#anticyclone

Tornadoes usually exhibit cyclonic circulation, meaning they rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere, which correlates to Earth’s rotation and the Coriolis effect (http://on.fb.me/1L1Xsuq). However, correlation does not equal causation. Tornadoes themselves are too small to be directly affected by the Coriolis. Instead, tornadoes almost always rotate in the same direction as the storm that created them (storm cells are influenced by Coriolis forces but even storm cells sometimes rotate anticyclonically). Anticyclone tornadoes are usually waterspouts or weak tornadoes not associated with supercells. Clearly the twister in this photo is neither of those. There are two possible ways it could have formed both of which are very unusual: it may be the result of intense wind shear boundaries along the rim of a mesocyclone (regions of rotating updraft 3 – 9km in diameter within a supercell), or it may have formed as a “twin” of the cyclonic tornado. While it’s hard to be sure just from a photo, reports indicate that the first scenario is more likely. Either way, it is very rare for an anticyclone tornado to form under a supercell, and Colorado had three of them in one storm! A storm chaser reportedly got one of the anticyclone tornadoes on video, which you can view here: http://bit.ly/1e4dp5H. Personally, I have a difficult time determining which way it is rotating. My suggestion is to put the video in full screen mode and pay close attention to the last part when he zooms in. - RE Photo Credit: Kelly DeLay http://www.kellydelay.com/ References: http://wapo.st/1QiCH17 http://bit.ly/1e4dkiB http://bit.ly/1MK74ba https://bit.ly/31wXpVV https://www.spc.noaa.gov/faq/tornado/