On 7 January 2014 an X1.2 flare and CME with a radial speed \approx 2500 km s ^ { -1 } was observed from near an active region close to disk center .
This led many forecasters to estimate a rapid arrival at Earth ( \approx 36 hours ) and predict a strong geomagnetic storm .
However , only a glancing CME arrival was observed at Earth with a transit time of \approx 49 hours and a K _ { P } geomagnetic index of only 3 - .
We study the interplanetary propagation of this CME using the ensemble Wang–Sheeley–Arge ( WSA ) –ENLIL+Cone model , that allows a sampling of CME parameter uncertainties .
We explore a series of simulations to isolate the effects of the background solar wind solution , CME shape , tilt , location , size , and speed , and the results are compared with observed in-situ arrivals at Venus , Earth , and Mars .
Our results show that a tilted ellipsoid CME shape improves the initial real-time prediction to better reflect the observed in-situ signatures and the geomagnetic storm strength .
CME parameters from the Graduated Cylindrical Shell model used as input to WSA–ENLIL+Cone , along with a tilted ellipsoid cloud shape , improve the arrival-time error by 14.5 , 18.7 , 23.4 hours for Venus , Earth , and Mars respectively .
These results highlight that CME orientation and directionality with respect to observatories play an important role in understanding the propagation of this CME , and for forecasting other glancing CME arrivals .
This study also demonstrates the importance of three-dimensional CME fitting made possible by multiple viewpoint imaging .