This Week's Storms - FORECAST, MODEL DISCUSSION ONLY

maquiladora

0Z NAE is similar to the 18z and at 48 hours has the structure of the low getting a bit complex while over the UK.

It was gone completely on the 12Z ECM, now its back on the 0z, though too far south to affect us if this came off.



Haven't noticed much change on other 0Z models.

Sponge Bob

UKMO still holding to their 'risk' warning for southern England and Wales issued yesterday lunchtime.

http://www.metoffice.gov.uk/weather/uk/uk_forecast_warnings.html

WolfeIRE

http://www.netweather.tv/index.cgi?action=convective;sess=
Possibility of thunderstorms later.

Met Eireann also warning for occasional storm force winds from Carnsore Point to Valentia tonight
http://www.met.ie/forecasts/warnings.asp

Sponge Bob

Jetstream forecast Thursday. Stream itself more northerly but overall less intense than forecast when it was shown off to our south. No wonder the models/forecasts are so odd and non commital.

Now



Older

Sponge Bob

06Z GFS shows the two lows interlocking and rotating each other on friday. This means that yesterdays low wanders far enough west to give us a cold NW airflow on friday as the new low marches up the English Channnel.

In other words we get a friday storm redux out of the tuesday storm in effect.....but the thurs fri system moves more quickly across Southern England thanks to the interlock.

All very mehh and brrrrrrrr.

WolfeIRE

Met Eireann removes storm reference from their weather warning for the south coast


Gale Warning

Southwest winds veering west to northwest will reach gale or possibly strong gale force for a time early tonight on Irish coastal waters from Carnsore Point to Roche's Point to Loop Head.

Sponge Bob

UKMO have become more specific about friday .....Cork people should note!

Issued at - 14 Dec 2011, 12:25
Valid from - 15 Dec 2011, 21:00
Valid to - 16 Dec 2011, 12:00

There remains a risk of very strong winds and heavy rain moving eastwards across parts of Southern England later on Thursday and Friday morning. There is still some uncertainty regarding the northward extent of any severe weather though southern parts remain most prone with southern coastal areas seeing highest gusts.

The public is advised to monitor warnings for this period, noting that the warning may be upgraded.

WolfeIRE

GEFS has shifted that storm system further north

Spindle

Sponge Bob wrote: »

UKMO have become more specific about friday .....Cork people should note!

We will see, I still have a feeling about this, even if the models don't agree, but when you least expect it, it will happen, it will be interesting anyway to see where the storm does actually hit.

maquiladora

According to posts on Netweather, BBC weather presenter said the Phantom Storm low is deepening faster than the models expected for this time.

Hard to know if that will have any impact on how plays out yet but worth keepin an eye on I suppose.

Sponge Bob

12z GFS apparently splits the low into one two then three see 00 and 06 and 12 , one stays put way off west, the middle one becomes amorphous.

The easternmost is the 'friday storm' and is a tad further north all right but not that intense at 12 o clock thursday.





Then by 1800

WolfeIRE

The centre of that LP system is directly on the souythern england coast and shifts further inland over SE England. Looks a lot weaker over England this time around.

maquiladora

No change on the 12Z GFS, maybe about 20 miles further south, same intensity Thursday night. Will probably have to wait for the 18Z to pick up on any adjustments if it is the case that it is a bit deeper than expected.

maquiladora

12Z NAE has the low about 10mb deeper than than the GFS at 30 hours. Same track.

12Z UKMO almost exact same at 0Z, slightly further south.

marvsins

Just had some lightning and long rumble of thunder in Carrigaline area of Cork

leahyl

marvsins wrote: »

Just had some lightning and long rumble of thunder in Carrigaline area of Cork

Cool! I'm near glasheen area - not near a window though so didn't see any lightning or hear any thunder for that matter

Deep Easterly

DMI 12z more or less similar to the NAE 12z regarding track though slightly less intense depth wise:



To think that the HIRLAM suite were not keen on this prognosis at all yesterday by keeping any potential much further south. NAE a lot more consistent this time around.

darol15

kinsale just had thunder lightning and crazy hail stone ! calm now do, bring on the worst of it !!:D

Deep Easterly

Guys, Thunderstorm report thread here!

http://www.boards.ie/vbulletin/showthread.php?t=2056477341

Congrats though, I begrudge no one thunder.

munsterlegend

Met Eireann update at 16 40:


Today


Wintry showers, some heavy and thundery, continuing in Munster and coastal parts of Connaught this evening in moderate to fresh, locally strong, southwest to west winds.
Tonight

A more prolonged spell of rain or sleet will develop across southern areas for a time early tonight, turning to snow in places further inland. This will clear later but wintry showers will continue in the north and west. Westerly winds will strengthen in the south for a time but will moderate later. Skies clearing in places will allow sharp ground frost and icy patches to form inland before dawn. Lowest temperatures +3 to -2 degrees.


Tomorrow

Further wintry showers will affect the north and west but other areas will be mainly dry. However, outbreaks of rain or sleet are likely to affect southern coastal counties later tomorrow evening. Winds slackening during the day but remaining cold; highest temperatures 4 to 7 degrees.

wonder how far inland they mean for snow! no mention of the dreaded high ground at least.

ninebeanrows

One of the GFS EPS members shows how this could but obviously wont (less than 2%) happen.

We would need to the system be a sub 980mb low to our southwest by 11am,
even lower than the chart below.

This chart results




in this

at 42hrs

darol15

dude what do these pictures mean ??lol the 2nd is storm anyway i presume

Musicman2000

darol15 wrote: »

dude what do these pictures mean ??lol the 2nd is storm anyway i presume

Its another run of what could happen, But its 95% sure to track south

John mac

darol15 wrote: »

dude what do these pictures mean ??lol the 2nd is storm anyway i presume

Dude read this

darol15

there still confusing ! the second one there is a possibility of snow so then ? cause its lower than 528 ? or am i picking this up all wrong

maquiladora

I know models have improved since 1999, but still, this shows why the UK Met Office will be still keeping a very close eye on things right up till Thursday/Friday.

http://www.eumetrain.org/satmanu/SatManu/main.htm

STORM CATASTROPHE 25 - 28 DECEMBER 1999 - NUMERICAL MODEL FORECAST PROBLEMS

by KNMI

Behaviour of the ECMWF model

The storm of the 26th (Lothar) only appeared in the 18 hour forecast from 12.00 UTC on the 25th and not at all in preceding forecasts (except D 71/2). Analysis of the storm was also difficult; the 9 and 6-hour forecasts were better for intensity rather than analysis. For the 27th (Martin) there was really nothing in the short range forecasts, even though it had been present in the D+6, 7 and 8 forecasts. The large-scale development was well predicted, associated with a strengthening of the sub-tropical high and the establishment of a straight and very strong jet. The track of the second cyclone could be followed in data assimilation over the Atlantic, but was lost during the 26th. There were data, particularly one SHIP, which were not used correctly and flagged. The main point is that these developments were, in principle, predictable since medium range forecasts showed correct developments. It was more a problem of data assimilation and the mis-use of data by the models somehow caused the cyclones to be lost.

Behaviour of the HIRLAM model

The KNMI Hirlam model performed badly in both cases. Although, for the forecast period less than 18 hours ahead, Hirlam did forecast the position of Lothar reasonably well, its development was greatly underestimated even in the nowcast period of less than 6 hours ahead. The analyses were not correct and resulted in an underestimation of central surface pressure. This makes a more thorough quantitative investigation difficult because of the absence of reliable data.
The +24 hours forecast from the Hirlam model run from Christmas day 25 December 1999/06.00 UTC showed only a weak trough in the 1000 hPa height field at the position of Lothar (see left chart below). A deeper trough is calculated over the Netherlands. By 26 December at 06.00 UTC, a deep low with its centre SW of Paris was a dominant feature, but there was no trough over the Low Countries (see right chart below) This was a result of severely underestimated development of Lothar (in terms of warm advection in front of the low).

Other models

Other NWP models across Europe also failed to predict the severity of the storms, although the French ARPEGE model and its high resolution sub-model ALADIN provided reasonable guidance for Lothar.
Most models were generally very poor in the forecast a day before the storms but improved with shorter lead times (see the illustration below from the behaviour of the UK model).

High-resolution models did not give significantly better results.
Even scattero-meter wind data and data from ATOVS (Advanced Tiros Operational Vertical Sounder) used in reruns of some models resulted in little improvement in forecasts.

maquiladora

Latest surface analysis showing the low starting to split, 993mb.

ninebeanrows

maquiladora wrote: »

Latest surface analysis showing the low starting to split, 993mb.

Yea, notice them charts are only useful every 3hrs, the 1hr ones just basically show what the model predicted for the period. The 12hrs and 18hr ones have a load more data and seem to be just drawn from this rather than combining model data. Just a heads up.

maquiladora

Weathercheck wrote: »

Yea, notice them charts are only useful every 3hrs, the 1hr ones just basically show what the model predicted for the period. The 12hrs and 18hr ones have a load more data and seem to be just drawn from this rather than combining model data. Just a heads up.

Yeh thats the 18 hours one I posted, is the low splitting off a bit sooner than expected and slightly deeper?

ninebeanrows

maquiladora wrote: »

Yeh thats the 18 hours one I posted, is the low splitting off a bit sooner than expected and slightly deeper?

Wouldn't have an idea to be honest!:D