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

[Frosty.]

The Gem 00z didn't even show a heatwave next week but the 12z is going for a full on spanish plume, very much like the gfs 6z. I don't think there's any doubt things will hot up next week. The potential is very exciting, there could be plenty for storm enthusiasts with the growing heat and humidity triggering intense T-Storms and also a threat of thundery weather spreading up from France. Lots to look forward to...roll on next week!

[Captain Shortwave]

The ECM puts us into the fire at just 6 days out.

Pretty much all of the UK under the 16C isotherm with 850s of 22C in the south.

[Cloud 10]

ECM 12z has +22c 850's into the south on Wednesday.

 

 

 

850's anomalies for same time.

 

 

 

Edited June 25, 2015 by Cloud 10

[Nick L]

The ECM puts us into the fire at just 6 days out.

Pretty much all of the UK under the 16C isotherm with 850s of 22C in the south.

 

Surface temperatures into the low 30s.

[Winter Cold]

Yes, and you dont usualy bet against the ECM at T144 and below do you. Things starting to come into semi-reliable timeframe now so lets hope we can firm up over the next 48-72 hours of these charts coming off!

 

 

Notice the nice little pocket of +20c uppers just for me in Sheffield hehe

Edited June 25, 2015 by Winter Cold

[Nick L]

Looks like the ECM develops a line of thunderstorms for Thursday across the spine of the UK, the east retaining the heat.

[Summer Sun]

Looks like the ECM develops a line of thunderstorms for Thursday across the spine of the UK, the east retaining the heat.

 

Yep could be some torrential thunderstorms breaking out too

 

 

More comfortable temperatures and more settled for the Friday

 

[Captain Shortwave]

The day 8 ECM chart is very deceptive, temperatures would be widely into the twenties with the south east remain very warm or even hot with the 12C isotherm hanging on with high heights and a southerly wind. The final charts could look fun with the heat potentially pushing back north again.

[Interitus]

The GFS is forecasting quite extraordinary temperatures for the low countries at the moment, values of 38°C are within a degree of the national records of Belgium and Holland.

[nick sussex]

Looking just upto T144hrs the ECM remains the hottest followed by the GFS and the UKMO which is the most progressive.

 

The ECM brings 20+ 850's in at T144hrs with the far se clinging onto this at T168hrs. After this it looks like a dogs dinner with a very complex set up.

 

Theres still a chance that a renewed surge of heat could occur later depending on the orientation of any troughing in the Atlantic.

 

Hard to say which model is right as the margins on a global scale are small however the further west the pattern is initially the higher chance of that heat getting in within the T144hrs timeframe.

 

Early phasing of that small and deeper low with the main one to the west of the UK is important to help pull the hot air north, at the moment the initial really hot weather looks like lasting max 2 days, it looks to still remain very warm afterwards, the changeover could see some severe thunderstorms.

Edited June 25, 2015 by nick sussex

[knocker]

Looking at this evenings GEFS anomalies the most noticeable detail is the phasing out of the trough to the west. So it looks good to go until the end of the ext period with HP in control perhaps becoming more Azores orientated. This still leaves the detail of a somewhat complex scenario for next week to resolved as the METO stressed:

 

 

It’s worth saying that there is some uncertainty about how much of the hot weather from the continent will reach us, and it may only last a couple of days before temperatures drop a little. As is traditional with hot weather in the UK in the summer it may end with thunderstorms.

 

 

[Nick L]

The GFS is the run of choice for heat lovers, the ECM for storm fans. 

 

Even though I hate hot weather this is thoroughly interesting.

[ANYWEATHER]

Evening Weather fans, , The Plume next week is out of the reliable timeframe, but the thing what excites me is the potential for some really big thunderstorms on what is shown on tonights  models.  We will have to see if this trend continues, because we all know that plumes across the Uk can be extremely difficult to model.....as experience as told me this far out , come Summer or Winter...    

[Captain Shortwave]

A pretty good set of ensembles from the ECM for next week

Even the mean has the 18C isotherm getting close to the south of the UK. It remains very warm to hot through the rest of that week, especially so in south east.

Still questions on the strength of the plume and how robust any heights are to our east. We still have a lot of answers to get though there is a high chance of 30C being reached next week.

 

BTW the GEM control run is fun to look at just for laughs.

Edited June 25, 2015 by Captain shortwave

[Frosty.]

The Ecm 12z ensemble mean this evening indicates an increasingly very warm / hot spell next week, hottest across the south and east with humidity levels rising considerably. I expect plenty of sunshine across the board and high uv levels, the sunshine is likely to turn more hazy over time as the air quality deteriorates and I think the heat will spark isolated intense storms, I think storms could possibly become a bigger feature of our weather through the second half of next week, especially during the breakdown phase towards the end of next week although I'm actually hoping the hot spell will stick around for some time since I think we have seen enough cool north westerly dross so far this spring / summer..bring on the heatwave

[Vorticity0123]

We are a couple of days closer to the start of a possible very warm spell for Western Europe. However, this is not the only place where there are chances on very hot conditions, as the same will be occurring in the Western US. Why do we see multiple areas having a relatively high chance on such warm conditions? The answer can be found by taking a look up high in the troposphere and even the stratosphere. In this post I will not look in detail on the current and future weather, but give a different insight in how the expected strong temperature anomalies in the weather next week can be explained.

 

Jet stream waviness

 

Currently, the polar jet stream behaviour is rather straightforward:

 

Jetstream analysis of GFS 12 UTC run (courtesy: Netweather).

 

The white lines indicate heights at a given surface (I think 300 hPa, but I stand to be corrected). A good article about the jetstream itself and its characteristics can be found here: http://www.netweather.tv/index.cgi?action=jetstream-tutorial;sess=.

 

What can be seen is that the jet stream is zonally orientated (east-to-west) over the Atlantic to the south of a large and broad trough. Above Europe, the jet stream starts to adopt a slightly wavier (i.e. meandering) pattern, meaning it flows more north-south than east-west. This is happening under the influence of a ridge that is extending from Spain via the UK all the way towards Greenland, bringing the settled conditions experienced today.

 

However, this pattern is going to change significantly in a week, as can be seen below:

 

Jetstream forecast of GFS 12 UTC run for next week Thursday 12 UTC (courtesy: Netweather).

 

Note how the polar jet stream has become very wavy, with it running in a north/south or south/north direction multiple times. This is called a meandering, or highly amplified pattern. Usually, such patterns are associated with ridges extending very far northward and troughs dipping very far southward. As can be seen, this is the case here as well.

 

In summary, a deep trough covers the area near Newfoundland, USA. Downstream (so to the east) a ridge is extending all the way towards Greenland. Near Iceland, another trough is located which points all the way down to the west of Morocco. Over Europe itself, a prominent ridge extends up to the northern tip of Scandinavia. By only the wording one can identify that this is not a straightforward pattern.

 

Stratospheric waviness

 

Another nice way to look at the 'waviness' of the atmosphere is to go up even higher into the stratosphere (100 hPa height). At this height, still something of a low pressure is evident. If one goes even further up, there is a relative high pressure over the pole relative to the equator.

 

 

For example, take a look at the 100 hPa heights of yesterday:

 

100 hPa heights analysis as of 12Z 24-06 by ECMWF. Courtesy: FU Berlin.

 

What can be seen is that there is a broad, but rather circular low pressure area present at this height. Some weak ridges (red) and troughs (blue) can be identified on the upper side of the image and over Eurasia. The circular nature of the low suggests most places are likely to experience a rather zonal (i.e. east-west orientated) flow at the mid-latitudes. This makes sense if one compares this to the jetstream analysis of today.

 

But as it was with the jet stream, things are also bound to change in the lower area of the stratosphere:

 

100 hPa heights forecasts as of 12Z 24-06 by ECMWF for 12Z 01-07. Courtesy: FU Berlin.

 

Note that this forecast is actually one day before the jetstream forecast image from GFS. This has been done because the signature of the low pressure area at the stratosphere was too vague to give a proper interpretation.

 

The main difference is that the low pressure area has become much wavier. In fact, a lot of deep troughs and high-amplitude ridges can be identified (like the one over Europe which is also forecasted to develop for that time period at 500 hPa height). These ridges and troughs also nicely overlap with the 500 hPa features, at least for Europe and the Atlantic.

 

Extreme heat (and cold) at multiple places

 

So why does this explain the fact that extreme warm (and to a lesser extent cold) conditions are also going to develop over for instance the UK? This is associated with the aforementioned wavy pattern of the atmosphere and jet stream that is forecast to develop. For example, we take into consideration the two well-defined ridges present over Europe and the western parts of the US. On the western flanks of such ridges (and thus on the eastern flanks of troughs to the west of these systems), a southerly flow will easily develop, often also at the surface. This brings/advects very warm air all the way from southern regions towards western Canada or Europe. On the other hand, on the eastern side of such systems (and thus on the western side of the troughs east of these systems), a northerly flow can develop, bringing arctic air all the way southward to for example the eastern US. When the flow is more east-west orientated, air masses usually originate at the same latitude as the country itself, and do not undergo much north/south transport. This explains why we have not seen a lot of 'extreme' temperatures across the globe at the midlatitudes, and why such temperatures will become more prevalent over the next week.

 

Summary

The jet stream (or the atmospheric pattern) is currently rather zonal (east-west orientated), bringing seasonable conditions on many places across the midlatitudes and westerly winds. Next week, this is going to change as the pattern becomes meridional/highly amplified globally, thereby increasing the frequency of northerly and southerly flows. This increases the chance on extreme temperatures (both heat and cold) across the globe.

 

All in all, it is a very interesting synoptic development, and great how this shows up the upper air patterns. Under such meteorological development things become also a lot more interesting weather-wise . Any feedback or corrections are greatly appreciated!

 

Sources:

www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/

http://www.netweather.tv/index.cgi?action=jetstream;sess=

http://www.netweather.tv/index.cgi?action=jetstream-tutorial;sess=

Edited June 25, 2015 by Vorticity0123

[knocker]

Very interesting Vorticity. Thanks. By coincidence I was just reading this in Jeff Master's blog which I have posted in the N. American weather thread.

 

 

The atmosphere over North America will slide back into a familiar pattern this weekend, as a powerful upper ridge and record heat take hold of the Pacific Northwest and western Canada while an unusually strong upper low for late June brings wet, cool conditions from the Ohio Valley through the mid-Atlantic into New England. It’s yet another variation on the warm-west/cool-east pattern that predominated through much of 2014 and early 2015.

[damianslaw]

After a couple of months dominated in the main by a typical atlantic albeit cool airflow, the models are now suggesting something very different for next week, with as explained above a meridional amplified flow, and this time we are on the right side of the trough in terms of something heatwise. Too early to call how warm things will become and how long lasting any very warm/hot spell will be. Low pressure will be lurking to the west and southwest ready to cast aside the plume quickly, in this respect its a fragile synoptical set up for anything sustained in terms of warmth, but a shortlived very warm/hot spell will most likely be welcomed by many at a time when we can maximise hours of daylight.

[Guest]

Looks like the 18z is going to be more progressive than the 12z GFS run, hotter earlier but over potentially over quicker with weaker (almost none existent) heights to the north east of the UK offering no resistance to the Atlantic.

[East_England_Stormchaser91]

Looks like the 18z is going to be more progressive than the 12z GFS run, hotter earlier but over potentially over quicker with weaker (almost none existent) heights to the north east of the UK offering no resistance to the Atlantic.

Still remains warm or very warm particularly in the East into FI stages on the 18z.

By my standards and for the UK, the 18z is still an exceptionally good run.

[Methuselah]

Looks like a good run to me: never cool, mostly very warm or hot, and two or three chances of storms...

[Captain Shortwave]

So far so good this morning with the GFS 00z an improvement on the last couple of runs.

 

The UKMO this morning also showing a much better solution compared to previous runs which have been progressive to say the least.

 

Day 6 charts

GFS

UKMO

 

Both models turn hot by midweek, potentially very hot in the south. Mid thirties again on the GFS by Thursday as 850s approach 24C in southern areas with the 20C isotherm covering most of England.

Edited June 26, 2015 by Captain shortwave

[Man With Beard]

After some suggestions yesterday that everything will be moved slightly east, this mornings runs pull the pattern back west. As CS has mentioned, direct hits from the plume next week from both GFS and UKMO. The GFS then brings the 20C 850s line back to the south coast another two times later in the run - so the idea of a repeating pattern still very much alive.

Another remarkable milestone in the GEFS ensembles - the mean 850s now exceeds 20C by T144.

Pressure never particularly high so storm potential exists at several stages.

Edited June 26, 2015 by rjbw

[Guest]

While still decent I'm not liking the trends in the last few runs, it's clear again on the this morning GFS 00z run heights won't build over the continent anywhere near enough to prevent the Atlantic spilling in. looks more like a messy breakdown into late next week assuming things don't get punted east which in reality still seems the most logical solution. Still a couple of days do seem likely to potentially produce the highest temos since July 2006. I think to achieve that we have the 1st August 2013 to beat??

[knocker]

Latest EC32 update (although I doubt there will be much interest for obvious reasons) starting on the 5th.

 

Quite strong ridging NW Europe and eastern Pacific with trough Russia and a weak trough west of the UK. Surface analysis HP NW Europe and western Atlantic with a broad area of LP to the NW of the UK. Resulting in a WSW flow over the UK and very warm particularly in the SE.

 

This scenario develops into a broad area of HP in the Pacific and Atlantic by the 12th with a weakening Atlantic trough. On the surface the Azores HP is in control with the HP slackening over NW Europe so a W/NW flow with temps returning to average,

 

For the next week until the 19th there is little change from this with temps around average or somewhat above.

 

From here to the 27th again little change with HP in control in the Pacific and Atlantic with a suggestion of a weak trough around Iceland so the W/NW flow persists with temps still around average.

 

Summary

 

After next week all one can say is things settle down under the watchful eye of the Azores HP and it looks like being a very pleasant month with temps average or even a little above.

 

Purely as a matter of interest it has the very hot weather touching the SW 00z Tuesday moving north and east until orientated SW/NE across northern France and Germany by Sunday. Obviously events on the mesoscale level are eagerly awaited.