Meteosat 8 Composite RGB - Convective Storms (WV6.2-WV7.3; IR3.9-IR10.8; NIR1.6-VIS0.6)

26 May 2006, 0900 UTC

The RGB composites helps us to better understand the structure and life cycle of the clouds. They provide the information about cloud depth, the amount of cloud water and ice, cloud particle size and phase and cloud temperature.

The interpretation of the colours in this composite goes according to these simple guidelines:

red: deep precipitating clouds containing large ice particles
yellow: Cbs with severe weather and strong updrafts; small ice particles (or thick high level lee cloudiness).
dark red: thin cirrus; large ice particles
purple: thin cirrus cloud; small ice particles
blue: thin to no clouds.

The frontal cloudiness over western Turkey consist mainly of ice particles, both large and small, and yellow spots embedded are signs of frontal convection. Some yellow spots can be recognized far ahead of the front, over the eastern part of Turkey. This is a sign of daytime convection, induced by the orography, common during summer months, and also convection caused by an upper level low.

26 May 2006, 1000 UTC

An increase in convectivity is seen within the frontal zone and over eastern Turkey. Some convective cells can be detected in front of the cold front.

26 May 2006, 1100 UTC

From now on, the development can be followed in a time sequences at 15 minutes intervals.

26 May 2006, 1115 UTC

The development continues.

26 May 2006, 1130 UTC

Several big, well developed convective cells can be detected within the front and also far ahead of the front. The bright yellow colour in the cores of the cells indicates the position of the strongest updraft. The greater the distance from the centre, the weaker the updraft, resulting in redder appearance of the cell edges.
The prefrontal convergence line is observed almost throughout the whole Turkey, from north to south.

26 May 2006, 1145 UTC

The development continues.

26 May 2006, 1200 UTC

The big MCS over Central Turkey intensifies very fast, and so does the prefrontal convection and the convection far ahead of the front. This RGB gives more details, distinguishing several convective cells within the particular system, while the IR10.8 image recognizes only the system itself as one big white spot.

26 May 2006, 1215 UTC

Some of the convective cells, especially the prefrontal ones, become reddish which indicates a change in the structure of the clouds - from small ice particle to large ones.

26 May 2006, 1230 UTC

The development continues.

26 May 2006, 1245 UTC

Cells within the frontal zone are merging into two bigger cells. The south part of prefrontal convection becomes weaker, while on the northern part some new yellow spots, as a result of the severe updraft, can be observed.

26 May 2006, 1300 UTC

The MCS over central Turkey becomes bigger in size but more orange in colour.

26 May 2006, 1315 UTC

All the cells discussed before have grown in size and turned orange. This is the sign of change in the cloud structure.

26 May 2006, 1330 UTC

The colour of the cells has changed, becoming more orange or even reddish, especially on the margins. The cells are becoming old and mature and consist of large ice particles.
The prefrontal convergence line and the big MCS will merge into one during next time steps.

26 May 2006, 1345 UTC

The process continues. There are some new isolated yellow spots on the back side of the big MCS, in the cold air, and also in the northern part in front of it.

26 May 2006, 1400 UTC

The MSC over central Turkey becomes bigger. The convection far to the east dies out and it will appear more reddish in the next time steps.

26 May 2006, 1415 UTC

The MSC over central Turkey grows.

26 May 2006, 1445 UTC

30 minutes later the situation is similar but with more purple colour which is more likely to be the result of less light over Turkey than less convectivity within the cold front. On the south-west side of the frontal cloudiness a new yellowish spot hence new convection can be recognised.
This RGB uses two visible channels (0.6 and 1.6 痠). Channel 1.6 acts as a near infrared channel which, especially in this situation of the late afternoon, will increase the amount of blue colour in this RGB (blue is the difference between the 1.6痠 and 0.6痠), which explains the purple colour.

Meteosat 8 RGB Composite - Severe Convection (WV6.2-WV7.3; IR3.9-IR10.8; NIR1.6-VIS0.6)