Everstorm/Timeline

This timeline is a chart of expected Everstorm arrival times, along with an explanation of the calculations involved.
= Everstorm Arrival Times =
The Everstorm's arrival at different locations can be predicted based on the typical cycle. The tenth Everstorm arrived approximately 4 days early and the regular cycle seems to have resumed with the eleventh Everstorm.
The times provided assume a 20-hour clock, with "00:00" as midnight and "10:00" as noon, and use 50 minutes per hour. Dates follow the typical Rosharan convention of 10 months per year, 10 weeks per month, and 5 days per week. All times are highly speculative, as the precise timing depends on the accuracy of the assumptions made and (more importantly) on the imprecise and variable nature of the Everstorm's movement.
Everstorm Cycle	Shinovar	Azimir 	Urithiru 	Vedenar	Thaylen City	Kholinar	Narak 	New Natanan	Notes
0 	N/A 	N/A 	N/A 	N/A 	N/A 	N/A 	(15:16)	(1:17) 	
1 	(6:01) 	(00:45)	(7:49) 	(1:09) 	(2:04) 	(12:04) 	(17:16)	(3:17) 	
2 	(8:01) 	(2:45) 	(9:49) 	(3:09) 	(4:04) 	(14:04) 	(19:16)	(5:17) 	
3 	(10:01) 	(4:45) 	(11:49) 	(5:09) 	(6:04) 	(16:04) 	(1:16) 	(7:17) 	
4 	(12:01) 	(6:45) 	(13:49) 	(7:09) 	(8:04) 	(18:04) 	(3:16) 	(9:17) 	
5 	(14:01) 	(8:45) 	(15:49) 	(9:09) 	(10:04) 	(00:04) 	(5:16) 	(11:17) 	
6 	(16:01) 	(10:45)	(17:49) 	(11:09)	(12:04) 	(2:04) 	(7:16) 	(13:17) 	
7 	(18:01) 	(12:45)	(19:49) 	(13:09)	(14:04) 	(4:04) 	(9:16) 	(15:17) 	
8 	(00:01) 	(14:45)	(1:49) 	(15:09)	(16:04) 	(6:04) 	(11:16)	(17:17) 	
9 	(2:01) 	(16:45)	(3:49) 	(17:09)	(18:04) 	(8:04) 	(13:16)	(19:17) 	
10 	 	 	 	 	 	N/A 	N/A 	N/A 	
11 	 	 	(morning)	 	 	 	 	 	
= Basis and Assumptions =
This section details how the dates and times in the above table were determined.
We believe that the Everstorm follows a great circle path around Roshar, extending outward in each direction, normal to the path, such that it covers every landmass on Roshar that we know of. Thus we assume a great circle path which crosses roughly through the center of mainland Roshar. This is the greatest point of potential error in the calculation as the selection is largely arbitrary. Most paths which cross through the center of the continent should provide results within a few hours of one another, however. For this analysis, a path was chosen which crosses the northern tip of Shinovar in the west and Dawn's Shadow in the East.
The Everstorm moves at a rate of 9.1 Rosharan days per cycle, which equates to an angular speed of 1.978 degrees per Rosharan hour. The colored map of Roshar released with Oathbringer includes lines of longitude (200 divisions) and latitude (100 divisions) for the continent. These "Rosharan degrees" can be converted to degrees for the purpose of calculating the position of locations relative to the path of the Everstorm. For simplicity, the map's central longitude, passing through the eastern corner of Kadrix and the eastern edge of the Purelake, is taken as the Prime Meridian. Based on other maps of Roshar, the latitude passing through the southern tip of Kadrix and just above Rall Elorim, is taken as the Equator. We use Narak as the point of origin along the great circle path, and determine the timing for other locations based on their angle parallel to the path from this origin. Their perpendicular distance from the path is not relevant to the calculation, though presumably the Everstorm fades notably in strength at some distance. 
The provided lines of longitude are also important in determining the "time zone" of any given location. We find that mainland Roshar spans nearly 120 degrees of longitude at the most extreme points, putting the east coast about one third of a day ahead of the west coast. Because the Everstorm moves from west to east, it's slow pace is exaggerated by way it moves with the planet's rotation rather than counter to it. Unlike highstorms, which generally come and pass within a single Rosharan day, the Everstorm takes several days to cross the continent. Tracking the exact local time that it arrives is important. These calculations use a 20-Rosharan-hour clock. As the entire planet consists of 200 Rosharan degrees, every 10 Rosharan degrees of longitude corresponds to a 1-Rosharan-hour difference in local time. Rather than dividing the continent into discrete time zones, these calculations determine a unique local time (relative to the Prime Meridian) for every location.
The final step is to synchronize this model with the timing observed. The most precise data point we know of concerning this was provided by Kaladin, who stated that the Everstorm passed "around noon" on the day he arrived in Hearthstone. Thus we use at noon (local time) in Hearthstone as our basis for the rest of the timing. Observations of other Everstorm arrival times appear to match this observation by Kaladin within a reasonable margin of error.
For detailed calculations, see User:Jofwu's spreadsheet.
= Sample Calculation =
This section walks through the calculation for the Everstorm's first arrival at Urithiru.
Urithiru is located at 21.0 Rosharan degrees South and 4.0 Rosharan degrees East, or (-21.0, -4.0). We divide by 200 and multiply by 360 to convert to degrees: (-37.8, -7.2). Next we convert to Cartesian coordinates, taking the XY plane as the equatorial plane, +Z as the northern hemisphere, and Y=0 as the Prime Meridian. Urithiru's coordinates corresponds to a unit vector of: (0.78392, -0.09903, -0.61291). 
The next step is to rotate to a coordinate system with the XY plane as the great circle path of the Everstorm. That plane is defined by the locations referenced above. In Rosharan degrees, these are northern Shinovar (-9, -25) and Dawn's Shadow (-13, 33). We rotate these coordinates such that Dawn's Shadow is located at (1,0,0). Applying the same rotation to Urithiru gives a unit vector of: (0.95433, -0.19377, -0.22738).
This is then converted back to a "longitude" (angle along the great circle, starting from Dawn's Shadow) and "latitude" (angle of separation perpendicular to the great circle), before one final rotation which sets Narak at zero degrees "longitude". Urithiru's final "position" (the "longitude", or angle along the great circle) is 308.9 degrees, indicating that the Everstorm travels 308.9 degrees around Roshar from Narak to Urithiru. It's final "distance" (the "latitude", or angle normal to the great circle) is -13.1 degrees, indicating that Urithiru is 13.1 degrees "below" the center of the Everstorm's path.
Calculations for the arrival of the first Everstorm at Hearthstone indicate that the storm was summoned at 12:11 UTC (local time at the Prime Meridian). At a rate of 9.1 days per cycle (or 1.978 degrees per hour), the Everstorm crosses the 308.9 degrees to Urithiru in 7.81 days. Thus, the Everstorm began at 12:11 UTC on and reached Urithiru at 8:19 UTC on . Urithiru's longitude (4 Rosharan degrees West) places the local time at 0:20 behind UTC. This gives a local arrival time of 7:49 on . 
== Notes ==
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