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Short range model discussion - into 2018


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Morning all,

Overnight blizzard across SW England and Wales now clearing away to affect Ireland this morning, where Met Eireann has a status red for blizzard conditions for Galway, Leinster and Munster. The heavy snow sweeping NW overnight across SW UK and now Ireland associated with surge of moisture aloft ahead of (ex?) Storm Emma low off Brittany this morning, the surge of moist and relatively warmer air at height (though below freezing) marked by upper warm front on fax chart for 6am,

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the moisture having its origins over the Azores looking at the PWAT loop since 00z yesterday., so a supply of copious amounts of moisture

loop_pwat.thumb.gif.c21d8904ad4aca6af8a23d1730577ee7.gif <------ click to animate

Very strong easterly winds overnight too, gusting to 67mph at RAF Culdrose in Cornwall, 66 mph at Aberdaron in west Wales. causing much drifting of large snow accumulations, reaching up to 50cm in south Wales, scenes of vehicles stranded for hours in snow drifted roads in SW and central south England.

Also issues overnight with freezing rain across southern coastal areas of England and more recently across Kent and Essex, where police have been closing sections of the M2 in Kent for ice glazing from rain falling on frozen tarmac and numerous crashes or cars into ditches elsewhere on the county's roads. 

A look at the 00z Herstmonceux (E Sussex) radiosonde ascent shows a layer of air between 800 and 900mb just above freezing if you trace the 0C line up, so this layer melting any light snow falling through into rain which when it falls on to frozen surfaces freezes. The less cold air from the south riding above temps below 0C at the surface and perhaps part of the weakening warm front shown on the fax chart above moving into S England and bringing the rain/drizzle or light snow well inland to W and N of London.

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Freezing rain or drizzle could continue to pose a problem through the day along southern coastal counties and far SE including Essex coastal areas, as less cold air from the south continues creeps in aloft of surface easterly flow that is below freezing. Further snow is expected to organise and push up from the south along a cold front moving up from France this afternoon, the cold front becoming occluded as it continues north across England and Wales overnight, as the cold front overtakes the warm front with cool air to the south and cold air to the north. Snow tending to peter out as it heads north into central areas.

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Scotland seeing further snow showers feed in from the north sea towards the east today, giving 5-10cm in places.

Staying on the cold side across the north this weekend, though not as bitterly cold, but still with snow showers affecting eastern Scotland on Saturday, drier and sunny across western Scotland. Further south across England, Wales and Northern Ireland  - generally cloudy with patchy sleet and snow spreading north through the day, though generally light, and snow becoming confined to northern England, north Wales and N. Ireland – tending to turn to sleet or rain across southern England and south Wales – as less cold air arrives from the south, leading to a thaw of lying snowSunday sees temperatures continue to rise across southern Britain, with some rain showers spreading in across southern England and south Wales, drier and brighter across central areas. Still cold across the north, with patchy sleet and snow affecting northern England, Northern Ireland and southern Scotland, snow showers across NE Scotland, while NW Scotland looks to stay mostly dry and sunny.

 

Staying cold across the far north early next week, with further outbreaks of snow at times for northern Scotland, sleet and hill snow for southern Scotland. For England and Wales, rain showers, perhaps sleet or snow over the hills in the north. Turning mild in the south.

 

Edited by Nick F
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Synoptic analysis Thursday to Saturday – update 21z 28/02/2018 Tonight T+00 fax chart for 6pm today shows a 1051mb surface high over Scandinavia, low pressure system between the Azores and I

A quick glance here confirms that.and a severe frost in morning and wind chill https://wow.metoffice.gov.uk/ Sid's okay

The witching hour is finally upon us and later today the very cold air will arrive from the east bearing gifts, wanted or unwanted depending on your inclination. Thus from tonight and through the next

Posted Images

The occlusion will continue to move north this evening and overnight taking outbreaks of patchy snow with it affecting Wales, the Midlands, the north and N. Ireland whilst snow showers will continue in the north east and Scotland, Behind the front showery rain into the south west, Another very cold night with a widespread frost and ice. Still some uncertainty on far north the 'warmer' air will push along the south coast.

5a997bf15cdd4_occ1.thumb.JPG.2d00462442a814b9c031d5a426135856.JPG5a997bf787efc_occ2.thumb.JPG.bf1fa21227271ab86745b062a20e069a.JPG5a997bfe98cd9_occ3.thumb.JPG.1831c34a1bc18dc7cac82bbcdd79fd8c.JPG

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Edited by knocker
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28 minutes ago, SnowChance24 said:

As we’ve just had about two hours of moderate snow in Exeter when rain had been shown is the cold being more stubborn to shift? Is the situation still regarded as marginal?

Not at the moment I wouldn't have thought

exeter.thumb.JPG.b82d83f5915e9397164e2b375b108ff1.JPG

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Again not much to report vis the anomalies this evening. Still a lobe over NW Greenland and ridging in the NW Atlantic into the Labrador Sea and a trough over the south east Untitled States. Thus two energy flows leaving North America, one around the ridge and the other from the south east seaboard.

The former is the flow that influences the UK as it swings south east into the eastern Atlantic to the upper trough in that area running south adjacent to the UK giving a flow over the UK between NW and just south of west. This is a tad vague because there are differences between the orientation of the ridge and the trough. Keeping that in mind we are still looking at a pretty static scenario with low pressure in the vicinity of the UK with perhaps systems tracking into the south thus remaining unsettled with temps a little below average generally but prone to regional variation.

ecm_eps_z500a_5d_nh_11.thumb.png.581aebf3518e75b9fa2ec410a543b305.pnggefs_z500a_5d_nh_41.thumb.png.675ce657ed44fc9b8acccd19aa9c0894.png610day_03.thumb.gif.4b11c39edfaa747a2500dcc352136a90.gif

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12 minutes ago, knocker said:

Again not much to report vis the anomalies this evening. Still a lobe over NW Greenland and ridging in the NW Atlantic into the Labrador Sea and a trough over the south east Untitled States. Thus two energy flows leaving North America, one around the ridge and the other from the south east seaboard.

The former is the flow that influences the UK as it swings south east into the eastern Atlantic to the upper trough in that area running south adjacent to the UK giving a flow over the UK between NW and just south of west. This is a tad vague because there are differences between the orientation of the ridge and the trough. Keeping that in mind we are still looking at a pretty static scenario with low pressure in the vicinity of the UK with perhaps systems tracking into the south thus remaining unsettled with temps a little below average generally but prone to regional variation.

ecm_eps_z500a_5d_nh_11.thumb.png.581aebf3518e75b9fa2ec410a543b305.pnggefs_z500a_5d_nh_41.thumb.png.675ce657ed44fc9b8acccd19aa9c0894.png610day_03.thumb.gif.4b11c39edfaa747a2500dcc352136a90.gif

What do you make of this precip in the channel heading for the south coast? 

A6423813-BA87-4B95-A522-0FF43B3A7D56.png

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18 minutes ago, c00ps said:

What do you make of this precip in the channel heading for the south coast? 

A6423813-BA87-4B95-A522-0FF43B3A7D56.png

Presumably it is the bunch of rain showers that were expected. The satellite at 2040

ch4.thumb.jpg.a8de207c74d8a3e1045c12e4dcd5a1e7.jpg

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We are slowly coming to the end of, understatement of the year, a period of very interesting weather, and slowly moving into a period best described as more mundane albeit, being the weather it will not be without interest. A quick and very short overview. Our weather in the medium term will be dominated by a complex upper trough fed by energy running east from the south east US seaboard under the high pressure to the north.

gfs_z500a_natl_9.thumb.png.3c4ced72edb98f6bed6ff9bf34b6abc4.pnggfs_uv250_natl_9.thumb.png.4e4746a0ae8d7c6c2613810eb04b476a.png

Back to more detail. It looks like the UK is entering into a N/S split period and at 00 the low and wrap around occlusion were over the south west and central England whilst the north still in the cold showery easterly. This regime will continue during today whilst further south one occlusion will weaken whilst a band of snow, sleet and rain associated with the second will push north, mainly affecting the west, from the south. It is this that finally introduce warmer air generally and initiate the beginning of the thaw during the day in the south (The sat image is for 0400)

PPVA89.thumb.gif.24c34d70921938d54c2b37490234ba6f.gifch4.thumb.jpg.7be0db62d592da00291c1209ee54bf79.jpgPPVE89.thumb.gif.bd69c19a9c15adea7186151bbeaf09ac.gif

 

gfs_t2max_c_uk2_4.thumb.png.24f1788db9ed76f53f58340d4de02736.pngoverview_015.jpg?2018030300

So in a nutshell tonight pretty cloudy in England and Wales with patchy rain and sleet in the south and snow further north in Wales and the Midlands and snow showers continuing in the north east and Scotland.

overview_030.jpg?2018030300gfs_t2min_c_uk2_6.thumb.png.5106ce887c4e3233e99bb5bd0018a8a2.png

By Sunday the N/S split is quite marked with low pressure dominating the UK with the centres to the south west. This leaves Scotland, N. Ireland and the far north of England still in the showery south easterly whilst the rest of the country is under a patchy rain, sleet and snow regime with the slow thaw continuing.

gfs_ptype_slp_eur2_7.thumb.png.1018a0fdd1ebce697ea9ffb3ca1b0f11.pnggfs_t850a_eur_7.thumb.png.e8c2827ccd68ec54eb5bd28810cfa37c.pnggfs_t2max_c_uk2_8.thumb.png.4ea06e44ac1b3a3704a7d2327ecc9f18.png

Keeping in mind the opening comments of this post vis the upper trough this is essentially where we stand Monday-Wednesday with low pressure influencing proceedings, Colder with snow showers in Scotland and the snow, rain and snow mixture continuing elsewhere as the slow thaw continues. The detail of this will vary but these are the gfs spot charts for the three days

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I've mentioned a slow thaw a few times and temps are certainly creeping up but realistically Spring is not yet bursting forth and temps are still below average.

gefs_t2ma_5d_eur_21.thumb.png.938d3f4d479ee20a0512e298e0a697a7.png

Edited by knocker
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Interesting to note that on the Albermarle midnight sounding the strong easterly cold advection in the lower layers with the much warmer air above a massive inversion of -12C at 796mb -7C at 706mb with the wind veering and becoming negligible.Gone is the convection heaven from the beast from the east.

2018030300.03238.skewt_parc.thumb.gif.4e83e1fe9e74bb1edfb0c49aa5de1099.gif

 

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Plenty of mist and fog in the south and moderate rain in the south west The Chiefs game should be okay this PM unless it's already been posponed

 

2018030309_uk.jpg

Edited by knocker
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Another classy high res, MODIS at 1100 (courtesy Dundee Satellite receiving Station) showing the low over the south west and the occlusion across France and interesting cloud over Scotland

ch38.thumb.jpg.9db346b924fc4988781af35d2af97da7.jpg

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The notable cold spell is now on it's last legs with warmer and moister air already mixing out the cold further south and over the next 24hrs will make further inroads northwards.

Before then NWshort range model indicates one last band of snow moving north this evening and tonight ahead of the occlusions before dew points,850/1000hpa thicknesses and finally surface temperatures rise bringing in the inevitable thaw.

Images for midnight tonight

 viewimage.pbx?type=nmmhi;date=20180303;tviewimage.pbx?type=nmmhi;date=20180303;tviewimage.pbx?type=nmmhi;date=20180303;tviewimage.pbx?type=nmmhi;date=20180303;t

A look at the fax for Sunday 12z shows the frontal systems moving up the country continuing to change the air mass.

fax36s.gif

By early next week we will be under a less cold and rather damp regime with low pressure setting up shop for a while under a quite slack setup,a far cry from the crisp,clear and bitter Siberian air of this last few days. 

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Something that cropped up whilst discussing the anomalies yesterday, the two upstream energy flows. One exiting nortthern Canad and the stronger one the US south east seaboard. Something like like this leading potentially to what ? :shok:

gfs_uv500_natl_18.thumb.png.cb41d3ac0c65bc13a8d5727787b09243.pnggfs_t850a_natl_18.thumb.png.133dea45d8b937c4b42e2b888d3c0e06.pnggfs_ptype_slp_eur3_18.thumb.png.5931213e41be4358861fb5e320643574.png

Edited by knocker
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1 hour ago, knocker said:

Something that cropped up whilst discussing the anomalies yesterday, the two upstream energy flows. One exiting nortthern Canad and the stronger one the US south east seaboard. Something like like this leading potentially to what ? :shok:

gfs_uv500_natl_18.thumb.png.cb41d3ac0c65bc13a8d5727787b09243.pnggfs_t850a_natl_18.thumb.png.133dea45d8b937c4b42e2b888d3c0e06.pnggfs_ptype_slp_eur3_18.thumb.png.5931213e41be4358861fb5e320643574.png

Some quite wet weather?  I must admit I'm not very good at understanding what happens when these are two distinct arms of the jet leaving the North American continent.

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On 3/2/2018 at 10:52, Interitus said:

Good question about the CET - the provisional values go to Feb 28th at the moment, which at -3.8°C would equal the daily record from 1785

The coldest March 1st is -3.5°C from that same year

Remarkably, the provisional value for March 1st is -3.5°C so tying the CET record daily lows from 1785 two days in a row!

But on checking the finalised value for 28th Feb fell short at -3.6°C

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19 minutes ago, chrisbell-nottheweatherman said:

Some quite wet weather?  I must admit I'm not very good at understanding what happens when these are two distinct arms of the jet leaving the North American continent.

Wet and windy a distinct possibility i would think but maybe favouring the southern end of the country.

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Pretty good agreement on the overall pattern with tonight's anomalies but disagreement on the  intensity and alignment of the ridge/trough combination in the arena of the amplified Atlantic.

Essentially still a secondary lobe NW Greenland and a trough over the south east US with the ridge/high cell in between around the Labrador Sea area. Thus two energy flows, one around the ridge to the north and the other stronger one exiting the seaboard of the south east United States, The two flows coalesce in mid Atlantic but there is no agreement on this because of the varying configurations of the trough in the eastern Atlantic as previously mentioned. Until this is sorted the detail of the evolution will be problematic as the area of the coalescence is an environmentally friendly zone for cyclogenesis  Suffice it to say at this stage looking like an unsettled period with the upper flow from the westerly quadrant, perhaps quite windy, with temps average or a little below.

ecm_eps_z500a_5d_nh_11.pnggefs_z500a_5d_nh_41.thumb.png.beaee77a7f852778f3469fcb561ff4b4.png610day_03.thumb.gif.df143a22a6d109011c5da38acf47ffd4.gif

 

 

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The slow change to a different pattern continues  with low pressure dominating our weather for the foreseeable with upper troughs and associated surface lows being the guiding feature. It's been awhile since we had to look W/SW for developments.

gfs_z500a_natl_11.thumb.png.c1c5d6c0fc3a0170cbf027496880318f.pnggfs_uv500_natl_11.thumb.png.037f59264ada7b9b785b3d14a204bbdb.png

So today with low pressure and a couple of occlusions drifting north sees patchy rain sleet and snow doing the same over England and Wales and N. Ireland leaving heavy rain showers in the south west  Further snowfall  expected in Scotland particularly the north east The 'warmer' air and slow thaw also moves slowly north and has already reached the south Midlands this morning but Scotland will remain cold.

https://wow.metoffice.gov.uk/

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The snow showers will persist overnight in north east Scotland whilst elsewhere  will be partly cloudy with mist and fog patches developing and this will be the general theme through Monday with persistent snow still across NE Scotland with showers developing across England and wales. But later in the day a band of more concentrated rain rain will track north affecting the western side of England and Wales and by now temps have recovered to be near average.

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At the risk of sounding like a stuck record this relatively mundane weather will be the order of the day through the middle of this week; Namely scattered showers with some longer periods of rain and still a chance of snow on the higher ground, some mist and fog overnight and in the mornings and temps still recovering.

gfs_ptype_slp_eur2_11.thumb.png.f9de27e88ba93dd58e3d355e729455d7.pnggfs_ptype_slp_eur2_15.thumb.png.d407d10462bbd047dfdc1646efe9d2be.pnggfs_ptype_slp_eur2_19.thumb.png.1dea50f2476c77381b89255ba7f5635b.png

gefs_t2ma_5d_eur_21.thumb.png.9b99b3217808cd3c7a163bc59fee897e.png

 

 

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