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phil nw.

Model Output Discussion 4th Dec.2013-12z onwards.

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look out for a rise in pressure towards iceland,slight but there at 186 hrsPosted Image

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Height rises towards Iceland maybe!!! Good spot swfc

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High pressure now directed/over Scandi, this is looking MUCH better...

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Edited by Panayiotis

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Pub run onto one.......doom and gloom can soon change...

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Looks like the greeny high also trying to show itself too on the 18z. Only if it were to link up with the euro high. Looking good. Posted Image

Edited by pip22

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The biggest differences on the 18Z is the alignment of the Euro/Scandi HP at t.120.  On the 18z, it is much more North and South. On the 12Z, the bulk of the HP was aligned West and East.

 

12Z

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18Z

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Edited by IBTHToThoseShortwaves

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Pub run or not, heights are building much towards Scandinavia which is a great sign.... Always loved the pub run.

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The prospects of cold have gotten a little bit brighter with the GFS 18Z run. The GFS 18Z is showing a Scandi high at T+126:

 

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However, when one looks at the 200 mb streamline analysis (that is at the height where the pressure is about 200 mb) shows that the jet stream is toppling this high pressure area, (T126)

 

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Though the upper troposphere-pattern is highly ampiflied, the jet on top of this high may indicate this high has a low chance of actually maintaining itself for a long time on that position. Also note that the highs are out of phase according to the forecast, with the 200 mb ridge lying to the SW of the surface high.

 

Also, the temperature charts at T136 indicate a mild +8 degrees during daytime.

 

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However, if the high can sustain a few days, then there might be an influx of rather cold air from the Balkan (which is very cold during this timeframe). 

 

Concluding (with the analysis of the GFS 18Z), the prospects of cold aren't convincing yet with a fragile high pressure setting up. However, if the pattern can sustain some time, chances of deeper cold could be on the increase.

 

Source:

http://www.wetterzentrale.de/topkarten/fsavneur.html

Edited by Vorticity0123

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So an upgrade in the reliable timeframe be it a small one.see what tom brings with this ridging but the 18z is slightly heading towards the gem!!Posted Image

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That HP needs to backup further with each subsequent run. If not, then I fear we are looking at a milder Euro HP establishing itself by mid week next week. If the LP in the mid Atlantic would sweep underneath into the med, then it would give us a good shot at getting the HP in the right location. As it is, the LP is progged to phase into the LP to our NW near Greenland. 

Edited by IBTHToThoseShortwaves

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Positive PDO on this run which wasnt really shown on the 12z, however what they both show is a 1035mb surface high near the North Pole..

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GEM, BOM also show this feature

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With this positive PDO sending heights into the Pole, the PV is disturbed which is something we need to see if the cold is what you want!

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I do feel a small step in the right direction on the 18z , disruption out west with very little Atlantic influence , and a slightly better southern arm to the jet , low pressure trying to push up from the south in fi which is always a good sign , and slightly better orientation on the high pressure in Europe . May not be cut and dry yet folks.

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Interesting how both the ECM and GFS develop that shortwave which runs se through the Baltic, oh for a bit more amplification upstream this little feature could have been the trigger!

 

Still some uncertainties as to the exact flow into the UK, the orientation of the high being crucial here for whether its a south/sw or se'rly, at this time of year even with mild upper air that se'rly could be  cold.

 

The UKMO has that shortwave but is less amplified upstream, shame we didn't have more time to play with re amplification, I'm not sure how much more we can squeeze out of the upstream pattern.

Edited by nick sussex

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ECM London ensembles not very encouraging (As expected after seeing the mean charts)

 

Posted Image

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The GEFS for the 18hrs run do show some interesting solutions and differences from quite early on, the aforementioned miracle shortwave plays its role in bringing some colder air closer from the east but the jet still running too close to the north and not amplified enough.

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Heres the GEM:

 

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Sorry guys. Posted Image  Looks like I'm wrong it is looking worst than I thought. Plus 10 uppers over the UK. Posted Image

 

Least I'm learning. Posted Image

Edited by pip22

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The GEFS for the 18hrs run do show some interesting solutions and differences from quite early on, the aforementioned miracle shortwave plays its role in bringing some colder air closer from the east but the jet still running too close to the north and not amplified enough.

 

I was just browsing them and raised an eyebrow, certainly more  encouragement out to the mid range with the Scandi ridge either just failing to link up with ridging further East or actually doing so. If we get a closed low over Europe that will help things enormously with amplification as it moves back West.

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Yes, the key really is leading into circa T+120. Comparison of UKMO-GM versus EC DET (latter with some agreement from other operational centres) concerns handling of the low running down across Poland/Ukraine, with the cold high cell developing behind. Now, variation in this evolution has potential to radically change evolution of the block (indeed UKMO have modified their GM to nudge more towards EC post T120). So, nuance changes are quite important even in what seems, on face value, a bland set-up. Equally, EC EPS exhibit a raft of resultant temperatures across S England by then, ranging from positively mild to cold. So, those who suggest forecasting within T+72 is 'boring' or a fait accompli will do well to consider how - alongside the clear nuances of broadscale detail - the boundary layer issues in day-to-day & regional forecasts have 'headache' stamped all over them.

Thanks for the update Ian, I think at this moment in time this uncertainty re the low might not end up delivering a cold easterly in terms of uppers but I think it could play a role in changing the orientation of the high to bring in that colder se feed. It is quite intriguing though because whats gone under the radar for the last few days is how some of the models have started bringing this into the equation.

 

Normally with more upstream amplification this thread would be obsessing over this as it  has over the years ended up being the trigger for an easterly, in this case I think it would be close to a miracle to get enough of a cut back in the jet towards the UK to bring this in with its very cold air, given the timeframes how much change in the upstream jet could we expect.

 

Anyway thanks again Ian for your input , much appreciated.

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Well the CFS 12z is another beauty following yesterdays 12z:

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Just been viewing that myself. Amazing run for cold lovers. More or less once it arrives it keeps the cold right up until the end of the month. Even the odd channel low in there too. ...Oh if only!!

Edited by SE Blizzards

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