Model Output Discussion - 1st June 2015 12z--------->

[Polar Maritime]

Then again isn't that the scenario that was being modelled for this coming week about 4 or 5 days ago? However now we're nearer the timescale tomorrow's frontal wave looks significantly weaker in the S/SW rather than a widespread heavy rain event and it's to be followed by a largely settled and possibly very warm week.

 

This was my musings for this coming week from the 6z 4 days ago. No 'widespread heavy rain event' was on the cards, Not much change only the main front being a few miles further South, Which is to be expected at the time-scale. With Tuesday being the driest nationwide day, Yes the extreme S/E may touch 26c by the end of the week..

A weak Low sitting over the UK pushing bands of showers possibly merging to give longer spells of rain in places as they cross the country.

 

Edited June 21, 2015 by Polar Maritime

[Man With Beard]

Interesting charts again this morning, very slightly in favour of a summery scenario from Tuesday onwards, with potential variance in latter stages between a hot spell and something more average - no real sign of anything particularly below average except in the NW.

The big theme, though, looks like being a European heatwave to end the month. Anomalies look strong and favourable for that. The question for the UK is - where will the northern boundary of this fall? Certainly the SE looks in good position to benefit from time to time. There may well end up being a line running WSW - ENE, with a very steep temperature gradient - perhaps even a 10C increase over a 300 mile stretch as one heads N to S as the final week in June begins. This line could yet be centred anywhere from the Channel to the Midlands, judging by current charts. Mushymanrob's "buckle" could allow heat to move further north too, as it would change the gradient to more of a SW-NE one, at least temporarily - not possible to predict this one yet but a very viable option.

Edited June 21, 2015 by rjbw

[Captain Shortwave]

The 06z GFS seems to be a pretty poor end game for the UK into week 2, with the jet really powering up with a huge squeeze over the UK, this develops some pretty potent secondary lows which could bring torrential and possibly thundery rain driven by the strong jet and the high thermal gradient. The far south seems to remain drier though.

 

Lets hope the GFS has gone on one of those zonal adventures.

Edited June 21, 2015 by Captain shortwave

[Polar Maritime]

Yes the 6z really ramps up the Atlantic into the turn of the Month. 

 

[Harsh Climate]

From looking at the charts I see one thing and one thing only, Very warm to hot air gradually filtering in from the south as we head through July. Over the last week or so out in FI i have seen a trend of the hotter air towards the med gradually filter north and by the end of June engulfing the whole of mainland europe. The question to me has been will this hot air mass cross the channel and allow us our first heatwave of the summer?  I think as we head into July the awnser is now yes as the jet stream seems to progged to head north, allowing high pressure from the south to fill the void and creep ever further north.

 

If that isn't good enough I think as things heat up it will quickly go off with a bang, with some spectacular thunderstorms developing in places not to mention imports crossing the channel. The reason I say this is because the hotter weather won't be the result of a big high pressure slap bang over us capping all convection, it will be from the jet stream weakening and heading north allowing shallow ridges of high pressure to creep ever further north towards us bringing the hot air with it. Once the hot air is established we will essentially be in a COL (a breading ground for thunderstorms when you add heat) and with the jet streams influence always knocking on our door step from the north/northwest any undercutting of cooler air/breakdown IMO would lead to BIG thunderstorms, perhaps severe .

 

Ovcoarse that is only my opinion but I am convinced this JULY will be a month to remember due to HEAT and THUNDERSTORMS

Edited June 21, 2015 by Harsh Climate

[phil nw.]

Very difficult to say where and when the best of any bright and warmer interludes will occur over the next 2 weeks.

The jet continues to run across our latitudes which means we rely on brief ridging between the Atlantic fronts moving in from time to time.

A suppressed Azores high means a generally flat Westerly flow with breezy and rather cool Summer conditions with again areas furthest south seeing the best of any warmth.

Not great for heat lovers but still some decent conditions available at times for outdoor activities.

It just means watching the daily forecasts if planning anything in this rather changeable pattern.

[Milhouse]

The 6z might bring the Atlantic in briefly to give a very unsettled few days but by the 1st July we already have high pressure building back across the south.

 

 

With a mean like this there is plenty to be upbeat about as we enter July. It shows us cutting off the NW flow and entering a much more favourable position for high pressure to build across the UK delivering some very warm conditions. The mid 20s are getting easier to achieve now that we are approaching July.

 

[Frosty.]

The Gfs 6z through low res turns into a BEAUTY across the south / southeast of the UK with high pressure building in and soaring temperatures into the 80's F. For what it's worth, I think there is a very good chance, it will be great for Wimbledon if it does.

[Cheshire Freeze]

The Gfs 6z through low res turns into a BEAUTY across the south / southeast of the UK with high pressure building in and soaring temperatures into the 80's F. For what it's worth, I think there is a very good chance, it will be great for Wimbledon if it does.

 

Are we really getting that desperate that we're looking into deep FI for something more akin to midsummer? I think it's slowly beginning to dawn on people that the end game is likely to be a spell of wet and unsettled weather. Still, I have a sneaky suspicion that we'll see a rather notable spell of warmth and thunder before July is out...

Edited June 21, 2015 by CreweCold

[Tamara]

Updating further from previous post - intended as continuity of thoughts, for clarity of progress (or otherwise) and not any lack of forum etiquette

 

The short to medium term caution mentioned in the previous post is well illustrated with an indeterminate MJO and the Global Wind Oscillation mirroring the lack of tropical forcing on patterns - with both frictional and mountain torques negative and a consequent erratic low amplitude orbit upcoming into Phases 0/1

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png

 

This signal is well reflected in NWP modelling - with a lower height anomaly in the N Atlantic sandwiched between weak heights further to the north of this, and sub tropical jet flow to the south an appropriate response to weak amplitude and indeterminate forcing GWO phases 0/1

Yes, this is indeed a contrary trend at face value to the longer term suggestions in the previous post of High pressure eventually becoming more extensive and a more settled summer pattern emerging more widely for the UK away from the south

However, in this respect it is also a very good example of where paying too much attention to intra day modelling, and making assumptive conclusions based what this output shows, and then trying to extrapolate that into longer term implications can be (and often is) hazardous and fraught with error.

 

The laddering up of the GWO orbiting through Phases 3/4 and back towards indeterminate 0/1 is a continuing willingness of an overall atmospheric shift to start singing in ever closer harmony with growing Pacific El Nino (adding westerly tendency to the atmosphere).

 

On that basis it is worth considering the upcoming modelling phase as something of a transition from  phases of low angular momentum to (overall) phases of higher tendency - and not any longer term pattern in itself

.

Such transition phases inevitably are messy and prone to forecasting uncertainties and errors

 

What happens from weak amplitude GWO Phase 0/1 is crucial to where the modelling heads in the medium/longer term. Any stalling in Phase 0/1 will certainly prolong changeable conditions - so no surprise at all to fully expect further possible "red herrings" in the modelling in the coming days. However, this masks the still likely end game - and so the possibility that the shoal of fish will change direction in mid current should also not come as much of a surprise either.

 

It remains a watching brief on a change to warmer and less changeable conditions. Putting aside the messy synoptics - the broad-brush assessment of best further south and more changeable further north and west remains the same theme as before. For the time being. The longer term suggestions though still look set to continue a gradual almost insidious theme towards some pleasant summer weather with decreasing cooler incursions from the north and greater influence from High pressure

As discussed above, the focus of Atmospheric trends continues to move away from the extended period of Spring-like low angular momentum phases that have surpressed seasonal temperatures, and into the transitional dawn period towards a Nino driven NH pattern, which, as modelled, is actively starting to build real summer heat to our south. 

 

The jet stream, picking up the seasonal temperature gradient differential as heat builds to our south and intereacts with the demise of the late season cool air pooling to our north, is augmented in the shorter term by tropical storm Bill - and this has rather exaggerated the emphasis of extended changeability to our weather.

 

For us for the time being, changeability continues to be the theme, with, as suggested might be the case, the GWO orbit set to be in an attractor state rather mired towards the vicinity of Phase 0, like a wasps legs glazed fixed to the bottom of a honey jar. But this is less than half the story - as discussed further below

 

The NW/SE split, much mentioned in recent posts, continue to be the buzz phrase, but it will take less and less to change prospects as time passes with only quite marginal adjustments to the jet stream pattern required to change coolest rain further north west into much more appealing conditions.

 

With this in mind, its worth remembering that whatever the weather, or suggested weather, this is the UK - and being a traffic light geographical crossroads for hemispheric weather patterns, and next to a vast ocean, persistent continental type summer heat is simply not our default pattern. Seasonal expectations need to be adjusted accordingly, in the same way as bitterly cold easterlies and northerlies in winter are a treat (for those so disposed to such weather) rather than a regular meal to be savoured.

 

However notwithstanding these usual applied caveats, recent posts have been discussing the requirements of the atmosphere to play ball first and foremost to give us a chance of tapping into at least *some* summer heat - and this principle primary obstacle is about to be achieved

 

As muted above, before the GWO heads into its indeterminate phase 0, it is what is happening first of all now that is of possible significance for us in the longer term.

 

A large clue wrt this, is gleaned from AAM/GWO forecasts and is the increase about to occur in positive frictional torques (in Phase 4) leading to a positive Asian Mountain torque heading into Phase 5

 

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png

 

 

This process serves to add westerly momentum tendency to the Atmosphere (Nino like) and it supports the development and persistence of an upper trough in the Atlantic and a downstream height anomaly (in contrast to the Nina like retrogressing High pressure and downstream UK/European trough). This, in accordance with more summer Nino-esque conditions, means in basic lay-person terms, a change of emphasis of airstream approach to the UK with the Atlantic not being flooded with cool air (as we have repeatedly seen), less polar maritime influence, and greater sub tropical influence

 

The absence of any subsequent loss of momentum tendency ( i.e without a follow-on negative torque/mountain torque) will indicate a break away from a suppressed jet stream (low tendency phases 1 into 2) and will signify a willingness for the upper low to our west to stall away from the UK, and encourage stronger and more resistant downstream ridging development. Such 'reverse' downstream amplification would pull the very warm uppers, gathering to the south, further and further north with time.

 

Following Phase 0, which supports the medium term modelling, means (in the hopeful absence of low AAM phase 1/2 orbit) any emergence back into Phase 3, and then after that, another repeat 3/5 orbit will ratchet up westerly tendency further and be the signal for less and less changeable weather backing away NW/wards from the UK. I think that extended ensemble data, which prematurely reacted to a warm-up about a week back, is now on a closer tack with longer term warming trends further south - to thereafter extend, eventually, further north and west.

 

This process, as discussed now and previously, is a longer term work in progress trend. But there is increasing reason and evidence to keep expecting a more wholesale change in better conditions in the UK to occur as we head further into and through July. It could well be this is the same theme that the METO are alluding to in their extended updates

[Frosty.]

Are we really getting that desperate that we're looking into deep FI for something more akin to midsummer?

I wouldn't call it desperate, even the met office think there will be periods of very warm and fine + humid thundery outbreaks for at least the south and east of the UK through towards the end of June and early July which is the main reason why I posted those 6z charts, because there is a good chance of very summery weather on the way...and there is a signal for more widespread drier than average conditions from mid July.

Edited June 21, 2015 by Frosty.

[cheese]

Are we really getting that desperate that we're looking into deep FI for something more akin to midsummer? I think it's slowly beginning to dawn on people that the end game is likely to be a spell of wet and unsettled weather. Still, I have a sneaky suspicion that we'll see a rather notable spell of warmth and thunder before July is out...

Like people do in winter you mean? I think we have a much better chance of getting some sustained warmth in July than we do sustained cold/snow in January.

Edited June 21, 2015 by cheese

[Summer Sun]

UKMO extends the high pressure into the weekend now

 

 

Whilst some showers could still makes it towards the UK they should be fairly isolated

[mushymanrob]

From looking at the charts I see one thing and one thing only, Very warm to hot air gradually filtering in from the south as we head through July. Over the last week or so out in FI i have seen a trend of the hotter air towards the med gradually filter north and by the end of June engulfing the whole of mainland europe. The question to me has been will this hot air mass cross the channel and allow us our first heatwave of the summer?  I think as we head into July the awnser is now yes as the jet stream seems to progged to head north, allowing high pressure from the south to fill the void and creep ever further north.

 

If that isn't good enough I think as things heat up it will quickly go off with a bang, with some spectacular thunderstorms developing in places not to mention imports crossing the channel. The reason I say this is because the hotter weather won't be the result of a big high pressure slap bang over us capping all convection, it will be from the jet stream weakening and heading north allowing shallow ridges of high pressure to creep ever further north towards us bringing the hot air with it. Once the hot air is established we will essentially be in a COL (a breading ground for thunderstorms when you add heat) and with the jet streams influence always knocking on our door step from the north/northwest any undercutting of cooler air/breakdown IMO would lead to BIG thunderstorms, perhaps severe .

 

Ovcoarse that is only my opinion but I am convinced this JULY will be a month to remember due to HEAT and THUNDERSTORMS

 

music to my ears...but tell me, have you and charts/data to support this?

[Daniel*]

music to my ears...but tell me, have you and charts/data to support this?

If you read the final sentence 'opinion' and I'm inclined to agree with him the models seem quite keen on a very warm start to July back in early Febraury I recall the models glued onto a cold start to March 3/4 weeks beforehand and this was predicted fairly successfully. I do know in summer verification rates are greater so even more so I think some are being too pessimistic.

[East_England_Stormchaser91]

12z again modelling a possible severe heatwave for France possibly heading into our territory too. With a few fine adjustments, I.e a push more to the north and west with this trend, it could potentially get into the "hot" category. One thing for sure is that the atmosphere would be like rocket fuel, especially with temps of 36-39c possibly the magic 40c over France!

[Frosty.]

The Gfs 12z shows a good deal of warm and fine weather for the south and especially the southeast and occasionally very warm. I think it won't take much change to the current pattern to see continental heat reach the UK in the coming weeks.

[Frosty.]

The GEFS 12z mean shows very warm continental air making significant inroads into the UK from next weekend onwards, we would see temperatures well into the 20's celsius quite widely across the UK and certainly very warm in the south and a lot of fine and sunny weather too with the Azores high ridging up through most of the uk...i'm really impressed by these charts.

[I remember Atlantic 252]

The GEFS 12z mean shows very warm continental air making significant inroads into the UK from next weekend onwards, we would see temperatures well into the 20's celsius quite widely across the UK and certainly very warm in the south and a lot of fine and sunny weather too with the Azores high ridging up through most of the uk...i'm really impressed by these charts.

 

Also Frosty, the UKMO doesn't seem to have the Atlantic crashing through

Edited June 21, 2015 by Ilovethesnow

[knocker]

Looking at the GEFS anomalies this evening is quite encouraging, Await the ECM version.

 

With ridging over the western US and western Atlantic there is decrease in the jet and a continued build up of heights western Europe as the mid Atlantic trough virtually dissipates. This tends to HP western Europe (including the UK for once) with temps for the latter rising to above average.

http://www.tropicaltidbits.com/

Edited June 21, 2015 by knocker

[Costa Del Fal]

Are we really getting that desperate that we're looking into deep FI for something more akin to midsummer? I think it's slowly beginning to dawn on people that the end game is likely to be a spell of wet and unsettled weather. Still, I have a sneaky suspicion that we'll see a rather notable spell of warmth and thunder before July is out...

Can we have some charts to support your assumption that the end game is unsettled? Or is this due to charts showing the weather you do not want?

Find it a bit hypocritical about looking at fi charts in summer? Same as people do in winter. But the trend has been quite firm in a return to average or warmer conditions for some time now. Should this be ignored?

Edited June 21, 2015 by Costa Del Fal

[Frosty.]

Also Frosty, the UKMO doesn't seem to have the Atlantic crashing through

Agreed, I'm really encouraged by the 12z runs so far, the gefs 12z mean offers hope for a widespread warm up through week 2.

[Captain Shortwave]

Well a potential plume gate is in the range of the operationals now, impressive to see the GFS ens still going for this.

 

The GEM has certainty bitten the line this afternoon

 

The GFS on the other hand looks mixed if still warm

 

It would be nice to see the operationals pushing this a bit more over the coming runs. Lets see what the ECM can produce in the 8-10 day range.

 

The ECM isn't great but a little better than this morning.

 

It would be nice to see that sharpening trough to really push the heat northwards as opposed to keeping it at bay with a fairly strong westerly jet.

Edited June 21, 2015 by Captain shortwave

[Methuselah]

TBH, I haven't really seen any indication of the 'Atlantic crashing through', just LP to our west (be that SW or NW) somewhere; and, there certainly is not any 2012-like northern blocking suggested...I suppose the odds-on bet would be for something, UK-wide, not too far off average. Of course, it'd only take a minor shift for us to experience either a heatwave or total garbage...

Edited June 21, 2015 by Ed Stone

[mushymanrob]

If you read the final sentence 'opinion' and I'm inclined to agree with him the models seem quite keen on a very warm start to July back in early Febraury I recall the models glued onto a cold start to March 3/4 weeks beforehand and this was predicted fairly successfully. I do know in summer verification rates are greater so even more so I think some are being too pessimistic.

Yeah, but opinion based on what?