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Winter 2013-2014 Discussion- Part 2


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I just posted this in the seasonal forecast thread, I thought some here might appreciate it.

 

 

Here's my winter 2013/2014 forecast.

 

For this forecast, I looked at 10 different teleconnections for their trends and averages in the last 6 to 9 months (and forecasts for MEI), and then compared those criteria with previous years, mostly back to 1951, and created a list of the years with the most similar teleconnections to this year.

 

Below are the 10 teleconnections and the criteria used with them.

 

Teleconnections ......................  ................... Criteria 

 

Arctic Oscillation (AO): Mean of the last 6 months (May to October) close to 0, and little month to month variation.

North Atlantic Oscillation (NAO): Mean of the last 9 months (February to October) close to 0, and a moderate to large amount of month to month variation.

Multivariate ENSO Index (MEI): Winters averaging between -0.5 and +0.5 for the October to February period.

Eurasian Snow Cover: Years that show an above average increase from September to October Eurasian snow extent.

Quasi Biennial Oscillation (QBO): Positive in Autumn and falling through Winter.

Solar Activity: An 11 year monthly sunspot mean of below 70

Atlantic Multidecadal Oscillation (AMO): Mean above average over the last 9 months.

Pacific Decadal Oscillation (PDO): Mean moderately below average over the last 9 months

Arctic Sea Ice: A September sea ice area minimum of less than 4 million km

Globally Averaged Angular Momentum (GLAAM): Mean of the last 9 months close to 0, with moderate month to month variation.

 

After going through the data, these were the most closely matched years

 

Year ... Criteria Matches out of 10

2010/11 = 7* 

2009/10 = 6

2006/07 = 6

2004/05 = 7 

2003/04 = 6 

2002/03 = 6 

1985/86 = 6 

1978/79 = 6 

1976/77 = 6

1973/74 = 6

 

So using this, each of the years with 6 matches would get 1 place in the composite maps, and 7 matches would get 2. *An exception here is 2010/11, which had a moderate El Nino, so that will only be included once.

 

So based on the above, here's the winter forecast.

 

--------------------- ------------------------------------- ------------------------------ ------------------------------------ -----------------------

 

DECEMBER

Posted Image

 

A strong Atlantic ridge stretching into southern Greenland, coupled with low heights stretching from Scandinavia to the Iberian Peninsula, look to be the main features for December. An increase in northerly orientated winds could be expected with this set up, but, if the trough moves much further west, the is a chance of some milder southerly winds occurring, sourced from the western Mediterranean.

 

Precip is likely to be close to average, with a slightly higher chance of above rather than below average monthly totals.

Temperatures are more likely to be below average, with a CET estimate of close to 4C

 

 

JANUARY

Posted Image

Northern blocking, a west based -ve NAO and a large trough across central Europe are the main features for January. Northerly and northeasterly winds are likely to be more common during the month.

 

Rainfall is likely to be average or slightly above, with the driest weather to the south and west.

Temperatures are likely to be below average once again, with the coldest conditions further east. The CET estimate is 3.0C.

 

 

FEBRUARY

Posted Image

 

At this stage, February looks like featuring some very strong northern blocking, centred toward Greenland, with low heights across our south and into Europe. The set should produce much more easterly winds than normal.

 

Precip is likely to be close to or above average in the south and east, and below average further north and west

Temperatures are likely to be below average everywhere, with a CET estimate of 2.8C

 

 

OVERALL

Strong heights over southern Greenland should be a recurring feature of the first 2 months of winter, bring plenty of northerly airflows, before more general blocking takes hold, carrying more easterly winds during February. With low heights nearby and plenty of cold sourced airflows, each month has the potential for spells of cold and snow. While precip looks like being near average overall, snowfall totals may well end up above average.

The coming winter seems quite likely to be below average temperature-wise, with a good chance of all 3 winter months being below the 81-10 average.

If I was to guess at a period with the highest risk of severe cold, I'd say late January and early February, as northern blocking strengthens eastward and brings a more easterly flow across the British Isles

 

Bloody hell BFTV, your forecast is pretty much bang in line with how I see winter panning out.......like, exactly how I see it. I can't top that in terms of presentation either. It's like you read my mind!!

Edited by CreweCold
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Bloody hell BFTV, your forecast is pretty much bang in line with how I see winter panning out.......like, exactly how I see it. I can't top that in terms of presentation either. It's like you read my mind!!

This is good....I always believe in CC s thoughts, even when other people think mil dish
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This is good....I always believe in CC s thoughts, even when other people think mil dish

I've just had a look, and it looks like he was saying that last winter wasn't looking too promising for cold and snow, especially during December! Let's hope you're right again CC!! :D
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How are the charts looking now, I heard it's meant to turn mild next week? Any reason why this thread is so dead?

 

You find if there is no cold and or snow on offer its very quiet in here, its the same in the mod thread

 

I wouldn't say mild, Its likely to become less cold from mid week but this depends on whether its foggy or not some places could see fog all day keeping temps around 1 or 2c

 

Posted ImagePosted ImagePosted ImagePosted Image

Edited by Summer Sun
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How are the charts looking now, I heard it's meant to turn mild next week? Any reason why this thread is so dead?

 

 

Where did you get that from?

 

Netweather certainly don't agree with it turning mild next week.

 

Looking ahead into next week, high pressure will remain with us throughout, so most places will remain fine and dry with sunny spells by day, though it will be on the chilly side, with a risk of frost and freezing fog patches forming overnight
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How are the charts looking now, I heard it's meant to turn mild next week? Any reason why this thread is so dead?

 

you probably heard it was going to turn milder due to people looking at the upper air temps but this can be misleading as we can still get cold air trapped at the surface under the warm upper air temps.

 

during slow periods people tend to move to the regional threads for chatting as theres no real winter weather to talk about.

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Regardless of what the NWP is showing at the present time RE synoptics in our locale, it's reassuring to see an unwillingness of the vortex to locate around Greenland. A Siberian side vortex is very much an important part of the foundations for a much colder spell of weather to take hold later on. The flat pattern (N Atlantic) we're seeing represented on some modelling in the medium range is very much a red herring and tells us little about likely synoptics as we head into winter proper.

 

I've picked 3 charts below which graphically represent the expected pressure anomalies for December, January and February. Today's CFS looks a good fit for my thoughts for December and January.

 

December

 

Perhaps the least 'wintry' of the 3 months but with the propensity for weak blocking or higher than average pressure at northern latitudes at times. However, a very mixed month with a mix of synoptics and no one pressure anomaly pattern dominant over another. I would suggest there will be periods of cold which will serve as a precursor for what is to come throughout January and February. An average to slightly below average month temperature wise.

 

January

 

Posted ImageJan forecast.png

 

A cold month, especially as the month progresses. I would suggest significantly higher than average pressure to our N with blocking centred Greenland-Iceland. I would anticipate several notable snow events for some areas and a mean temperature running between 1-3C below average by month's end.

 

February

 

Posted ImageFeb blocking.png

 

Again a cold month. As January, pressure anticipated to be higher than average to the N of the UK. Subtle differences though as the threat of dynamic snowfall increases for SW Britain with both an increase in jet strength and a change in projection sees Atlantic low pressure systems encroach slightly further. Mean temperatures ranging from up to 3C below the mean across the N of the UK to 1-2C below average across the south (as periods of milder uppers may encroach at times).

 

Summary

 

Winter 2013-2014 looking to feature a predominantly -AO and a fairly notable -NAO anomaly across winter as a whole. December looking to be the mildest of the three months with a mean temperature not deviating far from average. January and February to feature periods of severe cold which will likely see winter 2013-2014 significantly colder than average on balance.

 

In terms of methodology I can't really add much more to what BFTV posted yesterday. His forecast is very similar to mine and suggests that confidence is somewhat heightened on this prognosis.

Liking this forecast! What is the chance of a white Christmas then??Posted Image 

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AO will stay positive this winter?? Dr. Cohen’s method has changed. He used to look at total snow cover at the end of October. Now it’s the rate of change of the snow during October. That makes a difference this year, so, even though the Eurasia snow was the 4th most ever recorded, the rate of change wasn’t very large.

 

http://www.nbcphiladelphia.com/weather/stories/Hurricanes-Long-Range-Winter-Forecast-232835491.html

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Summary

 

Winter 2013-2014 looking to feature a predominantly -AO and a fairly notable -NAO anomaly across winter as a whole. December looking to be the mildest of the three months with a mean temperature not deviating far from average. January and February to feature periods of severe cold which will likely see winter 2013-2014 significantly colder than average on balance.

 

In terms of methodology I can't really add much more to what BFTV posted yesterday. His forecast is very similar to mine and suggests that confidence is somewhat heightened on this prognosis.

 

Thanks CC, another forecast that won't get any complaints from me it's close to the mark!  Just one observation, the CFS February chart you posted is from 26th September.

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Thanks CC, another forecast that won't get any complaints from me it's close to the mark!  Just one observation, the CFS February chart you posted is from 26th September.

 

Yep, I haven't used today's CFS to make a forecast.....I've used the pressure anomaly charts of random runs to highlight where I expect any blocking to set up. Ignore the fact it's a forecast model and just concentrate on the pressure anomalies at face value.

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Not good 12z models today, and not too many indications of a change yet. I still think the high pressure will sit further to the west... but with cool rather than cold the best that is on the horizon for the start of December.

 

The problem we have is this:

 

Posted Image

 

Temps in the polar strat are now lower than the average lowpoint for the season... and they have reached this 4 weeks early. This means the vortex is strong and hard to shift. Wave activity is present, but it is relatively low level and unlikely to bend and buckle this vortex too much.

 

Any straws to clutch? Well... there is one obvious factor looking at the graph above. It really cannot go too much lower. We are on or around the record November low point at present currently held by 1997/98 when temps in November bottomed out at -78C. The lowest point ever recorded is -84C reached in Jan 99/00. In other words the current rate of decline must stop and the fact that the steep decline in temps has happened so early fills me with more optimism for the second half of winter at least. Nature has a habit of balancing things out and I expect to see a bounceback from these temps with a consequent lagged effect on the trop.

 

Solar signals are also currently not good. The sunspot number has gone through the roof at times this month, higher than at any stage since 2011, and this will not be helping blocking currently to move to high latitudes. But... again... the pattern of solar activity over the last few years reveals that after every peak there is a substantial drop off.

 

So my conclusions are not based especially on science... but rather on observation. We have managed to get a bit of blocking and made a mess of the MetO Nov temp forecast issued at the start of the month with background signals that are not good. And those background signals in terms of strat temps and solar activity may well side with us in a few weeks time.

 

It is going to be a long haul through December I think. There have been some optimistic pressure anomaly charts and december forecasts released recently - I hope they are right... but I am still seeing a slow burner of a winter with some real interest in the second half.

 

Anyone noticed how the models are moving towards the mild start to December touted by RJS? I am hoping his overall winter call is pessimistic - but even his rather mild winter forecast sees a period of proper cold in January using methods that are miles away from conventional science.

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AO will stay positive this winter?? Dr. Cohen’s method has changed. He used to look at total snow cover at the end of October. Now it’s the rate of change of the snow during October. That makes a difference this year, so, even though the Eurasia snow was the 4th most ever recorded, the rate of change wasn’t very large.

 

http://www.nbcphiladelphia.com/weather/stories/Hurricanes-Long-Range-Winter-Forecast-232835491.html

 

The AO is currently negative, so I do believe he is wrong

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I do believe that we are going to get a winter like 08/09, I am basing that on my gut instinct and seeing now what we seen during 08/09, I cannot believe that so many people put their trust into the charts & science, when in the past both have been wrong,  instead they should just say what they feel is going to happen, sorry if that sounds strange but I have had a few vodka & cokes, lolPosted Image , I am just really looking forward to a white Christmas and everything is pointing that way, Posted Image

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The AO is currently negative, so I do believe he is wrong

No, in fact you are wrong Irish lad.

 

Cohen's work originally focussed on the Eurasion snow cover extent (SCE) and then moved onto the Snow Advance Index (SAI). Both of these could be calculated at the end of October and correlated with the following winters AO. Whereas the correlation may not be 100% it is sufficient to give us an idea where winter may be headed wrt the AO. Picking on one day in November, before winter has even started, when the AO has just dropped below 0 and then trying to suggest that this is indicative of the whole winters AO is possibly a little short sighted. I am sure that Cohen's papers are linked in the technical papers thread - perhaps if you search them out then you will have a better understanding of the principles and theory involved.

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I still think we will have a Winter similar to 11-12 with just a short cold spell sometime in Jan-Feb (although I suppose now could be considered cold it's frosty outside but it's not officially Winter) I reckon we'll have a mild Christmas, looks like this coming month will be mostly dominated by high pressure near or over the country. Certainly cannot foresee a December 2010.

Edited by Gaz1985
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The AO is currently negative, so I do believe he is wrong

 

I'm not sure we can consider the current state of the AO as being a factor as the forecasts he is mentioning are for the winter to come.

 

That being said, the CFS runs are still forseeing a negative AO for the bulk of the winter - I still think we may see some accepted correlations challenged this winter.

 

Posted Image

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