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 09/10 February 2009 Slight Risk in my Place

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Andre-ESCT

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PostSubject: 09/10 February 2009 Slight Risk in my Place   Sun Feb 08, 2009 8:15 pm



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... France, Belgium, the Netherlands and extreme NW-Germany ...

** An intense and potential life threatening extratropical storm affects parts of France during the forecast period with damaging wind gusts. However, no long-lived/organized convection is expected during the passage of the strongest wind field at roughly 21Z onwards over W-central France. A broad, low threat level was issued, which does not reflect the non-convective wind gusts threat! Please refer to your national meteorological service for more detailed informations about the intense depression. **


A rapidly strengthening depression approaches the English Channel from the west at 18Z. GEM is still the outlier with the weakest solution while the rest now is centered around a depression, peaking out at around 970-975hPa over the W-English Channel. The depression starts its occlusion process already during the late evening hours, as the cold front approaches NW /W-France but a constricting warm sector should persist all the way to Belgium. The connection to a subtropical airmass west of Portugal truncates as the depression approaches NW France, so the warm sector over France constantly loses its warm/moist quality betimes, which is important regarding the instability release along the cold front later-on. The positive tilt of this feature at mid-levels also keeps the atmosphere quite warm with mid-level lapse rates barely outrun 6K/km. Despite all those obstructive reasons, we still expect an active cold front passage, starting at around 18Z over NW/W France and reaching Belgium after midnight. A strong surge of dry low-stratosphere air spreads eastnortheastwards above the NE-ward moving cold front. A strong vorticity lobe also overtakes the cold front and we think that the stage is set for enhanced convective activity along the cold front. A solid line of showers/thunderstorms, possibly evolving into a LEWP, accompanies the front with the most active part likely evolving over the northrn parts of France and Belgium where forcing will be the best. The line weakens over central and east-central France during the night but re-activation over W-Switzerland and the Vosges during the morning hours is possible due to the topography and better LL moisture with a very isolated/short-lived thunderstorm risk. Winds at 850hPa rapidly increase to 30m/s along the cold front, so severe wind gusts are likely during its passage. LCLs of at or below 600m and LL shear up to 20m/s are present along the front and a QLCS-type spinup can't be ruled out, especially over far N-France, where some low-end 0-3km CAPE release is possible.

It looks like a sting jet event sets up over NW-/W-France at 21Z onwards, as an impressive 45m/s jet at 850hPa comes ashore. Widespread damaging wind gusts will occur, but deep convection is not likely in this rapidly descending branch of dry air and hence we don't reflect the serious wind threat in our final level decision.

The final area of thunderstorm chances will be just next to the depression's center, where deep convection is likely. The environment remains favorable to an isolated tornado event along the N-coast of France after midnight but the main hazard will be strong wind gusts and marginal hail.

A general thunderstorm area was not issued for the cold front, as lightning activity, if any, will be sparse. Hence just the track of the depression was included into this area. The same for W-Switzerland and the Vosges.


http://www.estofex.org/
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Andre-ESCT

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PostSubject: Re: 09/10 February 2009 Slight Risk in my Place   Mon Feb 09, 2009 6:52 pm

Only snow, then also rain storm low with gale gusts approaches.

Starting from the night to Tuesday the weather fronts of a storm low pulling from France to Germany bring strong precipitation with itself, which changes under brief moderating of snow into rains. Within the coastal range and in higher situations it can snow on Tuesday however also longer. Besides it becomes stormily with gale gusts in comb situations of the low mountain ranges. To the midweek then cold winter weather with snow showers adjusts itself, which still persists also afterwards.

At the night to Tuesday precipitation an area in the southwest expands rapidly northeastward and covers exit of the night already nearly completely Germany. Thus a moderating is connected, so that it later rains after a short, partly however violent phase with snow in the south and the west exclusive. There the temperature in the course of the night rises even to plus 4 to 8 degrees. Direction the north and northeast must be counted against it starting from the early hours at values around the freezing point on longer continuing snow.

he usually still southern wind increases thereby rapidly and strongly. In the comb situations of the western and southwest low mountain ranges first heavy storm gusts are possible. At the coasts the wind in gusts to strength 8 revives and there first still comes from southeast to east. On Tuesday the weather becomes turbulent. The wind blows common strongly, in the south and the west also stormily with individual gusts by 100 kilometers per hour. In high situations a heavy storm partly threatens with gale gusts by 150 kilometers per hour and snow banks. There is further, strong precipitation, which falls in the northeast and in the mountain country with 0 to 2 degrees often as snow. Otherwise becomes with 3 to 8 degrees briefly moderate, before with rapidly falling temperature it snows in the afternoon in the west and the south often again in the flat country. On Wednesday phases with snow showers as well as friendly sections alternate with winter temperature levels. Blows a strong northwest wind, which is to stormy in the high situations and in shower proximity still strongly. In the flat country only 0 up to plus 4 degrees is reached, in situations above approximately 400 meters height prevails to permafrost. Drivers must count generally again on winter road conditions, whereby the snows can provide particularly at the northern edges of the mountain combs still for larger handicaps. Also Thursday shows up winter with snow showers in the flat country. Occasionally there is also periods with sunshine, only in north pilot situations of the low mountain ranges is closely cloudy it in temporary snow partial longer time. With maximum values between minus 3 and plus 3 degree decreases/goes back the temperature some more. In many places further noticeable wind from west to northwest lets it appear partly even still colder.


http://www.wetteronline.de/wetter/wetter.htm
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Andre-ESCT

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PostSubject: Re: 09/10 February 2009 Slight Risk in my Place   Tue Feb 10, 2009 5:22 am

Headline: In the south tempest by gale-like gusts. In the north snow. Development of the weather and warning situation: A storm low pulls over northern Germany slowly eastward. At its south flank a storm field with gale-like gusts seized the southwest and expands over South Germany still eastward. In other places in Germany increases the wind in the course of the day of west after east altogether, regionally can then to storm gusts occur. The precipitation changes in the evening and anchts into deep situations again in snow, particularly into higher situations exists then the danger of snow banks. Note: The early warning symbols are " on the Internet site; Wettergefahren" due to a technical error only partly visibly, but in the background available. Please on the warning side click! Tempest preliminary warning before gale-like gusts and gale gusts: In the south storm from southwest with gale-like gusts and gale gusts 100 to 125 km/h (strength 11 to 12) up. Warning of snow: In the north and the east still more easily snow, direction coast longer persisting. Warning of wind and storm gusts: Near the coast and in middle Germany gusts of wind to 60 km/h, exposed situations storm gusts to 85 km/h (strength 9). Warning of continuous rains: In the west of Germany still continuous rain, precipitation sums of the last 24 hours partly more than 30 litres per square meter. Last actualization Tuesday, 10.02.09, 09,20 o'clock Next actualization at the latest Tuesday, 10.02.09, 10,30 am DWD/VBZ Offenbach
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