|MadSci Network: Earth Sciences|
Hi Anette. Hurricanes are a warm water phenomena and are born and active only in areas where sea surface temperatures are 28 degrees Centigrade (82 degrees Fahrenheit) or warmer. The spin of the earth on its axis eventually moves all tropical cyclones northward (southward in the Southern Hemisphere) toward the poles. As long as there is warm water to fuel the storm, they will remain a tropical cyclone. Some storms make it as far as 40-50 degrees North Latitude in the vicinity of the Gulf Stream (Atlantic) and Kuroshiro Current (Pacific) before losing their warm core characteristics and becoming extra-tropical storms. For more information on hurricanes and tropical cyclones see the Frequently Asked Questions pages at The National Hurricane Center at http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqHED.html As for tornadoes, tornadoes can occur anywhere on the planet where the precise weather conditions come together to support their formation. Tornadoes are born in severe thunderstorms. These thunderstorms need moisture, atmosphere instability, and a lifting mechanism to form. While rare at higher latitidues...it's hard to get the moisture and instability together at the same time as you go further north...they have been known to occur as far north as Alaska (see the news story from the Juneau Times in 1995 at http://www.juneauempire.com/stories/080205/loc_20050802011.shtml ) and Edmonton, Canada in 1987 ( http://www.iassistdata.org/tornado/ ). A good on-line reference for tornadoes is available from the Storm Prediction Center at http://www.spc.ncep.noaa.gov/faq/tornado/
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