Hi Just looking at the latest GFS output and once the cold front of this current frontal system clears, pressure rises quite strongly with an anticylcone of about 1026 mb sat over the Irish sea by Thursday 00Z, after that the high slips away E into the North Sea allowing a SE'ly flow to become established during Friday as pressure falls as a low slips E and then SE into Biscay. With 1000-500 hPa thicknesses rising and the 570 dm line nudging along the south coast by Friday it should translate to day maxima up around 28-30Â°C I would have thought across large areas. So from the current mobile W or CSW type we flip to an AC follwed by an ASE or SE before ending up with an E by Sunday the 25th if the GFS holds true. Bruce.
Please carry on here.
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Good afternoon all.
I hope you are all having a very pleasant Sunday afternoon.
Well, with the end of November rapidly approaching we are all wondering what the new season will bring. We have a multitude of signals suggecting that northern blocking is about to occur - but none of these have shown themselves in the reliable timeframe. So to recap and to help start this thread off, let's go through them all.
The GFS and ECM have jumped repeatedly in their outputs recently - often this lack of consistency is indicative of a change of pattern - and certainly there are clues that this could occur.
Currently, we are in a pattern that holds a trough to our Northwest for the next week or so.
There are suggestions that this trough will hold position and lead to height rises over Scandinavia which could give rise to an easterly - but it looks as though the height rises in Scandinavia will be slowly pushed by the trough to our west moving westwards.
There is numerous support for this occur in the 8+ day timeframe.
Here are the comparison H500 anomaly charts for the 8-10 day comparing the ECM and GFS.
Both are pushing troughing towards our SE - never a bad place for this to be!
Other H500 anomaly charts go further with the suggestion that height rises will replace the lower heights to our NW in the longer timeframe. They are all pointing in the same direction.
So is there anything else that can add credence to this scenario occurring?
The ECM and GFS MJO forecasts are both heading towards phase 1 towards the end of the month.
This is a good phase for support of GH blocking - in fact it is uncannily accurate when comparing to the anomaly charts above!
Now to the strat. The cooling seen in the autumn has been a fly in the ointment for those wishing to see a -ve AO winter. However there are signs that things are on the turn. During the last week wave 2 activity has put pressure on the vortex creating a monkey nut shape to the vortex. I suspect that this is likely to reoccur towards the end of the month and numerous forecasts right up into the middle strat have appeared. Yet again this has appeared on the latest GFS 06Z run - with the only difference being that the split is stronger and earlier!
30 hPa chart at T+ 12 days
The postion of the split vortex here is more conducive to NWern height rises and cross polar flows. Furthermore, these type of blocking patterns seen recently are precursers to stratospheric warming events, so that I wouldn't be surprised to see a stratospheric warming occuring after - into early December - how significant this will be is difficult to say currently but it will be useful down the line.
So, with a lot of pointers suggesting blocking towards the NW of the UK we are likely to see a cold pattern emerge from the start of December. In fact I can see it repeating and building towards mid December as the vortex takes repeated hits. If these hits can damage the stratospheric vortex and lead to warming then it willl be the perfect start to winter.
Besides the upper stratosphere, I haven't seen such pointers to a cold set up since the start of 2010 -and we all know what happened then.
Let's hope a repeat is on the cards.
Please keep on topic and be relevent as always
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