Volcanos and Hazards to Aviation

The Wellington Volcanic Ash Advisory Centre (VAAC) is one of nine VAACs that operate under an international system called the International Airways Volcano Watch (IAVW), set up and co-ordinated by the International Civil Aviation Organization (ICAO). More detailed information about IAVW can be obtained from the relevant ICAO web page.

The function of each of the nine centres under the IAVW is to respond to reports of volcanic ash within their region and provide forecasts to the aviation community of ash cloud extent and movement. Observations may come from ground stations and Volcano observatories, aircraft in flight or orbiting satellites. The ash warnings issued are in the form of Volcanic Ash Advisories and SIGMETs describing the current and future extent of ash.

Volcanic ash constitutes a serious threat to aircraft operations primarily due to the effect of the corrosive gases and abrasive particles on aircraft engines and airframe. In addition to loss of engine performance or even flameout, ash effects may include instrument and radio failure, visibility problems and damage to other external flying components as well as contamination of the aircraft interior.

Such potentially serious and expensive damage is best prevented by avoiding flying through ash altogether. Over recent years, improvements in observation networks, satellite technology, computer modelling and our increased understanding of the phenomena have led to improved volcanic ash forecasting methods.

The Wellington Volcanic Ash Advisory Centre area of responsibility covers the area:

The Wellington VAAC is operated by MetService on behalf of the New Zealand Meteorological Authority (CAA NZ), and is located in Wellington, New Zealand. The Wellington Meteorological Watch Office (MWO) is co-located with the Wellington VAAC. The Wellington MWO issues SIGMETs for the two New Zealand FIRs, NZZC (New Zealand FIR) and NZZO (Auckland Oceanic FIR).

A local enhancement of the Wellington VAAC, the New Zealand Volcanic Ash Advisory System (VAAS) is primarily provided for the New Zealand FIR through interactions of aircraft operators, Airways NZ, Meteorological Service of New Zealand limited (MetService), GNS Science Limited and the Civil Aviation Authority of New Zealand (CAA).

More information on VAAS can be obtained from the CAA web page Volcanic Ash Advisory System.


Information about T+0 confidence statement

Following the WMO Volcanic Ash Advisory Centre (VAAC) “Best Practice” Workshop 2016, it was agreed to trial the use of a statement outlining the forecaster confidence in the T+0 ash polygon (T+0 means the time of the observed or estimated ash polygon). The statement will appear at the start of the RMK section of the VAA and will take the form “T+0 CONFIDENCE HIGH” or “T+0 CONFIDENCE LOW”.
Note – for a VAA to be issued, a forecaster must first have high confidence in the existence of ash. The confidence statement in the VAA RMK then refers to the area of the ash depicted in the T+0 section.
If “T+0 CONFIDENCE HIGH” is used, this means strong observational evidence of volcanic ash and high confidence in model(s) prediction.
If “T+0 CONFIDENCE LOW” is used, this means weak observational evidence of volcanic ash and/or low confidence in model(s) prediction.