Model Output Discussions 06z 04/11/16

[Nick F]

Finally some agreement between GFS and ECM on Sunday's deep low track, at T+84 (12z Sunday) both have the centre tracking across SE England, as does the MetO fax updated this morning:

GFS and ECM indicating some high rainfall totals for southern counties south of M4, also GFS shows some strong southerly wind gusts Channel coasts ahead of the low. France bearing the brunt of strong winds (60mph+ gusts). Still time for the low to shift further north.

[Banbury]

44 minutes ago, northwestsnow said:

Nope, no sinker on Ecm, phew! Ecm 240 offers potential, and before that a cold high, lots to be positive about from the Ecm this morning in my humbly amateur opinion...

I agree , ECM is ok from what I can see......................certainly some chilly weather under that High, if that clears off to Greenland we'd be in business

[bluearmy]

45 minutes ago, knocker said:

The difference between the evolution of the ecm upper pattern and the gfs appears on the surface (no pun intended) to be along the lines that has been the difference over the last couple of days. It proceeds with the amplification a la gfs but then the ridge is attacked by a pincer movement from energy running up from the eastern seaboard phasing with energy from Canada which ends with a deep trough over Iceland squashing the ridge to a narrow band over the UK. In theory T264 should have deep upper trough over  the UK.

It would appear to be the handling of the upstream antics that is causing the problem

could be but not a deep surface low according to the eps

[bluearmy]

1 minute ago, Banbury said:

I agree , ECM is ok from what I can see......................certainly some chilly weather under that High, if that clears off to Greenland we'd be in business

The eps offered no mean/anomoly support for retrogression to Greenland. There could be a cluster hiding in there though! More likely retrogression to eastern Canada leaving a fairly wide envelope for the n Atlantic basin in general

[blizzard81]

Looking for retrogression in the 10 to 12 day time frame. Now that would be a nice opener to winter proper.

[blizzard81]

1 minute ago, bluearmy said:

The eps offered no mean/anomoly support for retrogression to Greenland. There could be a cluster hiding in there though! More likely retrogression to eastern Canada leaving a fairly wide envelope for the n Atlantic basin in general

The dreaded west based nao keeps hinting!

[Frosty.]

The GEFS 00z mean indicates below average temps and has a blocked  look to it late Nov / early Dec, there is potential for a cold / very cold outbreak during this period with height rises to the w / nw and a scandi trough..The mean has been showing this for a few days now.

Edited November 17, 2016 by Frosty.

[jvenge]

51 minutes ago, blizzard81 said:

The dreaded west based nao keeps hinting!

I'll bite. Can someone explain why a west based NAO is so feared by the cold lovers?

[Johnp]

The ironic thing is that although the GFS has back tracked, it's probably the coldest of it's operational runs in some time.

It's often the best way to start a cold spell imo ie a high cell drops anchor over us giving hard frosts and then retrogresses to bring in a northerly.

[Johnp]

2 minutes ago, jvenge said:

I'll bite. Can someone explain why a west based NAO is so feared by the cold lovers?

Because it can very easily lead to a euro high and south westerlies for us.

[Seasonality]

1 minute ago, jvenge said:

I'll bite. Can someone explain why a west based NAO is so feared by the cold lovers?

Hi there jvenge. They fear it because it can mean the positioning of the block means the cold air plunges into the atlantic while the uk is bathed in warm air on the 'wrong' side of the block. It is the near miss that irritates them I believe. But as some posters much more expert than I have pointed out, it isn't always a death knell for cold, particularly in December as opposed to later in winter. 

[jvenge]

2 minutes ago, Seasonality said:

Hi there jvenge. They fear it because it can mean the positioning of the block means the cold air plunges into the atlantic while the uk is bathed in warm air on the 'wrong' side of the block. It is the near miss that irritates them I believe. But as some posters much more expert than I have pointed out, it isn't always a death knell for cold, particularly in December as opposed to later in winter. 

I see, thanks for that and others who also answered.

GFS and a lot of its ensembles seems quite keen to bring a period of below average temperature to large parts of Eastern Europe, with some extending to Central Europe from around T138 onwards. It has played the last few runs with just how below average and how far west it will make it, but the trend is widely the same. Interestingly, this could bring some ice days to large parts and for the time of year, it is very unusual, although not unheard of.

[Summer Sun]

Certainly a chance for some heavy rain Sunday and or Monday with central, southern and southwestern areas taking the brunt with totals by Monday night quite high

Edited November 17, 2016 by Summer Sun

[carinthian]

Although the main models still forecast the development of a Mid Atlantic low along the Polar Front to cross South England this Weekend, its actual track is still in doubt. The latest North Atlantic synoptic chart still shows no development , but may be possible to detect by this time tomorrow. Looking at this chart, cyclonic development would be favourable where the Baroclinic Boundary ( thickness lines) are tightest. So I would think the greatest fall in pressure and track of the developing low would cross SW England and exit SE England. However, until we see further synoptic charts the exact track

is still open to debate. As NF says this morning could go a little futher North. However, as the lower thickness values dig in further south and west over the coming 24/36 hours, we could see the Low affect more of Northern France rather than Blighty. Its all matter of timing but at this stage I still favour the latter.

 C

Edited November 17, 2016 by carinthian

[Ravelin]

I know a lot of the posts this morning seem to say that the GFS has backtracked, ECM has 'won' etc, but surely the ECM has also moved towards a more amplification towards Greenland in the relative short term at least? Here's the 0Z charts for the 21st from this morning and the preceding 3 days...

You can clearly see the increased amplification towards Greenland and the consequential stretching of the trough down towards northern Spain.

Is the saga really over? I'm not so sure,

Edited November 17, 2016 by Ravelin
Got my charts slightly mixed up, twice

[booferking]

GFS will move slightly more to the ECM this run then we are in good agreement for mid-range.

[jvenge]

1 minute ago, booferking said:

GFS will move slightly more to the ECM this run then we are in good agreement for mid-range.

It's rolling out now, so let's see.

[knocker]

Regarding the difference between the gfs and ecm det. outputs the comment remains the same as last night after looking at the anomalies. It is still about the amplification and orientation of the Atlantic ridge

Ah. warms the cockles

[booferking]

2 minutes ago, jvenge said:

It's rolling out now, so let's see.

Its already less amplified 72hrs so looking good for agreement.

[feb1991blizzard]

Some of the runs with the most pronounced mid Atlantic / Greenland ridge have actually been the runs that have tended to have the WAA directed more on a SW-NE tilt as opposed to vertical, thus the CAA coming back around the ridge directed more towards the SW giving a west based -NAO, it might actually be a blessing with a *slightly* less amplified solution.

[andymusic]

looking good for Wales & Midlands early sunday morning now as long as things don't change anymore

 

[Ravelin]

10 minutes ago, booferking said:

Its already less amplified 72hrs so looking good for agreement.

Not by much though at t102...

0Z   6Z

Edited November 17, 2016 by Ravelin

[warrenb]

10 minutes ago, Ravelin said:

Not by much though at t102...

0Z   6Z

Well there  might be a pixel or two in it 

Edited November 17, 2016 by warrenb

[Banbury]

11 minutes ago, Ravelin said:

Not by much though at t102...

0Z   6Z

Very little change there ...............if any

Edited November 17, 2016 by Banbury

[Man With Beard]

Still looking at that D10-D15 period ... regardless of uppers, fairly cold at the surface on both ECM (De Bilt) and GEFS (central England) - that ECM control run looks frigid.

  

 

Got a gut feeling though that, slightly along the lines of the ECM, we may see another trough slip through the Atlantic block between T192 and T264, and a fresh build of pressure towards Greenland behind? In other words, a repeat of the D1-D5 scenario?