European Storm Forecast Experiment (threat level 2)

[Crostorm]

Storm Forecast
Valid: Tue 28 Oct 2008 06:00 to Wed 29 Oct 2008 06:00 UTC
Issued: Tue 28 Oct 2008 03:58
Forecaster: VAN DER VELDE

SYNOPSIS

An elongated upper trough following a cold front becomes quasi stationary and stretches from Scandinavia to the Iberian Peninsula. Behind the cold front is a vast area of maritime showers, and thunder can occur particularly in regions of coastal convergence or small troughs. Late in the period a cut-off low of Arctic origin, with weak thermal gradients but significant pressure gradients, enters the northern North Sea, with associated showers and thunder.
On the warm side of the upper trough, as it enters the Mediterranean, a large area destabilizes and cyclogenesis occurs along the cold front east of Spain, in the jet entrance region.


DISCUSSION

...southern Italy, eastern Adriatic Se a...

More than 250 m2/s2 of SREH in an area with a large 1-3 MJ/m2 of vertically integrated CAPE (ICAPE) could yield multi- and supercellular storms, though deep layer shear vectors are not forecast to be as strong, 15 m/s. Large hail is likely, and 0-1 km shear >10 m/s suggests also tornados and waterspouts are possible. 00Z sounding of Cagliari shows good instability with low LFC in support of this. LAMMA NMM 12/8 km models show a concentration within the level 2 area.
Sicily may be partly capped according to GFS.
Additionally, flash floods may occur.

...Balearic Islands area...

A narrow and steep thermal gradient at the cold front is marked by CAPE and strong low level buoyancy on the warm side and 500 m2/s2 storm-relative helicity (0-3 km) and highly superadiabatic low level lapse rates on the cold side. With some slope of the frontal surface, storms may profit of the shear environment, enabling a threat of large hail and tornadoes/waterspouts when updraft rotation occurs. GFS 18Z is in favor of development of a frontal wave and this increases also the threats associated with high precipitation.
An earlier (afternoon) storm NE of the area will likely become an MCS and may have some wind and hail threat as well.


...English Channel region, southern North Sea...

A number of waterspouts are likely to occur, as strong 0-3 km buoyancy and boundary layer superadiabatic lapse rates allow for rapid upward acceleration, and weakening pressure gradients are in favor. Current 00Z soundings suggest air is relatively dry, though.



More information about the risk system can be found on the FAQ page.

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Today also a big treath of severe weather



Storm Forecast
Valid: Wed 29 Oct 2008 06:00 to Thu 30 Oct 2008 06:00 UTC
Issued: Tue 28 Oct 2008 23:15
Forecaster: PUCIK

SYNOPSIS

A very deep trough has settled over W Europe, stretching from Scandinavia to Iberian penninsula. Its core is filled with cold airmass, especially in the north characterized by steep mid-level lapse rates. Several short waves will rotate around it during the period, promoting deepening of surface lows. Very strong flow will surround the trough, having more than 40 m/s at 500 hPa level. Underneath the trough, broad surface low pressure system exists. Three distinct centers can be identified - one on the SW coast of Norway, which should fill during the day. Another one will travel from Ireland southwards, deepening as short wave provides strong lift over its center. The last one has formed on the significant fronal system, which has now become quasi-stationary over the Middle Europe. Further deepening of the low is expected and its center will shift NNE wards with time. Strong WAA regime will develop ahead of the front. Eastern Europe will encounter stable conditions as ridge has settled over the region.

DISCUSSION

...Bay of Biscay...

As mentioned above, surface low will move southwards from Ireland. CAA behind the front which overlays relatively warm SST leads to the development of steep lapse rates. Moreover, significant lift is expected both from surface low and short wave above, so further destabilization might occur thanks to this factor. MLCAPEs above 500 J/kg should materialize and combined with favourable lift will result in TSTM development. Strong LL buoyancy will exist over the bay and with nice convergence signals shown by several consequent GFS runs, waterspout threat seems to be quite high. Therefore, marginal Lvl 1 is introduced.

...Sardinia, Corsica to Italy coast...

Several rounds of thunderstorms are possible. Nevertheless, severe threat should arrive with the approaching cold front, which shall affect the region from 15 to 21Z. Troposphere should be conditionally unstable during the whole day, but further destabilization will occur ahead of the front with MLCAPEs above 800 J/kg. Furthermore, strong mid and low level flow will establish over the area with DLS values around 20 m/s and shear in the lowest 3 km around 15 m/s should suffice for good storm organisation. From storm spectrum, multicells should prevail but supercell is not ruled out either. Large hail will be possible with stronger cells, especially by the Italian coast. Strong low level wind field, with windspeeds up to 25 m/s at 850hPa suggest that severe wind gusts may accompany the storms. On the coasts, friction will reduce the surface winds and increase LLS, reaching 10 -15 m/s, so one or two tornadoes might occur too.

...Gargano penninsula to Adriatic sea...

A tongue of steep mid-level lapse rates will point to the area with MLCAPE values above 1000 J/kg. DLS will be between 20 - 25 m/s and MLS above 15 m/s. What is more, favourable veering of the wind with height will raise the SREH, which should reach more than 250 J/kg in the 0-3 km layer. This suggests that rotating updrafts will become a distinct possibility. Although storms should stay mostly multicellular as GFS suggests storm clustering, few isolated supercells might occur. In such case, chances for large hail would increase significantly. Steep lapse rates and also quite strong flow at 700 hPa level will combine to promote a downburst risk. Few tornado / waterspout reports are expected as SREH 0-1 km should increase to 150 J/kg and coexist with high low level buoyancy. As very good storm organisation is anticipated, along with high storm coverage, LVL 2 is issued in the belt, where the highest threat will be present. Most of the severe weather should occur between 06 and 15Z, shifting eastwards. After this period, severe weather risk will gradually dimnish.

.... N Adriatics, N Italy...

Although instability should be relatively meager in this area, passage of the cold front and presence of upper level disturbance aloft should aid in TSTM development. Impressive wind profile will dominate the region, especially by evening hours, with 30 m/s of DLS and over 15 m/s of LLS. SREH in the 0-1 km might exceed 150 J/kg with veering wind profiles. As storms should be rooted in the boundary layer, such strong low level wind profiles will result in tornado / severe wind gust threat. After the cold front passage, threat will disappear.

.... E Germany, W Czech republic...

Mostly elevated instability is predicted over the region. Strong isentropic lift across the front will provide the initiation for thunderstorms. Despite the fact that favourable wind profiles for organised storms will be available, no threat is expected, as storms should stay elevated in nature and instability will be only marginal.

[Crostorm]

Storm Forecast
Valid: Tue 28 Oct 2008 06:00 to Wed 29 Oct 2008 06:00 UTC
Issued: Tue 28 Oct 2008 03:58
Forecaster: VAN DER VELDE

DISCUSSION

...southern Italy, eastern Adriatic Se a...

More than 250 m2/s2 of SREH in an area with a large 1-3 MJ/m2 of vertically integrated CAPE (ICAPE) could yield multi- and supercellular storms, though deep layer shear vectors are not forecast to be as strong, 15 m/s. Large hail is likely, and 0-1 km shear >10 m/s suggests also tornados and waterspouts are possible. 00Z sounding of Cagliari shows good instability with low LFC in support of this. LAMMA NMM 12/8 km models show a concentration within the level 2 area.
Sicily may be partly capped according to GFS.
Additionally, flash floods may occur.


More information about the risk system can be found on the FAQ page.

And of course the prevision was right

Reportage

Chronicle of a spectacular evening lived games
Furious storms in the south: the Strait of Messina hit ... and sunk!
MeteoWeb.it - The Mediterranean Meteoportale

The Strait of Messina has been taken into full multicellular thunderstorms from the system (MCS) that between the late afternoon and evening of Tuesday, Oct. 28 has affected many areas of the south, especially between Sicily and Calabria.
After the affected area of western Sicily, through litorale Sicilian Tyrrhenian cells thunderstorms, very intense, have just moved in Calabria through the Strait of Messina.


The storms, extremely violent, have further intensified on the ground resulting in violent storms just between Messina and Reggio, but especially in the Calabrian side of the Strait.

Here is the situation of Lightnings at 18.45: few minutes later would begin "dancing" in his strait.


The scenario is surreal.
The air, at times firm and immobile after the strong sirocco morning, it shakes with the noise of thunder that, from the west, are becoming closer.

The clouds covering the sky so compact in this day that had already passed with a flavor crisp autumn delivered by sirocco that has blown stirring waves of the sea.

But that October 28 will give more: will remain in history for an event Meteorological striking. And it succeeds.

The Lightnings begin to move closer to 19.00 and are close to Reggio.
Yet it does not rain, the Global Warming hit the side of the Strait of Messina.

But the thunder and lightning are the master: fall of the city and have a tremendous violence, unprecedented, with all their charm and their enchanting beauty.

Because the movement of air pollution from electric shocks, you destroy some windows of some houses.

Here are some shots:



Video http://www.youtube.com/watch?v=loXBQlN3hio


Shortly after, he started to hail so crazy.
Grains fall of hail large number "cm" causing damage to cars and beyond.
In cities falling cornices also due to violent gusts of wind accompanying the rain intensified.
At the end of episode will fall well 63mm of rain is the time contributions from pluviometrici more abundant in recent years.
Only the storm, 1-2 December 2002 was able to do better: 180mm in one night.
Rose almost 6 years, and in those 6 years were never exceeded the 40-45mm daily.
But the accumulation of Reggio is not the highest.

A Gambarie d'Aspromonte, for example, have fallen well 73mm of rain.
But that's not all here.

In Reggio Jonico, where the storm struck after 20.30, has rained even more.
Here are all the data from Reggina Jonico:

Gioiosa Jonica 84mm
Platì 67mm
Passo della Limina 59mm
Canolo Nuovo 58mm
Roccella Jonica 58mm
Ardore Superiore 45mm
Antonimina 44mm


The figures testify as dell'Appennino crossing from the Tyrrhenian to the Ionian occurred just nell'Aspromonte, where storms have traversed eastwards then hitting up Jonico Reggina, leaving completely dry the area of Melito di Porto Salvo, Saline Jonica and Bova, while in almost all the rest of the province was the finimondo.

Has been treated to an exceptional event, which brings the month of October in surplus water (as in September) and partially recover the annual precipitation deficit.

Whole text,pictures and video
http://www.meteoweb.it/cgi/intranet.pl? ... ioni_id=84

[Crostorm]

Forecast Update
Valid: Fri 23 Jan 2009 14:00 to Sat 24 Jan 2009 06:00 UTC
Issued: Fri 23 Jan 2009 14:06
Forecaster: TUSCHY

SYNOPSIS

Please refer to the outlook, issued at Thu 22 Jan 2009 20:36 UTC.

DISCUSSION

... NW/N-Spain and SW-France...

GFS/GME and UKMO all retarded the forward propagation of this depression somewhat, which made some adjustments necessary over SE-France.

The majority of the models now agrees in the passage of a strong/intense extratropical depression, which crosses the S-Bay of Biscay between 21Z-06Z and makes landfall just around 06Z over the W-central coast of France. Latest GOES-12 IR/VIS image has this feature now somewhere around 45°N/20°W and enhanced convection along the gradually evolving cold front is present as a dry slot approaches from the west, increasing the likelihood that GFS is on track with modest CAPE release along the cold front.

NW-Spain was included into the level-2 as the active cold front passes by and severe to damaging winds mix down to the surface. This risk continues eastwards along the cold front.

The SE Bay of Biscay and parts of SW-France were upgraded as the environment becomes supportive for an organized line of storms, crossing the level-3 area from the west at 00Z onwards. A combination of an eastward moving, intense vorticity lobe beneath aforementioned dry slot and the cold front itself should assist in the development of some moderate instability and a squalline, probably possessing a line echo wave pattern, is forecast. Forecast soundings (GFS) also indicate abundant CAPE release between 750-500hPa, also increasing below 3km. The main threat will be a widespread damaging wind gust risk with this line of storms as convective gusts likely exceed 33m/s. Otherwise, LCLs around 600m, LL shear of 25-30m/s, aforementioned LL CAPE release and intense directional shear also point to a significant tornado risk and strong tornadoes are possible.

Between 03Z-06Z, attention also turns to the approaching occlusion. As a result of the slow down and the earlier occlusion process of the depression, the back-bent occlusion now remains more displaced to the north, affecting the region around Bordeaux. Deep convection is likely with that activity as mid-/upper levels cool down and a sharp north-south wind shear gradient sets-up. Strong directional shear just onshore persists, so tornadoes and severe wind gusts are possible, especially if this occlusion runs a bit more to the south than currently thought. The risk continues after 06Z.

... The rest of the highlighted areas ...

The level-1 along the coastal areas of SW/W-Turkey and NE-Greece was downgraded as shear and instability start to relax.

The level-1 over E-France was re-issued as numerous convective lines evolved with gusts of 20-25m/s. This activity also diminishes during the next few hours.