Model Output Discussions 12z 01/09/2016

[knocker]

1 hour ago, Summer Sun said:

A more seasonal start to October with a northwesterly flow bringing some cooler air

More to the point I would have thought the possibility of 70KT gusts in Scotland and in this very mobile pattern the cooler NW only lasts 24 hrs. All a bit academic anyway with TS in the mix none of this will verify this far out.

[mb018538]

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

The 500mb anomalies are starting to firm up on low pressure taking more of a hold, and winds veering round to a cooler direction.

[johnholmes]

16 minutes ago, mb018538 said:

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

The 500mb anomalies are starting to firm up on low pressure taking more of a hold, and winds veering round to a cooler direction.

One output only. They are switching from Upper ridge being in control to more in the way of, either a westerly flow or the trough idea. So nothing in stone at all in my view just yet.

Below are the 3 main anomly outputs I use, the morning issue from EC-GFS and below that NOAA. I collect/check these every 24 hours and there is not enough total consistency across all 3 to give a confident 6-10 day assessment other than there is neither any signal to a cold outburst of any duration nor a heat spell.

But judge for yourselves with the two links below

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

The 8-14 day chart keeps the idea of a broadly westerly flow but still with a small 'signal' for some +ve height anomaly WSW of the UK.

On top of all this we have the probability of the latest Hurricane getting into the mix within the 4-6 day time scale so even less confidence in just what the upper flow, let alone that at the surface, may be post 6 days.

[knocker]

It does rather depend on what anomalies one takes, and given the current scenario caution is advised anyway, but certainly last nights NOAA and this morning's GEFS and EPS would not agree on firming up on low pressure taking a hold which is slightly contrary to this morning's det. outputs.

They all have a negatively tilted trough to the north of the UK and another trough in the western Atlantic allowing the Azores HP to push north a tad. The upshot of all this is a strong westerly upper flow, perhaps even S of W portending systems tracking NE on a strong jet.

EDIT

I see John has already replied.

Edited September 22, 2016 by knocker

[Nick F]

06z GFS whips up an intense depression early next week from the remnants of Karl - which gets swallowed up by the upper westerlies then falls under the developmental left exit of a strong jet where it deepens as it heads toward the Faroe Islands.

Gusts of 80mph+ for NW Scotland next Tuesday evening

Dragging in some quite warm air ahead of the system, so could see some warm temps to lee of Pennines perhaps?

00z ECM had more of an open wave formed from the remnants of Karl moving NE and clipping northern Scotland Tuesday afternoon, with tight isobars on the southern side of the wave likely to bring gales or severe gales for northern parts.

Obviously a good deal of uncertainty with the track of ex-Karl this far off, though would favour a track north of Scotland for now.

 

Edited September 22, 2016 by Nick F

[Man With Beard]

Now that's what I can a scatter:

This is London for the last four runs.

I'm guessing there's going to be a very, very steep temperature gradient this time next week as one goes north to south.

[johnholmes]

Looking at the possible development for the ex hurricane I would expect that it will tend to deepen again as it gets into the jet flow. How much will depend on its position within the jet. As Nick F shows above if it does come in that position then it will deepen. Its track is again up to how it interacts with the jet, indeed how the jst develops is not yet clear with the 00z and 06z runs showing how much difference there could be. Best estimate this far oft for its track is somewhere between the Faroes and the north of Scotland. Probably near enough to NW and N Scotland for severe gale force gusts at least. Interesting to see just what does happen to Karl.

Edited September 22, 2016 by johnholmes

[Summer Sun]

Hard to have much confidence going into next week take UKMO and GFS at t144 as an example

 

[mb018538]

Yes indeed summer sun. No agreement even out to day 5, so don't even bother further on yet. What happens in the next week will shape the 7-10 days beyond that.

[Frosty.]

9 minutes ago, mb018538 said:

What happens in the next week will shape the 7-10 days beyond that.

Not necessarily

[knocker]

The GFS has the remnants of Karl being absorbed by the main Atlantic depression and not actively engaging with the jet which is a tad more advantageously orientated vis the UK although still wet and windy on Tuesday with associated fronts and then a very unsettled westerly regime.  But it ain't done and dusted yet.

 

Edited September 22, 2016 by knocker

[Frosty.]

Saturday looks fine and warm with sunny spells across most of England and Wales with subtropical air pumping up across the uk with temps into the low to mid 70's F, especially for the southeast..it will be feeling summery according to the Gfs 12z.

[Frosty.]

According to the GEFS 12z mean, next week shows high pressure close to the south will have the upper hand with benign pleasant conditions, at least across the southern third of the uk, rather more changeable further n / nw.

[mb018538]

ECM shows Tuesday and Wednesday turning pretty warm, before things turn very unsettled and cool. The first blast of proper autumn weather if it verifies!

[DR(S)NO]

2 minutes ago, Frosty. said:

According to the GEFS 12z mean, next week shows high pressure close to the south will have the upper hand with benign pleasant conditions, at least across the southern third of the uk, rather more changeable further n / nw.

A bit like the majority of the Summer then Frosty...

[Frosty.]

1 minute ago, DR(S)NO said:

A bit like the majority of the Summer then Frosty...

True DR(S)NO.. 

[Matthew.]

The ECM op says October is going to start cool. A very different possibility to the warm recent months. 

Edited September 22, 2016 by Matthew Wilson

[Frosty.]

The Ecm 12z shows subtropical air pumping northwards across the uk for saturday with a fine and warm day across England and Wales with temps potentially into the mid 70's F, with plenty of sunshine further s and e..it becomes fresher and more changeable for sun / mon before another pulse of warmth spreads across the south of the uk during tues / wed But then autumnal weather arrives with a vengeance from the n / nw during the second half of next week onwards and becoming much cooler..first half looks summery further south though before that possible change..

[ANYWEATHER]

Evening All. The models show a volatile outlook in the days ahead , certainly detail will be illusive in the medium term but some Eyebrow raising synoptics in the days ahead" Makes a change from the boring synoptics of the last two Qctobers!!

[knocker]

The ecm also phases the remnants of Karl into the Atlantic depression and tracks the lot NE on the jet with the low 976mb just east of Iceland 12z Tuesday with frontal systems crossing the UK with moderate rain and very wind with gales in the north. Temps immaterial but slightly above average. 48 hours later is a repeat except the depression is closer to Scotland bringing some quite severe conditions to Scotland and very windy for the rest of the UK. Hopefully that won't verify.

Edited September 22, 2016 by knocker

[damianslaw]

A very changeable outlook with the atlantic forecast to ease into third gear thanks largely due to the influences of ex-hurricane Karl - at this stage it is far too early to call how thus feature will interact with the jet, though models are consistent in placing it on a NE path inbetween Iceland and Scotland resulting in a surge of tropical maritime air across the country. Before then we have a bout of heavy rain for the NW to contend with on Saturday, whilst the SE looks like having a predominantly fine few days ahead with further warmth especially on Saturday.

Longer term, the models remain consistent with the suggestion of a much cooler spell of weather with the trough anchoring down from the NW, and cold air that will pooling over Greenland in the days ahead making its way towards our shores. Met Office 6-30 day forecast also suggestive of quite a chilly start to October with temps average or a bit below. 

[legritter]

Tonights ECM  seems to be firming up on some very autumn proper synoptics ,pretty tame untill we reach the further outlook .

Still looks like more northern and western parts could see the lions share of gales and rain ,but we all could turn chilly and wet if low pressure digs south to our east , So perhaps our weather becoming less boring and of course something for many of us to have a moan at ,cheers gang .

[Frosty.]

13 minutes ago, legritter said:

Tonights ECM  seems to be firming up on some very autumn proper synoptics ,pretty tame untill we reach the further outlook .

Still looks like more northern and western parts could see the lions share of gales and rain ,but we all could turn chilly and wet if low pressure digs south to our east , So perhaps our weather becoming less boring and of course something for many of us to have a moan at ,cheers gang .

Good post legritter..yes Autumn proper could arrive later next week onwards if the Ecm 12z is anything to go by...T+240 looks unseasonably chilly!

[knocker]

Despite the death throes of Karl the 6-10 anomalies are not in bad agreement this evening. Maintaining the negatively tilted trough centered to the north and orientated into eastern Europe with Azores HP to the south west holding it's position with a weak trough in the western Atlantic. So essentially we are looking at an upper flow from a westerly quadrant (the GEFS tries to drag some some warmer air in to the south) which portends a N/S split with systems trackiing NE and the south perhaps with more influence from the Azores. Temps in general around average with the usual latitudinal variations.

Edited September 22, 2016 by knocker

[Frosty.]

The Ecm 12z ensemble mean certainly paints a more autumnal picture towards the start of october..especially across the north with lowering heights to the nw / n and a more suppressed Azores high..I'm hoping that October will bring some early cold shots from the nw / n!