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Model output discussion - 5th December 2016 - Into Winter we go


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ECMWF Monthly goes off-piste versus it's deterministic brother into & particularly beyond Christmas. The +ve GPH/MSLP anomalies out to our NE merely intensify again towards end of month, then show

My retired colleague Ian McCaskill, RIP, would have relished discussing this Christmas Kerfuffle on-air with typical humour.  GFS 12z deterministic very similar in final reaches of run to Thursda

EC MONTHLY: again like last run. Blocked & dry anomalies developing 1st half Jan as heights move W to north of UK. Colder than avg anomalies southern UK 2nd week Jan (not seen that signal for a wh

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21 minutes ago, snowice said:

00z ec 12 members had it the same as NAVGEM the placement of the high has a number of variables:)

Really, as many as 12, thats interesting, we are still 5/6 days out of course. I think that we may still have a few surprises in the short term, IE upto day 6, time to start checking out the fax charts from this evening onwards as things develop to out NW.

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4 hours ago, Singularity said:

UW96-21.GIF?27-17 arpegeeur-0-96.png?12

Here's UKMO on the left and ARPEGE on the right. The latter has a slight negative tilt to the Canadian trough while UKMO has a neutral - direct north - orientation.

Around 24 hours later, this slight difference grows exponentially, with dramatic results:

UW120-21.GIF?27-17 arpegeeur-0-114.png?12

While UKMO is progressing to a surprisingly quick dive down of a shortwave low from the northwest - with nice separation from the Canadian/NW Atlantic trough it has to be said - the ARPEGE solution sees an omega block established to the west which is going nowhere fast. The UK is in an increasingly unstable northerly as the jet angles NE to SW on the east flank of the OB. A rare and valuable setup and nice to see that the option remains on the table, especially coming from a high-resolution model, albeit not a particularly reliable one at such range.

The aperge will be the rank outsider with that solution, less than 10% - way to amplified - all other models have a circular high With a faster slightly faster jet- 

whilst it looks pretty @120 the big 3 wont be beaten by the aperge...

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The anomalies this evening, although on the same page, do not offer that much clarification regarding specifics

Upstream more or less okay with the strong Aleutian ridge,(and to quote MV very common during La Niña base states) Canadian vortex with associated trough and a cold arctic plunge down North America. Also a strong Russian vortex and trough the orientation of which may also be playing a part in the different interpretations of the amplification in the Atlantic alluded too above. For example they all have completely  different interpretations of the mid Atlantic ridge which probably doesn't alter the general prospect of systems travelling around the HP and dipping SE but it will effect the precise track that could impact on surface conditions such as winds veering N or NE and perhaps the severity of transient wintry outbreaks. Still to be resolved over the next few det. runs None of this should effect the general trend of temps to below average.

610day.03.gifgefs_z500a_5d_nh_41.pngecm_eps_z500a_5d_nh_11.png

The most obvious change in the 10-15 period is the strengthening of the Canadian vortex and the removal of the Russian (more or less). We are then left with ridging to the W/SW and fairly weak positive anomalies and a trough to the east curving SW and an upper flow from the NW/WNW and temps still below average.

814day.03.gifgefs_z500a_5d_nh_61.png

 

Edited by knocker
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4 minutes ago, bluearmy said:

Looking through the extended eps - wow! 

basically  sceuro trough and griceland ridge. The Azores trough then spreads east to join with the sceuro to bring the 'holy grail' of southerly jet flat across the Atlantic under the high anomoly into the broad euro low anomoly. I don't expect to see a better mean anomoly run for coldies. as Matt tweeted, need to see some consistency on it but it isn't a flip from previous output. 

 

Need to see something like this from the ops very soon though Blue...

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ECM Op was on the mild side of the DeBilt suite although with fair support / clustering.

There are still a good number of cold members to balance as well as some very cold solutions

PLUIM_06260_NWT.png

 

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7 minutes ago, northwestsnow said:

Need to see something like this from the ops very soon though Blue...

Gfsp has been hinting at it though has ended up a bit west based 

expecting the GFS ops post day 10 to get the right pattern is quite a stretch. ECM op isn't far off

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16 minutes ago, bluearmy said:

Looking through the extended eps - wow! 

basically  sceuro trough and griceland ridge. The Azores trough then spreads east to join with the sceuro to bring the 'holy grail' of southerly jet flat across the Atlantic under the high anomoly into the broad euro low anomoly. I don't expect to see a better mean anomoly run for coldies. as Matt tweeted, need to see some consistency on it but it isn't a flip from previous output. 

 

I think that looks like a very optimistic interpretation on the mean anomaly charts. There is no obvious 'joining' or 'phasing' of the Azores trough and the one to the east and a weak ridge is still retained between them. Although the negative anomalies do pay homage. And the 200mb wind field is pretty diffuse and weak.

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gfs-0-138.png?12 gfs-2-138.png?12

GFS(P), you total tease...

The momentum carried by the cold air looks sufficient for an undercut even if the low is more toward the SW of the UK - but only if it remains small enough that the flow into the UK is essentially from the southeast where the dewpoints are low.

Still a very transient event though; probably about an hour of falling snow at best. Falling on wet ground too and with the cloud and rain having timed itself such as to prevent a chilling of the ground in advance - though the frosts of the next few days may help with that aspect anyway.  

A slower frontal progression would not improve things much in terms of preconditioning - too much cloud in the airmass ahead of it - but could make things interesting for the south, particularly if it got held up a bit, which I imagine is more likely if the low is further east and not getting swept under the ridge so quickly.

 

@Steve Murr I agree with you in that I consider ARPEGE to be very unlikely to win. Nice to look at, nonetheless ;)

Edited by Singularity
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I ageee that the ecm eps mean chart at t240 is good. 

The problem I have is the differences though in the mean chart between the gfs and ecm eps/ens at t168. At this range they should be pretty similar but ecm has the low mid Atlantic on steroids after an energy pulse from the states. Whereas the gfs completely fails to engage and sends it north. 

In it self per se it's not the biggest of issues but when you get one model going one way and another going a different way. History tells us that a meeting of the minds normally takes place hence why even eps and ens beyond t144 should be treated with extream caution imho.  

I agree that cold is on the cards but the form it takes and when it might it are very up for grabs. 

IMG_0654.PNG

IMG_0657.GIF

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Looking at the mean charts this evening and even by T168hrs the subtle differences between the 2 suites start to show up with the ECM set more amplified

EDH1-168.gifgensnh-21-1-168.png

 

The better ridging from the PNA ridge on the ECM just shrinks that Canadian vortex a little more which helps to draw further Amplification downstream in the Atlantic around day 9 .

I think we can say the initial colder northerly is pretty much agree around NY but where the Atlantic high goes beyond there is very much undecided tbh  sinking se appears the least of the options looking at gefs clusters and both mean charts..

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