Ever since the young SLF listened to his first shortwave radio under the blankets, I've wondered this. I've never been able to find out. The two explanations I've uncovered in the past are first, the French one -- obviously from Voler, to fly, and Meteorological -- and second Volume Meteorlogical, ie a discrete dump of multiple data in one go. I've seen both mentioned in dictionaries.
Someone also suggested in the office today that it was a VOice List of METeorological information, but that was a guess.
So, I've emailed those nice people at the Oxford Word and Language Service (OWLS), part of the OED, with a request for some chapter and verse. If they don't know -- we're stumped.
R