Model Output Discussion October 2012

[chionomaniac]

Steve, I may be wrong here, but if I remember correctly the ECM toyed with the idea of a northerly previously in 2010 but was not consistent with it's outlook. It seems pretty consistent now though?

Case in point 12Z 12th Nov 2010 day 10 forecast:

[SMU]

HI Chiono- I didnt look at the ECM day 10- however that 500 chart is 'ok' although post that the model wasnt very consistent-

& Yes its been pretty consistent at the moment- still feels messy- also of note is the CPC discussion discounted the ECM in favour of the GFS yesterday...

S

[chionomaniac]

HI Chiono- I didnt look at the ECM day 10- however that 500 chart is 'ok' although post that the model wasnt very consistent-

& Yes its been pretty consistent at the moment- still feels messy- also of note is the CPC discussion discounted the ECM in favour of the GFS yesterday...

S

I saw that from yesterday though factors such as MJO phase, position of upper vortex, past examples of GFS going off on one, would make me very wary of the GFS at this point and I would stick with the ECM and UKMO (unfortunately).

[Frosty.]

also of note is the CPC discussion discounted the ECM in favour of the GFS yesterday...

S

Hopefully it will do the same today

There continues to be a lot of uncertainty about where we go after the very mild (warm) first half of next week and I continue to hope something like the gfs evolution verifies but a more reasoned view would probably be a halfway house scenario. The 528 dam line going beyond the south coast would be a stunner for so early in the season.

[BLAST FROM THE PAST]

Maybe so C but the ECM 00z run is messy yo yoing the HP until 240 when it almost finally links with its arctic friend. I just feel that particular run is messy and wishy washy. Isn't phase one to have trough over us and HP to arc from E/NE/NW/W of UK and bizarrely more akin to what 18z GFS showed in FI?

I think a halfway meet/blend looks plausible here either that or there'll be a biggish bactrack from one or two.

BFTP

[bluearmy]

that comment re the 528 dam line going south of the uk set alarm bells ringing in my head. the mean 564 thickness is in the channel on the noaa cpc charts yesterday evening and although we would need to take surface pressure into account to get to the actual thickness, it seems much too big a step to be taking.

[Frosty.]

that comment re the 528 dam line going south of the uk set alarm bells ringing in my head. the mean 564 thickness is in the channel on the noaa cpc charts yesterday evening and although we would need to take surface pressure into account to get to the actual thickness, it seems much too big a step to be taking.

It probably won't happen but I am showing it again just in case anyone missed it. It's as rare as hens teeth for so early but I hope the gfs will keep this general trend on track and for the ecm to head in the same direction soon.

[Gavin Hannah]

Extreme or not, you have to hand it to the GFS, it is definitly on a roll regarding a trend. The last few days have seen a very similar pattern emerge of a slight warming this weekend followed by a HP taking up recidence over the N.Atlantic/Greenland.

[Liam J]

I'm at work so only brief - after a quick glance Is the 6z falling more into line with the ECM? Certainliy looks different from the 00z., still early on in the run though!

Edited October 18, 2012 by Liam J

[Gavin Hannah]

I'm at work so only brief - after a quick glance Is the 6z falling more into line with the ECM?

Havn't seen the whole run but it's not so eager to bring in the polar blast. Will have to see the next few runs before we can say for sure what is the more likely outcome.

[Liam J]

Havn't seen the whole run but it's not so eager to bring in the polar blast. Will have to see the next few runs before we can say for sure what is the more likely outcome.

Yep - Never hang on each run and use it as gospel, keep focused on the trends.

6z is reather a wild swing - from -6/-8c 850's to +8c !! Rather extreme and a bit suspect??

Edited October 18, 2012 by Liam J

[Frosty.]

Havn't seen the whole run but it's not so eager to bring in the polar blast. Will have to see the next few runs before we can say for sure what is the more likely outcome.

It's not surprising to me as the 6z lacks data from critical areas compared to the 00z and 12z runs, the 18z likewise has less data so this run won't help to clear up the uncertain outlook and won't hurt it either.

[NorthYorksWeather]

Main difference on the 6z occurs around 99hrs, the low pressure in the Atlantic throw's off a shortwave into southern Greenland preventing the HP over Greenland building southwards. We may still get there as that low once moved east could trigger CAA but it's then being pushed back into the unreliable timeframe so it's likely to change once again. Interesting model watching currently nonetheless

[SMU]

I saw that from yesterday though factors such as MJO phase, position of upper vortex, past examples of GFS going off on one, would make me very wary of the GFS at this point and I would stick with the ECM and UKMO (unfortunately).

Hi Chiono All Im doing is highlighting an example- there are many more, however there are also many more occasions where the ECM was a lot better than the GFS-

Its when & where to choose those disparities to highlight them..

THe 06z offering at 186

http://modeles.meteociel.fr/modeles/gfs/runs/2012101806/gfs-0-186.png?6

Of note is the second day the 06z hasnt got a firm greenland high, but rather a split of atlantic high & higher pressure over greenland-

This is against the 12z & 00z & highlights the difference well with the 06z always wanting to drop the polar blocking...

The 12's will be of great interest today..

S

[johnholmes]

It's not surprising to me as the 6z lacks data from critical areas compared to the 00z and 12z runs, the 18z likewise has less data so this run won't help to clear up the uncertain outlook and won't hurt it either.

sorry Frosty-this is a red herring unless you can show me NOAA commenting on lack of data for the 06z run, in which case as usual with any errors on my part I will apologise?

[SMU]

http://www.accuweather.com/en/weather-blogs/weathermatrix/why-are-the-models-so-inaccurate/18097 ^^

[Summer Sun]

GFS is looking much more settled on the 06z run

All the cold air seems to be further east this morning

[Liam J]

In the shorter term outlook a good chunk of the UK will have some very pleasant weather early next week as we draw on some warmer continental air from the S/SE. Temps widely up into the mid-upper teens with 20c in a few locations and mild nights - A mini Indian summer to enjoy, where we go from this point, well we just don't know!

[Pixel]

http://www.accuweath...naccurate/18097 ^^

certainly a good read but would be interested to hear what and if anything has changed since Feb 2009 with regards to model data

[Frosty.]

sorry Frosty-this is a red herring unless you can show me NOAA commenting on lack of data for the 06z run, in which case as usual with any errors on my part I will apologise?

Hi John, I only mentioned it because people with more technical knowledge than me have mentioned about the lack of critical data on certain runs such as 06z and 18z with the 00z and 12z runs receiving maximum coverage, if i'm wrong I humbly apologise as I'm really not trying to confuse anyone in any way, also I would never attempt to go against your far superior meteorological experience.

[Gavin Hannah]

What is def certain is the settled period with warmer temps from this weekend. If I was going on gut hunch, I would suggest the Polar blast would be odds on over anything else 06Z has shown. It's just a gut feeling mide you so I will watching the runs over the next day or so.

Personally, I'm looking forward to a dry spell after all the rain we've had.

[Shunter]

and the actual quote from the Accuweather 2009 report was "Avoid the 06Z and 18Z runs when 00 or 12 is available; in the U.S. these runs don't include the weather balloon network data (balloons are only sent up twice per day), and are therefore radically different and more likely to have bias".

[SnowObsessor90]

The 06z does however try to have another stab albiet right at back end of FI and with High pressure still situated right over us so the potential for another bite of cherry further into November if the first attempt fails perhaps?

This assuming that the strat/PV just doesn't turn around and say an outright no at some point between now and the end of November/start of Winter which it could well do.

[johnholmes]

No need to apologise Frosty, ineed it is probably me that should do so.

see the part of a para I've quoted from the link Steve gave above

Avoid the 06Z and 18Z runs when 00 or 12 is available; in the U.S. these runs don't include the weather balloon network data (balloons are only sent up twice per day), and are therefore radically different and more likely to have bias.

I have not seen anything from NOAA that agrees with this view but would be very interested if anyone has anything?

Until then my apologies re missing data Frosty.

[BLAST FROM THE PAST]

Last month, a breakthrough was discovered: When the GFS is run with the ECWMF Initialization data (see above), the accuracy improves dramatically (you can read the AMS presentation here). Unfortunately, implementing that is not as easy as you'd think - outside of the cost of using the ECWMF data, it only runs twice a day, so the GFS would no longer be able to run at 06Z & 18Z (midnight & noon). I suppose one other option is that we fix our initialization data, but I haven't heard much about that option taking shape. It would probably be a big undertaking. In any case, I'm thrilled that we now know what's wrong with the GFS.

"So Now What?"

1. Be wary of forecasts that are only on one model. If nearly every model is on board with a solution, then you can be more confident in your forecast. Look at all the models, preferably on one map.

2. For the GFS, look at a couple days of 00Z and 12Z runs for consistency. Avoid the 06Z and 18Z runs when 00 or 12 is available; in the U.S. these runs don't include the weather balloon network data (balloons are only sent up twice per day), and are therefore radically different and more likely to have bias.

Above are bits I picked out of Steve MURR's link

BFTP