Temp data in different altitudes: sequence in time and altitudes

18th August 2004: 00UTC. Surface
The image shows the radisoundings at the surface. We recognise dewpoints between 15 and 18°C indicating a high potential for summer convection. Over the Western parts of France a sharp temperature contrast (22°C Bordeaux and 12° Brest) can be detected indicating an intense frontal zone.

18th August 2004: 00UTC. 925 hPa.
In comparision to the surface data we observe at many locations a vertical wind shear (increased wind speed and turning to southwest) equivalent to warm air advection in low altitudes.

18th August 2004: 00UTC. 850 hPa.
From that image we diagnose also warm air advection, however, of reduced intensity between 925 and 850 hPa. We see a strong horizontal temperature contrast over WestFrance (16°C, Bordeaux / 9°C Brest).

18th August 2004: 00UTC. 700 hPa.
Only negectable temperature advection happened between 850 and 700 hPa. We can conclude that in the lowest levels the temperature increased whereas above no significant advection existed yielding an increase of the vertical temperature gradient and a destabilisation. The mean wind speed over France is between 30 and 40 knots. As a first guess we can assume that gusts up to 40 knots will be possible in the case of thunderstorms (without consideration of the convective energy).

18th August 2004: 00UTC. 500 hPa.
Only negectable temperature advection can be seen

18th August 2004: 00UTC. 400 hPa.
An continouous increase of the wind speed reveals over Western France.

18th August 2004: 00UTC. 300 hPa.
As a hint to intense dynamical forcings the image shows wind speeds between 60 and 90 knots that are relatively high for August.

18th August 2004: 00UTC. 200 hPa.
As a hint to intense dynamical forcings the image shows wind speeds between 60 and 90 knots that are relatively high for August.

18th August 2004: 12UTC. Surface
12 hours later and within an area covering Central, Southwest France and West to South Germany temperatures between 24 and 28°C and dew points from 14 to 17 °C were registered. The strong temperature contrast over the West France still existed.

18th August 2004: 12UTC. 925 hPa.
The comparision of the wind directions with the image before indicates that the warm air advection within the lowest altitudes over Central and Western France had weakend during the last 12 hours whereas it still existed over Eastern France and the southern parts of Germany.

18th August 2004: 12UTC. 850 hPa.
Over big parts of Germany we observe a further, however weak, warm air advection between 925 and 850 hPa and an increasing wind speed.

18th August 2004: 12UTC. 700 hPa.
Again we see a small clockwise turning of the wind direction of many parts of Germany and wind speeds of about 40 knots indicating gusts of up to 40 knots as a first guess.

18th August 2004: 12UTC. 500 hPa.
Over Southwest Germany (Idar Oberstein) we recognise a weak counter-clockwise turning (cold air advection) whereas in the layer below we had an increasing temperature due to warm air advection. That leads finaly to a higher vertical temperature gradient within these levels and possibly to convection.

18th August 2004: 12UTC. 400 hPa.
Over France wind speeds up to 70 knots are measured.

18th August 2004: 12UTC. 300 hPa.
Near the niveau of the polar jet high wind speeds of up 95 knots were reported indicating an intense frontal zone and dynamical forcings.

18th August 2004: 12UTC. 200 hPa.
Brest was already influenced by the colder air west of the cold front. The wind speed decreased to 60 knots (300 hPa: 85 knots) However, East France and South Germany were affected by subtropical air with a higher tropopause. Therefore, the wind speeds remain similar to the values in 300 hPa.

19th August 2004: 00UTC. Surface
Another twelfe hours and weak wind and temperatures between 16 and 20°C were measured near the surface. The dew points were around 15°C.

19th August 2004: 00UTC. 925 hPa.
West of about 10°E temperatures between 14 and 17°C and only neglectable temperature advection can be observed. The radiosoundings further to the East reveal temperatures of about 23°C and clockwise turning of the wind direction indicating warm air advection and destabilisation. However, we find only neglectable vertical motion (see special link).

19th August 2004: 00UTC. 850 hPa.
In comparison to 925 hPa the temperature contrast at the front in 850 hPa is weakened. East of 10°E we recognise a weak warm air advection.

19th August 2004: 00UTC. 700 hPa.
There arises no significant difference to the image before. Wind speed in 700 hPa increased compared to 850 hPa indicating a strong frontal zone. The wind directions are similar to 850 hPa. Only between Nancy and Idar Oberstein we oberserve a weak cold air advection between 850 and 700 hPa.

19th August 2004: 00UTC. 500 hPa.
We see a width band of wind speeds between 45 and 65 knots.

19th August 2004: 00UTC. 400 hPa.
We see a width band of wind speeds between 50 and 85 knots..

19th August 2004: 00UTC. 300 hPa.
This image shows near the niveau of the polar jet wind speeds of up to 110 knots indicating a very intense frontal zone for August.

19th August 2004: 00UTC. 200 hPa.
No significant change in comparison to 300 hPa can be found.