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Q. How are tornadoes in the northern hemisphere different from tornadoes in the southern hemisphere? A. The sense of rotation is usually the opposite. Most tornadoes -- but not all! -- rotate cyclonically, which is counterclockwise in the northern hemisphere and clockwise south of the equator. Anticyclonic tornadoes (clockwise-spinning in the northern hemisphere) have been observed, however -- usually in the form of waterspouts, non-supercell land tornadoes, or anticyclonic whirls around the rim of a supercell's mesocyclone. There have been several documented cases of cyclonic and anticyclonic tornadoes under the same thunderstorm at the same time. Anticyclonically rotating supercells with tornadoes are extremely rare; but one struck near Sunnyvale, CA, in 1998. Remember, "cyclonic" tornadoes spin counter-clockwise in the northern hemisphere, and clockwise.
Wind sheerDirectional wind shear is the change in wind direction with height. In the image (right), the view is looking north. The wind near the surface is blowing from the southeast to the northwest.As the elevation increases the direction veers (changes direction in a clock-wise motion) becoming south, then southwest, and finally, west.Speed shear is the change in wind speed with height. In the illustration below, the wind is increasing with height. This tends to create a rolling affect to the atmosphere and is believed to be a key component in the formation of mesocyclones which can lead to tornadoes.Strong vertical shear is the combination of a veering directional shear and strong speed shear and is the condition that is most supportive of supercells.
Was tornado forecasting once banned in the U.S.? Yes. Before 1950, at various stages of development of the Weather Bureau, the use of the word "tornado" in forecasts was at times strongly discouraged and at other times forbidden, because of a fear that predicting tornadoes may cause panic. This was in an era when very little was known about tornadoes compared to today, by both scientists and the public at large. Tornadoes were, for most, dark and mysterious menaces of unfathomable power, fast-striking monsters from the sky capable of sudden and unpredictable acts of death and devastation. As the weather patterns which led to major tornado events became better documented and researched, the mystery behind predicting them began to clear -- a process which still is far from complete, of course. In 1950, the Weather Bureau revoked the ban (PDF) on mentioning tornadoes in forecasts.
Here are my 9 guesses!Alaska; Hawaii; Washington; Vermont; Rhode Island; Delaware; Maine; New Hampshire; District of Columbia
I wasn't doing the guessing but since you asknevada ?California ?