The Seasonal Forecast Thread

[feb1991blizzard]

Not sure what im going for exactly, I have looked through all the usual suspects analogues, was hoping to have a good 6 hours of tweaking them on the reanalysis NOAA page but as luck would have it its fell on a Saturday and I am pushed for time, I have  2 hours 20 minutes to decide, whilst an SSW isn't essential, I feel we will need a more favourable strat, we can almost certainly rule out an SSW for the foreseeable so that's December out of the way for persistent HLB, if these Aleutian ridges (possible buzzword of netweather this year) persist, I still think for this to be beneficial, we will need some squeezing from the Siberian side, I am tempted to go for a potent cold spell at some point in Jan or feb, 90-91 not a bad bet except perhaps a tad milder overall.

Edited November 30, 2013 by feb1991blizzard

[feb1991blizzard]

A bit of a guess really, not as much research as I would have liked but with some viewing of analogues very kindly posted by other people with more expertise.

 

DEC - Average Temps, cold start, mild end, precipitation - just below average, Dry start, Wet end.   CET - 4.9c

 

JAN   - Just below average temps, mild and stormy start, cold and dryer end, precipitation - average, Wet start, Dryish end,  CET - 3c

 

FEB   - Below average temps, well below to start off with with a milder end, precipitation - just below average, fairly dry start, fairly wet

 end,  CET - 2.9C.

 

 

Main points   -   Jan 20th - feb 10th the most likely for a bitter spell of weather.

 In the periods of dryer weather, Northern UK, especially Scotland could be very dry.

 

Any bitterly cold spell dependent on not necessarily an SSW, but certainly a more favourable stratosphere.

 

 

 

 

[Snowy L]

I made this a few  weeks ago but anyway here's my take on this winter:

 

Methodology

ENSO

The El-Nino Southern Oscillation (ENSO) is expected to remain neutral/slightly negative through the rest of Autumn and for most of winter. The effect of the ENSO on Europe is a weak one, though it can still influence our weather. In winter, an El Nino event tends to give a warm first half and a cold second half and the reverse is true with La Nina. However with a neutral ENSO it is suggested that it has very little effect on the weather in Europe.

 

ENSO is yet another factor in determining the strength of the polar vortex. It has been shown that El Nino events lead to a warmer polar stratosphere and therefore a weaker polar vortex. El Nino events often lead to anomalously low pressure over the Aleutian Islands, which is a tropospheric precursor to Wave-1 wave breaking. La Nina is more confusing and conflicting things have been said about it. It is thought that it gives a colder stratosphere but observations have shown that most SSWs happen during La Nina. A neutral ENSO gives far less SSWs per winter, though it's also worth noting that a neutral ENSO means that other factors, particularly the QBO can have much more of an influence than the ENSO. So the ENSO suggests we have a smaller chance of an SSW this yea

 

Solar Cycle and the QBO

The Quasi-biennial oscillation (QBO) is an oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere. How this influences the polar stratosphere depends on what phase the QBO is in. Currently, the QBO is in a strong westerly phase.


Until recently it was thought that an Easterly phase resulted in a warmer polar stratosphere with more vortex disruption, and the opposite to be true for when it's in a westerly phase. However in the last decade or so it's been found that the solar cycle can change this relationship. It's been shown this relationship is reversed under solar maximum years. During Solar Maximum and when the QBO is in a westerly phase, the geopotential heights are higher over the North Pole.



There is a very clear tendency for SSWs in the west phase of the QBO to occur during solar maxima. In contrast there are very few SSWs in the easterly phase during solar maxima. Also during a westerly phase, SSWs tend to happen later in winter rather than early. The recent solar maximum has been a weak one, though a recent surge in solar activity has seen the solar flux 10.7cm increase to levels found in the lower end of a solar maximum. This, accompanied with the westerly phase QBO, indicates that there is a fair chance of a SSW occurring towards the end of winter.




Arctic Ice, Eurasian Snow Cover and the Snow Advance Index

Recently, levels of ice in the Arctic have been linked with colder winters. Lower ice is correlated with a weaker polar vortex and a negative NAO. A lower than average ice minimum is also believed to increase the advance of snow cover in Eurasia during Autumn. This occurs because less ice provides a much larger area of open ocean, greatly increasing moisture availability in the area. This tends to make the Arctic warmer and the surrounding land masses colder. We have seen another below average ice cover minimum this year, though not quite to the extent of last year which was record breaking. Also, recent studies have suggested that lower sea ice leads to increased rossby wave incidence in the Pacific/North America region. We have already seen a few wave breaking events though none have caused damage to the vortex so far, due to the low ice we can expect to see more through the winter.



The advance in snow cover over Eurasia during October is an important step in the formation of a major tropospheric precursor to stratospheric warmings. This is measured using the Snow Advance Index (SAI). It is derived not from October mean snow cover extent, but rather as a function of how slowly or quickly the snow cover advances across Eurasia in October. This index is highly correlated with the AO. This is because it starts a chain of events where a high SAI aids the development of the Siberian high, which then enhances wave 1 activity, leading to weak vortex events and then to a negative AO. When snow cover advances rapidly across Eurasia in October, this is an indication that the upcoming winter will be more severe for the Eastern US, Europe and East Asia. Unfortunately the index was a poor one this year. As can be seen in the graph below, the rate of snow gain was slow thanks to the very high snow amounts to begin the month and the mild end to the month.


Sea Temperature Anomalies

While not a great indicator of future weather, a certain type of pattern in the North Atlantic sea temperature profile has emerged that is correlated with a negative NAO. The North Atlantic Tripole is a pattern of sea temperatures that sees a warm anomaly at around 30 degrees latitude, a warm anomaly in the area surrounding the south of Greenland and a colder anomaly in between. I have added a picture (not mine) explaining the pattern as well.


The sea temperature profile this Autumn closely matches the typical pattern so this is another factor that could give us increased tendency for the NAO to go negative this winter.



Winter Forecast

So now I will attempt to mix these factors and make a forecast out of them. My initial thoughts were a cold start to the winter and a cold end, with most of winter in being mild in between and I still expect we will see something along those lines. Currently an anomalous high pressure in the North Pacific is directly affecting the tropospheric pattern and indirectly affecting the stratospheric one. It has enhanced wave-2 breaking which is currently making a few minor dents in the lower stratospheric vortex, allowing some brief meridional patterns to emerge. Therefore I expect the rest of November to follow this pattern and I expect the next few weeks will see us have a chance at a brief cold spell before the vortex fully forms at all levels of the stratosphere.

I expect the rest of November to be changeable with cool zonal being the theme. We will see periods of mild weather and colder weather as brief meridional patterns give us short Northerly/Northwesterly blasts. Towards the end of the month and into December I think we will see a better attempt at a cold spell with a solid high pressure building to our Northwest and giving some areas some snowfalls. For the rest of December high pressure will remain close to the UK giving some settled weather but nothing particularly cold or mild. Into Christmas we will see high pressure move to our south, giving us some very mild weather for a time before zonal weather picks up in time for January.

I expect most of January to be dominated by unsettled weather. A zonal pattern will become strong and I think we will see some stormy periods of weather. Temperature wise January will be mostly above average but again I do think we will see some periods of brief cooler weather mixed in too. End of the month and into February the pattern will change into much more of a mild zonal with the possibility of the dreaded Bartlett high setting up. This should continue into February too.

However, I do expect a big change in the pattern sometime in February. Several factors support the chance of a sudden stratospheric warming happening towards the end of winter. The combination of the solar cycle being in a relative maximum phase plus the QBO, along with the fact that we have seen a low ice year, makes me think we have a fair chance of an SSW, not a great chance but certainly not a slim chance. I think mid-month in February we will see the vortex weakened/split and some form of Northern Blocking will occur. Obviously this is no guarantee of cold but about 70% of the time we will see a colder pattern come from this. The tripole in the Atlantic that often leads to negative NAO events makes me think that if we do get Northern blocking, the Atlantic will be a favoured place for high pressure to build, so the UK should be under this blocking and will see some colder weather.

So while I do think we're in for a mixed winter, the key word that would give widespread snowfall is blocking, and unfortunately I don't think we will see that for most of winter. Our best chance is in February I feel and the end of February and March are when our best chances of snow are. Overall this winter will be close to average, I'm favouring slightly above, and precipitation will be above average largely because of the unsettled pattern in January.

Edited December 1, 2013 by Snowy L

[Suburban Streamer]

hi all

 

I've had a go at my first LRF this year. You can view it here http://wp.me/p3v9wo-25

Edited December 3, 2013 by Suburban Streamer

[BornFromTheVoid]

Having a look back at how my Autumn forecast fared, I think the patterns of each month were captured quite well.

 

September

 

............... Forecast ...................... ........... ............. Actual

 

 

October

...... .... Forecast ............ .............. .................. .............Actual

 

 

November

....... .....Forecast............... ............... ................. ........... Actual

 

 

Pattern wise, October and November were very good I think, with September being the weakest of the bunch but still not too bad. Looking at the scale for September though, there was no strong signal that month so it's not too surprising.

 

Despite getting the general patterns quite well, the CET errors were 1.1C on average, being 1.1C out for Sept, 0.5C for October and 1.6C for November (though had I based my CET guess off the updated November forecast rather than the old one, it would have been 0.8C out, with an average error of 0.8C.). I think this shows how tricky it is to get the temperatures right for the UK.

 

I only started trying this in May this year, so there is still plenty of room for progress, refinement and improvement, and as always, suggestions and comments are welcome!

[Interitus]

 

Despite getting the general patterns quite well, the CET errors were 1.1C on average, being 1.1C out for Sept, 0.5C for October and 1.6C for November (though had I based my CET guess off the updated November forecast rather than the old one, it would have been 0.8C out, with an average error of 0.8C.). I think this shows how tricky it is to get the temperatures right for the UK.

 

I only started trying this in May this year, so there is still plenty of room for progress, refinement and improvement, and as always, suggestions and comments are welcome!

 

How did you decide on the temperatures, were they analogues as well or dictated by the pressure charts?

The former may produce temperatures that on the face of it don't fit well with the pressure charts whereas the latter relies on two calculations, first that the pressure charts are accurate (they aren't bad on the face of it) but then that they can be used to deduce a temperature that is accurate which would be a whole other skill in itself.

Ultimately though the acid test is are the predictions closer than the averages to the observations and I don't think they are.

[BornFromTheVoid]

How did you decide on the temperatures, were they analogues as well or dictated by the pressure charts?

The former may produce temperatures that on the face of it don't fit well with the pressure charts whereas the latter relies on two calculations, first that the pressure charts are accurate (they aren't bad on the face of it) but then that they can be used to deduce a temperature that is accurate which would be a whole other skill in itself.

Ultimately though the acid test is are the predictions closer than the averages to the observations and I don't think they are.

 

I used the analogues, but they rarely offer much in the way of a strong signal, and then consider the SSTAs and general predicted weather patterns when forming the CET guess.

 

It's true that the temperature predictions weren't any better than climatology and I don't expect great accuracy is possible for such a small area, but as the general patterns weren't too bad and the very anomalous October was picked out well, I'm hoping the temperature predictions just require some more refinement and experience.

[BLAST FROM THE PAST]

Just to touch more on my LRF before I do next months outlook,  I am still very keen on the potential 'gamechanger' storm over NY period.  I think there will be some substantial snow produced from this and may usher in a very cold period.  Its coming within deep FI of GFS now...and some wild swings as one would imagine.  Nice to see some PM and rPM air appearing with sub lows occurring now. 

 

BFTP

[cooling climate]

I forecast a very cold winter perhaps even severe and was in fact quite confident of

the forecast where as now that looks a million miles away.

The very cold stratosphere was definitely my undoing and did not foresee this at all

infact I expected the complete oposite after monitoring the above average ozone in

the lower stratosphere throughout the summer and autumn. The OPI ( October pattern

index) is verifing very well at the moment and along with the SAI (snow advance index)

 looks to be something that merits alot more attention in future.

Also the lack of any MJO induced wave breaking or Asian mountain torques has been

another of my predicted downfalls.

Until we see a significant warming in the lower to mid stratosphere I think we can put to

bed any notion of prolonged very cold wintry weather for the UK for without the warming

there will be no HLB's. Apart from the one or two cold snaps perhaps I think any chance

of prolonged winter weather for the uk lies in the second half of winter (10-15 January

onwards).

One other thing I would say is that there is a good deal of very cold air to the north this

winter because of the strong vortex etc and if we do see any warming that works in our

favour then we could see bitterly cold weather affect the UK (-15c to -16c) perhaps.

[BLAST FROM THE PAST]

Ok, instalment two.

 

So lets start with New Year, we have New Moon and a sun that recently has been showing spurts of activity and I think will increase even more.  I think we will see an effect on the jetstream with it becoming wildly meridional and a stormy period chucked in for our locale.  I think GFS is already giving a reasonable hint as to where we may be at as we go into 2014 so no surprises there.

 

General theme - first week to see deep LP to our NE with accompanying sub lows attacking the UK.  Winds becoming northerly maybe even NE'ly and very strong with gales/severe gales N/NE/E regions.  Northerly blast increasingly cold with Precip increasingly turning to snow and becoming heavy at times.  Not exclusively so but further N and E the bigger the impact [ travel disruptive weather possible] with coastal defences tested.  Calmer and less cold end of week

 

Second week an active LP crosses UK, bringing gales and severe gales to exposed coasts.  This to track into North Sea and winds will turn N'ly possibly NE'ly and becoming increasingly cold and wintry by latter part of second week. 

 

Start of third week - Full Moon on 16th so we are in a very active period , strong northerly winds with bitter wind chill with deep LP to our E and Atlantic ridge to our west.  Heavy snow feeding south and combined with strong winds travel disruption is possible.  North sea Coastal regions again under threat from a possible storm surge.  Becoming much quieter as week goes on and less cold with hint of big change to come.  HP extends from Continent and starts to build west WNW.  Winds become light and turn to  S'ly quadrant and temps become less cold by day but cold at night.

 

Fourth week HP dominated very calm for most, sunny and fairly mild by day and cold and frosty at night, as the HP from the continent migrates/extends ever so slowly WNW. Fog could be an issue and could keep temps cold by day particularly for SE and S.

 

Two ways from here I think, the HP stays close or over us generally or it continues its movement WNW towards Greenland.

 

We may have seen warnings/signs of strat warming occurring for this end of January period come January and I am suggesting  that a SSW may occur and that HP will continue to transfer to Greenland as we go into Feb and herald in a mighty Feb. More on that in 2014.  I wonder if there will be any effects on the strat during New Year and around mid Jan too.

 

So as ever a general theme/flavour, something for everyone if it pans out.  As ever, with northerly flows we are playing with fire and further S or SW then less affect there'll be.

 

Added notes, I think this weather period in Early to mid Jan is potentially v impactual

 

BFTP

Edited December 19, 2013 by BLAST FROM THE PAST

[Recretos]

I made two composites for El Nino and La Nina. Nothing new, but just as a reference to a "average" winter pattern in the specific ENSO phase. 

 

 

 

Regards

[cooling climate]

With a  top down warming forecast to the north of the UK  as we go towards the

middle of Jan it is worth remembering that downwelling in a +QBO is generally

quicker than in a -QBO. Jan 2009 along with Jan 91 which were both +QBO

winters.

I think what we are likely to see in the extended range of the model outputs over

the coming days is for pressure to rise over eastern north America and the

nw Atlantic with the troughing turning more nw/se across the Atlantic and pressure

remaining high across nw Russia. Then as blocking becomes more prevelent to

the north (17th Jan onwards) we should see trough disruption and undercutting as

the Russian high moves west.

Tentative signs that my long range forecast for the winter which has started so poorly

for the  second half of December and first half of Jan may become more of a reality

during the second half of winter.

[Weather-history]

I have just released my long term forecast for the Winter 2013-2014 season. It can be found here: http://www.norton-radstockweather.co.uk/NEW-Winter-Seasonal-Prediction(2922573).htm

Your December part of the forecast looks out by a bit I'm afraid.

[Bristawl Si]

Your December part of the forecast looks out by a bit I'm afraid.

Having just trawled thru a number of forecasts on here, most are 'out' re December and a number of them look like being 'out' for 1st half of January.

One or two are seriously 'out', as well.

Edited December 31, 2013 by Bristle boy

[Froze were the Days]

Having just trawled thru a number of forecasts on here, most are 'out' re December and a number of them look like being 'out' for 1st half of January.

One or two are seriously 'out', as well.

As for Gavin P's 'dry to very dry' forecast....appreciate the time that's put in though.

[DAVID SNOW]

Having just trawled thru a number of forecasts on here, most are 'out' re December and a number of them look like being 'out' for 1st half of January.

One or two are seriously 'out', as well.

 

Is there any forecast 'out there' that went for a mild wet and windy first half of winter?

[Bristawl Si]

Is there any forecast 'out there' that went for a mild wet and windy first half of winter?

Dunno.but it just goes to show how damned difficult it is to call UK weather more than a week to 10 days out imo.It's been said before on here but this is why the Pros rarely publicly announce LRFs past a month.IMO many of these LRFs are nothing more than guesswork; a few try to use science and other methods but despite all the info and high tech computer models (LOL) at our disposal these days they still cant beat 'the weather' and nature itself........thankfully.

[Roger J Smith]

Maybe you only looked back to 1st of November ... post 411 ... mostly mild and wet December, CET 6.1 C.

 

Not much chance of white Christmas.

 

Looks however as though the projected 8-12 Jan cold spell might be fighting for a chance against the relentless stream of Atlantic storms. Comments re North America are generally on track also, cold is pouring southeast through central Canada as expected, December anomalies as large as -10 C deg in northern plains states so far.

 

On a global scale, considering when the forecast was made, I am relatively happy with it and I continue to hope that the authorities in our science will relent from their evident long-term policy of planned ignoring (which amounts to suppression) and give some recognition for work that has proven on several occasions now to be better than other methods.

 

I'm hoping that 2014 will bring a change in attitude, but of course I am far from optimistic about that. Ask yourself how you would feel if you had a method that could have predicted the hot summer and now this unexpected (I gather) mlld, wet December.

[Weather-history]

Ask yourself how you would feel if you had a method that could have predicted the hot summer and now this unexpected (I gather) mlld, wet December.

Humility.Because they will be times when it will come and bite you on the backside.

[Bristawl Si]

Maybe you only looked back to 1st of November ... post 411 ... mostly mild and wet December, CET 6.1 C.

 

Not much chance of white Christmas.

 

Looks however as though the projected 8-12 Jan cold spell might be fighting for a chance against the relentless stream of Atlantic storms. Comments re North America are generally on track also, cold is pouring southeast through central Canada as expected, December anomalies as large as -10 C deg in northern plains states so far.

 

On a global scale, considering when the forecast was made, I am relatively happy with it and I continue to hope that the authorities in our science will relent from their evident long-term policy of planned ignoring (which amounts to suppression) and give some recognition for work that has proven on several occasions now to be better than other methods.

 

I'm hoping that 2014 will bring a change in attitude, but of course I am far from optimistic about that. Ask yourself how you would feel if you had a method that could have predicted the hot summer and now this unexpected (I gather) mlld, wet December.

Summer (June, July, August) wasnt hot though in the UK, Roger.

Yes it was the driest, sunniest, warmest since 2006 (according to official met office site) but not exceptionally hot. As a whole temps only 0.8c above the mean. The heatwave for a lot of July probably accounts for the perception it was a hot summer.

Dont get me wrong it was a welcome break from the run of wet, cool summers.

[Don]

Maybe you only looked back to 1st of November ... post 411 ... mostly mild and wet December, CET 6.1 C.

 

Not much chance of white Christmas.

 

Looks however as though the projected 8-12 Jan cold spell might be fighting for a chance against the relentless stream of Atlantic storms. Comments re North America are generally on track also, cold is pouring southeast through central Canada as expected, December anomalies as large as -10 C deg in northern plains states so far.

 

According to your forecast, if the January cold spell does not come off, then this Winter really won't be up to much because that was the only real window of opportunity for deep cold?

[Roger J Smith]

Humility.Because they will be times when it will come and bite you on the backside.

 

Well I'm sure when things go wrong, you'll be right in there with the boots, as always.

[Roger J Smith]

According to your forecast, if the January cold spell does not come off, then this Winter really won't be up to much because that was the only real window of opportunity for deep cold?

 

 

 

 

I suppose there has to be one wintry episode ahead, even 2007 managed one significant snowstorm.

 

From my research output, however, as you say, 8-12 Jan is the best opening and if it delays a few days it will run into the second-order warm signal of the full moon-northern max. That's always a good snowfall signal when cold is already established, but a fight for control situation after all this raging zonality could push any snow well back to the north.

 

However, I only claim about 65-70 per cent "right side of normal" verification with my research and would say we're banking up wrong days in this forecast period. Last year it turned very cold a bit later than I was expecting from the output. Maybe that will happen again. I would then have to seriously consider what was pushing things late from an otherwise reasonable output.

 

Anyway, I apologize if I sound a bit cranky, it is very frustrating to have these good results and no recognition at my age. If that's a problem for the Net-weather community, I can see the exit sign.

[Polar Maritime]

The J.H rule...If you are right say nothing, if you are wrong say why. 

 

I see you put hours of work into your methods RJS and im pretty sure your respected by many on here, including myself.

Edited December 31, 2013 by Polar Maritime

[Weather-history]

Well I'm sure when things go wrong, you'll be right in there with the boots, as always.

With all due respect, Roger, I am a humble person, I have won awards but never boast about them. Why should I self congratulate if others are doing it for me? My successes are enough, I don't need to boast or brag about them because they will be quick to point out failures. Edited December 31, 2013 by Weather-history