Storm Forecast
Valid: Fri 24 Nov 2006 06:00 to Sat 25 Nov 2006 06:00 UTC
Issued: Thu 23 Nov 2006 22:49
Forecaster: DAHL
SYNOPSIS

Upper flow over W and central Europe is expected to back somewhat as Atlantic upper trough amplifies in response to a vort max rounding the base of the trough. Vigorous SFC cyclogenesis is expected to accompany this vort max, affecting the Iberian Peninsula and the British Isles on Friday and Friday night. Otherwise, weak quasi-stationary upper trough persists over the E Mediterranean regions.


... British Isles ... France ... Iberian Peninsula ...

Challenging forecast over Iberia, France, and the British Isles. GFS is somewhat reluctant to come up with appreciable and deep CAPE along and ahead of the cold front associated with the developing Atlantic SFC low. NMM is somewhat more optimistic but has overestimated convective potential for Thursday and so little confidence is put in this solution at this time. Most likely scenario seems to be that quite widely scattered storms will develop along the cold front over Iberia and maybe France but coverage will likely remain quite low. Those storms that do form will have some severe potential given quite impressive shear profiles but activity should be too isolated to warrant a thunderstorm/categorical forecast. Highest chances for more focused activity may exist over the central British Isles late in the period where latest GFS runs indicate some CAPE late in the period. Massive shear will be in place ... and this activity may augment the already severe large-scale wind field ... and also produce a couple of tornadoes. This forecast is still somewhat uncertain, especially over France and the Iberian Peninsula and an update may be necessary on Friday.

European Storm Forecast Experiment - ESTOFEX

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Current GFS charts, seem to show a weakening in the wind atm. It will be interesting to see how this reflects in the METO warning update later

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Meto Warnings have been updated.

As well as bringing everything forward to be in effect from 21:00 tonight, the area of disruption has changed dramatically too. The system is moving so fast, its difficult to predict.

Early Warning: Severe Gales 25 Nov 2006

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A "vigorous" autumn storm will bring severe gales of up to 75mph to England and Wales this weekend, forecasters have warned.


The Met Office says Wales, the Midlands and northern and eastern counties of England are most likely to be hit by the "potentially damaging" winds.
Scotland and the Midlands are also being warned to expect flooding.
The worst of the weather is predicted to hit England and Wales at midnight on Friday and continue into Saturday.
The brewing storm has been described by the Met Office as "a developing, severe weather situation".
But its precise path remains uncertain, say forecasters. "Although the very strong winds are expected to be the main concern, the storm will also bring heavy rain and an increased threat of flooding," the Met Office said in a statement.


The Coastguard Agency has also issued a severe weather warning to mariners all around the UK.
It said there were "extremely high winds forecast for the next few days" and said the outlook from Friday suggested "gale force eight to storm 10, perhaps even violent storm 11 later - storm 11 is one force less than a hurricane."
Coastguards also warned against wave watching from promenades or piers because of the increased risk of being swept into the water.
People are being advised to watch weather forecasts and to ensure they plan well for any weekend activities. The warnings have come after Britain enjoyed the warmest extended summer period on record.


BBC NEWS | UK | 'Vigorous' storm warning for UK

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Story has now been updated:

A "vigorous" autumn storm will bring severe gales of up to 75mph (120km/h) to England this weekend, forecasters have warned.


The high winds are expected to move from southern and eastern areas northwards towards Lincolnshire.
The worst of the weather is predicted to hit England at 0300GMT on Saturday, but will have died down by 0900GMT.
The brewing storm could disrupt transport and power supplies, the Met Office has said.
"Gusts to this strength are infrequent across the southeast and likely to lead to disruption to transport and power supplies," the Met Office said in a statement.
A spokesman added that there was also the potential for high waves which could reach seafront parades and promenades.
Parts of the Midlands have also been warned to expect flooding.
The BBC's Weather Centre said the gusts, which are expected to reach between 65mph (105km/h) and 75mph (120km/h), should die out by 0900GMT on Saturday.
But it will remain blustery throughout the UK, a spokesman said.

Mariners warned

The Coastguard Agency has also issued a severe weather warning to mariners all around the UK.
It also warned against wave watching from promenades or piers because of the increased risk of being swept into the water.
People are being advised to watch weather forecasts and to ensure they plan well for any weekend activities.
The Highways Agency is advising motorists to take extra care.
"Drivers should follow the advice on signs at locations vulnerable to high winds, slow down and pull over at the next safe stopping place during severe winds," a spokesman said. The warnings have come after Britain enjoyed the warmest extended summer period on record.

BBC NEWS | UK | 'Vigorous' storm warning for UK

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Latest charts from Ogimet gfs

Looks like the low has moved further east that first forecast. Still going to be windy, but the main force seems to be across the SE quadrant of the UK. With high winds across central parts the risk for damage is likely to be high as trees and things will not have been subject to these conditions for some time.

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Storm Forecast
Valid: Sat 25 Nov 2006 06:00 to Sun 26 Nov 2006 06:00 UTC
Issued: Fri 24 Nov 2006 21:28
Forecaster: TUSCHY
SYNOPSIS

An intense upper-level trough just west of Europe will continue to advect an unusual warm airmass over most parts of Europe.
Intense cyclogenesis will occur on both sides of this trough, one affecting areas N/NE of Scotland and another one over the N-CNTRL Atlantic. An interesting side not is the intense pressure drop of the latter one with the Ocean Prediction Center forecasting an estimated pressure drop down to 948 hPa till the end of the forecast period.

Although cold temperatures are present over parts of NW Russia, no significant southward advection of this airmass can be expected due to the current synoptic constellation.
Most parts of the Mediterranean will stay dry and warm.

DISCUSSION

... United Kingdom...

First time frame and area of interest will be S / CNTRL - UK at 06 - 11Z . Models like GFS indicate a dragging and slowly NNE-ward shifting upper-level trough, crossing most parts of UK till 12Z.

18Z IR images (24th November ) showed an already well defined cyclonic swirl just west of NW Spain, but cloud tops were still pretty warm and no thunderstorm activity had been seen till 21Z. This system will rapdily shift towards the NNE.
No significant strengthening of this system will be expected, because it is well displaced of the best upper-level divergence.
A pronounced warm-up at 850 hPa should help to cap the warm sector covering all of S/SE UK at 06Z, although mid-levels will feel no significant change ( also indicated by still fine 2-4 km lapse rates ).
Main concern for a few thunderstorms to evolve will be a slowly eastward shifting cold front, where best UVV values and low-end instability are forecast to overlap.
A broad level-1 was issued because only small changes in the set-up could cause a signficant eastward shift and don't want to exclude an isolated storm east of the cold front ( over SE UK ) due to the general thermodynamic set-up ( regarding the lapse rates ).
Low-end instability is forecast and will be coupled with outstanding shear values ( DLS of 30-40m/s and about 15m/s LLS ) so each convective development ( not necessarily electrified ) can cause severe wind gusts and marginal hail.
The tornado threat will be enhanced along the cold front, where LCLs will be very low.

The forecast gets only more complicated after 12Z, when first upper-level trough will finally depart UK towards the NE, while another one will approach Ireland and Scotland during the early evening hours. At the same time, another upper-level trough is forecast to slowly come closer to UK from the SW.
All those systems will bring a prolonged period of locally enhanced lift over a pretty broad area and this also makes it difficult to pinpoint special areas of enhanced severe weather risk that far out due to frequently switching vorticity advection fields.

A pool of significantly colder mid-level air will arrive during the early afternoon hours over UK and should support a rapid steepening of the lapse rates. Hence strong convection can be expected with a risk for isolated large hail and severe wind gusts.
Negative LI values and low-end instability release mainly along the W/SW coast of UK and Scotland, coupled with low LCLs and strongly enhanced SRH values indicate the risk for a couple of tornadoes over the broad level-1 area.
The main inhibiting factor for a more significant thunderstorm event looks like to be the failure of a compact UVV field combined with pretty dry mid-level air over CNTRL UK.

European Storm Forecast Experiment - ESTOFEX

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The low is now taking form, on time too looking on the radar. Its to the SW UK just clipping south wales. Current heading NE.

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