Speaking to reporters in Geneva, WMO Secretary General Petteri Taalas said Libya's main challenge in managing the aftermath of floods that have killed thousands was that the government was "not functioning normally", Reuters reported.
"If they would have been a normally operating meteorological service, they could have issued a warning," he said.
"The emergency management authorities would have been able to carry out evacuation of the people. And we could have avoided most of the human casualties."
The comments came after a tsunami-sized flash flood hit eastern Libya at the weekend, killing at least 4,000 people, with thousands more missing and feared dead.
The enormous surge of water burst two upstream river dams and reduced the eastern city of Derna to an apocalyptic wasteland where entire city blocks and untold numbers of people were washed into the Mediterranean Sea.
“The flooding events came and there was no evacuation taking place, because there was not the proper early warning systems in place,” Taalas said.
If evacuations had taken place, the human toll would have been far lower, he said.
“Of course we cannot fully avoid economic losses, but we could have also minimized those losses by having proper services in place,” he said.
Libya’s National Meteorological Centre (NMC) did issue early warnings for the extreme weather coming 72 hours in advance.
It had notified governmental authorities by e-mail, urging them to take preventative measures.
But WMO said it was “not clear whether (the warnings) were effectively disseminated”.
It said that while there had once been close cooperation between meteorological services and disaster management throughout Libya, this was no longer the case.
Libya is currently politically divided and has been at war on-and-off with no strong central government since an uprising toppled Muammar Gaddafi in 2011.
An internationally recognized Government of National Unity (GNU) is based in Tripoli, in the west.
A parallel administration operates in the east, including the city of Derna, which has been devastated by flooding.
Taalas said WMO had previously been in touch with Libyan authorities to assist them in reforming the meteorological system, but that these efforts had been hampered by security threats.
"Since the security situation in the country is so difficult, it's difficult to go there and improve the situation," he said.