At the speed of a bullet train

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Category 5 Cyclone Winston made landfall in Fiji on 20 February, damaging and destroying thousands of homes and buildings. It left in its wake a death toll of 44 and more than 50,000 people in evacuation centres.

Also enduring the cyclone were numerous weather stations, designed by NIWA and installed over the last decade for the Fiji Meteorological Service (FMS). The stations gather data about Fiji’s climate variability that provide information to help reduce the impacts caused by severe weather and climate events.

300 kph winds

During the cyclone, some FMS weather stations recorded wind speeds of over 300 kilometres per hour and saw barometric pressures plummet to 930mb. “Three hundred kilometres per hour is nearing the speed of the Japanese bullet trains (320kmh). A piece of debris in the wind travels just as fast and can cause catastrophic damage to objects in its path,” said NIWA Principal Scientist Environmental Monitoring Graham Elley.

The weather stations are located on Fiji’s main and outlying islands and are designed to record wind speeds, wind direction, air temperature, humidity, barometric pressure and rainfall. All data collected are sent to a secure central database accessible by FMS and remotely by NIWA. It is used to provide both real-time and historical information, including warnings of inclement weather.

Despite being erected on robust steel poles and protected by steel casings, withstanding these 300 kilometre per hour wind speeds in the cyclone proved too much for some of the stations.

Near-total destruction: The Fiji Meteorological Service quarters in Vanua Balavu. [Fiji Meteorological Service]

“Our data logger housing is mounted on a 10 metre tubular steel mast and is covered in two layers of steel. At one station, the wind had blown the outer layer right off the main housing, almost like a banana being peeled. Vibrations set up by the wind actually broke a nickel cross arm supporting the wind direction sensor, and we suspect other damage was caused by debris flying at such high speeds,” Elley said.

For the stations that survived the cyclone, Elley was impressed they were able to continue transmitting data over the duration of the cyclone.

Getting data from remote locations

“By using satellite communications to transmit data from the weather stations, we are able to reduce the ‘weak link’ caused by damage to land-based communications alternatives. It is also the best way for us to get data back from remote places such as Fiji’s outerlying islands where the land-based infrastructure is less common,” Elley said.

The data extremes measured at the stations were able to be independently verified using global weather satellite data and imagery from a local Doppler radar. The information made it possible for FMS to analyse the track of the cyclone, estimate the diameter of its eye and the locations of the most intense rain bands in the eye wall.

Note: This feature originally appeared in Water & Atmosphere,June 2016