Model Output Discussion 1st Nov.2013

[johnholmes]

The UKMO and GFS do show differences upstream as early as T96hrs, the former does look better at that time. The GFS at T156hrs again looks too flat, we need to see more interaction between the polar jet and that shortwave.

 

I don't understand that comment Nick? Why/how would it interacting with the jet affect things for the UK please?

[UV-RAY]

Everything that's bitterly cold or snowy seems to be getting pushed back into FI, that's the only trend I can see this evening.

There was nothing ever forecasted  for bitter cold within the next 7-10 days to start with, cold with below average temps yes.

[mountain shadow]

Polar Vortex on the move to Scandinavia in November according to the 12z GFS.

Believe it when I see it. Incidentally, is this potential cold spell still being driven by the Aleutian High?

[Yarmy]

UKMO is stuck at T96?

[Met4Cast]

I think we just have to come to terms with the fact that although it's going to be cold, even bitter. Its going to be very short lived. People say look for trends. Well the overriding trend is that this high will topple almost immediately.

 

I'd say the overriding trend at the moment is for colder weather across the UK. We don't know the details yet. The models have continuously modeled cold air reaching the UK in one form or the other for almost a week now.

 

Whether the high then ends up toppling or building further into Greenland isn't known. Lets get the cold here before worrying about how it's going to break down, eh? Cracking GFS run, though it does seem to go a little crazy with the dissapearing and then re-appearing Greenland High once we get into the low-res.

[johnholmes]

 The operationals and some of the ensembles did have a decent high topple towards Scandi which would give a chance of some cold in from the east, not a proper Scandi high so I agree with you there. But that won't happen unless the high gets far enough north initially and theres less energy spilling over the top.

 

I have to say I would be amazed if the high, within the time scale being discussed ended up east of the meridian, north or south of the UK.

[Gaz1985]

There was nothing ever forecasted  for bitter cold within the next 7-10 days to start with, cold with below average temps yes.

 

Some runs were going for -8 uppers for parts of the UK, for November that's darn cold.

[nick sussex]

I have to say I would be amazed if the high, within the time scale being discussed ended up east of the meridian, north or south of the UK.

I never said it would. But if it topples favourably after the initial cold shot it could still pull in a ne/e flow on the southern flank. For example look at this mornings ECM operational and a few of the GFS operationals from yesterday.

[SomeLikeItHot]

Some runs were going for -8 uppers for parts of the UK, for November that's darn cold.

the GFS 12Z still does what are you talking about?

 

-10 in Scotland, -8 north England and -6 midlands south.

[SnowObsessor90]

So is the first bite of cherry  at least looking likely to be gone or are people just overreacting as per usual?

[bluearmy]

whilst low res gfs is generally only fit for the bin, its always pleasing to see the p/v in a state

[MR EXTREMES]

yeah same ere ukmo has blown its computer lol

[Gaz1985]

the GFS 12Z still does what are you talking about?

 

-10 in Scotland, -8 north England and -6 midlands south.

 

I was talking about other runs, never said "the 12z" did I?

[Captain Shortwave]

The main problem with the GFS is once again its too flat and the comments from NOAA have to be taken into account with the polar jet, preferably we want this to engage the shortwave moving east across the Rockies, we don't want a weak feature, the high needs some help to get further north and so we need to see a more developed low with a more favourable tilt.

GEM looks a lot better with the low engaging the polar jet

Hope the GFS is pulling a winter 12/13 shocker here

[MR EXTREMES]

sorry people cant post charts but by god do we want the gem to be right

[johnholmes]

Maybe a little suggestion might help both visitors and newcomers as the model thread gets into overdrive with the first sign of colder weather?

If you want the roller coaster ride of ups and downs in optimism then fine watch every bit of every run from GFS and the others. If you want to see a model showing cold then by all means switch from one model to another whichever is showing the coldest option on any particular run.

If you want to get a reasonable idea on what the most likely weather is then it does need a different approach.

Assuming you want to 'read' the models and not simply read the 6-15 and 16-30 day outlooks produced daily by Exeter then the following might help.

At time scales beyond T+144 and sometimes less compare the models for the same run and the same prdiction, be it T+120 or whatever. I know this next bit will attract flack but believe me it is fact not fiction. Compare the same time each day. Choose your favourite, for whatever reason and stick to that from T+240 or with GFS T+384. Drop down the time scale each day but use the same issue and the same end date/time. Once the time scale gets below T+144 almost always, note almost(!) the models will begin, if they are not already, to move to similar charts for similar times. Below T+144 possibly less then by all means watch each run of each model if you have the time. By the time you get to T+96 or 72 then the later data will by then have a significant impact on the accuracy of the output from whichever model you prefer. Beyond T+144 and certainly at T+240 and beyond please believe me that is not the case. Don't just take my word for it e mail the 3 main centres and ask them, Exeter, ECMWF, NOAA.

Whatever is your preference just try to nejoy the huge amounts of data we can now access and become amateur weather forecasters-its fun, but don't let it ruin your day and PLEASE don't be unpleasant to someone who does not seem to view the model output as you are doing.

 

end of jh sermon-I will do a fuller check on the 500mb anomaly charts in the technical thread as promised. Again PLEASE do not be put off by the name of that thread. What I post and others too is far from technical. If someone does make technical points and does not explain them-ask them to do so.

[nick sussex]

GEM looks a lot better with the low engaging the polar jet

Hope the GFS is pulling a winter 12/13 shocker here

Even the NAVGEM is looking better at T96hrs, I think the GFS can go into the cat litter tray this evening. It always does this, picks up the pattern then drops it whilst the others go ahead and then finally comes to its senses after its reputation has been trashed further!

[Zenarcher]

The stratosphere temperature has risen very quickly lately a possible reason why the models are taking their time to get the hang of things,

 

 

Some very wintry conditions in FI from the GFS widespread across the UK,

 

 

Very nice chart PV takes a holiday,

 

[SomeLikeItHot]

I was talking about other runs, never said "the 12z" did I?

 

"Everything that's bitterly cold or snowy seems to be getting pushed back into FI, that's the only trend I can see this evening."

 

Then you defined that -8 was bitter.

 

So what is "This evening" if not the 12Z runs?

[Cheshire Freeze]

Even the NAVGEM is looking better at T96hrs, I think the GFS can go into the cat litter tray this evening. It always does this, picks up the pattern then drops it whilst the others go ahead and then finally comes to its senses after its reputation has been trashed further!

 

I believe it's having a major overhaul next year?

 

The way I see it is it often picks up the correct pattern in FI before going AWOL in the supposed more reliable timeframes. This suggests that it is in fact a programming error rather than a data issue.

[weatherguy]

To the more learned posters here, regarding the PV:  What are the background signals, if any, causing the trend over last week or so to model a deeply disrupted PV?  With no SSWs taking place and PV disruption appearing to be more than you would expect in terms of "wobble" in shape/organisation, any idea as to the cause?  

 

Edit: Weathermaster appears to have beaten me to it!  The answer appears to lie with the state of the stratosphere again, perhaps.

Edited November 12, 2013 by weatherguy

[Gaz1985]

"Everything that's bitterly cold or snowy seems to be getting pushed back into FI, that's the only trend I can see this evening."

 

Then you defined that -8 was bitter.

 

So what is "This evening" if not the 12Z runs?

 

I was referring to the 6z Manchester runs I posted not long before. Also everything that is bitter is still in FI, nothing has changed in that regard has it? 6 days to a week away is not reliable things can change.

Edited November 12, 2013 by Gaz1985

[SomeLikeItHot]

sorry people cant post charts but by god do we want the gem to be right

Synoptically it looks great but it doesn't bring very cold T850s in. Only Scotland gets to below -4. I find it hard to believe given the charts to be honest but that's what it is saying.

[radiohead]

An interesting 12Z NAVGEM. Not the grearest of models though.

 

[legritter]

As i said earlier i dont go by every single run ,but taking all modells over a period of a couple of days and also listening to the professionals in what they say on their extended outlook .i say listen to the professionals simply because they have access to more extended outlook information than us on Net weather do ,yes we can discuss the modells and we have some very knowledgeable Members among us .as for GFS 4runs per day so we will see a big variation in its outputs .we have a fantastic forum ,have a look at others in northern hemisphere we are blessed with ex met and very talented posters .roll on later modell runs what will they show ,but whatever enjoy and have your say and ask those questions ,catch up later .