Short range model discussion - into 2018

[knocker]

The EPS has a similar upper pattern to the GEFS in the relatively short term but ends up with the high cell closer to the UK. Nothing untoward here but the NW may still be susceptible.

Edited May 1, 2018 by knocker

[knocker]

The 0900 geostationary (courtesy DSRS)

[knocker]

Satellite at 1015 UTC. After a clear sky earlier Cs is now rapidly covering the sky here with Cu below

[knocker]

The 1500 UTC geostationary and 1200 analysis

[knocker]

The detail of this evening and tomorrow was touched on this morning so suffice it just to post the midday chart for tomorrow which indicates the front and small wave still straddling the country on their slow progress east and which are well clear into the North Sea by 00 Thursday.

Over Thursday and Friday the upper pattern (also touched upon earlier) of a major trough to the north west, high pressure to the east with ridging also into the Arctic and an upper low over the Mediterranean all facilitates the Azores to ridge north east over the UK. On the surface this tends towards a NW/SE split Thus dry, light winds, and increasingly getting warmer for the latter with patchy rain in the fresh south westerly for the former

So on to he weekend where pressure is being brought to bear on the Azores ridge by the energy exiting North America and the trough to the north west which acts to consolidate the high cell to the east of the UK. On the surface this re-orientates the blocking ridge leading to a couple of warm, dry and sunny days Sat/Sun with perhaps just some patchy rain for the far NW on Saturday. This is of course the gospel according to the gfs.

Edited May 1, 2018 by knocker

[knocker]

There is still the question of the orientation of the ridge.high cell over the weekend as the ecm illustrates which, although still portending light winds and dry, does tend to impact the regional distribution and range of the temps and cloud amounts. Thus the ecm does not make as much of the Atlantic trough as the gfs and promotes the Bermuda high pressure again which forms a horizontal high cell mainly west of Scotland by 1200 Sunday.

[Ice Man 85]

21 minutes ago, knocker said:

There is still the question of the orientation of the ridge.high cell over the weekend as the ecm illustrates which, although still portending light winds and dry, does tend to impact the regional distribution and range of the temps and cloud amounts. Thus the ecm does not make as much of the Atlantic trough as the gfs and promotes the Bermuda high pressure again which forms a horizontal high cell mainly west of Scotland by 1200 Sunday.

Really can't see how temps that low can come from those 850s. Gets even worse early next week. Any hope of pleasant temps coming from this "warm" spell are dead. Can see 30 being reached easily at this rate. Wouldn't it be novel if Nathan Rao was right for once

Edited May 1, 2018 by Ice Man 85

[knocker]

33 minutes ago, Ice Man 85 said:

Really can't see how temps that low can come from those 850s. Gets even worse early next week. Any hope of pleasant temps coming from this "warm" spell are dead. Can see 30 being reached easily at this rate. Wouldn't it be novel if Nathan Rao was right for once

850 temps are a very unreliable guide to surface temps as anything that compromises the surface to 850mb temp profile, such as advection or cloud, leaves you guessing the lapse rate. This can be reasonable close if you have a fair idea of the characteristics of the airmass but on other occasions can be way off. This is what on occasion makes the orientation of the high cell important.

[Jordan S]

A rough guide to where the rain is likely to be at 7 tomorrow morning giving 5 to 10mm widely with perhaps upto 25mm on Western hills should clear all parts by around 4pm tomorrow afternoon with sunshine and showers behind.

[knocker]

Today will be the last generally wet, cool and windy day for a while. The front and rain belt are currently running down the spine of the country as they move slowly east, clearing East Anglia and the south east by late afternoon. Sunshine and showers in the wake of the front, initially in  N. Ireland and Scotland but spreading elsewhere as the day progresses. Temps no great shakes.

The showers will die out later leaving a mainly clear night with ground frost likely in places.

The overall NH pattern approaching the weekend was covered yesterday and this has not altered so the 500mb geopotential height and anomaly chart should suffice this morning.

Thus by Thursday with the Azores high pressure ridging north east and low pressure to the north west a NW/SE split is initiated with a fresh WSW wind and patchy rain affecting the former whilst the south and east are drier and with temps beginning to rise.

Not much change from this scenario overnight and into Friday with patchy rain in the north west and England and Wales remaining dry and warm but just to note that in mid Atlantic there is an active front with waves forming on it

Over Saturday the aforementioned front edges slightly closer thus the patchy rain/drizzle may push slightly further south but the bulk of England and Wales will remain dry, sunny, and warm

Overnight Saturday and through Sunday yet another wave forms on the front and nips north east so a continuation ofa fresh SW wind and patchy rain in the north west whilst further south, with no wind, temps are progressing well above average. But changes are afoot and as the front eventually clears high pressure again starts ridging north east and by 00 Monday is generally established over all of the UK but not to forget that there is still a fair amount of energy exiting north west North America.

Edited May 2, 2018 by knocker

[knocker]

Edit

The last words of the above should of course read, exiting north east North America. Get a grip knocker.

Anyway the sun rising on the 0600 geostationary.

[knocker]

The ecm evolution not a million miles from the gsf with the active front mid Atlantic at T72 which slides north east as the high pressure starts to ridge north east again by T96 and by T120 a high cell has formed and tracked east into the North Sea. So initially a brisk south westerly over the NW with patchy rain drizzle before clearing on Sunday whilst elsewhere dry, light winds and quite sunny

.

 

[knocker]

Sunshine and clear shy here now as indicated on the 0900 geostationary

[knocker]

Nice high res. MODIS at 1130 UTC

[knocker]

The active front in mid Atlantic is the boundary between the colder air of the trough originating in N. canada and the tropical air to the south and it is the movement of this NE over the top of the ridge that produces a south westerly airstream over the north west with patchy rain and drizzle as we go into the weekend. whilst the rest of the country is warming up on light airs. Fortunately it then fizzles out on it's journey north east as there is renewed ridging behind,

[knocker]

According to this evening's ecm the transition to some renewed ridging after the passage of the front north east of Scotland over the weekend will likely only adversely affect N. Ireland and Scotland, particularly on Sunday.

 

Edited May 2, 2018 by knocker

[knocker]

Pleasant evening in many areas as the front is now in the North Sea with showers in the north and west as seen on the 1800 geostationary

[knocker]

Essentially today can be divided into a NW/SE split (no surprises there)  With cloud and patchy rain/drizzle in the north west and, after a quite cool start, it will be sunny and quite warm in the south east in the light winds.

Overnight and though tomorrow, broadly speaking, similar conditions will prevail once early mist and fog has cleared giving another sunny day for many and increasingly warmer.

On saturday most of the UK is still under the influence of the ridge connecting the Azores and European high pressures so another fine and warm day for most but the active front in the Atlantic, orientated SW/NE is not a million miles away from N. Ireland and the north west so breezy with patchy rain still in these areas. Also some coastal areas may well be cooler with some sea fog. By 00 sunday a wave has formed on the afprementioned front and is west of Ireland.

Through Sunday the wave tracks slowly north east and becomes somewhat diffuse as high pressure once more ridges in the eastern Atlantic but it will still bring cloudy conditions and patchy rain.drizzle to N. Ireland an NW Scotland..But that aside, with the high pressure remaining influential, another warm day bodes, very warm in the south, with the usual caveat vis coasts.

But come Bank holiday Monday midnight changes are afoot with another upper low spewing forth from the displaced vortex lobe in the Canada/Greenland area and sallying into the Atlantic. The surface depression associated with this moves east through Monday as the wave dissipates over Scotland so again we are looking at a very warm day in areas to the south, not so much in the north west and coastal areas. And there we must leave the gospel according to the gfs.

This morning's GEFS anomalies are not unsupportive of this scenario

 

Edited May 3, 2018 by knocker

[knocker]

The ecm has the wave over the Hebrides at 1200 Sunday en route to the west coast of southern Norway by 00 Monday. Thus patchy rain off NW Scotland during the day on Sunday. It also has the upstream energy beginning to show it's hand by 00 Tuesday.

[knocker]

The 0600 geostationary (courtesy DSRS)

[mb018538]

Those ECM 2m temps for Monday look a bit off to me. Only showing 23c maximums with that set up?? The last heat wave in April was similar, we were getting 25/26c shown as a maximum temperature when in reality we got 2-3c higher. I'd expect Monday to be in the 25-26c range, which is starting to appear in the human inputted forecasts on TV etc. Either way, it's going to be a glorious bank holiday weekend....enjoy it!

[knocker]

1 hour ago, mb018538 said:

Those ECM 2m temps for Monday look a bit off to me. Only showing 23c maximums with that set up?? The last heat wave in April was similar, we were getting 25/26c shown as a maximum temperature when in reality we got 2-3c higher. I'd expect Monday to be in the 25-26c range, which is starting to appear in the human inputted forecasts on TV etc. Either way, it's going to be a glorious bank holiday weekend....enjoy it!

I'm afraid I have no idea whether they are off or not but a couple of musings. The UK is in the center of a tentative ridge between two high centers with one to the north east which puts the southern half of the UK a slack NE flow off the North Sea (according to the ecm).so possible it is factoring in some low level advection. And if I remember correctly the previous hot spell had a long southerly fetch so not quite comparable.

At the end of day though I personally don't bother too much with max model temps, I only post them as I assume some people are interested and it is model discussion, particularly with large urban complexes involved, as long as it's dry and warm.

 

Edited May 3, 2018 by knocker

[knocker]

High res. MODIS at 1200 UTC (courtesy Dundee Satellite Receiving Station.)

[knocker]

As a break from the snooker a quick look at last night's NOAA and this morning's GEFS and EPS medium term anomalies to try and get some sort of handle on the evolution in general terms.

Upstream the key features are the Aleutian low, ridging in NW North America and a quite intense vortex/lobe northern Canada with associated trough aligned south east across southern Greenland into the Atlantic.

A strong westerly upper flow swings south of this across the Atlantic but on reaching the eastern Atlantic backs south west in the vicinity of the UK thanks to high pressure in the east ridging strongly into Scandinavia, whilst a secondary flow continues SE into Iberia towards low pressure in the Mediterranean area.

This would portend some unsettled weather, particularly in the north where it could also be quite windy at times, as systems track east and then NE with perhaps the south escaping the worst, Temps around average, maybe a little above but probably a fair bit of geographical variability. As always the det runs to sort the detail on this..

[knocker]

Not much to add to this morning's yap about the gfs so just to reiterate the evolution still moving towards the key players being the Canada/Greenland trough complex, the block to the east and the Azores ridging NE (aided by low pressure to the south) All of which merely emphasize the the trend towards the NW/SE split which is illustrated by the rainfall distribution and, I suspect sunshine.

Edited May 3, 2018 by knocker