Model Output Discussion 31/07/14 onwards.

[ANYWEATHER]

So what has been a lovely summer ,August has done us a bad deal , no point in arguing that fact the month will go on a negative note for heat lovers .....

[phil nw.]

Looking at the T120hrs charts suggests that most of us may yet squeeze a decent weekend out of the modeled ridge.

 

The charts showing the Atlantic low with it's attendant fronts closing in to the west overnight Sunday now.

We lose the chilly northerly by the end of Friday and as winds drop off temperatures have a chance to recover with values back up towards 20c in the south in the late Summer sunshine.

 

A window of fine weather to enjoy over the BH weekend before the Atlantic south westerlies move in at the start of next week which will see more normal temperatures but with changeable conditions.

 

The NOAA 6-10 day anomaly chart above indicating the pattern going into next week

 

 

 

 

[Frosty.]

Tonight's Ecm 12z op shows an improvement by the weekend as we finally lose any remaining influence of the scand trough and a ridge of high pressure builds in from the west bringing drier and sunnier weather with lighter winds but still with chilly nights, however, by the end of sunday, low pressure is cranking up to the west of the uk as the ridge subsides..this takes us into BH Monday or should that be BH Moan day since it turns wet and windy from the west, not much change by tuesday either with low pressure still over the uk but a bit further east, at least temperatures recover early next week with warmer upper air wrapped up within that low. The rest of next week stays unsettled, especially further north, the south seeing weak pressure rises with some longer dry and brighter spells but then another trough swinging down from the north west later next week with a dig of cool, unstable polar air, much as we have now...pretty autumnal in my opinion.

[knocker]

Latest for the middle f next week.

 

The anomaly charts are still showing broad agreement  Trough east/west across the UK, warm air NE North America and cold pool over Greenland.

 

Leading to cyclonic development over the UK although the GFS is more bullish with the low than the ECM so by Thursday there is the hint of the Azores ridge edging in from the SW. Temps are about average with the usual caveat that it may be quite warm the further south you are.

 

Further ahead both the GFS and ECM are going for a more homogeneous zonal flow and developing the Azores high but that's in lulu land at the moment.

 

 

[knocker]

This morning’s GFS for the BH weekend

 

Saturday

 

Low 992mb mid Atlantic and another  1002mb Oslo with a ridge just to the west of the UK. The east of the UK is under the influence of the Oslo low with the west the ridge. Temps not brilliant mid to high 60s but much lower in northern Scotland.

 

Sunday

 

The low now 998mb 400 miles west of Ireland with associated fronts much closer but high pressure is the order of the day for the UK. Temps around 70F in south east but 60F in northern Scotland.

 

Monday 1800z

 

Low now 995mb Irish Sea and a generally foul day for all of the UK. Temps struggling to mid 60s in England and mid 50s in northern Scotland.

 

Outlook

 

This apparent slowing down of  it’s surface evolution has a knock on effect into next week and the intense low originally forecast for Wednesday is no more and the chart on Saturday is an indicator for the weekend and rather puts the kybosh on the idea of a developing Azores ridge. But hey this is one run, one model, so just mention it out of interest considering the rapid change in the last 24 hours.

Edited August 20, 2014 by knocker

[IDO]

FI remains post Monday's LP systems. There has been lots of variations on how much energy arrives with the LP and consequently how these potential different LP masses react with the in situ flow. No different this morning. The LP on the GEFS has 100% support but how deep it lands, how fast it leaves and it's exit strategy remain uncertain.

 

This morning's London ensembles have the LP departing faster than last night with the hi-res switching camps to the quicker route:

 

0z: yesterday"s 12z: 

 

So the GEFS by D8-9 are all over the place with three equal clusters offering a variety of solutions:

 

N/S split:  Transient ridging:  LP slowly moving east: 

 

With variations within those themes. GEM goes in the n/s cluster: 

 

ECM maintains the westerly flow though less active than recent runs: 

 

Into the GEFS and it is not till the first few days of September till there is a more concerted effort to build pressure over the UK, with about 33% going on by D16 to develop some interesting charts. One to watch to see if this can trend.

 

Sunday is the least coolest day for the BH weekend but with just average temps at best and those for the south. Saturday and Sunday look mainly dry, but Monday looks a washout with the low and its accompanying warm front.

 

The developing short wave feature tomorrow in Scotland edges south over 36 hours bringing heavy rain to the north but should be less of a problem the time it hits the south:

 

Edited August 20, 2014 by i'm dreaming of...

[Thermohaline Conveyor]

 

During the last week low pressure has remained stubborn across Scandinavia with high pressure strong and assertive to the West & North West across the North Atlantic ridging into the Arctic. This set-up ensures that cold air usually locked up across Northern latitudes (the Arctic region) is unlocked and given permission to flood South.

Friday: Sunshine & Showers – Most Frequent In The East/Driest In The West

The ECM mean above continues to forecast low pressure anomalies to the East and North East of England, Scotland and Wales across Scandinavia and high pressure anomalies to the West and North West across the North Atlantic. Friday 22nd August will remain on the showery side of the low with a continuation of the variable cloud cover, sunny spells and enough heat from the sun to spark off a few heavy showers, possibly heavy and thundery. Temperatures will remain on the cool side everywhere, although there is a possibility of 20ºC in the South which is close to average.

Saturday: Drier & Brighter Across West England, Scotland and Wales, A Few Scattered Showers In the North & East

The ECM data above shows higher pressure anomalies beginning to tentatively nudge into much of Western England, Scotland and Wales during Saturday 23rd August with drier, brighter and marginally warmer weather expected. Low pressure is still present across East Anglia, Eastern England, North East England and much of Eastern and Northern Scotland with the risk of a few isolated showers. What is noticeable is that the air will begin to be sourced from a milder South West direction across Southern and Western parts with temperatures ranging approximately 17ºC to 20ºC, just below average. Cooler across the East/North East.

Sunday: Generally Dry to Start With Variable Cloud & Sunny Spells – Cloud Thickening From The West Later With Showery Rain by Evening

The ECM data for Sunday looks encouraging as a temporary ridge of high pressure continues to build across much of England, Scotland and Wales. It will be a day of variable amounts of cloud, some good sunny spells and staying mostly dry. A feature that is particularly noticeable and is being monitored for the potential of severe weather is the area of very low pressure to the West and South West of Ireland; which will edge closer to South West/West England, Scotland and Wales during Sunday Evening. This area of low pressure will bring thickening cloud into Western areas toward late afternoon and evening with patchy rain beginning to spread East later on through the period.

Monday: Potential for Wet & Windy Weather, Unsettled With Spells of Rain Clearing To Sunshine & Heavy Blustery Showers – Risk of Thunderstorms.

That brings us onto a sneaky glimpse at Monday. ECM data consistently models the deep area of low pressure to the South West of Ireland on Sunday to begin to make inroads across all of England, Scotland and Wales on Monday. An unseasonably unsettled day can be expected with bands of rain sweeping East, winds unseasonably strong with coastal gales and the added risk of scattered thundery showers following on from the passing of the warm sector.

In general the weekend is an improving one for much of South West, West and North West England, Scotland and Wales with drier weather, sunny spells and a more limited risk of the odd isolated shower.

Further North and East across England and Scotland there will be more in the way of cloud, some occasional sunny spells and a higher risk of scattered showers – improving by Sunday.

Sunday generally looks rather pleasant through the morning and afternoon before cloud thickens from the West and South West and patchy rain begins to move in by early evening.

Temperatures remaining marginally below average and not feeling at all bad in the South. Cooler in the North. Wet and windy by Monday with much milder air spreading in.

[knocker]

The GFS and ECM anomaly charts for the end of next week basically agree with the trough lying to the NW of the UK The jet zips around this upper low and south of the UK delaying for the moment any major push by the Azores ridge, So still looking at a cyclonic analysis but not on the scale of the GFS ops. Not much point in further detail at this range and this is just a dabble.

 

[phil nw.]

The GFS and ECM anomaly charts for the end of next week basically agree with the trough lying to the NW of the UK The jet zips around this upper low and south of the UK delaying for the moment any major push by the Azores ridge, So still looking at a cyclonic analysis but not on the scale of the GFS ops. Not much point in further detail at this range and this is just a dabble.

Yes changeable westerly type pattern is how i would describe itand seems to be well agreed by the outputs next week Knocker.

Meanwhile the T84hrs fax shows the modest and transient(48hrs?) ridge moving in by Saturday

 

which should be just enough to dry things out with some sunshine but with cooler air still aloft no great heat but perhaps low 20'C for some further south.

 

After that the winds back towards a somewhat warmer south west ahead of Monday's modeled low.This will see temperatures nearer to normal but with rain or showers moving through at times.

[Thermohaline Conveyor]

Monday's area of low pressure is proving troublesome not only in the phasing, evolution and tracking but also the severe weather potential it could bring ie. wind, rain and again the potential of a few thunderstorms.  It needs close monitoring.  ECM-mean takes the centre of the low through Northern England with the strongest pressure gradient to the South across England and Wales, GFS operational offers up numerous solutions on the intensity of the system, the tracking and the exact evolution ie. A single primary low or the vigorous development of a secondary low within the parent low.  Quite complex but one thing is for sure Monday is looking rather Autumnal.

[knocker]

Monday's area of low pressure is proving troublesome not only in the phasing, evolution and tracking but also the severe weather potential it could bring ie. wind, rain and again the potential of a few thunderstorms.  It needs close monitoring.  ECM-mean takes the centre of the low through Northern England with the strongest pressure gradient to the South across England and Wales, GFS operational offers up numerous solutions on the intensity of the system, the tracking and the exact evolution ie. A single primary low or the vigorous development of a secondary low within the parent low.  Quite complex but one thing is for sure Monday is looking rather Autumnal.

 

Sorry but I don't understand " GFS ops offers up numerous solutions" bit. Isn't the ops giving it's solution or am I missing something?

[mushymanrob]

id advise against pinning too many hopes on fi predictions of a mini heatwave, the noaa anomaly 8-14 dayer is having non of it and unless it changes then id suggest itll not happen. sorry to be negetive, id prefer to call it realistic.

 

 

ps..... one of the first lessons i learned on here was NOT to take fi seriously, it appears that in desperation some are trying to overlook that snippet of advice.

[phil nw.]

Sorry but I don't understand " GFS ops offers up numerous solutions" bit. Isn't the ops giving it's solution or am I missing something?

Certainly different solutions on the 06Z gfs ens members Knocker.

 

I would think that's what the op meant?

[knocker]

Certainly different solutions on the 06Z gfs ens members Knocker.

 

 

I would think that's what the op meant?

 

Ah right another senior moment. I see the ops (meaning not the ens) at 12z has the low 1001mb over Nothern Ireland and pretty wet but not that windy at 12z Monday.

Edited August 20, 2014 by knocker

[mhielte]

Monday looks and absolute horror show on the 12z GFS. I can deal with a bit of rain but under these temperatures, in August?!

 

 

That chart above shows a ridiculous contrast in temperatures over northern France as well, with some heavy rain to blame.

 

 

As Thermohaline Conveyor alluded to earlier, there is the prospect of a few thundery showers developing behind the front, chiefly in the south and west. CAPE + LI charts show a marked upgrade in potential compared to yesterdays 12z, which limited potential to Ireland only. However I can't shake the 'straw clutching' vibe off with this. It's all we got!

 

 

Deep into FI, the early September burst of warmth is still there, but it has been pushed back a day or so with a rather dreadful weekend to round off August.

Edited August 20, 2014 by mhielte

[Captain Shortwave]

Well the ECM has throw a very strange solution even at 4 days out

That second low in the Atlantic was not on its previous output or on the UKMO/GFS/GEM output this afternoon.

The consequence is a rather different chart for Monday

Slack, probably still with some rain around but not the wet and windy weather the other outputs suggest. Unless the ECM has thrown an absolute clanger, this drops certainty for the second half of the weekend and into next week.

 

ECM taking the mickey or onto something?

Edited August 20, 2014 by Captain shortwave

[mhielte]

Well the ECM has throw a very strange solution even at 4 days out

That second low in the Atlantic was not on its previous output or on the UKMO/GFS/GEM output this afternoon.

The consequence is a rather different chart for Monday

Slack, probably still with some rain around but not the wet and windy weather the other outputs suggest. Unless the ECM has thrown an absolute clanger, this drops certainty for the second half of the weekend and into next week.

Good catch CS,

 

ECM out on its own with its t+120 evolution. Very strange!

 

Conditions quieten down through Tuesday and Wednesday with high pressure influencing briefly before the Atlantic looks set to return for the latter part of the working week.

 

 

GFS has us under slack conditions Tuesday before a low skirts along the south coast on Wednesday, with the majority of the rain staying over the channel/continent.

 

GEM isn't having any of it Comfortably the most unsettled model output for this week, with deep lows waiting in the wings later next week, with only the briefest of respites on Wednesday.

 

Navgem looks good, but tenuous IMO

Quite a bit of variance it must be said, with ECM throwing an interesting spanner in the works for the beginning of next week. Anything after t+120 is pure speculation with a lot of scenarios on offer *not all bad either!*

 

One could argue that the trend for increasing high pressure influence towards the south is there, albeit in FI.

Edited August 20, 2014 by mhielte

[Frosty.]

 

 

ps..... one of the first lessons i learned on here was NOT to take fi seriously, it appears that in desperation some are trying to overlook that snippet of advice.

I don't agree mushy, FI is a good place to spot potential trends, sometimes the models pick up on a signal for a pattern change from a few weeks out and occasionally it comes off. I think FI is a crystal ball to look for longer range heatwaves in summer and freezes in winter..when the reliable timeframe is dire, FI offers hope of better things to come.

[knocker]

Yes CS the anomaly has an upper low and has the main trough to the east and a ridge to the west which probably ex[plains the surface evolution. Await the ens me thinks

Edited August 20, 2014 by knocker

[Frosty.]

Looking into the all important BH weekend, whilst saturday sees a ridge of high pressure building in, it's sunday which is the highlight with a dry and sunny day across much of the uk with light winds, after a cold start, temperatures recovering and a pleasantly warm afternoon with 18-21c being the expected range..turning wet and windier from the west on sunday night and into BH monday, monday looks like the worst kind of holiday with outbreaks of rain, and in the persistent and heavy bursts, feeling decidedly on the cold side with 8c as a maximum, but generally low to mid teens c and high teens for the southeast..sunday is the day to enjoy.

[Man With Beard]

Well the ECM has throw a very strange solution even at 4 days out

That second low in the Atlantic was not on its previous output or on the UKMO/GFS/GEM output this afternoon.

The consequence is a rather different chart for Monday

Slack, probably still with some rain around but not the wet and windy weather the other outputs suggest. Unless the ECM has thrown an absolute clanger, this drops certainty for the second half of the weekend and into next week.

 

ECM taking the mickey or onto something?

When the ECM goes off on one at T168 I kind of ignore it, but if a change is afoot at T120 I always expect to see it first on the ECM. I don't actually consider the GFS to be that different from next Tuesday onwards, just with a minor disturbance mixed in, but the principle of building heights to the north of Scotland is also there. An interesting 24 hours of model watching ahead, perhaps?

If ECM did verify, 25C not unlikely by the end of next week in central/eastern parts.

[mushymanrob]

I don't agree mushy, FI is a good place to spot potential trends, sometimes the models pick up on a signal for a pattern change from a few weeks out and occasionally it comes off. I think FI is a crystal ball to look for longer range heatwaves in summer and freezes in winter..when the reliable timeframe is dire, FI offers hope of better things to come.

i dont disagree karl, i said fi shouldnt be taken seriously and i dont think anyone does do they?the point is that when something in fi gains support it no longer becomes fi. so yes, look for the trends, spot something new, but dont place too much faith in it varifying, if that was half accurate then forecasts would be alot more accurate long term.

[ANYWEATHER]

Fantasy island is just that'' no trends can be made from that, Models agree a very unsettled spell of weather in the near future.......

[damianslaw]

Ooh its a chilly synoptical pattern for the rest of the week - the kind of charts I'd be very happy with in the depths of winter - indeed almost perfect a locked in northerly with arctic air maxima would be held down at freezing levels with the promise of a snowy frontal feature tomorrow then back to clear skies and deep frost for the weekend - then a major snowfall from the west, alas its August and instead just chilly sums it up.

 

However, pleasing to see the ridge looks like holding for Sunday keeping the frontal attack at bay. Monday could be decidedly chilly in the north with an onshore wind and heavy rain which will suppress air temps - the warmer air will take its time to filter through the cold layers which will have entrenched themselves for some time.

 

Longer term - mmm the models look a little uncertain but the theme appears to be an unsettled one with the atlantic ruling the roost but perhaps heights both to the north and south will cause the trough to unbuckle over the country becoming a slow slack feature - for some parts more so the NW and West a very wet affair could be the end result, southern and eastern parts may end up with some decent warmth and dry weather.

[Polar Maritime]

Well I agree with Frosty, Where else in the Models are you going to spot a new trend/pattern change in it's first instance ? 

Edited August 20, 2014 by Polar Maritime