Radiating Dendrite Winter Forecast

[Radiating Dendrite]

Well I have decided to dip my toes into the water and issue my own LRF for winter.

Please be gentle with me is something is not quite accurate, I am new to this game.

I will try and answer any questions you may have

Please note that I struggled to upload the images, these are available to view in the download at the bottom of the page (CFS Data.doc).

Winter Forecast:

Current state of play:

Low Solar Activity (compared to what has been the case during previous cycles). Activity is increasing though as we build up towards the maximum, but despite this I believe that a lag effect is experienced and the build up in activity will not influence the atmosphere until later on next year. With this in mind, the troposphere will continue to be cooler than normal; this it is believed leads to a greater frequency of Northern blocking and a more southerly tracking Jet Stream.

QBO is currently negative and east based (this strengthening) with a Negative QBO tending to lead to increased blocking, and colder weather through the January and February winter months. However, recent models have shown it may become less easterly with time through the winter, possibly becoming positive as well. A positive QBO which is west based is usually associated with boosting the La Nina, generally leading to a milder end to winter, with a more active Atlantic with increased zonality.

La Nina is predicted to strengthen during the winter, but should not become as strong as we saw last winter, as seen in the chart below:

As we can see though, this is not “nailed”, with the strength still ranging from strong to weak, depending on what models you look at. I think the only sensible thing to do is use the average for this forecast and base any predictions on the average that is currently being shown/predicted.

CFS model data is currently showing a mixed winter, with periods of high pressure dominated weather, as well as low pressure dominated weather and a more active Atlantic. The CFS shows a colder January at present with blocking in the mid-Atlantic during the first half of the month:

This is broken down though, with a trough establishing itself over Scandinavia during the second half of the month:

NAO/AO I believe are influenced by the factors laid out above, being reactive rather than pro-active when it comes to having an influence on the atmosphere and weather. As seen below both are slightly positive for the current month

October NAO +0.27

October AO +0.18

Early last winter saw both become strongly negative, to record levels in some instances, with strong Northern blocking developing during late November and December. Current values would indicate a mix or blocking as well as cyclogenesis in the Arctic and Atlantic, this being what is currently being shown in the GFS and ECM, with neither gaining a firm grip and the UK in a no mans land situation. I believe that we will see a negative NAO and AO during winter, in response to the lower solar activity lag, however, the figures will not be as extreme as what occured at the beginning of last winter.

Other minor factors:

Building Blocks - As has been discussed in the MOD thread, we do currently have a European high in place and a sluggish Atlantic stalling against this. Is this a theme that will continue to occur in winter?

Recent Past – With the last three winters containing significant cold spells, have we now turned a corner and finally rid ourselves of the even larger teapot curse that seemed apparent in the 90s/00s?

NH Snow Cover – Currently around average, however, sea ice did reach the second lowest extent on record, will this have a major impact?

Personally, I see these other factors as more minor in the development of winter than the teleconnections discussed above. However, the development of favourable synoptics during late autumn and increasing amounts of cold pooling are certainly a good thing if a cold winter is what you are looking for, however, this does not mean that a cold winter will be the end result, if the overriding back ground signals are not favourable.

So……..what do I expect from the winter?

CET Predictions??

November 7.0c

I see November as being a fairly benign and average month. We will continue with the theme of a high to the east and Atlantic troughs to the west during the beginning of the month, with the second half of the month seeing a more mobile Atlantic, with the high slipping into southern Europe, giving us a feed of SW winds for a time. Temperatures will be slightly above the long term average, with rainfall around average, perhaps above average in the North and West.

December 4.4c

December will start where November left off, with temperatures slightly above average and a succession of weather fronts crossing the country. By the middle of the month I expect the Atlantic to start to become quieter, in response to the Negative East based QBO and cooler troposphere. High pressure will start to develop, possibly from the west, with it becoming stationed over the UK as we move towards the Christmas period. I see Christmas as being quiet and anti-cyclonic with some cold nights and chilly frosty days. At the end of the month, we will start to see retrogression of the high away from the UK.

January 1.6c

I believe that January will contain the core of the winter cold, similar to what we saw in winter 09/10. Currently the CFS shows high pressure located around Iceland during the first half of the month:

As we can see, this would bring cold NE winds to the UK and snow. Although I agree with the signal for High Pressure, as shown by the CFS for this period (carrying on the theme from the end of December) I believe that we could see a significant high pressure cell forming over Scandinavia, having retrogressed from the UK and linking up with developing high pressure over Iceland and SW Greenland. This would see significant cold for the UK from the east, with the low pressure undercutting the high, with a southerly tracking Jet Stream. The CFS shows a breakdown during the latter part of the month:

I would agree with this breakdown, but I think that we will have a period of cold zonality as is shown above, with Northerly and North Westerly winds. January will return the coldest CET of the winter, potentially significantly cold, though this depends on the depth of the cold during the early part of the month and whether any unsettled weather at the end cancels this out to a certain degree.

February 4.4c

February I see as quite a mobile month (unusually so) in response to a slight strengthening of La Nina and the QBO becoming more west based and less negative. I see February as fairly average temperature wise, with blocking struggling to establish itself to the North. A mid Atlantic high may develop during the middle of the month (currently being predicted for March by the CFS as shown below):

This has the possibility of bringing some colder weather from the North, but I do not see it as a permanent feature, possibly slipping to our South West, with lower heights developing to the North.

Winter Overall 3.5c

(http://www.newtownwe...etaverages.html)

CFS Data.doc

[Backtrack]

^{Very interesting read, thanks.}

[summer blizzard]

Well done for making a forecast and i hope you are correct.

The only thing i would comment on is that the chances of the QBO weakening or becoming westerly are remote. It is much more likely that the westerly bursts stalling development are leftovers from the +QBO wave seen for the previous year and that these will dissipate.

My thoughts are actually fairly similar to yours in December or January although i will not be making my official punt for another month.

[Radiating Dendrite]

That is interesting. I still expect an average February, certainly not as warm as last year.

[ZONE 51]

Very interesting forecast and i am especially interested in the factors you are using to make your lrf,

Low Solar Activity (compared to what has been the case during previous cycles). Activity is increasing though as we build up towards the maximum, but despite this I believe that a lag effect is experienced and the build up in activity will not influence the atmosphere until later on next year. With this in mind, the troposphere will continue to be cooler than normal; this it is believed leads to a greater frequency of Northern blocking and a more southerly tracking Jet Stream.

This is what i am expecting to happen, the effects on the oceans and atmosphere/jet stream have already been done, things wont start shifting back to normal that fast i dont think, im watching the jet stream, i cant imagine it hanging around up this way for all of winter, its going south and with it the lows, with atlantic high, i expect a drier than average winter on a whole.

[Radiating Dendrite]

Yep.

Nearly everything in life/nature has a lag period and I see solar effects as being no different.

I think we will have to be patient, but by the end of December will see high pressure on the advance. Even the breakdown of this will not mean a warm period for the rest of winter, with February still seeing some colder interludes, these tending to be transient in nature though.

[greybing]

Yep.

Nearly everything in life/nature has a lag period and I see solar effects as being no different.

I think we will have to be patient, but by the end of December will see high pressure on the advance. Even the breakdown of this will not mean a warm period for the rest of winter, with February still seeing some colder interludes, these tending to be transient in nature though.

With respect everything in lfieand .natuure does not have a lag effect.

[Fozfoster]

best of luck

[BLAST FROM THE PAST]

I think an excellently thought of and put together forecast. That has as must chance of coming off as any I will read this approach of winter.......good reasoning, good assumption of responses to certain drivers and of why they will arrive there.

Two things if I may, the impending solar increase and max is still very low compared to 20th century cycles. Indeed sunpsots that have been counted would IMO not have been counted back on Wolf days. This max will have no discernible warming effect. Ther second is if a trough develops over Scandi...I see this as positive for cold chances.

Good stuff, good luck

BFTP

[Radiating Dendrite]

Thanks bftp.

Yes I agree in regards to the Scandi trough. I still think the second half of January will be cold, just not as cold as the first half, becomming increasingly more mobile as we head towards Feb.

[reef]

Consolidated Winter forecast thread here:

http://forum.netweather.tv/topic/71325-the-winter-201112-forecast-thread/

Thanks