In this study , we present a new method for forecasting arrival times and speeds of coronal mass ejections ( CMEs ) at any location in the inner heliosphere .
This new approach enables the adoption of a highly flexible geometrical shape for the CME front with an adjustable CME angular width and an adjustable radius of curvature of its leading edge , i.e .
the assumed geometry is elliptical .
Using , as input , STEREO heliospheric imager ( HI ) observations , a new elliptic conversion ( ElCon ) method is introduced and combined with the use of drag-based model ( DBM ) fitting to quantify the deceleration or acceleration experienced by CMEs during propagation .
The result is then used as input for the Ellipse Evolution Model ( ElEvo ) .
Together , ElCon , DBM fitting , and ElEvo form the novel ElEvoHI forecasting utility .
To demonstrate the applicability of ElEvoHI , we forecast the arrival times and speeds of 21 CMEs remotely observed from STEREO/HI and compare them to in situ arrival times and speeds at 1 AU .
Compared to the commonly used STEREO/HI fitting techniques ( Fixed- \phi , Harmonic Mean , and Self-similar Expansion fitting ) , ElEvoHI improves the arrival time forecast by about 2 hours to \pm 6.5 hours and the arrival speed forecast by \approx 250 km s ^ { -1 } to \pm 53 km s ^ { -1 } , depending on the ellipse aspect ratio assumed .
In particular , the remarkable improvement of the arrival speed prediction is potentially beneficial for predicting geomagnetic storm strength at Earth .