ecm mean running very late tonight
Originally Posted by: Polar Low
Clearly the ECM mean (above left) is strongly in support of an outcome much like the model consensus (GFS, GFSP, JMA and to some extent GEM, with UKMO also displaying the breakaway shortwave on day 6).
So the way the ECM op run evolves is about as out of kilter as it gets!
When you look at the jet charts on the likes of GFSP, you can see a streak running toward the south of England, which is following the boundary between the upper trough toward Svalbard and the ridge west of Iberia (below-left):
What happens next is a bit complex looking, but it appears that a new, flat section of jet forms N. of the Azores as the subtropical air mass clashes with the Arctic air mass, and this jet forced to head due east because that route is quite frankly a lot easier going (avoids a piling up of air as it meets the jet coming SW from Greenland).
Based on this, it could be that on the ECM run, the jet through Greenland remains fully connected to the jet running down west of the Azores instead of breaking free and moving east to connect with the jet streak running SE through the UK.
I suppose what all models but ECM do is move toward cutting-off the Azores low, which almost completes before the jet out of the U.S. extends down to meet with it.
This disparity results in ECM having a ridge-trough-ridge pattern across the Atlantic when the other models have trough-ridge-trough! * facepalm *
Going much further into this 'outsider' ECM run is arguably a fool's game, but I will add that its solution requires about as much amplification as can possibly be achieved days; when you have such extreme jet contortions the jet behaves much like a river would do in that situation - it wants to find a much quicker route from A (SW Greenland) to B (the UK) by cutting-off the loop.
The notion that ECM tends to over-amplify is often put out there on various forums, but rarely has it seemed apparent within the 6 day range. I say 'seemed' because, well, you know how it is...
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