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clusters that are characteristic of this zone were present, with a significant spatial
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heterogeneity and lifespan of a few hours.
Infra-red images taken every fifteen minutes by the geostationary satellite Meteosat 9 are the
best source of information at this stage to appreciate the evolution of these clusters, but they
did make it possible to directly observe the conditions encountered at FL350. Moreover, the
two most representative images were taken approximately seven minutes before and after
the last ACARS message from flight AF447.
The infra-red imagery analysis does not make it possible to conclude that the stormy activity
in the zone where flight AF447 is presumed to have disappeared was exceptional in
character, but it shows the existence of a cluster of powerful cumulonimbi along the planned
flight path, identifiable from 00 h 30 onwards. This cluster is the result of the fusion of four
smaller clusters and its east-west extension is approximately 400 km.
Though the analysis of the imagery leads one to think that, towards 2 h 00, the cumulonimbi
forming this cluster had mostly already reached their stage of maturity, it is highly probable
that some were the site of notable turbulence at FL350. There is a possibility of significant
electrical activity at the flight level, but the presence of super cooled water at FL350 is not
very probable and would necessarily have been limited to small quantities.
1.7.2 Comments on the information available
1.7.2.1 Forecast charts
The TEMSI chart for 00 h 00 (Appendix 2) shows that the planned route touches the two
East-West oriented cloudy masses, located on both sides of the equator and mentions:
ISOL/EMBD CB between levels XXX (base located below FL250) and FL450. The highest
altitude of the tropopause along the route is estimated at FL500. A 280°/85 kt jet stream is
indicated around the 10° North parallel, to the West of the route, at FL410 and FL430. The
following illustration shows the superimposition of this TEMSI with the infra-red image for
00 h 00.
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IR -40° 1st June 00 h 00 + extract TMSI London 1st June 00 h 00
Note: the TEMSI charts and the wind and temperature charts are forecasts based on a digital model at
a synoptic scale produced 24 hours before a specific validity time, for the South America region.
These charts present the large convective activity zones in the area described but do not indicate the
specific position of the cumulonimbi and the cumulonimbus clusters.
The wind and temperature charts show that the average effective wind along the route can
be estimated at approximately ten knots tail-wind. On the chart for FL340, the highest air
temperature is located around the equator. It is estimated at – 40 °C, that is to say, Standard
+ 13 °C.
The CAT charts do not forecast any clear air turbulence along the route.
1.7.2.2 SIGMET
SIGMET 5 issued for the RECIFE FIR on May 31 at 17 h 58, valid from 18 h 00 to 22 h 00,
reported a storm forecast in the layer with tops at FL350.
SIGMET 7, issued for the ATLANTICO FIR on May 31 at 17 h 58, valid from 18 h 00 to
22 h 00, reported a storm forecast in the layer with tops at FL370.
SIGMET 7, issued for the DAKAR FIR on May 31 at 16 h 33, valid from 16 h 35 to 20 h 35,
reported the observation of isolated storms in the layer, with tops at FL450, moving towards
the west at 10 kt.
The zones covered by these messages are shown in the following image, superimposed on
the Meteosat 9 infra-red image for 20 h 00.
Note: crews do not have access to such a view.
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SIGMET 5 issued for the RECIFE FIR defines the zone affected by storms as being to the
south-west of line AB shown in the figure above. This SIGMET reads as follows:
WSBZ31 SBRE 311752
SBRE SIGMET 5 VALID 311800/312200 SBRE-RECIFE FIR EMBD TS FCST SW OF
CLARK PSN/ PEPER PSN/ NEURA PSN AREA TOP FL350 STNR NC=
The validity of this message is questionable for two reasons:
• line AB is in the south-west/north-east direction and yet, in such a case, a "SE OF" or
"NE NW OF" mention would be expected, and not "SW OF" as is the case in the
SIGMET,
• the satellite images during the period of validity of the SIGMET show the convection
zone to be located to the North-West of line AB rather than to the South-East of the
same.
It is thus possible that this SIGMET includes an error, with a SW OF mention instead of a
NW OF mention. On this assumption, SIGMET 5 SBRE would complete the zone identified in
the ATLANTICO FIR, as represented by the green line in the figure below:
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SIGMET 10 was then issued for the ATLANTICO FIR for the period from 31 May at 22 h 00
　
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