Models, teleconnections and nowcasting

[knocker]

A very pleasant two or three hours here this morning as the cloud in the warn sector dissipate but around midday a lot of high and medium cloud encroached and it's not particularly obvious why. Upper trough maybe?

[knocker]

The combination of troughs associated with the tpv dropping into the Atlantic and the cut off upper low around the eastern Mediterranean. aided and abetted by the ridging of the subtropical high, results in further strong WAA up through Europe next week. Whilst the UK, on the western flank of this, continues unsettled

Edited March 7, 2020 by knocker

[knocker]

And this is reflected at 50mb where currently it is -52.C at Lerwick as against -80C in the core of the vortex

Edited March 7, 2020 by knocker

[knocker]

Once the cold fronts clear quite quickly to the east the country will be in a breezy NW unstable airstream (see Valentia sounding)

So today will be a day of sunny intervals and heavy showers. These could be quite concentrated at times, particularly in the SW/S and N. Ireland and Scotland, with hail and thunder in the mix and snow on the high ground in the north. These will continue through this evening and then gradually die out as a very transient ridge moves east

But by midday Monday as the old upper moves away to the the NE so yet another has tracked into the Atlantic and another frontal system is moving in from the west and rain from this will start to effect western regions by 1400 and then move east through the afternoon and evening with ,I'm afraid, more heavy rain in areas that don't need it

Over the next three days the country remains under the auspices of the upper trough and thus unsettled and windy but with sunny intervals and some marked temp contrasts as fronts whistle through

 

Edited March 8, 2020 by knocker

[knocker]

According to the ecm the upper trough continues to receive boosts from northern Canada and ther unsettled weather continues over the weekend with another surface low bringing more wet and windy weather

Edited March 8, 2020 by knocker

[knocker]

Worth a look at the brief visit of warm air from a ling way south in the warm sector on Tuesday

 

[knocker]

The gfs continues to indicate unsettled weather next week without anything drastic after tomorrow and by t144 has another trough bringing more wet and windy weather.

But as this trough passes through the next trough(s) dropping into the western Atlantic initiates amplification of the subtropical high. Await to see whether the ecm follows suite and whether the ridge is sustainable against the energy tracking across the Atlantic

Edited March 8, 2020 by knocker

[knocker]

The ecm has variation to the gfs (no big surprise) next weekend

And subsequent to that no great amplification of the Atlantic subtropical high

Edited March 8, 2020 by knocker

[knocker]

The North Atlantic 500mb and surface analysis for midnight

A few showers around in north western regions but generally not a bad start to the day and it will remain this way in eastern regions but the frontal systems associated with the low out to the west will bring cloud and then rain by rain by midday to western regions  This will quickly move east through the afternoon with some heavy pulses over Wales and it will become increasingly windy.

The initial frontal rain will clear to the east quite quickly this evening but the waving trailing cold front will bring further pulses of heavy rain over Wales and the NW which is not good news

The fronts and rain slowly clear away to south on Tuesday, at the same time removing the warmer air leaving behind a windy day of sunny intervals and showers

Overnight and through Wednesday further additions have consolidated the upper trough to the west so essentially a windy day with sunny intervals and showers whilst back in milder air in the south

Over Thursday the scenario becomes quite complex as the trough moves away to the NE and surface features move across the UK. This will bring periods of showery rain to many areas and as the wind veers northerly these could be wintry in the north

By Friday the trough is well clear and the UK is in a slack gradient with a relatively weak jet stream. Again sunny intervals with some showery/rain courtesy of an occlusion

Edited March 9, 2020 by knocker

[knocker]

Over the weekend the gfs has the frontal wave away to the south west on Friday, tracking northeast and phasing with the trough to the north east. But the subtropical high amplifies in mid Atlantic as another trough moves down from northern Canada resulting in the aforementioned low tracing south east over Scotland by midday Sunday. Thus more wet and windy weather, particularly north of the midlands, with snow over the high ground in Scotland. If of course this is correct

[knocker]

No big surprise that the ecm varies with the detail next weekend although loosely in the same ballpark

[knocker]

The METO have raised the rain warning for parts of mid Wales to amber this evening and overnight. presumably due to the waving fronts trailing across the country

[knocker]

According to the ecm following the movement of this low the next trough that drops into the western Atlantic initiates amplification of the subtropical high

Leading to the next question. Is the ridge strong enough to combat the pressure from the west?

 

Edited March 9, 2020 by knocker

[knocker]

The cold fronts are the problem overnight and tomorrow

[knocker]

Still indications from the ecm this morning that much of the country may get a break from the unsettled weather at the beginning of next week. Once the travels of the low are near enough out of the way to the east

From this point further troughs enter the fray in the western Atlantic, initiating amplification of the subtropical high. And over the next three days it's about the ridge hanging on against further energy emanating from the eastern seaboard

And note yet another formation of a cut off upper low

 

Edited March 10, 2020 by knocker

[knocker]

The EPS mean,goes along with this but in the longer term is still reluctant to lose the trough influence in the Atlantic, unlike the GEFS

[knocker]

From this point the UK trough as amplification takes place to the west and the east

And it is the ongoing strength of the ridge and subsequent high cell  where the models have tended to differ with the gfs being quite bullish vis the durability atop the cut off upper low to the south

Edited March 10, 2020 by knocker

[knocker]

There is still some minor differences between the ext anomalies this evening but they are very close to singing off the same hymn sheet. The re-orientation of the tpv and Atlantic trough is coupled with impressive amplification of the subtropical high (the GEFS still a tad more bullish) which portends a much more settled period with perhaps just the far north missing out a little

[knocker]

There is no consistency at the moment either between individual evolutions and model comparison over the ext period. The GEFS and EPS have shifted again this morning with the former being much more amplified regarding the trough/subtropical high combination (even giving the trough a slightly negative tilt) Obviously this needs to be sorted before one can have any great confidence in the detail although the percentage play is still a more benign Atlantic and some quieter weather for most

Edited March 11, 2020 by knocker

[knocker]

A quick glance at tomorrow and the weekend

The upper trough moves NE and merges with the tpv lobe and a couplex surface area of low pressure crosses the country with periods of rain and strong winds

This clears to the NE overnight leaving Friday as not a bad day by current standards with a slack gradient

By Saturday further troughs have arrived to the west and surface fronts cross the country bringing some showery rain interspersed with sunny interval

But by Sunday the pattern is getting quite complex as Another trough drops into the western Atlantic accompanied by general amplification of the subtropical high zones. All this resulting in the trough over the UK being 'squeezed' with surface fronts bringing a period of moderate rain, giving way to sunny intervals and showers.

 

 

Edited March 11, 2020 by knocker

[knocker]

An icy and snowy start to many areas in the north in the morning, courtesy of heavy showers earlier and then clearing skies, and a rather cold start elsewhere as well

But as can be seen the low to the north west of Ireland is filling and moving east and the first heavy showers from this will effect western Scotland by 0500 and the rest of northern Scotland by 0900. Whilst simultaneously a trough will track a line of rain across Wales and southern England. Thunder and hail in the showers cannot be ruled out

The heavy showers continue in northern regions where it will also very windy as the low continues east and a area of more persistent rain will track south east with the occlusion. and behind this the wind will veer northerly in what is now quite a chilly day for all with wintry showers in particular over norther Scotland with snow down to low levels

 

 

Edited March 11, 2020 by knocker

[knocker]

I touched on the beginning of the week earlier today as the subtropical high zones amplify and the trough over the UK breaks up

Through the middle of the week the ridge struggles to resists the pressure from the west but further amplification on Thursday reasserts the high pressure It's all a tad messy with cut off lows and frontal systems to the south west involved

Edited March 11, 2020 by knocker

[knocker]

Around t168 appears to be a key turning point as the second amplification wave gets underway

[knocker]

The re-alignment of the tpv and the subsequent precise Atlantic/Euro amplification is key to the upcoming surface analysis if all of this pans out. Or put another way, Where will any high cell park itself? And obviously looking at this evening's GEFS and EPS that cannot be answered at the moment

[knocker]

And this evening's NOAA