Evaluation of the IRI model efficiency for operational forecast of HF propagation conditions

New approaches for adaptation of the International Reference Ionosphere model IRI to current ionospheric parameters are used to improve determination of maximum usable frequency MUF and path length D for HF waves propagated via the ionosphere with an example of one European path. Parameters foF2 (maximum frequency of the F2 layer) and TEC (total electron content) are used as adaptive ones. In additional the analytical approximation is proposed for the IRI model residual error. Its influence on MUF and D errors is given.