From the Wikipedia page on the Swiss International Airlines Flight 850 crash investigation, it was stated that the initial METAR did not reflect the situation and the METAR less than an hour (a moment before the approach was started) was drastically different.
EDDT 04001KT CAVOK 30/17 Q1002 A2959 0998 2947 NOSIG.
EDDT VRB01KT 9999 FEW040CB SCT120 BKN260 29/17 Q1002 A2959 0998 2947 TEMPO 27025G55KT 2000 +TSRA BKN009 BKN015CB COMMENTS: OCNL LTNG AND CB SW OF STN.
I'm not very familiar with these reports, or how they are generated. From some research it sounds like the second report is much more serious, however I'm having trouble understanding a few things:
This seems to suggest variable visible range, but I'm not sure what the 01KT means.
- Can someone clarify?
The later report first mentions scattered cumulonimbus clouds, but then says the coverage is up to broken.
- Why are there multiple mentions of the same types of clouds?
- Are they talking about different height/direction?
The Wikipedia article seems to suggest that there was a massive storm moving rapidly into the area. My understanding is that NOSIG means the weather is not expected to significantly change in the next two hours.
- What would cause the initial report to include NOSIG?
- Given how much worse the weather seems to be in the later report, why would it take the station almost an hour to file a new report?
- Why wouldn't they file a new report as soon as it seemed like the weather was degrading?