"Extreme weather confirms s2 cell boundaries"

#PokemonGO: The South Bay area was hit by Extreme weather lockdowns the weekend of Dec. 15-17 due to a red flag advisory for hills in the surrounding area. The actual advisory did not apply to most of the communities in the area and some of us on our local discord were amused at how some towns CLOSER to the hills had "Windy" weather in-game while towns further away had "Extreme" weather blocks. This led to a discussion about the boundaries of the Extreme weather areas and whether they coincided with s2 cells. I started screencapping whenever I noticed a change of weather.Initially I thought town boundaries were relevant but later I realized that I just happened to be in places where they coincided with s2 boundaries, which actually fit the data better. In the four instances documented below, I use level 10 as my point of reference. It is possible that smaller cells are used by Niantic for in-game weather but the examples I witnessed are satisfactorily accounted for by level 10.Example #1The first time I saw the weather shift away from the dreaded Extreme was when we drove down San Antonio past Central Expressway (image #1). This was close to the boundary of Palo Alto and Mountain View but in fact what we crossed was an s2 cell boundary (image #2). We were driving at a fairly slow speed so I screencapped the windy weather very close to the actual line. When we crossed back over the same boundary, the weather changed back to Extreme.Example #2That night we drove on Highway 101 bound for San Jose and I saw the weather shift a second time, from Extreme to Clear (image #3). I screencapped this image just as I was approaching Shoreline Blvd in MV. As the following map (image #4) shows, I had just passed another s2 cell (actually two).Example #3Then the weather changed back to Extreme in Sunnyvale. Unfortunately, we were traveling very fast on the freeway and I had a slow reaction time (needing to click out of the popup), so I did not screencap (image #5) the map view until we were approaching San Tomas Expwy (image #6). I wondered if Calabazas Creek, which coincided with a municipal boundary, was relevant so I paid closer attention on the shift in weather on my return trip in the opposite direction. This time I did not have to click out of a popup, and screencapped (image #7). the change closer to the s2 boundary than the first time around. The first screencap was taken right as I was approaching Calabazas Creek and the second was taken just before Lawrence Expwy (image #8), immediately after we had passed the s2 boundary. I had a third chance to capture this boundary the following morning and this time screencapped the very instant the popup appeared (image #9). Again, this was just after we had passed the s2 boundary (with probably a slight delay for server response), and the popup appeared prior to reaching Calabazas Creek (image #10).Example #4For my last example, I present the boundary on Highway 87 alongside Guadaloupe Park (Guad as the SJ PoGo community calls it). There I saw the weather flip from sunny to Extreme (image #11). As the map shows (image #12), the first screencap was taken well before we had reached W Taylor St. and then the popup appeared close the s2 boundary. My screencap of the alert was taken just ahead of Coleman Ave. (with a minor reaction delay), and then after clicking out of it, the third was taken as we were passing Ryland St.ConclusionsThe foregoing I believe demonstrates the relevance of s2 cells for weather boundaries, as others have observed previously with respect to various aspects of the game (including raids and biomes). Similar results would be obtained with any weather boundaries, but because Extreme weather lockdowns are often sustained, these might offer a more reliable means of assessing cell boundaries than ordinary in-game weather which is subject to weather fluctuations. A significant flaw in the foregoing is that with the exception of the first example, all my screencaps were taken at significant speed on freeways. Hopefully others experiencing Extreme weather alerts can give more precise results by standing stationary on both sides of a boundary. However with the case of Example #3, I was able to replicate the boundary twice and anticipate it enough to screencap the alert the instant it appeared. via /r/TheSilphRoad http://ift.tt/2Di0RUQ