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Costa Del Fal

European Storm Forecasts

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Hi there this Thread is for European Storm Forecasts With Help from Estofex!

Feel Free to Discuss Storms Related to the Maps put up Here! :)

Mods Please Lock if this thread is around or Not allowed!

______________________________________________________________

March 9th 2007

Storm Forecast

Valid: Fri 09 Mar 2007 06:00 to Sat 10 Mar 2007 06:00 UTC

Issued: Thu 08 Mar 2007 20:26

Forecaster: TUSCHY

SYNOPSIS

A huge and strongly tilted omega-like weather pattern will continue over the N-Atlantic and Europe .

Strengthening WAA downstream of the low pressure complex south of Greenland will support rising geopotential heights west of Europe with a strengthening anti-cyclone over the Azores.

The upper-level low pressure area over the S-CNTRL Mediterranean will continue to wobble slowly towards the east although numerous re-formation procedures of the LL depression center make it hard to define an exact track.

DISCUSSION

...S-CNTRL Mediterranean...

No significant changes will occur compared to yesterday. Cool mid-levels will support moderately steepened lapse rates and a broad area of up to 1000 J/kg SBCAPE ( especially offshore, where dewpoints are pretty high ).

Shear will stay pretty weak and only slightly enhanced over Sicily. Confidence in an enhanced severe weather threat is too low for warranting any higher probabilities.

Additionally, a tongue of extremely dry air will circulate towards the center of the depression, which should constrict thunderstorm activity for most of the forecast period SE of Sicily. Still highlighted such a broad area, because GFS inidcates that dry air will probably get mixed out and storms will be able to re-develop during the latter part of the forecast period.

...Parts of UK, Scotland and Ireland...

A pool of pretty cold mid-level air will support widespread low-end instability release in a weakly sheared environment.

LCLs stay low and SRH-1 values are slightly enhanced so an isolated tornado can't be ruled out especially long the coastal areas.

...An area between SE France and Corsica...

Rapidly cooling atmosphere between 00-06Z will support some low-end instability release.

Shear will stay too weak for any storm organisation.

A side note:

Conditions for a well developed Mistral event will evolve during the latter part of my forecast period ( about 21Z-06Z).

Gusts near hurricane force can be expected mainly offshore.

This event will also have an impact on final westward expansion of the general TSTM line west of Corsica.

post-6797-1173468775_thumb.png

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Saturday 10th March 2007

Storm Forecast

Valid: Sat 10 Mar 2007 06:00 to Sun 11 Mar 2007 06:00 UTC

Issued: Fri 09 Mar 2007 23:49

Forecaster: TUSCHY

SYNOPSIS

Inclined omega weather pattern continues for the northern Atlantic and Europe.

An extensive pool of low geopotential heights can be found over the S-CNTRL and SE Mediterranean. A cold upper-level low will cross the W-CNTRL Mediterranean, moving towards the south, while another strongly inclined depression over the far eastern Mediterranean will shift towards the east.

An outstanding depression will evolve SE of Greenland peaking out with an estimated pressure of around 940hPa ! This system will maintain its strength during my forecast period under extremely favorable conditions.

Downstream of this intense system, rising geopotential heights over parts of western and central Europe will provide stable conditions.

The same for NE Europe, where cool and stable air will suppress any convective activity.

DISCUSSION

...Sicily - Crete...

Complex synoptic weather pattern continues for the next 24 hours over this area.

Again, global models like GFS indicate a broad area of at least low-end instability release. Trapani ( 12Z 09 March 07 ) indicated that only marginal cooling at mid-levels / some moistening in the PBL would have been needed for better instability release.

Numerous small UVV maxima are forecast to cross this area, but thermodynamic profilers won't change compared to yesterday.

Therefore the large TSTM area of yesterday will be divided into one area of enhanced TSTM possibility between Sicily and Crete and another region further towards the west, discussed below.

GFS indicates a constant mix - out of very dry air, penetrating towards the center of the depression .

Steep lapse rates, combined with nice PVA will provide enough instability release for scattered thunderstorms to develop. Shear will stay weak and no storm organisation can be expected.

...Balearic Islands - Sardinia...

Aforementioned upper-level low pressure will move towards the south, crossing the area during the daytime hours.

Attendant cool-down of the atmosphere will provide some low-end instability release and a few thunderstorms will develop.

Main uncertainty will be the effect of pretty dry air over the western Mediterranean.

Latest synop reports ( 22Z ) from S-France indicate strong offshore flow ongoing.

I went pretty far north with the TSTM area, because of nice dewpoints and a developing convergence line during the morning hours.

Shear will be too weak for any storm organisation.

A few storms outside of the highlighted areas can't be excluded, but coverage will be too low for including those regions into a general TSTM area.

...SW Norway / Sweden

A negatively tilted short-wave trough will rapidly cross the area from the west during a 12Z-18Z time-frame.

A combination of ~ -35°C at 500hPa and somewhat higher Theta-E values over SW Norway / Sweden will support some marginal instability release.

Forecast soundings from this region indicate that some low-end instability release will be possible.

Any convective system will be able to produce gusts at or above the severe weather limit.

Although speaking against climatology, parameters for an isolated tornadic supercell look reasonable, given the aggressive kinematic environment.

Main limiting factor will be the missing instability and therefore a level-1 will not be issued.

post-6797-1173512933_thumb.png

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Saturday 10th March 2007

Since Todays Forecast there have Been Severe Gusts Reported in South Western France and North West Spain.

post-6797-1173562977_thumb.png

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Sunday 11th March 2007

Storm Forecast

Valid: Sun 11 Mar 2007 06:00 to Mon 12 Mar 2007 06:00 UTC

Issued: Sun 11 Mar 2007 02:01

Forecaster: VAN DER VELDE

SYNOPSIS

A blocking high pressure system over western/central Europe maintains stable conditions, except for the weak low pressure zone over the southern Mediterranean Sea to the Aegean Sea, where strongly convergent near-surface flow provides lift in a slightly unstable airmass.

Most active should become the areas around Sicily and around Crete. In the latter, deep layer shear will be moderate and some patches of SREH and low-level shear linger around, but these seem not that much collocated with instability and lift. Expect at most a marginally large hail event or an isolated flash flood due to a possible slowly moving, long lived storm.

Thundery convection is forecast to shift east/southeastward during the day for the eastern half of the Mediterranean, while the convergence zone southeast of Sicily is progged to shift northwestward.

The small southwest-Mediterranean area could yield some activity during the early hours of the forecast, associated with very steep mid level lapse rates and low level convergence.

Deep Atlantic convection behind a long cold front could reach Ireland by the end of the period.

post-6797-1173629907_thumb.png

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Sunday 11th March 2007

Storm Forecast

Valid: Sun 11 Mar 2007 06:00 to Mon 12 Mar 2007 06:00 UTC

Issued: Sun 11 Mar 2007 02:01

Forecaster: VAN DER VELDE

SYNOPSIS

A blocking high pressure system over western/central Europe maintains stable conditions, except for the weak low pressure zone over the southern Mediterranean Sea to the Aegean Sea, where strongly convergent near-surface flow provides lift in a slightly unstable airmass.

Most active should become the areas around Sicily and around Crete. In the latter, deep layer shear will be moderate and some patches of SREH and low-level shear linger around, but these seem not that much collocated with instability and lift. Expect at most a marginally large hail event or an isolated flash flood due to a possible slowly moving, long lived storm.

Thundery convection is forecast to shift east/southeastward during the day for the eastern half of the Mediterranean, while the convergence zone southeast of Sicily is progged to shift northwestward.

The small southwest-Mediterranean area could yield some activity during the early hours of the forecast, associated with very steep mid level lapse rates and low level convergence.

Deep Atlantic convection behind a long cold front could reach Ireland by the end of the period.

Thank you Blizzards, i keep meaning to check those every day but i forget, that is until you started posting them.

As we are in a warming phase of global climate generally(ether man made or not) i hope to see a lot more thunder for the next few years. Hope being the key word there :rolleyes:

Regards :)

Russ.

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Thank you Blizzards, i keep meaning to check those every day but i forget, that is until you started posting them.

As we are in a warming phase of global climate generally(ether man made or not) i hope to see a lot more thunder for the next few years. Hope being the key word there 8)

Regards :)

Russ.

Thanks! :good:

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Sunday 11th March 2007

Since Todays Forecast there have been some More strikes around the Tunisia area.

post-6797-1173640489_thumb.png

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Monday 12th March 2007

Storm Forecast

Valid: Mon 12 Mar 2007 06:00 to Tue 13 Mar 2007 06:00 UTC

Issued: Sun 11 Mar 2007 20:16

Forecaster: GROENEMEIJER

SYNOPSIS

Monday at 06:00, a high-over-low blocking pattern is present over northern Europe. A ridge stretches from central Europe to eastern Scandinavia. Two cold-core low centres are located over the western Mediterranean Region: one over E Spain, another over S Tunisia. An intense mid-level cold-core low over the central Ukraine will move to the central Black Sea during the forecast period. A shortwave trough NW of Scotland will move eastward during the forecast period.

DISCUSSION

Scattered thunderstorms are forecast in the range of the cold mid-level air associated with the aformentioned low centres.

A few strikes of thunder are expected with convection over northern Scotland and the southern Norwegian Sea.

Severe convecive weather is unlikely across Europe in this forecast period.

post-6797-1173644592_thumb.png

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Monday 12th March 2007

Since Todays Forecast was Made there has been Lightning in Southern Italy, Around Tunisia and around the North Sea.

post-6797-1173717951_thumb.png

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Thats ok!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Estofex Archives- The Oldest Forecast from Estofex Available today!-Thursday 10th October 2002

Here is a Forecast from the Past!

VALID 06Z THU 10/10 - 00Z FRI 11/10 2002

ISSUED: TUE 08/10 23:10Z

FORECASTER: HAVEN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR WRN MEDITERRANEAN SEA...ITALY

GENERAL THUNDERSTORMS ARE FORECAST OVER AREA SURROUNDING THE SLGT RISK AREA

GENERAL THUNDERSTORMS ARE FORECAST OVER S FRANCE...WRN BALKAN STATES

SYNOPSIS

UPPER LOW OVER SPAIN IS MOVING SLOWLY EAST TO THE WRN MEDITERRANEAN SEA. STRONG JETSTREAM ON ITS SRN FLANK WILL ROTATE ALONG IT AND IS EXPECTED OVER TUNESIA, POINTING TWRDS CNTRL ITALY IN THE EVENING. AT THE SFC...COMPLEX SFC LOW OVER WRN MEDITERRANEAN IS MOVING EAST WITH COLDFRONT REACHING ITALY AT THE VERY END OF THE PERIOD.

DISCUSSION

...N-ITALY...

LATEST ECMWF MODEL CALCULATES STRONG LOW LEVEL PRESSURE GRADIENT N AND E OF THE SFC LOW THURSDAY AT DAYTIME: H85 WINDS WILL EXCEED 50 KT OVER PARTS OF NRN ITALY, NEAR THE LIGURIAN SEA. IN THIS HILLY TERRAIN SHEAR PROFILES CAN BECOME MODIFIED, CREATING FAVOURABLE CONDITIONS FOR SHORT-LIVED SUPERCELLS. GIVEN THE HIGH HODOGRAPH LENGHTS... DAMAGING WINDS WILL BE THE MAIN THREAT. A TORNADO WILL ALSO BE POSSIBLE, BUT HAIL SIZE WILL BE LIMITED DUE TO LOW CAPE.

...WRN MEDITERRANEAN SEA...CNTRL AND SRN ITALY...

AS 100+ KT H30 SPEEDMAX OVER N-ALGERIA, AT THE BEGINNING OF THE PERIOD, ENTERS THE MEDITERRANEAN IVOF ITALY, STRONG UVM WILL OCCUR, ESPECIALLY IN THE LEFT-FRONT QUADRANT OF THE JETSTREAK. AIRMASS WILL BE MOD UNSTABLE /CAPE ARND 1000 J/KG/ AND IN COMBINATION WITH 0-6 KM SHEAR IN EXCESS OF 50 KT...THIS WILL LIKELY RESULT IN STRONG TO SEVERE TSTMS WITH LOCALLY LARGE HAIL AND DAMAGING WINDS. JUST EAST OF THE COLDFRONT, WHERE SFC WINDS ARE HIGHER AND MORE BACKED... 0-3 KM SRH CAN BECOME SUFFICIENT FOR STORMS TO ROTATE, SO SUPERCELLS AND PERHAPS A TORNADO CANNOT BE RULED OUT. ELSEWHERE IVOF THE JETSTREAK... SHEAR WILL BE SUFFICIENT FOR SPLITTING TSTMS. AS IN MANY CASES WITH STRONG UVM, STORMS WILL LIKELY CLUSTER INTO LARGE COMPLEXES/MCS'S.

......

NEAR SW-TIP OF IBERIAN PENINSULA, ON THE SW-PERIPHERY OF THE UPPER LOW...VERY STRONG VERTICAL SHEAR IS EXPECTED. HOWEVER... CAPE WILL BE QUITE LOW, AND SUBSIDENCE DUE TO AN APPROACHING RIDGE WILL SUPRESS DEEP CONVECTIVE MIXING.

post-6797-1173723286_thumb.png

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Monday 12th March 2007

Since the Update earlier there have ben More Lightning stikes in the North Sea, Southern Italy and around the Balearic Islands.

post-6797-1173732669_thumb.png

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Thats ok!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Estofex Archives- The Oldest Forecast from Estofex Available today!-Thursday 10th October 2002

Here is a Forecast from the Past!

VALID 06Z THU 10/10 - 00Z FRI 11/10 2002

ISSUED: TUE 08/10 23:10Z

FORECASTER: HAVEN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR WRN MEDITERRANEAN SEA...ITALY

GENERAL THUNDERSTORMS ARE FORECAST OVER AREA SURROUNDING THE SLGT RISK AREA

GENERAL THUNDERSTORMS ARE FORECAST OVER S FRANCE...WRN BALKAN STATES

SYNOPSIS

UPPER LOW OVER SPAIN IS MOVING SLOWLY EAST TO THE WRN MEDITERRANEAN SEA. STRONG JETSTREAM ON ITS SRN FLANK WILL ROTATE ALONG IT AND IS EXPECTED OVER TUNESIA, POINTING TWRDS CNTRL ITALY IN THE EVENING. AT THE SFC...COMPLEX SFC LOW OVER WRN MEDITERRANEAN IS MOVING EAST WITH COLDFRONT REACHING ITALY AT THE VERY END OF THE PERIOD.

DISCUSSION

...N-ITALY...

LATEST ECMWF MODEL CALCULATES STRONG LOW LEVEL PRESSURE GRADIENT N AND E OF THE SFC LOW THURSDAY AT DAYTIME: H85 WINDS WILL EXCEED 50 KT OVER PARTS OF NRN ITALY, NEAR THE LIGURIAN SEA. IN THIS HILLY TERRAIN SHEAR PROFILES CAN BECOME MODIFIED, CREATING FAVOURABLE CONDITIONS FOR SHORT-LIVED SUPERCELLS. GIVEN THE HIGH HODOGRAPH LENGHTS... DAMAGING WINDS WILL BE THE MAIN THREAT. A TORNADO WILL ALSO BE POSSIBLE, BUT HAIL SIZE WILL BE LIMITED DUE TO LOW CAPE.

...WRN MEDITERRANEAN SEA...CNTRL AND SRN ITALY...

AS 100+ KT H30 SPEEDMAX OVER N-ALGERIA, AT THE BEGINNING OF THE PERIOD, ENTERS THE MEDITERRANEAN IVOF ITALY, STRONG UVM WILL OCCUR, ESPECIALLY IN THE LEFT-FRONT QUADRANT OF THE JETSTREAK. AIRMASS WILL BE MOD UNSTABLE /CAPE ARND 1000 J/KG/ AND IN COMBINATION WITH 0-6 KM SHEAR IN EXCESS OF 50 KT...THIS WILL LIKELY RESULT IN STRONG TO SEVERE TSTMS WITH LOCALLY LARGE HAIL AND DAMAGING WINDS. JUST EAST OF THE COLDFRONT, WHERE SFC WINDS ARE HIGHER AND MORE BACKED... 0-3 KM SRH CAN BECOME SUFFICIENT FOR STORMS TO ROTATE, SO SUPERCELLS AND PERHAPS A TORNADO CANNOT BE RULED OUT. ELSEWHERE IVOF THE JETSTREAK... SHEAR WILL BE SUFFICIENT FOR SPLITTING TSTMS. AS IN MANY CASES WITH STRONG UVM, STORMS WILL LIKELY CLUSTER INTO LARGE COMPLEXES/MCS'S.

......

NEAR SW-TIP OF IBERIAN PENINSULA, ON THE SW-PERIPHERY OF THE UPPER LOW...VERY STRONG VERTICAL SHEAR IS EXPECTED. HOWEVER... CAPE WILL BE QUITE LOW, AND SUBSIDENCE DUE TO AN APPROACHING RIDGE WILL SUPRESS DEEP CONVECTIVE MIXING.

My god the graphics are awful thank god they updated :whistling:

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My god the graphics are awful thank god they updated :)

Thats exactly what i thought!

Tuesday 13th March 2007

Storm Forecast

Valid: Tue 13 Mar 2007 06:00 to Wed 14 Mar 2007 06:00 UTC

Issued: Tue 13 Mar 2007 01:55

Forecaster: VAN DER VELDE

SYNOPSIS

Calm weather persists under a blocking high pressure area over the European mainland, while active depressions affect Scotland and Scandinavia. A shallow low with an unstable airmass lingers over the southern Mediterranean Sea. Upper cut-off lows cause somewhat unstable conditions around Portugal and the southern Black Sea/Turkey region, into the eastern Mediterranean Sea later in the period.

This latter system is associated with moderate deep layer shear here and there, but low boundary layer mixing ratios could inhibit somewhat the development of storms and the chance of marginally large hail. An isolated waterspout is not ruled out over the Mediterranean Sea.

Some thunder may be possible west of Norway where equilibrium level temperatures reach -30C, with actually not that low mixing ratios (higher than Turkey), with surface convergence (GFS) providing lift, as well a mid level vorticity maximum (SW-Norway, afternoon). An isolated strong gust could occur.

A small area is indicated in the upper trough over N-Portugal/Spain where GFS indicates very steep 2000-4000 m temperature lapse rates, with also sufficiently cold EL temperatures (-30C), while surface convergence may trigger convection during the afternoon. As of 00Z, La Coruna sounding has a cap that could be overcome if the temperature manages to reach 21 degrees.

post-6797-1173771379_thumb.png

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Tuesday 13th March 2007

Since the forecast earlier today there has been more Lightning around Southern Italy, Alegria and Tunisia. (Map at the bottom of the post)

Wednesday 14th March 2007

Storm Forecast

Valid: Wed 14 Mar 2007 06:00 to Thu 15 Mar 2007 06:00 UTC

Issued: Tue 13 Mar 2007 16:05

Forecaster: GATZEN

SYNOPSIS

High over central northern Atlantic Ocean ridges into western and central Europe. At the northern flank of this ridge, moderately strong westerly jet forms a trough over north-eastern Europe that evades into eastern Europe during the period. Over south-eastern Europe, an upper cut-off low is located over central Turkey. At lower levels, relatively cold/dry air mass is present over most of Europe. Relatively warm air mass remains south of the ridge axis from Iberian Peninsula to northern Balkans. Both air masses are stable due to warm mid-levels in the range of the ridge. Best chances for convection is expected underneath the vort-max/trough axis of upper cut-off over Turkey. Given quite cold mid-troposphere and warm water surface temperatures over the Mediterranean Sea, expect that rather steep low-level lapse rates will develop. Downslope flow over the Turkish coast is forecast to limit chance for convection due to dry boundary-layer air mass. Further south, a few thunderstorms may form. But given weak CAPE and vertical wind shear, severe thunderstorms are not expected.

Todays Updated Map------------------Tomorrows Storm Map

post-6797-1173805523_thumb.png

post-6797-1173805605_thumb.png

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Wednesday 14th March 2007

Since the Forecast for today was issued there has been very few lightning strikes Reported. Only areas Around Southern Greece and Turkey have something to talk about.

post-6797-1173890743_thumb.png

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Wednesday 14th March 2007

Since the Earlier Update earlier there has been more Lightning around the forecast area.

This is the Last update of the Day.

post-6797-1173905838_thumb.png

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Thursday 15th March 2007

Storm Forecast

Valid: Thu 15 Mar 2007 06:00 to Fri 16 Mar 2007 06:00 UTC

Issued: Thu 15 Mar 2007 06:22

Forecaster: GATZEN

SYNOPSIS

High over Atlantic ridges into Alpine region. At the northern flank of this high, polar trough evades into Scandinavia, where intense vort-max will affect especially the northern portions late in the period. Maritime air mass with neutral lapse rates are expected, and showers will likely develop. Given rather weak low-level moisture with dewpoints around 0°C, it seems that buoyancy will be too weak for strong convection and associated lightning. Best chances will exist along the western coast, where orographic lift may be strong enough for a few isolated thunderstorms, but current thinking is that thunderstorms will not occur. Vertical wind shear with 20 m/s DLS and also 10 m/s LLS will be present, but given weak CAPE, organized thunderstorms seem to be very unlikely.

South of the ridge axis, low geopotential is present over Mediterranean. However, latest soundings do not indicate instability due to rather warm/stable mid-levels and poor boundary-layer moisture. Best chances for instability will exist near the Balearic Islands, where at least shallow moisture has build as indicated by latest ascends. As latest model forecasts suggest that center of a weak cut-off low will move across the western Mediterranean, mid-level height falls may be strong enough for some instability to develop. However, weak forcing is forecast today, and chance for thunderstorms is low.

post-6797-1173944509_thumb.png

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Thursday 15th March 2007

Since todays Forecast there has been lightning around Morocco, Algeria, Southern France, Northern Greece and Southern Russia.

post-6797-1173978681_thumb.png

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Friday 16th March 2007

Storm Forecast

Valid: Fri 16 Mar 2007 06:00 to Sat 17 Mar 2007 06:00 UTC

Issued: Thu 15 Mar 2007 23:10

Forecaster: GROENEMEIJER

SYNOPSIS

NWly mid-level flow off the northern Atlantic translates eastward. A large mid-level high is located over the Atlantic around 45 N. A remnant cyclonic circulation filled with relatiely low mid-level air is present over the western Mediterranean.

DISCUSSION

S Scandinavia...

A northwesterly jet streak translates SEward off the Northern Atlantic into southern Scandinavia. A surface low in its left exit region is followed by relatively deep unstable polar air, in which deep convection is widespread. Some storms are likely thundery and affect southwestern Norway and adjacent waters mainly during the latter half of the forecast period.

W Mediterranean...

Strong insolation over the land masses of the Wrn Mediterranean is likely able to heat the lower troposphere sufficiently to overcome convective inhibition. Local thunderstorms are therefore forecast in the indicated areas. Low values of CAPE and weak wind shear suggest a very low threat of severe weather with these storms.

post-6797-1174030562_thumb.png

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Friday 16th March 2007

Since the forcast for today was made there has Been Lightning in Southern France, Spain, Morroco, Algeria, Tunisia, North Sea and Norway.

post-6797-1174070884_thumb.png

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Saturday 17th March 2007

Storm Forecast

Valid: Sat 17 Mar 2007 06:00 to Sun 18 Mar 2007 06:00 UTC

Issued: Fri 16 Mar 2007 19:36

Forecaster: TUSCHY

SYNOPSIS

Significant changes in the upper troposphere / lower stratosphere will occur during the next few days. The western part of an elliptical shaped polar vortex will broaden and will expand towards Europe, which will produce a complete shift in the prevailing weather pattern, compared to the past few months.

Pretty busy period is already underway for northern Europe with one upper-level trough crossing an area between Norway and Belarus from the west, while another, even more powerful upper-level trough will approach Europe from the NW and will affect Ireland, Scotland and United - Kingdom during the latter part of my forecast period.

A pretty well defined cold-core upper-level low will continue its SW-ward shift, crossing Spain and S-Portugal from the NE, while high geopotential heights over central Europe will suppress any convective activity.

Cool and stable conditions prevail over eastern / northeastern Europe.

DISCUSSION

... Spain, Portugal, Sardinia and the coastal areas of Algeria and Tunisia...

A region of low geopotential heights over SW Europe will stretch from Portugal towards the east, while a constantly weakening cold-core upper-level low over Spain will shift towards the SW.

Compared to yesterday, lapse rates at mid-levels will relax somewhat and this should limit storm coverage, although strong diabatic heating will be sufficient again for a few thunderstorms to evolve.

A marginal cool-down of the lower tropospheric thermodynamic profile south and southeast of Sardinia will be the conducive for a few thunderstorms to develop, too.

Predominating thermodynamic / kinematic parameters won't justify any severe thunderstorm threat.

...Scotland...

A strong cold front will traverse the region from the NW during a 22Z - 03Z time-frame.

Right now there are no signs of any robust instability release along the frontal zone.

The main focus for a few thunderstorms arises in the postfrontal airmass, where up to 200 J/kg SBCAPE and rapidly steepening lapse rates will support a more favorable environment for thunderstorm development.

LL shear of more than 17m/s and SRH 1km values of up to 200 J/kg will be fine for an isolated severe wind gust and local tornado threat.

Uncertainties regarding the magnitude of the thunderstorm coverage ( best environment will approach during the end of my forecast ) and regarding the final airmass quality ( pretty high LCLs / low dewpoints ) don't justify any higher probabilities....at least for the moment.

... Parts of Poland...

An eastward rambling upper-level trough will bring an intense cool-down at 500 hPa over most parts of Poland with an attendant increase in mid-level lapse rate strength.

Modified soundings from this area indicate some low-end instability release . Convective activity should stay low-topped, also indicated by EL-heights in the range of 3.5 - 4.5 km.

Despite the fact that only a trickle of expected 25-40m/s DLS can be utilized, 25m/s at 850hPa should be easily mixed down in stronger convective segments. Beside the severe wind gust risk, there will also exist an isolated tornado risk...especially in storms, which tend to move off the hodograph.

A level-1 was issued for N-Poland, where the strongest instability release can be expected ( about 100-200 J/kg SBCAPE ).

Would not be surprised to see a few SFLOC reports beyond the general thunderstorm area, but sporadic coverage of storms would not support a broader region.

post-6797-1174117475_thumb.png

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Saturday 17th March 2007

Since todays forecast there has been Organised Lightning around Spain, Morocco, Algeria, Tunisia and Italy.

post-6797-1174148446_thumb.png

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Sunday 18th March 2007

Finnaly we have a Warning Issued.

Storm Forecast

Valid: Sun 18 Mar 2007 06:00 to Mon 19 Mar 2007 06:00 UTC

Issued: Sun 18 Mar 2007 13:07

Forecaster: VAN DER VELDE

SYNOPSIS

A drastic change of weather pattern occurs during the present and next forecast period over much of western Europe as the blocking high makes way for a pool of cold maritime air of arctic origin sinking SSE-ward into mid-latitudes with the meridional flow at the west side of the low pressure centered over southern Scandinavia. Main convective activity should occur near the postfrontal trough affecting the area from Ireland into France. This is quite far behind the cold front. Elsewhere behind the front open-cell type of convection is shown by Meteosat at this time.

Some cells currently make it into southern Sweden, while the occlusion of the low regenerates chances for convection over Denmark. Although overall thunder coverage will be low, conditions for deep convection are favourable over a large area.

DISCUSSION

Both level 1 areas will be exposed to enhanced convective activity and low level shear greater than 10-15 m/s, low LCL heights, and at least moderate deep layer shear >15 m/s, up to 40 m/s over SW Ireland into France. Although no strongly veering winds with heights are anticipated due to cold air advection compensating friction, chances seem present that tornadoes could occur at isolated scale from storms that are able to develop a mini mesocyclone. Occasionally SREH reaches over 100 m2/s2 or more (Denmark, 250 m2/s2) but instability may be reduced in these local areas of warm air advection.

Most of all action in the level 1 areas should occur during the evening and night, e.g. northwestern France 00Z according to GFS timing. Average boundary layer mixing ratios are progged by GFS to stay over 3 g/kg in areas with instability where air is drawn inland from sea, which may allow reasonable lightning activity. Besides the isolated tornado chance, severe gusts may occur.

post-6797-1174226786_thumb.png

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Monday 19th March 2007

Storm Forecast

Valid: Mon 19 Mar 2007 06:00 to Tue 20 Mar 2007 06:00 UTC

Issued: Sun 18 Mar 2007 17:22

Forecaster: TUSCHY

SYNOPSIS

Dramatic changes are underway / have already occured over Europe.

Southward expanding polar vortex will reach the extreme northern part of the forecast area during the end of the forecast period .

At lower levels, a combination of a stout 1040hPa anticyclone over the Azores and a slowly filling low pressure area over Norway and Sweden will support an outbreak of arctic air over parts of western, southern , northern and central Europe. A broad area will be affected by this type of airmass and will see an active convective day.

Strong WAA on the downstream side of the impressive upper-level trough will bring warm conditions well towards the north, affecting eastern / northeastern Europe.

A developing lee-cyclogenesis over N-Italy will be another area to watch out for enhanced thunderstorm activity.

DISCUSSION

...Scotland, Ireland, United Kingdom, France, Belgium, the Netherlands, Germany, Switzerland and parts of Spain...

Temperatures of -35 to -40°C at 500hPa, -15°C at 700hPa and -5°C at 850hPa will cover a huge area, supporting mid-level lapse rates of 8-9K / km !

This kind of atmospheric stratification will admit SBCAPE release in the order of 100-300 J/kg.

Such a postfrontal convective event makes it difficult to pinpoint areas of enhanced (severe) thunderstorm activity that far out... especially over such an huge area.

GFS indicates numerous lines with enhanced moisture advection, various upper-level impulses and small UVV maxima, which will cross the area from the north. Topography and fluctuating boundary layer moisture will play a role as well as possible small-scale polar low development, which are hard to forecast by global models.

Summarized we can say that a broad area will see isolated to scattered thunderstorm development during the next 24 hours.

LL shear of 10-15m/s was calculated for Ireland, Scotland, UK and northern / western France with decreasing values further towards the east / southeast.

Boundary layer moisture is forecast to be very shallow and constant mixing will bring the LCLs to values of 750-1500m, which will lower the tornado possibility.

Storm relative helicity values stay pretty low , besides UK, Scotland and Ireland.

Decided to issue a level-1 for regions, where 850hPa flow is at least somewhat enhanced ( e.g. Ireland, Scotland and UK with 25m/s ), which poses a threat for an isolated severe wind gust. Shear / instability combination also points out the possibility for an isolated tornado in those areas.

Exactly the same for SW / W / NW / N France, where LL shear and instability favor the evolution of an isolated tornado/ severe wind gust event.

During maximum heating, storms could produce mostly sub-severe hail, although an isolated large hail event can't be ruled out, given still 10-20m/s DLS.

...Central Mediterranean...

Constantly deepening lee-cyclogenesis over N-Italy will be the focus for another area of enhanced thunderstorm possibility.

During the latter part of my forecast period, the atmosphere will start a rapid cool-down over the Balearic Islands, Sardinia and Corsica and 400-600 J/kg SBCAPE can be expected.

Despite the favorable environment, thunderstorms will have problems to evolve just south of France / east of Spain, because of expected long fetch, before dry continental airmass will be mixed out.

Further torwards the south, scattered thunderstorms can be expected in an environment with up to 50m/s DLS.

Low / mid-level flow won't be that strong, but don't want to exclude an isolated severe wind gust risk with the stronger storms.

LL shear of 10m/s, low LCLs and fine instability will also support an local tornado threat along / over Sardinia and Corsica, which was the reason for issuing a level-1.... otherwise confidence is low that storms will be able to gain severe thunderstorm status.

The same for an area between Sicily and CNTRL Italy.

Further towards the east, over Italy and the Adriatic Sea, conditions for isolated to scattered TSTMs will become favorable, too, especially during the latter part of the forecast.

DLS of 30-40m/s and locally up to 17m/s LL shear favor an isolated tornado / severe wind gust risk. Expected pretty strong forcing will compensate the warm temperatures at low / mid-levels.

...Aegean Sea...

A weakening upper-level trough will cross the Aegean Sea from the SW during the late hours and a few thunderstorms will manage to develop. Strongest shear will just be out of my forecast area ( south of Turkey ) and therefore no organized thunderstorms can be expected .

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