3 Method

To be able to analyse the credibility of the forecasts available to pilots, an examination has been done of a few forecast products that include information about convective weather and/or  its effects. The study focuses on Sweden, and as a way of further limiting the study, mainly products designed especially for the private sector of the air traffic were examined. This was done because the ‘private sector’ is mostly comprised of small aircraft, which are the ones most exposed to convective weather. The study is also limited in that only products produced by the Swedish Meteorological and Hydrological Institute (SMHI) and published by the Swedish aviation administration (Luftfartsverket) were examined. These were chosen as they are often the only products private airplane pilots in Sweden use prior to a flight.

Any information found regarding the accuracy or reliability of these products was summarized and for further details a literature study was made. The literature chosen focused on evaluations of the ability of NWP-models to simulate and forecast convection and convective events. The models looked at were those which SMHI uses to produce the products examined. Studies evaluating different convective indices were also included.

Additionally , two interviews with experienced aviation weather forecasters were included in the study. These were done as a result of a lack of available evaluations of the studied forecast products. They also contributed with ‘a forecaster’s view’ of predicting convective events and how much information is possible to give a pilot before a flight. The interviews were done with Tomas Fyrby, aviation meteorologist and air traffic client manager at SMHI, and lieutenant colonel Per-Ola Jakobsson, meteorologist at the Swedish military’s METeorological and OCeanographical Centre (METOCC). The latter was included because the forecasters at METOCC use the same models as those in use by SMHI and because METOCC focuses almost exclusively on aviation meteorology. The interview with Fyrby was done through a visit at SMHI in Upplands Väsby, Sweden, and through complementary e-mail correspondence. Jakobsson was interviewed solely by e-mail.

Information about the Swedish model configurations has been gained through additional e-mail correspondence with several employees at SMHI. One of them was Emil Björck, the author of one of the studies examined, who was also asked questions in person at a lecture at Stockholm’s University. Other correspondents were Karl-Ivar Ivarsson and Esbjörn Olsson.

The questions posed in the introduction were answered by weighting together the type of information a pilot can get from the different forecast products with the models’ abilities to handle convection. For this purpose, the evaluations of the models were summarized and compared to the insights gained from the forecasters at SMHI and METOCC. A few own conclusions were also made.