in the Correct position In terms of to the North West, North & North east-

Especially when you consider the Febuary patterns of the Westerly Years....

:(

The Forecast for this Seasons QBO trend is based on an analysis of the historic data trends from data measured since 1948-

Westerly Phases of the QBO last on average ~ 11 / 12 Months, The record for Shortest Westerly QBO was 1959 at only 8 Months & the longest was 16 Months in 1985 & 1999-

Looking at the data & the Incremental Changes from Month to month I would say the Longivity of this QBO will be 13 Months Peaking November / December at between 11 & 12- with a declining trend thereafter-

The Analogues for this Winter Would be- 1963/64 1966/67, 1990/91, 1980/81, 1975/76

3) El Nino Intensity-

Where do we Start with El Nino........

Much Discussed topic of late - Especially with respect to the Weather observed in the UK-

So For a start if you are still not sure about what the El NINO is ( Often reffered to as the ENSO- El Nino Southern Oscillation) here are a couple of Links to get you Going- ( Pinched one from GP's forecast)

For Current Conditions-

http://www.cpc.noaa.gov/products/precip/CW...html#discussion

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/eln/home.rxml

http://www.elnino.noaa.gov/

The centre of Attention from here on in need not be what phase of El Nino are we in- But more so Where do we go from the Current Starting point of around 0.9 on the Nino 3.4 index-

Modelling of El-Nino has always been a difficult one to pin down- however we have both the IRI & NOAA Producing an Ensemble analysis from the various model outputs- In terms of Model Accuracy here I wouldnt pin ALL my faith on the ECM as other models specifically deal with this data- However the key line is the ensemble Mean-

NOAA

IRI

What I deduce from these is the 'Trend' of the ENS mean - firstly is a decline from the current 'Peak' down - The model reasoning behind this must be the subsurface trends & the Current trend of the PDO being that you dont get Strong El-Nino's in Negative PDO years-

Here is the PDO data & the reference Material for the PDO is in last years Forecast-

http://jisao.washington.edu/pdo/PDO.latest

Secondly by late Winter the index could be as low as 0.8-

So what do all these numbers mean for Our patch-....

Well no-one has EVER put a definiative Answer to NW Europe because I guess no-one has been bothered to look at the Correlation data & the Sample Size is still quite low-

Also of due note is whether in Weak to borderline Moderate ENSO years the Signal from this Overwhelms or is muted by the Westerly QBO & AO Relashonship for NW Europe-

For reference though & Comparison with the QBO here is the December for Current ENSO state years-

However for refernce We can still investigate what El-Nino Delivers in terms of Northern Hemisphere Winter pressure Anomalies-

El-Nino when at its Strongest ( Including its inverse La nina) Will have the power to influence the global pattern because the SST's Anomalies in the nino regions create a Sea Surface Temperature Couplet or 'Bipole' where by Stronger Areas of high & Low Pressures form due to this Anomaly- When the Nino index is at its Strongest it is the MOST Superior SSTA that effetcs the Jet Stream across the globe-

As a result the 2 Graphs below illustrate the Nino & La nina top 5 years of Strength recorded from here:

http://www.cpc.noaa.gov/products/analysis_...ensoyears.shtml

This is just to put into perspective what the 'Extremes' mean for us-

Strongest NINO-

1958,1973,1983,1992,1998-

Strongest La NINA-

1950,1971,1974,1976,1989-

As you can All see- We want neither A strong el Nino OR worse Still a Strong LA nina...

Fortunatly we are not in that postion-

ENSO Forecast Winter 2006/07 Combining the Current Subsurface trend & the Ensemble data I would forecast a Negativly trending El-Nino with the DJF Figures ruunning 1.2 down to 0.9 with the Average panning out ~ 1.1/1.0 This then working with an error rate of 0.2 gives me a range of Nino Index analogues between 1.3 & 0.8 these Are:

1963/64,1965/66,1986/87,1987/88,1994/95,2002/03

re-Analysis Graph- Here:

Shows a Classic Strong Southern Stream & High Lattitude blocking...

4) Northern hemisphere Snow Cover-

There has Been a LOT of debate over the last Couple of Months with Respect to Snow & ice Cover & its relashonship between Flow patterns-

Ive Summarised my Opinions & Pinched a Couple of Links from Nick Sussex-

Anyway.......

The Snow & ice extent is covered by the term 'Cryosphere' ( Hence the name ofthe site Cryosphere today)-

The cryosphere 'region' is an area that is condusive to ccoling- As we already know Snow & Ice have a large Albedo compared with open water or 'green' snowless areas-

Having a wider area of ice & Snow cover suspends higher amounts pf incoming solar radiation from being absorbed -Granted, above 67N latitude there is darkness for much of the cold season due to the tilting away from the ecliptic, which falls beneath the southern horizon. So we ask, “what difference would it make then”.. Well, there is a background OLR even the polar-regions that is calculated to have a less than negligible effect on the lower troposphere. Thus, in years of advancing snow cover at high latitudes, these 2 factors feed back in a process of heat sink. The end result is the production of cold air masses and has been statistically correlated to increased frequencies of the negative Arctic Oscillation phase states, when the NH snow pack is more abundant. For more than this, a good website the covers all this in better refinement is:

http://nsidc.org/cryosphere/questions/index.html

Obviously 'seasonally' the Cryospheric region is variable- so this is why we look towards the change in seasons ( latter Sept, Oct & Nov) to see the build up of the snowpack & Ice extent across the various regions extrapolated in the data-

You could say simply- The 'overall ' anomaly of cryosphere against the norm observed the more chance there is of negative Artic Oscillation setting up-

This can then be subtended to the NAO that has a statistical linear correlation to the AO of +0.7 meaning that they are highly correlated.

Hart also Provided me with a chart the winters that followed from Northern Hemisphere Sept-Nov Snowcover expanses that were greater than 1SD from the mean-

Also More evidence here from A LONG PDF Around Stratospheric Warming & Northern Hemishpere Snowcover-

PDF here:

There will be sceptics that comment that these factors do NOT matter, However the way to look at is this, Our Coldest 2 Winters have arrived on the Back of Strongly negative AO's-

& whilst the AO Going Negative ISNT a Guarentour of Cold for the Uk Its part of the fundamental process of Delivering Cold air to the Mid lattitudes- of Which we are one....

More Links-

http://www.columbia.edu/~gg2138/GongEtal2005.pdf.

http://web.mit.edu/jlcohen/www/papers/Cohen_SaitoGRL03.pdf.

5) Artic Cloud-

The reason behind the warming of the stratosphere POSSIBLY lies with the ARTIC Cloud Fraction being on a linear increase for the last 20 years, trapping warmer air into the system-

This IMHO has been the one of the biggest contributors to the weakened state of the jet stream over the last few years, which now combined with the Phase of the Sunspot activity finds itself at its lowest ebb for some considerable time-

6) The Solar Minimum is NOT my specialised subject, however there is General Consensus amoungst the Meteorogical Community that in periods of LOW sunspot activity the Polar Vortex is Weakened, There IS a Correlation of this against the Phase of the AO which is demonstated by this re-analysis graph from the data given by solar cycle 23-

Weak Sunspot Activity-

The Sunspot Activity SHOULD be at approaching a minima over the next 2 years- but is certainly NOT an overwhelming factor versus the other measures involved in this forecast-

North Atlantic Oscillation-

The NAO, the most bantered about teleconnection across the forums & wherever one you visit you will see links & Images on how the NAO block ( Whether that be Greenland/Canadian, Iceland etc) has manifested itself & what it has meant for that particualr persons part of the world- indeed if we pick the MOST negative 5 NAO Jans since 1950 A present the 500MB Anomalies & Surface temp anomalies then you see why people blue regions crave the Negative NAO-

The Key driver to the NAO when it has a chance to develop is the atlantic basin SSTA's-

I have produced from the CDC site a correltaion map which lends itself perfectly for a -NAO...

The above correlation maps from CDC of the SST anomaly pattern for -NAOs.(NEG) Focusing on the Atlantic. Notice the correlations? A negative NAO correaltes best with an Atlantic setup where, there are above normal SSTs in the tropics to 20N. Below normal water above that up to around 50N. Another belt of above normal water, above this north of 50N, to south and west of Grenland. And another band of below normal SSTs above this north of Iceland and east of Greenland-

This is the Current State of play in terms of Atlantic SST's-

What we have is an Atlantic Bipole - NOT the Classic NAO State like the Re-Analysis chart & the Tripole image from the early 60's- but none the less its Not bad-

The Discussion point around the NAO though really only comes into play WHEN we have to rely on a Mid Lattitude block when the AO is Neutral or Positive-

This is when there is No dicernable High lattitude block over the pole, so we are left with a zonal-ISH mid lattitude jet flow that is usually influenced at best by only ONE block, either a +VE / -VE PNA ridge or the NAO Block- it is here & only here we need discuss the Pacific V Atlantic Scenario-

Its a case of whether a PDO & PNA Signal overwhelmes the Westerly QBO & NAO SSTA Profile-

Or in Laymens terms the point where the jet is easiest to buckle- WEST ( The US ) or EAST-Greenland-

Here would be the Estimated forecast for the NAO across Winter 06/07 Based on the SSTa's, The State of the PDO ( Staying Pretty neutral), The historic Westerly QBO data & the PREMISE of Increased Stratospheric Warming events Late season-

Dec- 0.5 to 1 positive, Jan 0 to -0.5 Neutral Feb -0.5 to -1 Negative-

Winter Forecast Summary

Seasonal flow Profile with anticipated Monthly Temperatures & Precipitation-

The way I expect this Season to go is one of Steady decline against the Average--This is in almost Equal incriments with respect to Temperature & Precipitation-

December-

From the outset,the Signal from the Westerly QBO,Neutral/Pos AO & enhanced Southern Stream I expect Next to NO blocking over the Pole & Greenland, the ONE mid lattitude block looks to be a moderate PNA ridge Centred Somewhere over the Central/Northern States-

This ridge is also fed by the current drought conditions in these areas-

Also ive attached my impression of the Overall flow Pattern for DEC-

With an accompanied Temperature Profile of Between +0.5 & 1C Above the Norm-

Also Precipitation clearly above Normal-

January

As we Move into the Latter stages of Dec/Early Jan ( remember we cant define at EXACT date of pattern change so there may be some overlap) with the QBO & AO relashonship Still overwhelming the ENSO Signal I expect a Significant Pattern Change Away from the Polar Vortex Sitting Over Iceland, The seasonal feedbacks, The Weakening QBO, The Potentially Stronger signal from the atlantic over the Pacific for De-stabilizing the Northern arm of the Jet will see the Polar vortex lift out & be replaced by ever incresing heights to the West-

The core of the Vortex will start to drop into Scandi & perhaps a secondary vortex Over the Eastern US- the flow over the UK will move away from the Strong Westerly Progressive to a slacker but more Pronounced Northerly-

The Re-Analysis Graph below looks pretty imense, & I think it will be pretty accurate but NOT quite as dominating & overwhelming as it looks at first glance-

The Accompanied Temperature profile looks Distinctly below average, however like I Said I dont think it will be that flattering So I will go for Average to 0.5C below Considering the prominence of the Atlantic blocking & Scandi troughing-

Precipitation Pretty much Average to Slightly below-

Febuary-

The Final Winter Month, & if this was an episode of its a knockout then I would be player my joker here-

If we ever had a good Chance in getting a month that panned out greater than 1C below the Ave it would be this-

By now I would expect both the QBO & ENSO to be relaxing away from peaks-

The Combination of a Weakening QBO & a Marked Warmth of the Startospheric temps will promote a Negative AO profile- One that Could range in the -1 to -2 field-

Becuase the Signal for the -AO exists the NAO SHOULD teleconnect to a -VE mode as Well because after Extensive study these are VERY highly Correlated-

The Other thing to Consider would be the Cryospheric Conditions across Siberia- I Am monitoring the effects of these Versus the State of the POL Pattern-

The january index was -1.8 for 2005 & I am anticipating a similar return for Jan 2007-

My Projected 500 MB Profile looks like this-

The NAO Blocking looks pronounced, Again I DONT expect it to remain for the WHOLE Month but the significance of Blocking to the North & NORTH EAST of the SHOULD ensure the Temperture profile is below Average-

This then sets us up for a Winter that Averages Just below the 71/00 mean average of 13.5C Cumulative-

My Seasonal Estimate is between 12.2 & 13.2 C Which give me a scope of just 0.3C Below Average at the top end & a 1.3C below Average Scope at the bottom end-

Precipitation Wise I would go Average to ABOVE average based on the tendancy of the Subtropical Jet stream to bring enhanced rainfall/Snowfall to the UK-

This is the first forecast ive produced which has gone as far as to give Presure Pattern anomalies for Each Month- the way I have produced these is for each month have My primary analogues for the 'total weighting' of Pressure distribution & then for each individual month apply additional years to the re-analysis to weight towards the Scenario I believe will Happen-

Because I have predicted the AO to be Neutral Dec & Feb the Primary Years used for the Base Pressure Distributions on Dec & Jans Maps are from Strong Westerly QBO years, then further weighting applied from PNA, & NAO Analogue Years-

Because I have predicted the AO to be negative in Feb there is HEAVY weighting to historic -AO years on top of the Original Analogue years-

I hope this helps in terms of understanding where the thought process comes from-

Note I HAVENT mentioned snowfall extent in the forecast- Should the forecast be accurate in terms of Pressure profiles across the months then a Below ave december is Likely but most probably compensated in Late Jan & feb-

In the Mid January update I will also be studying the above mention data to derive a forecast for march because I am begining to think the seasonal shifts from Summer - Autumn & Autumn to Winter are arriving 2 to 3 weeks later-

Any questions around the forecast are welcomed-

Best regards

Steve ;)

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  • Location: Co Dublin, Ireland
  • Location: Co Dublin, Ireland

Steve, that is absolutely superb! Thank you so much for your huge efforts and providing the best bed-time reading in ages! :(

Hope your right about January, ive a good feeling about the latter stages of this month!

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  • Location: Seven Springs, Cotswolds 212m ASL
  • Location: Seven Springs, Cotswolds 212m ASL

Thanks for the time and effort involved in your forecast Steve. Its even longer and more complicated than GPs! Its going to take a few reads to understand thats for sure.

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