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Possible severe storm Monday 28th October 2013 Part 2


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A bit later than planned as my computer decided to freeze and then cause all sorts of problems with trying to post this Posted Image

 

ECM still has a tighter squeeze developing on the back edge:

post-7593-0-12367300-1382858864_thumb.pn post-7593-0-46874000-1382858871_thumb.pn

 

 

Best seen on the 925mb charts (ignore the coloured shading, which is 925mb humidity, I'm just using these as it shows more isobars and in more detail than any other charts)

post-7593-0-24492000-1382858848_thumb.pn post-7593-0-30292800-1382858855_thumb.pn

 

Which creates an area of stronger winds:

post-7593-0-25876100-1382858877_thumb.pn post-7593-0-17844700-1382858884_thumb.pn

 

Not as strong as some runs before, but mean speeds of 28-35 knots (32-40 mph) inland at 6am for the West Country and other southern counties at 6am, transferring east and giving mean inland speeds of 35-40 knots  (40-46 mph) over East Anglia at 9am

Gusts would obviously be higher, I'd guess around 60mph for the west country and perhaps 70mph over East Anglia.

 

Average speeds of 45-50 knots (52-58mph) shown for southern coasts, with a small area of 50+ knots developing off east Anglia.

 

Still a notable though short lived blow perhaps, though not worthy of a red warning I'd have thought (unless things change by late morning) or the press hype of course.

 

Seems very knife edge with how the finer detail develops, and how this finer detail effects development/timing of things, e.g. does the tight squeeze in isobars on the back edge develop over the UK or a few hours later after the low has cleared.. a forecasting headache I can imagine.

I certainly don't envy the job of the Met Office forecasters right now, they can't really do anything more than what they have done. For us sat here it's a lot easier to watch developments without having to tell the country what will happen, even though we can't be sure.

 

I wonder if the jump from observational data to model forecast data when the system is forming/deepening can cause issues for the models, and if it's possible that this is happening now?  

Edited by Stormmad26
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Surely if this was a snow event we wouldn't be using GFS / ECM much this close in but switching to UKMO Fax charts? Those fax charts don't look downgraded to me. 

When I looked at those FAX charts, I thought they looked downgraded to me but it hard to tell without seeing 30 hour FAX chart.
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Has anyone noticed that on the GFS, the system seems to develop as it moves over the North Sea?

The isobars seem to become tighter as well. Is it just going to develop too late?

6 am: post-18097-0-94928300-1382859470_thumb.p

9 am: post-18097-0-69067900-1382859493_thumb.p

Midday: post-18097-0-29392500-1382859513_thumb.p

3 pm: post-18097-0-65248700-1382859531_thumb.p

6 pm: post-18097-0-69344100-1382859549_thumb.p

9 pm: post-18097-0-79656400-1382859571_thumb.p

Edited by interestingweather
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Here's the GEFS ensemble analysis for Heathrow,

 

post-5986-0-29571300-1382860058_thumb.pn

 

Still a drop in reliability regarding the depth of pressure that we'll see. It's easy to conclude that the forecasting models still haven't got this spot on. I suggest some good old fashioned pen and paper professional meteorology is going on in Exeter; along with sat obs, too.

 

Main differences in GFS ensemble is the depth of the low over Scotland, and this seems to be the mitigating factor of the final track of the low. Here's the 75% cluster, and subsequent dendrogram,

 

post-5986-0-87943100-1382860187_thumb.gipost-5986-0-66988400-1382860199_thumb.gi

 

Observations from bouys and such like, should confirm which ensemble member is closest to reality.

Edited by Sparkicle
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03Z run of the UKV model.

 

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Looking at these even if the intensity of the wind may downgrade it appears the intensity of the rain looks to be full on, here in Lincs its pretty much rained every day for the past two weeks so i would expect localized flooding at the very minimum.

 

LO

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mean wind speeds on the south coast appear lower by around 10mph and for a shorter period on ecm 00z compared to ecm 12z

 

the trend on the models for a little less deepening means we lose some of the area of england/wales likely to be affected plus around 10/15% of the intensity -  this is reflected in some of the less understanding posts this morning. roll on winter !!

 

would be typical if we see a repeat next weekend which is naturally less hyped by the media, only for it to cause more disruption and damage !  thats the weather innit !

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http://eumetrain.org/eport/euro_06.php?width=1360&height=768&date=2013102706&region=euro

 

Tick MSLP on the bottom left, then tick IR 10.8 in the top right. This overlays the ECM chart over the real satellite image. Then toggle the Pseudo IR option on the right to show what the model thought it would look like at that time. That way you can compare and contrast reality with model to see if there are changes. Problem is it only updates every 6 hours. It's using the 6am frame now though so fairly recent.

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Looking at these even if the intensity of the wind may downgrade it appears the intensity of the rain looks to be full on, here in Lincs its pretty much rained every day for the past two weeks so i would expect localized flooding at the very minimum.

 

LO

That is a good point, and York saw flooding too, many parts have been very wet recently. So there will be water problems whatever the winds do

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Just going to copy my post from the convective thread as I think there is a risk of some convective activity before, during and after this storm and may be relevant in here. The risk of some severe weather over the next 2 days:

 

A difficult one to forecast for the next 48 hours relating to convective activity what with so much change in the models from run to run. GFS has downgraded the storm system and also appears to push it through that bit earlier but this is just one run of one model. 

 

Latest GFS and lightning wizard (which very much uses the GFS to my knowledge) shows the chance of some thundery activity in the showers today, more so in the north and west of the country where the risk is there from the word go - maybe western Scotland and NW England in with the highest risk. Any heavy showers and thunderstorms that do form across the England portion will have some 30-50 knts of DLS and moderate to high levels of helicity to play with which will allow activity to organise and bring the risk of strong convective gusts of wind/tornadoes (hence a level 1 from Estofex, although more relating to after midnight for England). Convective activity does look to die out in England after around mid afternoon. Further north in Scotland the risk goes on into the evening, but these look to be more pulse type storms, albeit with lightning possibly more prevalent here due to lower ELT's and higher CAPE.

 

Tonight, as part of this storm system, there looks an interesting zone to the south of the UK - although this is based on an ever changing suite of runs - whereby a small amount of CAPE (100-200j/kg) overlaps DLS of up to 100knts, 0-1km helicity that is off the scale and 0-3km helicity of over 400m2/s2. Currently this region is in a line from around the IOW to the Wash eastwards. To my eye this combination brings the risk of some very high convective wind gusts in association with any convective activity and a high risk of one or two, perhaps quite sizeable, tornadoes. Rainfall rates in southern parts could also pose a problem, with a lot of rain likely to fall in a 6-9 hour period. This activity is in addition to storm force winds gusting up to 80-90mph along the south coast, particularly to the eastern half of the south coast - which are bound to create havoc for the morning commute tomorrow.

 

After this there is the risk of further convective activity in southern and central parts tomorrow in the sunshine and squally showers regime in the wake of this storm.

 

A level 1 from Estofex for the Midlands south, more so relating to tonight. Please bear in mind the rapidly changing situation though, things could still go either way with regards this storm - it could downgrade further or it could still hit the UK head on. In my view, met office warnings still stand and they are right to keep plugging this thing as it could still prove to be a nasty little feature.

Edited by Supacell
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IF the storm is majorly downgraded - it does make you wonder the point of releasing warnings so far out

 

I mean what exactly takes 4 days to "prepare" for ?

 

would the morning before - ie 24 hours before not be enough ? its not like we are in the US where a major hurricane advances and people need time to board up houses etc

 

no criticism on models etc - these are complex systems to model

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BBC forecast now downgraded as in they not saying hurricane force winds but 80mph winds and very heavy rain, not as severe as 1987

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