Models, teleconnections and nowcasting

[knocker]

The GEFS medium term mean anomaly

[knocker]

Nice midday sat image showing frontal cloud over southern UK and convection to north

Edited May 3, 2020 by knocker

[knocker]

For next weekend the ecm has the subtropical high amplifying strongly NW with two energy flows running around it which by Sunday have initiated a strong northerly and the advection of colder air over the UK The detail of course subject to change

 

Edited May 3, 2020 by knocker

[knocker]

The North Atlantic 500mb and surface analysis for midnight and sat image

A fair bit of cloud around over south Wales and southern England at the moment but it should break to some extend resulting in a quite pleasant day. Elsewhere plenty of sunshine but showers developing along NE/E regions during the afternoon. The usual caveats re, eastern coastal regions with an onshore wind apply

Tonight some frost patches under the clear skies in the north but the low to the south west is pushing north and the associated fronts will bring some heavy rain, perhaps thundery, into the far south west and becoming quite windy

The rain will continue for a time on Tuesday but ease through the morning. albeit still windy, but another sunny day further north

No significant change to the pattern over Tuesday night through Wednesday resulting in sunny day with a few showers

By Thursday there has been some slow developments in the Atlantic and an occlusion that has sneaked into the Irish sea may bring a few more showers to western regions. Otherwise another warm and sunny day

The slow developments continue on Friday and there may be a few more showers around from the stray fronts but essentially another warm day with plenty of sunshine

 

Edited May 4, 2020 by knocker

[knocker]

Continuing over the weekend with the gfs and caution recommended regarding the detail

Essentially the energy flows establish high pressure to the north west and low over western Europe resulting in unsettled weather pushing up from the south on occasion and a strong NE/E wind developing and thus much cooler air spreading to all of the country over Sunday/Monday

[knocker]

The GEFS mean anomaly gives a fair overview of where the gfs is this morning. It is relatively obvious that there is a fine balance between the main players and any shift will impact the surface analysis in the reion of the UK

[knocker]

And there is a slight, but significant, shift with the ecm

[knocker]

There is a general agreement on the overall NH pattern between the ext anomalies this morning but some significant differences remain that need to be ironed out

Upstream there are ridges NW North America into the western Arctic and Russia adjacent to the tpv which has significant troughs into northern Europe and northern Canada/NW Atlantic. Downstream, and between the latter two features, the subtropical high amplifies in the Atlantic with the complicated addition of low pressure around Iberia. Precisely how the features in the Atlantic/European arena align will dictate the surface analysis in the region of the UK. Suffice it to say at the moment it doesn't look like heatwave weather but could well be relatively dry. We shall see

 

Edited May 4, 2020 by knocker

[knocker]

It is certainly looking as if the front tracking south in the early hours of Sunday morning is a pretty good percentage play

[knocker]

Rain encroaching the south west through tonight as the frontal system slips east. And for a time it will be very windy

Edited May 4, 2020 by knocker

[knocker]

Veil of Cs here now

Edited May 4, 2020 by knocker

[knocker]

Jet-stream cirrostratus over Iceland

[knocker]

Obviously the detail regarding the beginning of next week has still to be established and it would appear to be all about the alignment of the ridge as it intensifies and the tpv lobe as it phases, or not, with the cut off upper low to the south, The ecm this evening

 

Edited May 4, 2020 by knocker

[knocker]

The North Atlantic 500mb and surface analysis for midnight and sat. image

Heavy rain and strong winds are currently effecting Cornwall and Devon and the rain will move a tad north as the frontal system tracks east across northern France through today, but it will also start to fizzle out albeit the cloud will linger. Elsewhere not a bad day with the usual caveats vis the eastern coastal areas

The cloud still lingering tonight in SW/S regions with patchy rain/drizzle but elsewhere quite clear with some ground frost around

A sunny and warm day for most on Wednesday but cloudy with showery rain over Cornwall/Devon and SW Wales courtesy of fronts associated with the low to the south west of the country

Another sunny and warm day on Thursday with the country remaining under the  influence of the ridgewith with perhaps the odd shower popping up

By Friday the energy flows around the high pressure are making some inroads with some frontal rain encroaching Scotland and N. Ireland whilst further south another warm day with showers developing in central areas

By Saturday troughs are converging from the north and south west and colder air is on the way south behind the cold front with snow showers quite likely over Scotland

 

[knocker]

The gfs over the next three days. Essentially the cold air sweeps south into Europe behind the front but the UK is on the periphery of this as the high cell to the NW regains some influence

During this transition it will be generally quite cold with temps below average and on Sunday very windy and wet in southern regions with some wintry showers in the north

By Tues/Weds drier with the wind abating but the detail is of course subject to change

Edited May 5, 2020 by knocker

[knocker]

The ecm for same time period. Cold but warming slowly. Dry

[knocker]

Merely out of interest. A forecast sounding for midday Sunday in th north of Scotland. Colder and unstable air in the lower regions but warmer and drier air from the anticyclonic airmass to the west pushing in over the top putting the kybosh on any deep instability

Edited May 5, 2020 by knocker

[knocker]

0600

[johnholmes]

2 hours ago, knocker said:

Merely out of interest. A forecast sounding for midday Sunday in th north of Scotland. Colder and unstable air in the lower regions but warmer and drier air from the anticyclonic airmass to the west pushing in over the top putting the kybosh on any deep instability

That really is a good example

[knocker]

The tpv lobe might be skimming us but not Finland

[knocker]

Midday

[knocker]

The southward movement of the cold air behind the front on Sunday

 

Edited May 5, 2020 by knocker

[knocker]

Medium term gfs mean anomaly this evening appears to be moving towards an NH pattern that the ext anomalies have been indicating of late

[knocker]

Further to the above the ext anomalies this evening are on the same page but still with some differences that require a little sorting. Upstream some quite strong ridging into the Arctic via NW North America and Russia adjacent to the tpv with trough extensions into NE Europe and Canada/NW Atlantic.Between the latter two features ridging in the eastern Atlantic with the added, still, complication of low pressure near Iberia. It's the alignment and intensity of these features in the Atlantic/European arena that are causing some problems so the surface analysis best stay as a watching brief for the time being, albeit not looking overly pessimistic

Edited May 5, 2020 by knocker

[knocker]

The North Atlantic 300mb wind field and surface analysis for midnight and sat image

After a clear start with the odd frost patch today will be another warm and sunny day for most, with the usual caveats, except the far south west where cloud will linger with perhaps the odd shower in Cornwall

Cloud perhaps a tad more extensive into SW Wales tonight but elsewhere clear and quite chilly  with frost and mist/fog patches by dawn

Tomorrow portends another warm and sunny day in many areas and the odd shower may bubble up, but a frontal system has taken closer order in the west bringing rain to N. Ireland, Wales and the SW of England

Another warm and sunny day on Friday but the much discussed pattern change is underway with the extension of the tpv lobe tracking east and weakening fronts touching northern Scotland

This process continues on Saturday but a much more active cold front and a band of rain tracks south during the day with much colder air in it's wake resulting in some wintry showers in the north

By Sunday the trough continues to move into southern Scandinavia and the front clears the south coast all of which results in a much colder day with some wintry showers mainly in the north east