In Depth Model Discussion, Analysis and Summaries

[phil nw.]

Thanks for that well presented,as ever, post GP.

If i understand you then less cold post Christmas as the surface cold is mixed out somewhat but then after a few days the trough alignes to our East down into Europe as a renewed piece of the vortex drops down over Scandi/W.Russia with heights rising further West towards Greenland/NWAtlantic.

Maybe a Northerly for the new year from this then?.

[winterfreak]

Current indications are for our coldest winter month to be somewhere between 0.5C and 1.5C below average.

Might that be January GP?

[Snowmad79]

I think the teleconnection models are fliping and struggling just like the weather models ! The GWO was showing Higher amplitude in phase 6 but weakening today it back in phase 5 ... what the eck is happening I dont know. I think there updating the Glaam charts now coz that part of the maproom is currently down.

I did notice this morning that Firction Torques were again trending negatve, mountain torques were also dropping. Relative Glaam etc were Flattening out once again but im not sure what the status is yet becuase as i said those charts are N/A atm.

Pretty sure GP will reanalyze this for us by tomorrow afternoon.

"Phase 5 – the global relative AAM tendency is positive. This means that negative AAM is being removed from the atmosphere by surface friction and mountains. At the same time, westerly wind anomalies are intensifying in equatorial regions of the Western Hemisphere. Fast, zonally oriented Rossby wave dispersion events in both hemispheres are a coherent feature of this phase and Phase 1. A cold regime is probable across the central USA. "

[pyrotech]

You do your own monthly forecasts and make suggestions as to how the models may pan out in the FI period (and beyond) so I am not sure that discussions about the further outlook here are any different or any less valid than your own - even if we are not 'forecasters' and are just humble members.

You have conceeded on a different thread that your own predictions for December have not panned out (which is quite acceptable of course ) but I think on that basis we should all be entitled to assess the further outllook on the basis that it is at least based on some background signals that are relevant to the outlook. I would agree with your own thinking that the models may just be defaulting to a zonal basis, but the thinking that I am applying here is, nevertheless, based on some facts.

Ironically as a well renowned cold and snow fan I am discussing a potential return to a milder type here, of which usually I would be put in a box as not ever being willing to discuss - so it seems a case of not being able to win perhaps

The models do not default to anything. They take all the information available at the time ( More info available for some runs than others) Then they run forwards with that data. Some run 10 runs with slightly diffrent data to allow for anomalies. Them 10 runs will end up wildly different by the time they reach FI. So as you can see a slight change makes huge differences as run goes onwards. The 12z may see a height of 1020 over greenland and predict reaching 1040 in 48hrs, 18z may then see actual height is now 1030 and so its run may put it at 1050 in 42hrs ( Same time as 12z) But 12z may be correct as height then builds more slowly to reach 1040 at the time forecast. That is why runs are often different and why watching same run is more beneificial and or looking for trends.

Hope that helps

[kold weather]

The models do not default to anything.

Hope that helps

Actually they do tend to go thier default, thats because every model will have an inherent bias in the system, the Americans take a lot of time in figuring out what these are, over there the ECM for exmaple tends to be too far west and holds back upper lows.

One such example of a bias with the GFS is the fact it quite often overdoes the outpouring cold air from the Arctic (how many times have we seen cold events be downgraded to weaker events?) This was actually done on purpose as the GFS was creating a mental amount of warm cored systems in the tropics (I think back in the early 00s it produced something like 50 hurricanes over the season, when only 10-15 of them really were real systems, they call them phantom systems!) so the GFS was tweaked a few years ago and whilst it reduced hurricane rates it seems to have caused the model to forecast things often a little too cold (how many times have you seen the GFS forecast give certain temps at 850hpa whilst the ECM has temps a few degrees higher, same goes with the UKMO) and in the longer term it becomes an issue. Think of what effectivly in simple terms drives the jet stream and thus the creation of lows...the thermal gradients...if the GFS is overpowering the cold post say 72-96hrs then its equally going to have a knockon effect furthger into the run...thats why so many times the GFS creates these massive lows and they often don't end up nearly as strong as that...knock that effect into FI where the resolution becomes far lower and the model can't pick up shortwave effects as well which also tend to make the main low weaker then progged and you can see why people say the GFS tends to default to zonality...because in truth thats what happens...thats why we only get say 30-40% of the big lows GFS forecast come in close to the strength it progs, and also the reason why we fairly often see the cold become downgraded.

Anyway tonights models still show a big spread, the ECM isn't a poor run but the PV is strengthening in a rather worrying way that run, however the last two op runs have kept it weaker so it maybe the model would be on the milder side of the ensembles if it ran as long as the GFS does. The 18z GFS is quite stunning, a very 60s feel to those charts...however probably not all that likely.

I suspect both models have a good idea, both are possible given the global signals and the truth may well end up something between the two of them, with the PV merging but not being as strong as the ECM suggests, whilst the GFS idea of keeping weak heights to our north may be good as well given signal but probably end up being somewhat displaced further east, so probably a weak high just to our NW with a cold flow from the east, though if the PV did merge that set-up isn't going to last that long...but we will see.

[Thundery wintry showers]

Looking further at the Christmas Eve/Day low, I note that the main difference re. UKMO/ECM isn't the track of the low (though it does have the low slightly further north), the main difference is its intensity- 975mb as opposed to 990mb. Quite a big difference at just T+72! I feel that the GFS may just be overdoing that low a touch and tomorrow's runs, to the disappointment of some and relief of others (including myself) will most likely back UKMO and ECM in going for a less intense depression.

Very interesting post regarding GFS's inherent biases btw- that taught me a few things I didn't already know- especially the part about the overdoing of cold outpouring from the Arctic and creation of monster lows, that is entirely consistent with the main failings of the model that I've seen. Perhaps NOAA should look into toning that down a touch because if they can solve that problem then GFS has potential to be the most accurate model in the world.

Looking at the ECM out to T+240 the PV does strengthen to the NW but the mid-Atlantic block looks like settling over the UK rather than allowing westerlies in- plus pressure rises substantially over Scandinavia. I don't think even that T+240 chart is without its long-term cold/snow potential.

Haven't had snow on the ground Christmas morning since 93 (I think), with the last 2 white Christmases with snow showers in the evening 01 and 04.

Yes, that sounds about right- Christmas Day 1993 had a band of precipitation move down the western side early in the day which fell mainly as sleet or wet snow at low levels, but some areas saw lying snow from it at fairly modest altitudes.

[kold weather]

Yeah TWS, the problem is though if they did try to change it you could go back to the issue the model had in the first place which was to create too many warm-cored systems, which is if anything an even greater problem because developing powerful hurricanes in months like December/January (which at times it did do in the past!) is clearly not going to very often verify and they have the ability to shift the pattern totally beyond what will happen...the overdoing of cold is of course an issue but its unlikely to really globally cause the model to have huge eras...but here in the UK where we are much more prone to those deep lows, it can be a big issue but in many ways its the lesser of two problems that have come up.

Also your right about the ECM at 240hrs, but I'd have a funny feeling the PV will be shunted eastwards after that 240hrs chart as the Canadina PV absorbs the Russian vortex and in turn the Candian vortex comes eastwards as the other PV swings round the main PV. So you'd see the high indeed settle over the UK but quite shunted into Europe I'd have thought and a flat westerly type pattern develops...

However anything could come from it...the 18z GFS shows what even a weak upper high can do with a southerly jet stream...

[pyrotech]

Actually they do tend to go thier default, thats because every model will have an inherent bias in the system, the Americans take a lot of time in figuring out what these are, over there the ECM for exmaple tends to be too far west and holds back upper lows.

One such example of a bias with the GFS is the fact it quite often overdoes the outpouring cold air from the Arctic (how many times have we seen cold events be downgraded to weaker events?) This was actually done on purpose as the GFS was creating a mental amount of warm cored systems in the tropics (I think back in the early 00s it produced something like 50 hurricanes over the season, when only 10-15 of them really were real systems, they call them phantom systems!) so the GFS was tweaked a few years ago and whilst it reduced hurricane rates it seems to have caused the model to forecast things often a little too cold (how many times have you seen the GFS forecast give certain temps at 850hpa whilst the ECM has temps a few degrees higher, same goes with the UKMO) and in the longer term it becomes an issue. Think of what effectivly in simple terms drives the jet stream and thus the creation of lows...the thermal gradients...if the GFS is overpowering the cold post say 72-96hrs then its equally going to have a knockon effect furthger into the run...thats why so many times the GFS creates these massive lows and they often don't end up nearly as strong as that...knock that effect into FI where the resolution becomes far lower and the model can't pick up shortwave effects as well which also tend to make the main low weaker then progged and you can see why people say the GFS tends to default to zonality...because in truth thats what happens...thats why we only get say 30-40% of the big lows GFS forecast come in close to the strength it progs, and also the reason why we fairly often see the cold become downgraded.

Anyway tonights models still show a big spread, the ECM isn't a poor run but the PV is strengthening in a rather worrying way that run, however the last two op runs have kept it weaker so it maybe the model would be on the milder side of the ensembles if it ran as long as the GFS does. The 18z GFS is quite stunning, a very 60s feel to those charts...however probably not all that likely.

I suspect both models have a good idea, both are possible given the global signals and the truth may well end up something between the two of them, with the PV merging but not being as strong as the ECM suggests, whilst the GFS idea of keeping weak heights to our north may be good as well given signal but probably end up being somewhat displaced further east, so probably a weak high just to our NW with a cold flow from the east, though if the PV did merge that set-up isn't going to last that long...but we will see.

well according to the discussion john holmes had with NOAA about what the models use and do not use that is incorrect

It would seem they ONLY use CURRENT DATA. It may overdo things with the initial programing at fault like go forward making deeper lows but that is more to do with the program not historic data ie not that it thinks less winter cold or more winter cold over recent years. It just runs a program forward each run the same way forward but from a different stating point. If the program is set to deepen lows for instance more than it should, that will be constant in every

run as the same program is run, with diffrent data starting points .I enclose the discussion in full below

There have been a nymber of comments over recent weeks about what is in each 'run' with GFS. Where does the information come from. Are the 'teleconnections' part of that data etc. I exchanged e mails with NOAA about this and had their answer back.

Below is the exchange and below that a list of links to see exactly what does go in and a complete list of the way in which the multitude of parameters are dealt with.

This will be placed in the NW Guides section.

I asked

> 1. What do you 'feed' into your model for it to go out to T+384 hours?

> Is it simply the basic data available, surface/upper air etc, every 6

> hours and then run using the basic laws of thermodynamics? Or are other

> factors fed in?

> 2. Once you get beyond what I would call synoptic forecasting, about

> T+144/168, although I know ECMWF are charged with attempting to make it

> synoptic type predictions to T+240, do you factor in items like

> ENSO/AO/NAO? If so how, is there a weighting factor as one gets further

> down the T+line?

I will try to answer your questions. If I don't do them justice, please

let me know.

1. All models get the same input to start them off whether they are run

out to 12 hours or 384 hours. They begin with an analysis that is a

combination of a short-term forecast and all available data at the

time. All of the data is interpolated to the model's grid using data

assimilation techniques. The model uses this as a starting point and

using the basic thermodynamic equations and as sophisticated

parameterization of meteorological processes as the power of the

computer being used will allow, proceeds merrily forward in time,

spitting out forecasts of temperature, wind, pressure, moisture and

whatever other parameters might be programmed in.

2. Nothing particularly special kicks in at day seven and beyond, as far

as the model goes. We know that accuracy can decline past the useful

point once most models reach day seven or eight. In the U.S., once we

are beyond that timeframe, we do not issue forecasts like "the high will

be 73, with a 30% chance of showers in the afternoon." In the eight to

14 day range, we issue categorical forecasts like "temperatures will be

above normal" or "precipitation will be below normal". At this point

in the evolution of forecasting, that is as far as skill of the models

will take us. Here is a link to our forecasts beyond day seven so you

can see the types of forecasts that are possible:

http://www.cpc.ncep.noaa.gov/ We do run a numerical climate prediction

model that runs out to 9 months. But the output of this model is only

one source of what goes into compiling our seasonal forecasts.

As this did not appear to answer my query about the longer term drivers I asked again about ENSO/AO/NAO etc.

this was the reply I got

Specific ENSO, AO, NAO information is not fed into the numerical

models. However, one could say that since each of these indices is a

reflection of the state of the atmosphere and oceans, and the current

state of the atmosphere and oceans (pressure, temperature, winds, etc.)

is known to the models through their initialization, then the models

do know a bit about what the indices are attempting to quantify.

To me that appears to clear up any ambiguity. The ONLY data fed in is the observed data at the start of each run

Below is a comprehensive list of links about what is fed in and how and when for each run.

To me that appears to clear up any ambiguity. The ONLY data fed in is the observed data at the start of each run.

There are also the Ensembles, see below for an explanation of what they are

http://www.netweathe...showtopic=25663

See the link below as to what this is.

http://www.netweathe...showtopic=35985

To me that should make it clear that there is no such thing as, 'GFS defaulting to its Atlantic preference' or something along those lines?

At T+00 the operational run is fed the basic raw data and goes on out to T+384 with NO other input. The software/programme showing what this involves is pretty complex; but that is all that is fed in.

Below are some of the links into NOAA to 'see' what data is routinely fed in and for updates to this.

http://www.emc.ncep....info/index.html

http://wwwt.emc.ncep...oorthi/gam.html

http://www.nco.ncep....z.pgrbanl.shtml

The list above is only a fraction of what you can browse through!

And for anyone still wanting more information then this link MAY help or give you some indication on items mentioned in various model threads

http://www.netweathe...php?showforum=5

It is a link to the NW Guides with information on most topics.

Edited December 22, 2009 by pyrotech

[swilliam]

Actually they do tend to go thier default, thats because every model will have an inherent bias in the system, the Americans take a lot of time in figuring out what these are, over there the ECM for exmaple tends to be too far west and holds back upper lows.

One such example of a bias with the GFS is the fact it quite often overdoes the outpouring cold air from the Arctic (how many times have we seen cold events be downgraded to weaker events?) This was actually done on purpose as the GFS was creating a mental amount of warm cored systems in the tropics (I think back in the early 00s it produced something like 50 hurricanes over the season, when only 10-15 of them really were real systems, they call them phantom systems!) so the GFS was tweaked a few years ago and whilst it reduced hurricane rates it seems to have caused the model to forecast things often a little too cold (how many times have you seen the GFS forecast give certain temps at 850hpa whilst the ECM has temps a few degrees higher, same goes with the UKMO) and in the longer term it becomes an issue. Think of what effectivly in simple terms drives the jet stream and thus the creation of lows...the thermal gradients...if the GFS is overpowering the cold post say 72-96hrs then its equally going to have a knockon effect furthger into the run...thats why so many times the GFS creates these massive lows and they often don't end up nearly as strong as that...knock that effect into FI where the resolution becomes far lower and the model can't pick up shortwave effects as well which also tend to make the main low weaker then progged and you can see why people say the GFS tends to default to zonality...because in truth thats what happens...thats why we only get say 30-40% of the big lows GFS forecast come in close to the strength it progs, and also the reason why we fairly often see the cold become downgraded.

Anyway tonights models still show a big spread, the ECM isn't a poor run but the PV is strengthening in a rather worrying way that run, however the last two op runs have kept it weaker so it maybe the model would be on the milder side of the ensembles if it ran as long as the GFS does. The 18z GFS is quite stunning, a very 60s feel to those charts...however probably not all that likely.

I suspect both models have a good idea, both are possible given the global signals and the truth may well end up something between the two of them, with the PV merging but not being as strong as the ECM suggests, whilst the GFS idea of keeping weak heights to our north may be good as well given signal but probably end up being somewhat displaced further east, so probably a weak high just to our NW with a cold flow from the east, though if the PV did merge that set-up isn't going to last that long...but we will see.

A very interesting post if what you say is true. It is certainly true that the GFS produces lots of dartboard lows that never materialise and cold scenarios that frequently downgrade (although it did particularly well with this spell - easterly predicted well in FI at times and the parallel run very consistent unlike the Euros which showed some horrible charts). Do you have any evidence or information that the model has a programmed bias as I would be interested in reading about it. What about the other models - do they have a programmed bias?

Thanks

Stewart

[kold weather]

well according to the discussion john holmes had with NOAA about what the models use and do not use that is incorrect

It would seem they ONLY use CURRENT DATA. It may overdo things with the initial programing at fault like go forward making deeper lows but that is more to do with the program not historic data ie not that it thinks less winter cold or more winter cold over recent years. It just runs a program forward each run the same way forward but from a different stating point. If the program is set to deepen lows for instance more than it should, that will be constant in every

run as the same program is run, with diffrent data starting points .I enclose the discussion in full below

You make my point for me in many respects in that part of the post..it IS a fault with the program, well not so much a fault, rather a change that was made in the past by the programers to prevent constant deep warm cored lows from blowing up, I believe this change may have been made around 03-04 time but I'm not totally sure about that. Since I'm heavily involved with the hurricane side of things thats how I got to know this information.

Remember, the model skew the data depending on inherent bias, all models have them, usually because they help to reduce even bigger problems that may well be present within the mode. I know many on American weather forums who try to discover what the biases are based on constant looking at the forecasted synoptic set-up and then comparing them to what happened, thats how I learned about the ECM bias for keeping cutoff lows too far west in longer ranges.

Its nothing to do with historical data as you correctly say, but more to do with the models actual system. As I said a slight cold bias issue is a far smaller issue then creating random hurricanes which can totally mess up synoptics...

So you've probably just fleshed out my whole debate there in that one single paragraph, its the programing thats the issue, not the data...though obviously the lack of it over places like Greenland obviously makes it all that bit less certain as well.

Edited December 22, 2009 by kold weather

[pyrotech]

You make my point for me in many respects in that part of the post..it IS a fault with the program, well not so much a fault, rather a change that was made in the past by the programers to prevent constant deep warm cored lows from blowing up, I believe this change may have been made around 03-04 time but I'm not totally sure about that. Since I'm heavily involved with the hurricane side of things thats how I got to know this information.

Remember, the model skew the data depending on inherent bias, all models have them, usually because they help to reduce even bigger problems that may well be present within the mode. I know many on American weather forums who try to discover what the biases are based on constant looking at the forecasted synoptic set-up and then comparing them to what happened, thats how I learned about the ECM bias for keeping cutoff lows too far west in longer ranges.

Its nothing to do with historical data as you correctly say, but more to do with the models actual system. As I said a slight cold bias issue is a far smaller issue then creating random hurricanes which can totally mess up synoptics...

So you've probably just fleshed out my whole debate there in that one single paragraph, its the programing thats the issue, not the data...though obviously the lack of it over places like Greenland obviously makes it all that bit less certain as well.

Thanks for clarifying, i think we were both singing from the same song book but the song sounded different lol

Cheers Kold.

[kold weather]

Yeah I think so as well!

NOAA have a bias page for the models and indeed as I thought there is the cold bias in the GFS, its nothing too extreme but for Western Europe after say 120hrs it starts to have a pretty big impact on our weather. This is what they say about it for North America:

Prediction of southward progression of cold air over done.

Model a bit too extreme in temp patterns

beyond 84 hours Precip Type Algorithm off of GFS too eager to depict snow

We've seen the top 2 happen over and over again...from looking at when the bias was noted it seems the change over was in 2002, which was roughly the period I thought the change happened, as it was in response to the many warm cored hurricanes it produced...I believe the Candian model has had similar problems with warm cored systems in recent years, a change was made to it last summer that has improved it somewhat on that front.

Also another model bias is convective feedback, which is clearly a big issue in the summer.

Edited December 22, 2009 by kold weather

[Glacier Point]

Extended long range tools:

GEM 11-15 day mean height anomaly -

http://raleighwx.easternuswx.com/models/cmcensemble/12zCMCENS11-15day500mbHeightAnomalyNH.gif

GFS 11-15 day mean height anomaly -

http://raleighwx.easternuswx.com/models/gfsensemble/12zENS11-15day500mbHeightAnomalyNH.gif

Day 8-10 operational ECM and GFS 12z mean height anomalies -

http://www.meteo.psu.edu/~gadomski/ECMWF_12z/hgtcomp.html

CPC derived 8-14 day mean height anomaly forecast -

http://www.cpc.ncep.noaa.gov/products/predictions/814day/814day.03.gif

GWO in phase 7, likely to persist in orbits 5-6-7 as we progress into January although falling momentum likely as (1) poleward transport of momentum bringing the northern arm of the jet into play; and (2), tropical convection builds in the Indian Ocean associated with the next MJO wave -

http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

http://www.cpc.ncep.noaa.gov/products/people/wd52qz/mjoindex/index/diagram_40days_forecastGFSOP_CFSOP_GEFS.gif

All of the model guidance and analysis of ocean-atmospheric coupling points solidly towards a -NAO signal developing during early January with a ridge in the Atlantic being thrown up to build heights around southern Greenland and Iceland with low heights over Azores, probably extending into Europe as colder air builds back south from the north and north east.

[Cal]

Thanks Stewart, certainly no blowtorch on the horizon.

[Don]

Thanks Stuart. Liking the sound of your thoughts for January! The only thing that's concerning me slightly at the moment is the recent increase in solar activity, although I can't say I really know much about it.

[SteveB]

Thanks Stuart. Liking the sound of your thoughts for January! The only thing that's concerning me slightly at the moment is the recent increase in solar activity, although I can't say I really know much about it.

It is annoying, but will have little effect on our weather. And even with the activity, it still at low levels.

[Optimus Prime]

Isn't there something like a 5 year lag in Solar output from sun to earth?

[SteveB]

Isn't there something like a 5 year lag in Solar output from sun to earth?

There is a general consensus that there is a lag, but nobody really knows what the time span is. Many have guessed & 5 years sounds fair enough.

Edited December 23, 2009 by SteveB

[MR EXTREMES]

There is a general consensus that there is a lag, but nobody really knows what the time span is. Many have guessed & 5 years sounds fair enough.

i think maybe 3 years i think the effects are being felt right now but not here in southern england lol.

but on a serious note america and most of europe without jumping the gun to much 2008/2009 and maybe 2010 looking alot different to years proceeding thease,

so although a little activity on the sun and with it set to go quiet again in the next day or two who knows,

but where in a minimum the last time this happen ws in the mini ice age maybe we will not suffer as much but another couple of year and where know for sure.

im certain it causes effects with the jet and this is one big factor in a cooling climate.

but to be honest im waiting to see how this winter turns out

and merry christmas.

Edited December 24, 2009 by badboy657

[BLAST FROM THE PAST]

There is a lag with the solar irradiance but effects from the suns magnetic fields and disturbances are felt almost real time. The slight waking up of the sun will only send out disturbances bringing stormy periods. Reminders of what IMO has set up this winter and last winter. Solar and lunar driven pattern... The jetstream heading south [has been for 3 years now], the approx 36 year Perturbation cycle and since Feb 2007 been in La Nina domination phase. This cycle snugly fits with the NAO and when in La Nina domination state a -ve NAO cycle dominates. -ve PDO IMO directly affects the El Nino effect as we see this winter. There is lots more to it but that is the very basic gist

BFTP

[SteveB]

There is a lag with the solar irradiance but effects from the suns magnetic fields and disturbances are felt almost real time. The slight waking up of the sun will only send out disturbances bringing stormy periods. Reminders of what IMO has set up this winter and last winter. Solar and lunar driven pattern... The jetstream heading south [has been for 3 years now], the approx 36 year Perturbation cycle and since Feb 2007 been in La Nina domination phase. This cycle snugly fits with the NAO and when in La Nina domination state a -ve NAO cycle dominates. -ve PDO IMO directly affects the El Nino effect as we see this winter. There is lots more to it but that is the very basic gist

BFTP

Hi Blast,

Where do you think we will go from here as far as cycle24 into cycle25 is concerned. Do you think this is cycle24 peak?.

[Glacier Point]

http://raleighwx.easternuswx.com/models/gfsensemble/12zENS11-15day500mbHeightAnomalyNH.gif

http://raleighwx.easternuswx.com/models/cmcensemble/12zCMCENS11-15day500mbHeightAnomalyNH.gif

Long range ensemble mean height anomaly tools day 11-15 have, if anything, become more aggressive towards height rises further north building into Greenland. If there is a weakness here, the models are not showing it.

[Uncle_Barty]

To answer Steve B's question - Cycle 24 is just getting underway. Solar minimum looks to have been Dec 08, Cycle 24 max is likely to be about 2013 or so.

[BLAST FROM THE PAST]

Hi Blast,

Where do you think we will go from here as far as cycle24 into cycle25 is concerned. Do you think this is cycle24 peak?.

Merry Christmas all...Steve 25 anticipated to be MAUNDER minimum values. Cycle 24 will be building but weak and fairly long.

BFTP

[pyrotech]

Merry Christmas all...Steve 25 anticipated to be MAUNDER minimum values. Cycle 24 will be building but weak and fairly long.

BFTP

I agree it will probably be weak, for more on the effects of solar min for uK see http://forum.netweather.tv/index.php?app=forums&module=post&section=post&do=reply_post&f=8&t=48837&qpid=1630978

Merry xmas all and freesing cold new year !

Edited December 25, 2009 by pyrotech