Model Output Discussion 17th Dec.2013-12z onwards.

[Summer Sun]

Latest NAO update shows little change with it staying around neutral during the first half of January

 

 

The latest AO update shows it staying negative early on before a steady rise to neutral during week 2 of Jan

 

Edited December 31, 2013 by Summer Sun

[johnholmes]

Latest NAO update shows little change with it staying around neutral during the first half of January

 

 

The latest NAO update shows it staying negative early on before a steady rise to neutral during week 2 of Jan

 

 

cor=AO  for the second series of graphs SS

Edited December 31, 2013 by johnholmes

[johnholmes]

just to give an explanation of the term PV which newcomers will see splattered around in many posts.

below is a link to a NOAA site, the official USA Met Office. In it they describe it and also use the link to show how it impacted on to the winter of 2009-10 in both North America and Europe.

http://www.noaa.gov/features/02_monitoring/warmarctic.html

 

well wort a read and perhaps bookmark it or copy and print to read now and again?

Edited December 31, 2013 by johnholmes

[SMU]

I think, like I mentioned the other day we are heading towards a crossroads for January-  We have a clear split in the model trends- one CAN develop a Scandi High, the other is another big bout of +AO dominated weather-

 

If the latter lands on ~ 10 Jan then there is a high chance it COULD** wipe out the rest of jan.

 

If that's the case we could be staring down the barrel of a 90's type winter with zilch snow for most. I hope not.

 

The more positive news is the stratosphere ( surprised it isn't in the swear filter ) is beginning to show signs of a huge warm up which allowing for the @~ 16 day propergation time would set Feb up nice.

 

Roll on the 12z & hope for a strong correction west on that low & an inward track!

 

S

[Blizzardof82]

just to give an explanation of the term PV which newcomers will see splattered around in many posts.

below is a link to a NOAA site, the official USA Met Office. In it they describe it and also use the link to show how it impacted on to the winter of 2009-10 in both North America and Europe.

http://www.noaa.gov/features/02_monitoring/warmarctic.html

 

well wort a read and perhaps bookmark it or copy and print to read now and again?

Thanks John, it is information like this that makes things easier for a novice like myself.

 

Are we to believe that we can not have a cold winter or spell if the PV is strong?

[Nick L]

Thanks John, it is information like this that makes things easier for a novice like myself.

 

Are we to believe that we can not have a cold winter or spell if the PV is strong?

 

It's not impossible, but a "weakened" PV makes our prospects for cold much better.

Edited December 31, 2013 by Nick L

[shedhead]

It's not impossible, but a "weakened" PV makes our prospects for cold much better.

I think it is impossible to get a cold winter IF like now the core of the vortex meanders around Baffin/Hudson/Newfoundland throughout. Given the jet profile and associated depth of cyclogenesis in that area we would really struggle to get any meaningful cold into the UK and to be honest that is still how Winter 13/14 could end up panning out - like it or not it certainly isn't a complete non runner, but it's still a long way from becoming the form horse too though....at least for now.

Edited December 31, 2013 by shedhead

[IDO]

The five closest GEFS members on the 06z run to the more amplified ECM Atlantic ridge are:

 

  

 

 

 

Moving forward to T384 they become: Scandi High> zonal>

 

Slider> Atlantic ridge> Zonal> 

 

The two zonal FI runs were the least akin to the ECM out of the five at T240.

 

About half of the remaining 17 continue strongly zonal and the rest are a mixed bag, with a minority of cold runs.

 

So this backs up Steve's and Nick's knowledge that there is a greater chance of something less zonal if the ECM 12z op of last night verifies. GEFS still have it as an option so no lost cause.

Edited December 31, 2013 by i'm dreaming of...

[fergieweather]

Hi all. I think some may have misinterpreted or even mis-cited any earlier posts re UKMO take on next 10-15 days and onwards into 30d territory. I've been very clear on these (and on Twitter) & ensured exact terminology employed by Dep Ch Forecaster. So to recap, based on latest analysis just issued, and avoid any further confusion:

Their assessment remains consistent & replicates many views expressed today based on EC ENS; a continuation (strongly signalled) of the unsettled SW pattern for a few days; threat of meaningful rain totals & gales/severe gales (eg Sun-Mon in SW especially)... thereafter, some hints (medium confidence) of cyclonicity waning and more anticyclonic bias to S, with lessening of unsettled weather but steady drop in temps to average or below ('rather cold' category to use UKMO terminology). Coincident with this comes increased chance frosts/snow mostly at elevation. Longevity of this phase unsure as mobility perhaps then resuming (e.g., EC32 shows the drop in UK temps too via clear areal anomaly, before resuming the mobile cyclonic story again later Jan with striking low height anomalies to NW).

[johnholmes]

thanks for the insight into Met O thinking Ian.

2+2 always=4 except in here at times!

[fergieweather]

One further addition is UKMO noting how latest EC ENS have moved away somewhat from the more benign phase and hence they express only limited confidence in the reduction of the ongoing cyclonic theme, albeit the more meridional patterns out past d8 suggest at least a slowing of the Atlantic train. Worth adding that Gibby's recent summaries have broadly replicated the thoughts of Ops Centre: decent unbiased cross-model assessments, IMO.

[shedhead]

Hi all. I think some may have misinterpreted or even mis-cited any earlier posts re UKMO take on next 10-15 days and onwards into 30d territory. I've been very clear on these (and on Twitter) & ensured exact terminology employed by Dep Ch Forecaster. So to recap, based on latest analysis just issued, and avoid any further confusion:Their assessment remains consistent & replicates many views expressed today based on EC ENS; a continuation (strongly signalled) of the unsettled SW pattern for a few days; threat of meaningful rain totals & gales/severe gales (eg Sun-Mon in SW especially)... thereafter, some hints (medium confidence) of cyclonicity waning and more anticyclonic bias to S, with lessening of unsettled weather but steady drop in temps to average or below ('rather cold' category to use UKMO terminology). Coincident with this comes increased chance frosts/snow mostly at elevation. Longevity of this phase unsure as mobility perhaps then resuming (e.g., EC32 shows the drop in UK temps too via clear areal anomaly, before resuming the mobile cyclonic story again later Jan with striking low height anomalies to NW).

Thanks for clarifying your previous comments with the above Ian. If correct (and its a big IF...again in the interest of clarity for some) it does looks as though the best chance of meaningful cold will be across the final third of Winter, which hopefully will prove to be well worth the wait.

[Methuselah]

Thanks for clarifying your previous comments with the above Ian. If correct (and its a big IF...again in the interest of clarity for some) it does looks as though the best chance of meaningful cold will be across the final third of Winter, which hopefully will prove to be well worth the wait.

But - arguably - a smaller 'if' than applies to some of the other prognostications?

[bluearmy]

following on from the above, the question yesterday revolved around the Atlantic ridge at day 9/10. Nothing has changed. As far as the return of mobility is concerned, a strong east Canadian vortex is not a guarantee that the UK cannot be cold. A block can establish in an advantageous locale to either deflect the jet south, or indeed, north, should we see heights rise to our ne. it does seem that Exeter see this Atlantic ridge putting up a bit of a fight as it gets flattened. Look out for the Iberian trough re invigorating. That's become a control run theme and could liven things up.

[shedhead]

But - arguably - a smaller 'if' than applies to some of the other prognostications?

Agreed, I currently cannot see anything to suggest what Ian has indicated should not be the most likely outcome for Jan, but as I'm sure he would agree it must come with the usual caveats given the timeframe involved.

[Paul]

Latest week ahead forecast from Jo:

 

http://vimeo.com/83030286

 

Happy New Year

[johnholmes]

just before the GFS 12z starts to roll out some may wish to read yet another pdf from me, about how a more objective outlook to the GFS 168-240 hours could be taken. I hope some find it useful.

 

Comparing current 500mb anomaly output with the latest GFS synoptic output.pdf

 

also copied into the technical thread

 

[shedhead]

just before the GFS 12z starts to roll out some may wish to read yet another pdf from me, about how a more objective outlook to the GFS 168-240 hours could be taken. I hope some find it useful.

 

Comparing current 500mb anomaly output with the latest GFS synoptic output.pdf

 

also copied into the technical thread

A good, clear PDF John, well worth a read by those keen to learn.

[stodge]

Afternoon all

 

Nothing teribly surprising in Ian's clarification. The output has taken several steps away from mid-month cold in the past 36 hours and even the previously-touted break from the prevailing cyclonic outlook is now looking less and less likely.

 

None of this of course rules out colder conditions in the last third of January let alone February.  Many UK winters have been "late starters" and even the poor winters of the late 90s and early 00s often had colder spells in mid and late February so even if you write off the next two weeks or so there's still half a winter left.

 

I originally thought the winter was going to be very anticyclonic and that Christmas would see a lot of fog and frost so perhaps my prognostications aren't as reliable as Ian's but then I have my rabbit's foot and dice whereas the technology at Ian's disposal is slightly superior.

[nick sussex]

Oh well the time is fast approaching to see what happens with the upstream low, inland runner or out into the Atlantic. Theres a small window of opportunity but its all to do with that low.

 

Even if that low does us a favour we still need to see the low over the UK fill more quickly with more energy going east/se, currently the models are reluctant to do that so its not just upstream that we need to see some changes.

 

I doubt a low thousands of miles away will grip the attentions of coldies again in here quite like this one modelled for around T144hrs, it probably speaks for the utter lack of anything remotely wintry UK wide so far that this low is garnering so much attention!

[mcweather]

Afternoon all

 

Nothing teribly surprising in Ian's clarification. The output has taken several steps away from mid-month cold in the past 36 hours and even the previously-touted break from the prevailing cyclonic outlook is now looking less and less likely.

 

None of this of course rules out colder conditions in the last third of January let alone February.  Many UK winters have been "late starters" and even the poor winters of the late 90s and early 00s often had colder spells in mid and late February so even if you write off the next two weeks or so there's still half a winter left.

 

I originally thought the winter was going to be very anticyclonic and that Christmas would see a lot of fog and frost so perhaps my prognostications aren't as reliable as Ian's but then I have my rabbit's foot and dice whereas the technology at Ian's disposal is slightly superior.

 

Quite so Stodge 1947, the snowiest of the last 100 years is one that springs to mind.

[legritter]

Well at least we have the possibility of some colder conditions in the further modeled outlook .And bearing in mind that the middle of January is 15 days away its whats beyond that which at the moment is realy hard to predict even with supercomputers .I would like to say what a fantastic year weatherwise its been and a great treat every day to see so many Informative posts a great learning forum THE  BEST ,a good new year to all my fellow posters and Cheers ,STELLAS all round .  

[Mucka]

Hi all. I think some may have misinterpreted or even mis-cited any earlier posts re UKMO take on next 10-15 days and onwards into 30d territory. I've been very clear on these (and on Twitter) & ensured exact terminology employed by Dep Ch Forecaster. So to recap, based on latest analysis just issued, and avoid any further confusion:Their assessment remains consistent & replicates many views expressed today based on EC ENS; a continuation (strongly signalled) of the unsettled SW pattern for a few days; threat of meaningful rain totals & gales/severe gales (eg Sun-Mon in SW especially)... thereafter, some hints (medium confidence) of cyclonicity waning and more anticyclonic bias to S, with lessening of unsettled weather but steady drop in temps to average or below ('rather cold' category to use UKMO terminology). Coincident with this comes increased chance frosts/snow mostly at elevation. Longevity of this phase unsure as mobility perhaps then resuming (e.g., EC32 shows the drop in UK temps too via clear areal anomaly, before resuming the mobile cyclonic story again later Jan with striking low height anomalies to NW).

 

Hi Ian,

I'm not sure if this in response to a post I made but if it is I'm not sure where I miscited or misinterpreted anything? 

If your post wasn't referencing my post then you can pretty much ignore the following though I am still interested in their thinking regarding any Atlantic ridge or interruption/slow down of cyclonic westerly domination.

 

I wrote.

 

"Hi Ian,

Are they still "discounting" anything other than a Westerly flow through to mid month at the very earliest?

and if so does that take account of an interruption to that flow such as the latest ECM?

In other words even if we get stronger Atlantic ridge and deeper European trough are they expecting it to be quickly brushed aside by a renewed Atlantic onslaught?

 

Thanks"

 

That was in response to your posts;

 

Dec 27th

Latest MR assessment from Ops Centre notes strong signal from MOGREPS, DECIDER and EC EPS (plus EC32) for the cyclonic westerly theme to dominate into 10-15d trend period. They note a minority of members offer either high pressure, very deep lows or an easterly but, quote, "these are all discounted." As previously mentioned, EC32 retains a strong cyclonic westerly regime, albeit with nuance variations, effectively right through towards end of Jan.

 

and

 

Dec 28th

UKMO note only circa 10% of EPS members offer blocked solutions by mid-Jan with easterly components... these remain discounted for now based on current evidence.

 

 

My question and the way it was posed seemed perfectly legitimate to me since "cyclonic westerly theme dominating" does not imply Atlantic ridge to me or any interruption to the flow so it seemed natural to ask if that was considered in their appraisal to better understand how they saw things developing in that area.

Today's update states medium confidence on cyclonicity waning with less unsettled weather which to me is more suggestive of a disruption of the westerly flow than, "cyclonic westerly theme dominating" but it may be both or neither appraisals took account of a possible Atlantic ridge.

Personally I would say the first did not and the second has the ridge toppling over the UK but any clarification would be much appreciated.

 

Thanks in advance and also for all the valuable updates you provide. 

Edited December 31, 2013 by Mucka

[Gaz1985]

Quite so Stodge 1947, the snowiest of the last 100 years is one that springs to mind.

 

Well if there is one straw to clutch for coldies it is that Winter - which didn't properly get going until the 21st January.

 

Today in 1946

 

 

Today

 

Edited December 31, 2013 by Gaz1985

[MR EXTREMES]

Oh well the time is fast approaching to see what happens with the upstream low, inland runner or out into the Atlantic. Theres a small window of opportunity but its all to do with that low.

 

Even if that low does us a favour we still need to see the low over the UK fill more quickly with more energy going east/se, currently the models are reluctant to do that so its not just upstream that we need to see some changes.

 

I doubt a low thousands of miles away will grip the attentions of coldies again in here quite like this one modelled for around T144hrs, it probably speaks for the utter lack of anything remotely wintry UK wide so far that this low is garnering so much attention!

to be honest nick ive given up on anything cold even into feb as ian f has just suggest a return to another zonal grim outlook.

this winter will go down like the winters of the late 90s dreadful outlooks if your looking for real wintry stuff.

it does go to show how the spotless sun at the start of cycle 24 really did have an outstanding effect. as for this winter the ramp up with solar activity at the start of autumn really did have a real effect on the vortex extreme cold.

 

the models don't like the vortex either more because its not really had to deal with a strong vortex in the last few years.

so I think im tired of chasing a cold spell and will now wait for the next solar lull then things will be exciting.