Weather, and particularly severe weather events, can significantly impact airlines and airport operations. The frequency and severity of these extreme events, and the resulting losses have been increasing for the last few decades. Greater disruption to global aviation services may be anticipated.
Lightning is one of the most dangerous and frequently encountered weather hazards. It can crucially and significantly disrupt the operations of airlines, airports and air traffic control. Leveraging meteorological science and technological advances promises fresh opportunities to mitigate these impacts and better manage disruptions.
Aviation weather forecasting in New Zealand
MetraWeather’s parent company, MetService, is New Zealand’s National Meteorological Service (NMS) and the ‘official’ forecaster and ‘noted authority’ in accordance with the World Meteorological Organisation (WMO) guidelines.
MetService is the Civil Aviation Authority of New Zealand (CAA) certified provider of aviation weather information for all six categories, in accordance with Civil Aviation Rule, Part 174. MetService is also certified to AS/NZ 9001:2015 standards.
MetService provides commercial airlines and recreational pilots with high-quality aviation weather forecasting to safely and efficiently conduct flight operations, and minimise weather-related risks and disruptions across New Zealand and the Pacific region.
MetService is a partner for New Southern Sky, the implementation phase of New Zealand’s National Airspace and Air Navigation Plan.
It provides a suite of MET-CDM products and services which are helping to shift the focus of aviation weather guidance from interpretation towards impacts and decision support for collaborative decision making by airlines, airport operations and air traffic management.
Thunderstorm forecasting and lightning detection in New Zealand
Aviation services in New Zealand, both in the air and on the tarmac, are sometimes disrupted by severe weather events, thunderstorms and lightning strikes.
MetService integrates real-time lightning data to inform aviation forecasts and decision support services geared to improving safety, operations and customer experience both in the air, on the tarmac and in the terminal.
The usefulness of lightning data to aviation forecasting – the forecaster’s view
Amanda De Monte
MetService – Te Ratonga Tirorangi
It is well documented that thunderstorms and cumulonimbus clouds are among the most hazardous weather affecting aviation.
The reason thunderstorms are avoided by aircraft in flight include the following dangers:
- the risk of lightning strike
- severe turbulence associated with strong up and down drafts
- severe icing
- poor visibility in heavy rain and hail.
These dangers are even more concerning for aircraft on arrival and departure as during these phases of flight, a headwind is necessary to create the lift necessary to maintain altitude. A sudden change in wind direction caused by the outflow from a thunderstorm can severely impact this required lift and cause an aircraft to suddenly sink which needless to say is quite dangerous when in close proximity to the ground.
When lightning is reported within a certain proximity of an airport (usually 5 nautical miles), all ground operations are suspended because airport managers do not want to put their personnel at risk of being struck by lightning and it is unsafe to refuel an aircraft when lightning is present.
Knowing these dangers makes the forecasting and monitoring of thunderstorms a crucial responsibility of any aviation forecaster. At MetService almost every aviation product we create will include a mention of thunderstorms if these are expected.
In real time aviation forecasters use satellite, radar and lightning data in order to issue thunderstorm SIGMETs which are warnings to the industry to avoid a given piece of airspace as within this area they can expect to encounter embedded, frequent, obscured or squall type thunderstorms. Within these warnings the forecaster will also specify if hail can be expected with these thunderstorms.
Where lightning data is most helpful is in the creation of SIGMETs as well as in the creation and correcting of our Graphical New Zealand Significant Weather Chart. We differentiate cumulonimbus cloud from thunderstorms requiring a SIGMET using lightning data.
When the lightning data available to us indicates thunderstorms approaching any of our TAF (Terminal Aerodrome Forecast) aerodromes, we often proactively amend the TAF for that aerodrome to include the expected arrival time of the thunderstorms and expected time they will cease to impact the aerodrome. We do this because of the known impacts of thunderstorms on arrival, departure and ground movements around the aerodrome. When a significant line of thunderstorms is expected to impact a major airport such as Wellington, Christchurch or Auckland; if time allows, we’ll also call the tower of the impacted aerodrome to give them a personal warning of the approaching storms and how long these are expected to affect the terminal. We’ll also call Christchurch radar control so they know to hold aircraft back from entering the airspace around that aerodrome.
The cirrus cloud associated with an area of thunderstorms can often spread far from the centre of the storms, thus we use lightning data within and outside the NZZC to better issue SIGMETs for a more targeted area of concern. Without lightning data we often find ourselves issuing these warnings for areas much larger than is likely necessary.
Forecasters are however far from the only user of real time lightning data. Air Traffic Control will use radar and lightning data to route aircraft around areas of thunderstorms in real time and to determine when to delay aircraft on arrival or departure to avoid these crucial phases of flight be performed in a thunderstorm.
Airlines will use this data to plan routes around areas of thunderstorms. Airport managers will use lightning data to determine when to halt ground operations when lightning come within a certain threshold distance to maintain the safety of their ground crew.
On the evening of 11 April 2018, a lightning strike at Wellington Airport strike knocked out some its runway lights shortly after 7pm, grounding flights and stopping landings.
About 8.15pm, Airways New Zealand reported that the lights were restored and operations had resumed.
MetService aviation meteorologists had forecast showers, hail and thunderstorms for the evening.
The weather event at Wellington Airport was the latest in a string of weather-related travel disruptions. Flights were grounded at Auckland International Airport the day before, when winds of 90km/h were recorded, and gusts reached up to 120km/h.