Short range model discussion - into 2018

[knocker]

The 1800 geostationary highlighting the huge area of low pressure to the west

 

[knocker]

A quick look at last night's anomalies to try to see where we are going with this as a pattern change is in the offing after next weekend.

There are differences in detail, (see the GEFS and EPS vis the Greenland trough/European high pressure) .but they are in the same ball park. The key features being twin vortex lobes northern Canada, with associated trough Greenland/Iceland and N. Russia with the east European trough. There is a pretty flat westerly flow across North America, which is reasonably strong across the Atlantic and into the UK, which portends a much more changeable scenario as systems track east, but depending somewhat on the strength and position of the weakening European high how much of a N/S split materializes. Something the det. runs will need to sort.. Temps returning to near average perhaps a little above.

Today the frontal system associated with the deep low to the west of Ireland is already bringing strong winds and rain into western parts. The frontal band of rain will slowly track south east during the day but will gradually fizzle out during the afternoon as it struggles against the block to the south east. Heavy showers may develop behind the front in the north west and remaining windy but in the south east temps quite respectable in the sunshine

But all the time the block to the south east is intensifying with the help of the Azores and European ridges and a high cell has formed of Germany and is spreading it's influence west over the UK whilst the trough to the west re-orientates to a neutral tilt. Thus light winds and a fine and sunny day for the UK with temps significantly above average except for N. Ireland and the north west which will still be on the fringes of the trough with some patchy rain.

By Thursday a not dissimilar picture but the High cell to the south east is taking a positive tilt and the trough to the west starting to deconstruct under pressure from the energy exciting North America. This introduces a south westerly drift into north western areas which results in a tight NW/SE temp gradient to the very warm south east.

By Friday the trough has deconstructed and the high cell taken on a much more positive tilt resulting in a surface cell settling over the UK. Thus another calm very warm day but the orientation of the cell does lead to quite a sharp temp delineation along a line roughly North Wales to Newcastle with temps NW of the line a fair bit lower, particularly near the coast.

The only difference on Saturday being a slight adjustment to the orientation of the high cell leading to a more uniform temp distribution with the temps not so high in the south but still a dry and warm day for all

Just to add the temps are obviously just according to the GFS and should certainly not be taken as definitive.

Edited April 17, 2018 by knocker

[knocker]

The 0600 UTC geostationary showing the back end of the front. Quite windy down jere gusting 41kts at Culdrose

[Man With Beard]

Now that temperatures are going to be main talking point, it will be interesting to track which model has the best handle at short range. (At least for me!)

Tomorrow afternoon on some of the models we use (either charts for 4pm, or maxes between 3pm and 6pm used)

          

Quite a lot of similarities there, but some differences too.

Focusing towards the southern half, HIRLAM the warmest (20C widely for England, 22C-23C across parts of the SE) - NNM also 20C widely across England away from SW with northern cities slightly higher.

ARGEPE, GFS and ECM take the middle ground with a smaller area of 20C-22C and most areas 18-19C. 

EURO4 the coolest with just the SE getting above 20C, and northern/western areas often a couple of degrees down on other charts.

Further north, differences more exaggerated - the GFS and NNM see fairly warm days through the main Scottish cities with 18C possible, but some charts far cooler. ARGEPE/EURO4 pretty chilly for western Scotland.

It'll be interesting to see exactly what figures are achieved and how they compare to these models. I've seen some forecasts of up to 25C for London tomorrow (24C on BBC website), which would be quite different to all of these models except perhaps the HIRLAM.

[knocker]

The 0900 geostationary (courtesy DSRS)

[chrisbell-nottheweatherman]

51 minutes ago, Man With Beard said:

Now that temperatures are going to be main talking point, it will be interesting to track which model has the best handle at short range. (At least for me!)

Tomorrow afternoon on some of the models we use (either charts for 4pm, or maxes between 3pm and 6pm used)

          

Quite a lot of similarities there, but some differences too.

 

What strikes me, from a partially IMBY (or at least regional) point of view is that the highest forecast temperatures are shown in the Cambridgeshire Fens, west Norfolk, southern Lincolnshire and, in some of the models, parts of the east midlands and Yorkshire, as opposed to the usual areas around the Thames Estuary or west of London.

[knocker]

At 1200 the cold front had cleared N. Ireland and Scotland with England and Wales in th warm sector.

 

[knocker]

Follow the plume with the GFS

 

[seaside 60]

7 hours ago, chrisbell-nottheweatherman said:

What strikes me, from a partially IMBY (or at least regional) point of view is that the highest forecast temperatures are shown in the Cambridgeshire Fens, west Norfolk, southern Lincolnshire and, in some of the models, parts of the east midlands and Yorkshire, as opposed to the usual areas around the Thames Estuary or west of London.

One presumes its wind direction over cold sea takes while to warm up over land. As its a S/SE wind.

As you say bit unusual, shows the early season.

[knocker]

The 1800 UTC geostationary showing the front straddling the country and the trough

[knocker]

Just a quick heads up on the GEFS 3-8 anomaly to start as it gives an idea on the direction of travel of the short term evolution.

Today patchy rain/drizzle will track north along western coasts as a wave to the west moves north but will quite quickly clear all areas apart from north west Scotland where it will linger all day. Quite breezy particularly in the north west. Elsewhere dry and sunny resulting in a very warm day. The rain may linger a while in NW Scotland during the night before clearing but generally a fine clear night with perhaps the odd fog patch by morning.

The next three days essentially develop into a skirmish between east bound troughs/energy in the Atlantic, with low pressure over Iberia also playing a key role, and retreating high pressure to the east and the Azores ridging north east, with the UK sitting in the middle which is fine, albeit it leads to some quite marked regional variations of temp, but gets a tad complicated over the weekend.

So keeping this in mind Thursday sees the UK in a very slack pressure gradient as the two high pressure areas rather tenuously try to connect as the trough disrupts to the west. Thus a dry and sunny day in most areas and warm, very warm in the south east, with temps significantly above average,

Friday a not dissimilar scenario but the lows to the west and south west are taking closer order and another sunny and very warm day, the exception being the far north west of Scotland where there may be some showery rain. Temps again significantly above average particularly in the south east.

Saturday portends another very warm day but the analysis is getting  tad messy with the upper low to west moving closer with some cooler air (relatively speaking)  and towards late afternoon the weather could become more unsettled in Wales and the west with thundery showers entering the mix,

On Sunday the unsettled weather gathers pace as the upper low moves north west of Ireland and front associated with the surface feature tracks east and the thundery showers become more widespread. Temps still above average in the east but nearer average in the west.

This is of course the gospel according to the GFS

 

Edited April 18, 2018 by knocker

[knocker]

The 0600 geostationary and fax for 1200

[knocker]

The ecm not dissimilar to the GFS

The analysis at T96 & 120

Similar mini breakdown over the weekend with thundery showers.

https://weathermodels.com/index.php?r=site%2Fmodels&mode=animator&set=9-km ECMWF Europe Surface&area=United Kingdom&param=6-h Precipitation&offset=0

[knocker]

East/west contrast on the 0900 geostationary. (image courtesy Dundee Satellite Receiving Station)

[Man With Beard]

Just for my own interest, comparing the models with what it actually happening:

By 11am this morning, London was already at 21C. Many other places in the SE were already at 20C.

Comparison with very latest model output:

ARPEGE for 11am: 18-19C

GFS for 11am: 18C (according to Meteociel outputs)

EURO4 max by 12pm: 19C

ECM max by 1pm: 20C (couldn't get closer than this timeframe)

HIRLAM 0.1 for 11am: 18C

But the champion so far today is the AROME 06Z, which accurately put London in the 20C-21C category at 11am

 

 

[knocker]

London City airport is 22C at 1050 UTC

 

[knocker]

Nice MODIS at 1109 UTC showing the clear weather south of the front and mist and fog around the coasts. (courtesy DSRS)

[knocker]

The upper low with the little cold pool at Saturday midnight.

Then moving east through Saturday/Sunday

And the front impacts late Saturday/Sunday resulting in thundery outbreaks and quite a west/east temp gradient

Edited April 18, 2018 by knocker

[Man With Beard]

On 17/04/2018 at 10:31, Man With Beard said:

Now that temperatures are going to be main talking point, it will be interesting to track which model has the best handle at short range. (At least for me!)

Tomorrow afternoon on some of the models we use (either charts for 4pm, or maxes between 3pm and 6pm used)

          

Quite a lot of similarities there, but some differences too.

Focusing towards the southern half, HIRLAM the warmest (20C widely for England, 22C-23C across parts of the SE) - NNM also 20C widely across England away from SW with northern cities slightly higher.

ARGEPE, GFS and ECM take the middle ground with a smaller area of 20C-22C and most areas 18-19C. 

EURO4 the coolest with just the SE getting above 20C, and northern/western areas often a couple of degrees down on other charts.

Further north, differences more exaggerated - the GFS and NNM see fairly warm days through the main Scottish cities with 18C possible, but some charts far cooler. ARGEPE/EURO4 pretty chilly for western Scotland.

It'll be interesting to see exactly what figures are achieved and how they compare to these models. I've seen some forecasts of up to 25C for London tomorrow (24C on BBC website), which would be quite different to all of these models except perhaps the HIRLAM.

And here's the actual. Big differences!

As mentioned in a previous post, AROME seems to have had a slightly better handle on localised urban heat. Here's what is has for 4pm tomorrow (sorry doesn't seem to cover Scotland): heat generally east of high ground, 24-26C for many and 26-28 in London (A really close look at this chart has a tiny area at 28C or above around Heathrow - incredible definition!!)

ARGEPE similar this time

compared with other models which are 1C/2C lower

    

Finally, I guess the April record is probably safe but not 100% unreachable: 29.3C. 

[MattTarrant]

4 minutes ago, Man With Beard said:

And here's the actual. Big differences!

As mentioned in a previous post, AROME seems to have had a slightly better handle on localised urban heat. Here's what is has for 4pm tomorrow (sorry doesn't seem to cover Scotland): heat generally east of high ground, 24-26C for many and 26-28 in London (A really close look at this chart has a tiny area at 28C or above around Heathrow - incredible definition!!)

ARGEPE similar this time

compared with other models which are 1C/2C lower

    

Finally, I guess the April record is probably safe but not 100% unreachable: 29.3C. 

It would seem unrealistic to reach such a record, though more pertinent here is the high res models tendency to upscale heat rapidly within the 24 hour range. London is frequently up-scaled as the dynamics of urban heat containment are controlled with greater accuracy! The models ability to locate sea mist formation is an area of interest also, with some coastal regions suffering short notice downturn in weather prospects (for most people). 

[Daniel*]

43 minutes ago, MattTarrant said:

It would seem unrealistic to reach such a record, though more pertinent here is the high res models tendency to upscale heat rapidly within the 24 hour range. London is frequently up-scaled as the dynamics of urban heat containment are controlled with greater accuracy! The models ability to locate sea mist formation is an area of interest also, with some coastal regions suffering short notice downturn in weather prospects (for most people). 

Up scaled but often not enough, it’s such a common occurrence and it can be seen all corners of the country. H-res not even right with the ‘now’. As to record it will be a step too far seeing how 1949 panned out, but UHI is more ‘intense’ than then with more urban sprawl. I think we’ll see 28C reached fairly sure, up there with 1949. And I think we’ll outdo 2011 on face value it doesn’t look as good as now.

[MattTarrant]

1 hour ago, Daniel* said:

Up scaled but often not enough, it’s such a common occurrence and it can be seen all corners of the country. H-res not even right with the ‘now’. As to record it will be a step too far seeing how 1949 panned out, but UHI is more ‘intense’ than then with more urban sprawl. I think we’ll see 28C reached fairly sure, up there with 1949. And I think we’ll outdo 2011 on face value it doesn’t look as good as now.

You raise a notable point of interest regarding deficiencies within the +1/2 hr time range. This for me constitutes a significant barrier to verification capabilities, observational frameworks do require greater investment to prevent deviation at such short range. These deficiencies represent themselves frequently in warm/hot synoptic episodes, even seen in the most recent cold spell. This rhetoric was indicated somewhat at the Met Office (Visit Day). 

Edited April 18, 2018 by MattTarrant

[Man With Beard]

AROME now showing much of London at either 28C or 29C by mid-afternoon. Is that April record reachable?

For 10am the model was bang on compared to actual temperatures in the region. It's going to be interesting tracking this today.

[mb018538]

We are already past 24c in a number of locations....with a good 3-4 hours of heating left, who knows!

[knocker]

The front lingering to the west of the UK has made a massive difference to the temps in the far west as a belt of cloud has persisted all day.

Thus the temp at Culdrose at 1150 UTC was just 13C and at Heathrow at 1220 UTC 27C

The high res. MODIS ( courtesy DSRS) at midday and surface chart

 

Edited April 19, 2018 by knocker