Model Output Discussion - 31/8/14 Onwards.

[Ross Andrew Hemphill]

I know its deep in Fl but a sub 940mb low in September is just wow!

 

Edited September 8, 2014 by Ross Andrew Hemphill

[knocker]

I think you will find that's a tropical storm 91L they are running with. Charts from the GFS Tropical. 931mb is it's lowest pressure.

 

It's loaded them out of sequence

Edited September 8, 2014 by knocker

[Frosty.]

There has been no real change in the overall picture since yesterday, the models are still showing settled and pleasantly warm weather all this week with high pressure in control, pressure then falls across the south / sw with a trough edging north bringing showery outbreaks by the weekend to the SW & SE and into next week it's the south of the uk which looks most unsettled, high pressure holding to the NE keeps many northern areas fine and warm.

[summer blizzard]

High pressure rules through the high resolution timeframe.

 

[Milhouse]

Winds swinging round from a northeasterly midweek to a easterly by Sunday bringing in added warmth raising temps to the mid 20s in the Midlands.

 

 

[Polar Maritime]

GFS continues from this morning to show the Atlantic biting back by just after mid-month, With some impressive lows further into the run.

 

[IDO]

Very strong support from the GEFS that a change is on its way from around D8 as the Scandi high edges east. The mean:

 

D8:  D9  D10 

 

So the Atlantic trough will migrate to cover the UK. GEM agrees at d10: 

 

This morning's ECM mean also suggesting this:  

 

GFS op FI keeps  us under the trough till D16 with the polar lower heights moving towards NE Canada and reinvigorating the westerly flow. The op looks a wild one, but with the block to the east it is feasible (and about 20% support in the GEFS):

 

 

Early days for that with the GEFS unsure how much energy feeds the trough in the early stages.

 

So about 7-8 more settled days from the Scandi high and with a plume of African uppers from Saturday over Europe potential from Sunday-Tuesday for a warm feed for the South, S/E, Midlands:

 

 

 

[Milhouse]

Above average upper temperatures hanging on till the end of the run on the ECM mean. Remaining warm for the next 10 days judging by the GEFS mean too.

 

 

[Milhouse]

ECM 12z continues to pump a lot of very warm air in our direction for the start of next week. Low cloud and mist would peg temperatures back for NE England and England. Summerlike temperatures inland though.

 

[Frosty.]

Tonight's GEFS 12z mean just outside the reliable timeframe shows increasingly warm weather being drawn into the uk from france but at the same time, pressure begins to fall in the south by the end of this week as a trough arrives from the southwest, the northeast of the uk holds on to the fine and warm weather for longest before the scandi high eventually drifts further away. For the rest of this week it looks anticyclonic with warm sunny spells and light winds, nights locally chilly where skies clear but the trend is for days & nights to slowly become warmer but turning unsettled from the south with showery weather eventually reaching all parts of the uk, some of the showers are likely to contain hail and thunder and it would be feeling humid. By the end of the run it turns much cooler from the northwest with an atlantic regime gaining the upper hand.

[Blessed Weather]

I think you will find that's a tropical storm 91L they are running with. Charts from the GFS Tropical. 931mb is it's lowest pressure.

 

Well spotted Knocker. Thanks to this model thread and posts such as yours I've enjoyed the learning experience of how these tropical storms impact the UK weather. We had ex-Bertha parking itself to the NE of the UK and being largely responsible for bringing us a disappointing August. ex-Cristobal ran further north and arguably helped usher in the settled weather we've been enjoying of late. And now the models are suggesting that (in FI) another ex-tropical storm will maybe be the catalyst that allows the Atlantic to finally break through with a vengeance. Here's some charts showing how this might happen.

 

First today's Atlantic chart from the US NHC showing the fledgling storm and in their view with a >50% chance of developing into a tropical cyclone over the next 5 days.

 

 

Today's GFS 12z picks up the storm and shows it entering stage left on Saturday 20th Sept. Finally by Wed 24th Sept a direct hit on the UK. A long way to go and with the fickle nature of tropical storms, it will no doubt end up differently. But an interesting one to watch.

 

 

[Frosty.]

Towards the end of tonight's Ecm 12z op run the anticyclonic spell is crumbling as the scandi high drifts further away eastwards, it's then a trough just to the west which is in the process of taking over, however, it's very warm and humid by mid month, especially across the south of the uk with an increasing risk of heavy showers and T-Storms extending north and east.

[Polar Maritime]

Out to the 18th the ECM also shows the Atlantic breaking through.

 

[BLAST FROM THE PAST]

 

Lol, 1 mile high waves in the Atlantic.....good old GFS

 

BFTP  

[ANYWEATHER]

The long way to unsettled weather looks likely next week, but before then some fine Autumnal weather to be had........

[knocker]

NOAA is playing silly buggers tonight by putting the wrong date on.

 

Anyway the anomalies are showing low Hudson bay area with the high Scandinavia but ridging east/south east. The through to the south  west is the principle affecting the UK ( activated a tad by the jet being forced further south by the low Hudson Bay?) thus bringing shallow low over the UK.

Edited September 8, 2014 by knocker

[phil nw.]

It seems we will squeeze another week or so of dry and warm weather before any real change.

Models showing the Atlantic trough edging closer to western districts early next week would suggest some showery rain then moving to the south west.

it may not herald a change to an active Atlantic just yet though Naefs beyond day10

http://www.meteociel.fr/modeles/naefs_cartes.php?code=0&ech=348&mode=0&map=&runpara=

Still showing a relatively quiet Atlantic jet with low anomalies.

[knocker]

Yes  NOAA 8-14 still showing strong pressure to the east/north.

 

[knocker]

ECMWF 12z slower w/91L development but still gets to 960-mb by Day 9 as it recurves out to sea. WMO-MSLP: pic.twitter.com/kiNVqPIU2x

Edited September 8, 2014 by knocker

[Captain Shortwave]

The GEM this morning is the first to suggest that a potential breakdown could fail

This comes from the low near iberia deepening earlier than in previous runs and allows the high over Scandinavia to start backing west again. 

UKMO also sees this idea

 

GFS is slower, but again the pattern struggles to break down with low pressure becoming cut off again.

 

The GFS ens are showing that the Atlantic will struggle with the prefered patter being heights to the north and low pressure to the south, even out to day 10 and possibly beyond.

 

Whilst this time period was ear marked for a breakdown, I would not be surprised if the breakdown just simply doesn't happen. Just like the FI breakdown which was mentioned for this week.

[Polar Maritime]

Some very unsettled/cool charts showing out in the run this morning, With Hight's pushing up into Greenland.

 

 

[Frosty.]

The GEFS 00z mean shows no sign of a chink in the anticyclonic armor until early next week, indeed, the high intensifies later this week and the fine and warm weather continues throughout next weekend, the far north stays settled until the end of next week but for most of the uk, next week shows a gradual descent into more unsettled weather from the south as the scandi high drifts away further east and a trough pushes north from france bringing warmer and increasingly humid air with showers becoming heavy and widespread with thunder but with sunny periods too, temperatures by early next week could be into the mid 20's celsius across southern uk, nearer low 20's c further north.

[IDO]

The GEM this morning is the first to suggest that a potential breakdown could fail

 

 

This comes from the low near iberia deepening earlier than in previous runs and allows the high over Scandinavia to start backing west again. 

UKMO also sees this idea

 

 

GFS is slower, but again the pattern struggles to break down with low pressure b

 

The GFS ens are showing that the Atlantic will struggle with the prefered patter being heights to the north and low pressure to the south, even out to day 10 and possibly beyond.

 

 

Whilst this time period was ear marked for a breakdown, I would not be surprised if the breakdown just simply doesn't happen. Just like the FI breakdown which was mentioned for this week.

 

 

We have a pattern change upstream and all models agree on this. A vortex is sinking into the US around D7 and this will amplify this part of the NH and send waves downstream:

 

 

 

A weak Atlantic ridge will build in front of the US trough and push the current Atlantic trough towards the UK. GEM as it normally does makes more of the Atlantic ridge and cuts off the trough allowing the Scandi ridge to retrogress to the north of the UK for a tentative link with the Atlantic ridge:

 

GEM:   GFS: 

 

GFS currently does not on the op, although there are a cluster in the GEFS going this way. That US vortex will then spill east and what happens with the Atlantic trough, cut off low will determine the initial mid-late September's weather. GFS has the op sending that US vortex energy into a UK trough whilst GEM has the  jet further north with the energy transported to our north. We still have the cut off low to the SW on the GEM but it is not being fuelled by the Atlantic so it is more showery compared to the washout FI GFS op.

 

Just to make it interesting ECM is caught between the two at D9: 

 

A few more runs needed to see which direction this change will take.

Edited September 9, 2014 by i'm dreaming of...

[phil nw.]

Yes the 00z charts continue to suggest the heights over Scandinavia will prove quite stubborn,even into next week.

The Atlantic coming against the block showing no signs of breaking them down,indeed as already mentioned signs of rising heights regressing towards Iceland over the top of a cut off low to our south.

It may well be tropical storm activity will shake the pattern up later, as shown in the later GFS Op run, but this is still to far away to be anything other than a possibility.

[Frosty.]

Yes, a breakdown from the south next week is a good bet, could become very warm and humid for a time too..more like summer than autumn me thinks.