Bellingcat Challenge #10 "Synoptic Code" Writeup

This article was automatically translated from Japanese by AI.

Challenge

Bellingcat Challenge #10 “Synoptic Code”

This is a morse code transmission received on the 13th October 2024. The sender is thought to be the Yelnya, a Russian ship operating on the Black Sea.

.-. -.-. …- / -.. . / ..- -.-. - .- ….. / .—- …– .—- —.. .—- / —-. —-. …– ….- ….. / .—- —– …– ….- -…. / ….- .—- -…. —-. —.. / …– ..— ….- —– ….. / .—- —– ..— —.. —– / ….- —– .—- ..— —– / ….. ….- —– —– —– / –… —– ..— —– —– / —.. …– ….. —– —– / ..— ..— ..— ….. ..— / —– —– ..— —.. —– / .—- …– —– .—- ..— / -… - / .- .-. / ..- -.-. - .- ….. / -.

Can you decode the message?

What was the reported air temperature in degrees Celsius? (give your answer to one decimal place i.e. “12.3”)

Solution

Decoding the Morse signal produced the following text:

RCV DE UCTA5 13181 99345 10346 41698 32405 10280 40120 54000 70200 83500 22252 00280 13012 BT AR UCTA5 N

Searching for the opening string, RCV DE UCTA5, led me to an X post decoding the signal. Using the post as a lead, I followed its link to a SHIP observation decoding table and checked the numeric groups.

The table defines the surface air temperature group as 1snTTT. Applying this format to 10280, the initial 1 identifies the surface air temperature group, sn = 0 indicates a positive or zero value, and TTT = 280 represents temperature in tenths of a degree Celsius. The reported temperature was therefore 28.0°C.

Flag

28.0

Notes

The meteorological part of the Morse transmission uses FM 13 SHIP, the WMO code form for reporting surface observations from a sea station. The detailed specification is available in the official WMO Manual on Codes.

Reading the meteorological groups shows that the surface air temperature observed at 34.5°N, 34.6°E at 18:00 UTC on the 13th was 28.0°C.