When strong storms appear in Forecast Models, it is tempting to trace back in the atmosphere where the system originates. The water vapor animation above, from GOES-13, ends with the future East Coast Storm developing over the lower Mississippi River Valley (where it produced severe weather). The rocking animation, below, shows that the storm moved in from the Pacific Ocean on January 19th.
How did the impulse traverse the Pacific Ocean? The animation above, from GOES-15, shows the system approaching the West Coast at the end of the day on Monday 18 January. It is by no means the strongest-looking system in this animation, and it has the characteristics, at 2100 UTC on 18 January, of a developing cyclone west of San Francisco. The rocking animation, below, shows that the system crossed the Pacific Basin, moving well north of Hawaii, in about two days. What did the storm do before GOES-15 could view it?
The animation from Himawari-8, above (note that Himawari-8 produces Full Disk imagery every 10 minutes; GOES-13 and GOES-15 time resolution for full disk imagery is every 3 hours, and the time resolution of the Himawari-8 animation here is degraded significantly to match that of GOES-13 and GOES-15; GOES-R will have temporal resolution equivalent to Himawari), shows a series of impulses moving off the coast of Asia, with the final impulse maintaining integrity into the central Pacific (shown here at 2100 UTC on 16 January 2016; here is the view from GOES-15 at the same time). The rocking animation, below, allows for easier tracing of these impulses. The impulse that would track across the Pacific, enter North America and become a strong storm appears to be a small enhancement in the Water Vapor imagery at 0600 UTC on Friday 15 January southwest of Japan, north or Taiwan, just emerging off the coast of Asia. It can be traced back to a large low pressure system over Siberia at the beginning of the Himawari-8 animation (on 13 January).
This animation strings together Himawari-8, GOES-15 and GOES-13 Water Vapor imagery from 14 January through 21 January, showing the evolution, in 3-hour steps (the native GOES-13/GOES-15 temporal resolution for Full Disk Imagery), of the system as it moves from Asia across the Pacific into North America. The images below, are annotated water vapor imagery stepping back in time showing the impulse.