Jump to content
Snow?
Local
Radar
Cold?
IGNORED

Tuesday/Wednesday's Event


SP1986

Recommended Posts

Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

Some difference in guidance from 12z UKMO and GFS on the arrival and progression of the low on Tuesday, the low currently ESE of New Foundland, 993mb on 18z Fax:

post-1052-1186949446_thumb.png

... and continues to deepen under left exit of a strong jet streak zooming out of Nova Scotia/New Foundland across the North Atlantic, 12z progs for 12z tomorrow:

post-1052-1186949557_thumb.pngpost-1052-1186949732_thumb.png

... then on Tuesday UKMO progresses the low quicker than GFS NE across the UK, here the 12z positions for Tuesday, notice UKMO has the low centred somewhere over the Irish Sea with heaviest rain running up the Western side of the UK by then, while the GFS has the low kept back to the SW of Ireland with heavy rain running into the SW:

post-1052-1186950001_thumb.pngpost-1052-1186949876_thumb.png

Strong winds are suggested for the English Channel and the SW approaches during Tuesday, with perhaps gales along exposed places in these areas.

UKMO clears the heaviest rain away from much of England and Wales by Weds 00z - with rain hanging on over Scotland, GFS has the rain hanging on further South over Northern England while it clears further South.

Early Wednesday UKMO and GFS develop a wave along the cold front trailing SW, this can be seen clearly on the T+60 (00z Weds) UKMO Fax:

post-1052-1186950657_thumb.png

UKMO and to a lesser extent GFS develop this wave into a secondary low under the left exit of another strong jet streak running NE across Sern England -the low progged to get down to below 988mb by 12z Weds, with heavy rain developing along the wave axis , another feature that needs to be watched:

12z UKMO (t+72) 300mb winds/slp and rainfall/slp for 12z Weds:

post-1052-1186950925_thumb.pngpost-1052-1186950953_thumb.png

So a fairly complicated low pressure system arriving during Tues and Weds which looks to bring the threat of heavy rain to all areas of the UK, the West and North in particular on Tuesday and the South perhaps on Wednesday.

Link to comment
Share on other sites

Posted
  • Location: Rossland BC Canada
  • Location: Rossland BC Canada

I think the main story with this event may be severe thunderstorm potential. There looks to be a good set-up for an active cold front slicing into warm, humid air brought up across southeast England from the Biscay source region.

These severe storms would be likely to develop around 1100 to 1400 BST across counties from Hampshire to Norfolk, with gradual eastward drift of the zone during the late afternoon. Some of these severe storms could become locally tornadic. I would not be surprised if this event produced a significant tornado, and the max risk for that would be in a SW to NE corridor similar to the above (Hampshire to Norfolk) but somewhat further east possibly as the storms take time to become tornadic.

Heavy rainfall would occur both with these storms and ahead of the system warm front across southern Ireland, Wales and north-central England probably from about Cheshire and north Shropshire to Yorkshire, 30-50 mms could be fairly widespread in that zone as well as from some of the thunderstorms further south.

Outside of the thunderstorm wind gusts, I would think the S-SW flow ahead of the front might produce gusts to 45-55 mph in coastal areas, but of course these would increase locally when the front comes through, to 60 mph briefly.

Link to comment
Share on other sites

Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

Interesting post Roger wrt severe thunderstorm potential on Tuesday, some parameters from GFS do lend to this, 12z GFS suggested rather high theta-w (wet bulb potential temps) values at 700mb being drawn in to the low ahead of the cold front, this would suggest potential for strong instability if convection can transpire, also strong 0-6km deep layer shear and strong low-level 0-1km shear is indicated over England and Wales on Tuesday:

post-1052-1186952728_thumb.pngpost-1052-1186952744_thumb.png

... however, GFS currently suggests little in the way of CAPE during Tuesday, due to low lapse rates with warm air advecting NE aloft, as can bee seen on the 500mb temp/height chart below:

post-1052-1186953042_thumb.png

IMO possibly a better chance on Wednesday for severe thunderstorms, due to a dry air intrusion spreading in aloft from the SW across England and Wales, with cyclogenesis over Sern/Ern England under the left exit of a strong 120kt jet streak modelled too.

Of course such details for Tuesday and Wednesday are subject to change.

Link to comment
Share on other sites

Posted
  • Location: Dunoon, Argyll Scotland
  • Location: Dunoon, Argyll Scotland

John :angry:

I know you all work very hard on this site and i appreciate it. :angry::angry:

I was just saying no warning updated from this part http://www.netweather.tv/index.cgi?action=...ts;reg=1;sess=;

But there is no reason to update it anyway i was just saying has been no update on that part.

:angry:

Link to comment
Share on other sites

Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield

Rodger always likes to err on the side of mass destruction.

Forecast this morning rain 10 - 15 mm nothing to write home about but the 75mm in places is. Mainly in the West. I've heard gusts up to 50 mph mentioned in our area. However we're sheltered from that direction so we can rule that out for us. The system should bring us the first rain of August and this year being this year it would be about right to have the months rainfall in one day. I don't think it'll happen like that though hopefully.

Link to comment
Share on other sites

Posted
  • Location: south London
  • Location: south London

A general 25 to 50mm of rain is possible almost anywhere, but more especially across Central and Western parts of the UK. However up to 75mm is possible in one or two locations, as a result there is a risk of flooding. Looks bad for Wednesday

Link to comment
Share on other sites

Posted
  • Location: Herts
  • Location: Herts
A general 25 to 50mm of rain is possible almost anywhere, but more especially across Central and Western parts of the UK. However up to 75mm is possible in one or two locations, as a result there is a risk of flooding. Looks bad for Wednesday

yeh i thought earlier it looks quite bad on wednesday but it has not really been recognised yet

saint :o

Link to comment
Share on other sites

Posted
  • Location: Dunoon, Argyll Scotland
  • Location: Dunoon, Argyll Scotland

Tuesday 46mph in sea 31mph near the sea 24mph on land

Wednesday 38mph in sea 31mph near the sea 38mph on land in some areas..

North Scotland thursday 46mph gusts

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

Gosh - I'll be battening down the hatches for this one :o

An inch of rain and a gust of 40mph. Hold the front page :o

EDIT: In fact it's raining with gusts of 44mph in the Western Isles right now.

Link to comment
Share on other sites

Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield

Ah well this Dinner time forecast doesn't look to bad for us. Rain clearing before Eight pushing on towards Scotland then cloudy with the odd bit of light rain. Looks like I will be topping up the ponds then. Got a feeling that forecast will change somehow back to more general rain.

Link to comment
Share on other sites

Posted
  • Location: Rossland BC Canada
  • Location: Rossland BC Canada

Comments above concerning mass destruction seem not to be based on anything I actually said, the general comments about rainfall amounts and wind speeds are about the same as most other forecasts I have read. As for severe storms and the possibility of a tornado, this all depends on location, obviously a tornado in a wooded or rural area, if actually seen by anyone, will not do much damage to property, but as seen in 2005, a tornado in an urban area can do a lot of damage even if it is fairly weak. The high thickness values being advected into southeast England make the risk for a tornado fairly significant IMHO so it's just a heads up suggestion, not a warning of doom.

The potential for severe weather seems to be somewhat later with the 06z model run, and I would now place it more from about Dorset to the southeast Midlands and Lincs later on Tuesday afternoon, then redeveloping a little further south and east on Wednesday when the front is more from about west Sussex or east Hampshire to East Anglia.

Warm, humid air continues to stream northeast ahead of this frontal zone and by the time the system arrives later Tuesday it will have 23-25 C temps in parts of southeast England to work with, and a sharp wind shear developing, so I continue to think that severe storms may be a highlight of this weather situation; I am not so concerned about sustained winds in the air mass flow outside of this frontal boundary although these will become unpleasant and perhaps hazardous for sailing (smaller boats in particular) off the western coasts and Channel.

Link to comment
Share on other sites

Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

the first 'key' is about to be shown.

Below is the latest infra red sat picc with the fax chart soon to follow.

On the sat picc the cold front is pretty weak at the moment; it can be seen trailing sw'wards from the main cloud bearing area.

post-847-1187011356_thumb.jpg

the euro computer chart, not the most reliable in my view quite often, does show the centre pretty near what the Met O Fax for T+36 hours from yesterday showed. Centre on that around 50N 36W pressure below 989mb

this is the latest for the open Atlantic from UK Met

http://www.metoffice.gov.uk/weather/marine...on&type=All

things appear about on track

Edited by johnholmes
Link to comment
Share on other sites

Posted
  • Location: Northampton (90m ASL)
  • Location: Northampton (90m ASL)

The Accuweather addon for Firefox which shows the weather for the next 3 days in my area, has "Heavy afternoon thunderstorms" on Tuesday and "Thundery rains" for Wednesday.

I do hope so! Storm potential doesn't look that good on the latest GFS run though, so we shall see.

Link to comment
Share on other sites

Posted
  • Location: Washwell, Wilts
  • Location: Washwell, Wilts

Hi

Not a great model expert so after a little help on this. I'm taking the overnight Ferry from Portsmouth to St Malo on Thursday night - leaving at 20:30. Will the worst of the winds be gone from the channel by then ? Having endured a sea of vomit from the kids on the boat back to the UK last summer I'd like to know whether to plan for the worst B)

Link to comment
Share on other sites

Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

looks about 15-20kt westerly so not sure what sort of swell that means, not flat for sure, but not that bad.

Link to comment
Share on other sites

Posted
  • Location: Dunoon, Argyll Scotland
  • Location: Dunoon, Argyll Scotland

Buoy Reports

K5 Buoy North West Scotland:

Wind speed 18mph

Temp 11c

Pressure 999mb

Wave Height 10ft

M4 Buoy Northern Ireland:

Wind speed 18mph

Temp 14c

Pressure 1004mb

Wave Height 7ft

M3 Buoy South Ireland

Wind speed 13mph

Temp 15c

Pressure 1006mb

Wave Height 4ft

62125 Buoy North East England

Wind speed 24mph

Temp 16c

Pressure 1008mb

Wave Height 7ft

62114 Buoy North East Scotland

Wind speed 22mph

Temp 14c

Pressure 998

Wave Height 5ft

Link to comment
Share on other sites

Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

the 12z Met O Fax shows the low spot on from its T+36 predict from yesterday at 50N 36W centre 984mb(forecast was for <988mb), so anywhere from 984-987mb.

the first buoy to show any signs of the low is this one at 53.50 N 19.50 W (53°30'0" N 19°30'0" W)

1005.2 falling 1.4mb in past 3 hours

it does not have wind speed and direction data.

Edited by johnholmes
Link to comment
Share on other sites

Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

It will be interesting to see just what shape the surface low has through tomorrow. GFS has quite consistently tried to elongate it whilst the UK Met has dabbled with that idea but has now got a reasonably round style surface low.

Why the difference? Well we don't have much info from the UK Met but GFS shows the upper air pattern in its forecast is very conducive to that type of development. That is a cold front being stretched north south due to what is called a converging upper trough over the top of it. In some cases it does cause a 'ripple' or 'wave' to develop on the cold front, slowing its eastward progress and enhancing rainfall on it.

I suspect, as on so many occasions, what we will actually see is some kind of half way house between the two models.

another case of watching events unfold through tomorrow.

Edited by johnholmes
Link to comment
Share on other sites

Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield

Slight change on the evening forecast. Wind speeds have gone up a lot so it could be very Windy in the South West. Rain band seems to the strongest over Northern Ireland Southern Scotland and Northern England.

Link to comment
Share on other sites

Posted
  • Location: Powys Mid Wales borders.
  • Location: Powys Mid Wales borders.
Slight change on the evening forecast. Wind speeds have gone up a lot so it could be very Windy in the South West. Rain band seems to the strongest over Northern Ireland Southern Scotland and Northern England.

Wind mean speeds 30mph in places which from the south which I don`t mind from that direction and also find a S-ly isn`t usually that strong here anyway when forecast and looking at the fax it`s the south/coasts central east and SW Wales that gets the strongest winds and what XC map shows too.

http://85.214.49.20/pics/brack0.gif

Some very patchy rain showing on the radar at the moment it doesn`t look like it`ll dampen the dust yet :D ...dry but getting cloudy here and calm.

Edited by Snowyowl9
Link to comment
Share on other sites

Posted
  • Location: Tiree
  • Location: Tiree
Gosh - I'll be battening down the hatches for this one :D

An inch of rain and a gust of 40mph. Hold the front page :)

EDIT: In fact it's raining with gusts of 44mph in the Western Isles right now.

it wasnt that windy lol! yup heavy rain hear today

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

South Uist - gusts of 50mph :D

http://www.metoffice.gov.uk/weather/uk/he/...her_graphs.html

Tiree - 45mph

http://www.metoffice.gov.uk/weather/uk/st/...her_graphs.html

Up at Stornoway it was less windy :)

(I've never looked at those pages with graphs before - they're excellent).

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...