New Zealand tornadoes were harder to predict than larger ones such as in the United States because they were too small to see on radar.
Corbett said warnings for the strong gusts were issued to Auckland Council and Civil Defence.
Tom Stowers, 42, of Massey; Keith Langford, 60, of Tuakau, and Brendon Johnson, 22, of Massey were killed at a construction site during the storm.
About 250 people were left homeless and thousands of homes were without power after the storm, which is estimated to have caused $11 million worth of damage. Vector said yesterday it hoped to have the final 30 homes without power reconnected overnight.
Prime Minister John Key told media on Friday the Government would look to improve its weather forecasting capabilities.
"As a general rule, you think you can pick these things up. I think there were predictions for heavy rain but not necessarily tornadoes so that's something we're going to have to go back and have a look at."
Phillip Duncan from WeatherWatch said he sent a low tornado risk warning through to Civil Defence the night before the fatal tornado.
"But I wouldn't have expected Civil Defence to have acted on that on their own without MetService saying anything.
"They do trust WeatherWatch but they wouldn't act on a warning from us alone."
Duncan said the tornado highlighted the need for more communication with state-owned MetService.
"I think it is time MetService and WeatherWatch work together like we did years ago with Bob McDavitt."
Duncan agreed tornadoes were hard to predict but said a warning about an increased risk or possibility was better than none at all.
