why does a tropical storm have to reach 74 mph before its concidered a hurricane?
438807
Because that's what we say it is.  This is just an arbitrary standard.  There is no particular reason why it couldn't be 70 mph or 80 mph.  It is just that we know from experience what damage can be caused by certain windspeeds, and storms with winds less than 75 mph are typically not too dangerous.
1000247
In approximate terms, yes.  It's called cyclostrophic flow: the pressure gradient force provides the centripetal acceleration to maintain circular motion.  (pressure gradient force balancing centrifugal force)\n\nGive or take...\n\n*************\nSide note....\n*************\nThe coriolis effect certainly dictates the *direction* of circulation (clockwise in the southern hemisphere, counterclockwise in the northern hemisphere) thus the lack of tropical cyclone formation near the equator.\n\nHowever the apparent acceleration we attribute to the 'Coriolis Force' plays an insignificant role in determining the equilibrium trajectories of air parcels near a hurricane's core.  The distances involved are simply too small (10-100km) - the distance from the surface to the earth's axis changes very little on these scales in the tropics.
254503
If it's on hurricanes, then try searching the National Hurricane Center's website--they have a lot of information.\n\nwww.nhc.noaa.gov
333143
By "accure" do you mean "accrue"?  Well, hurricanes do increase in size (accrue) but only over moist, warm areas.  This increases wind speed and overall area (also why most hurricanes grow over warm oceans and occur near the Equator).
1130792
tornados have a much higher wind scale than hurricanes do.  an F5 tornado has winds up to 318mph.  hurricanes go up to category 5.  a category 5 has winds higher than 155mph, but I've never heard of one that's had winds higher than 200mph.  it's a misconception that hurricanes cause more damage b/c of their sheer size, but the most damaging part of a hurricane is the Northeast side of the storm.  whereas a tornado is damaging no matter where it hits you b/c it just sucks everything right on up and can go on for miles and miles.  hurricanes almost always weaken when they completely come ashore.
277515
Extreme?\n\nCaught on a caribbean island in the middle of a class 5 hurricane with 250mph winds, a 30ft storm surge while pinned in a 2 story condo 10 feet above sea level.\n\nDon't believe me?  I took video: http://www.youtube.com/user/Brythonic
459150
Hurricanes are in the Atlantic ocean and Northeast Pacific Ocean east of the dateline, Typhoons in the pacific, cyclones in the Indian ocean. \n\nIn general they are the same thing. Hurricanes spin counter clockwise. There are minor differences in how the strength and wind speed of these storms are catagorized. For example wind speed in hurricanes is 10 minute sustained winds while typhoons it is only 1 minute. So Typhoons may appear to have stronger wind speeds than their Atlantic relitives. There are minor differences in the wind speed catagories of hurricanes and Typhoons. Both get different sets of names as well. For all functional purposes it is only a regional name for the same kind of storm. \n\nI could swear I read somewhere that Typhoons and or cyclones south of the equator spun clockwise but cannot verify this.
1170368
Heavy rains and thunderstorms created from the hurricane may cause flooding in the area or high winds might spawn tornadoes, localized flooding.  Essentially by 200 miles inland, the storm energy caused by warm moist air has been dispated as winds and heavy rains.  This disruption in the atmosphere could spawn toronados.  Hope this helps.
662087
water temperature is a biggie..and more recently..since they've been collecting data on hurricanes for around 30 years now...they're using trend maps to try to see any kind of pattern in Hurricane occurances each year\n\nthere are "ups" and "downs" when it comes to the numbers of hurricanes each year..and this up/down period lasts for several years...we are currently in one of hte "up" periods..and using that past history..correlated with water temperatures off the coast of africa and the location/temperature of the jet stream..its fairly safe to assume a good number..due to large amounts of moisture down there..and the always predictable convective activity (what starts hurricanes..a lifting force that gets the clouds to build)
307489
It's because of something called the Coriolis effect, which is due to the earth's rotation. (First reference).  The basic idea is that, because the earth is rotating fastest at the equator, things moving north or south feel a slight deflection to the west or east.\n\nAir spirals into the center of a hurricane. So, imagine a lump of air that starts to the north of the hurricane's center. As that air moves south, it's going to enter areas where the earth is moving slightly faster. Since the earth spins toward the east, this lump of air will fall behind slightly, and, from our point of view, move towards the west.  A lump of air starting on the south of the hurricane, sees the reverse: it moves north, and is thus moving slightly faster to the east than the hurricane center. \n\nIn the southern hemisphere, this is reversed, and cyclones there spin clockwise.
1150130
It's pretty dang hard with such cold water & the jet stream pushing it away. In order for it to happen the Jet stream has to move out of the way, which would make it colder & further weaken the storm. Maybe a real strong hurricane could be a tiny little tropical storm by the time it got there, but nothing like as strong as what we get hit with down here.
710530
Several reasons\n1) A hurricane is larger and covers more area while a tornado is much smaller and may only hit one house and leave the neighbors house.  A hurricane can be 500 miles wide, while a tornado is 2 miles wide at most.\n2) A hurricane has storm surge and flooding rains, while a tornado is usually rainless.  A tornado can do more damage to one particular location, but hurricanes have widespread damage.
1135874
well, to be honest, i think all the options above suck. \n\nstorm surges are related to a lowering of atmospheric pressure allowing the sea water beneath a storm to rise. they are typically associated with hurricanes, but could occur with large thunderstorms under teh right conditions. \n\nhurricane winds typically reach over 180mph. when have you ever been in a thunder storm with winds that high?!? the hurricane classification system is based on wind speeds and damage. a thunderstorm is towards the lower end of the spectrum, followed by tropical storms and hurricanes. so no, a thunderstorm does not have faster winds than a hurricane, that is just ridiculous. \n\ni find it hard to belive that thunderstorms have more evaporated precipitation than a hurricane, but i may be wrong. thunderstorms mainly release built up electrical charge whearas hurricanes are a culmination of evaporating water over the warm, deep areas of the atlantic ocean. \n\nhurricanes winds do spiral due to the corriolis effect. i cant remember which way though. i wouldnt say that thunderstorm winds blow in a straight line, there is bound to be turbulence to some extent. \n\nso in short, none of the statments suggested in the questions is really correct.
833485
People NEVER have 2-3 weeks warning for a hurricane.  Hurricanes form in much less time than that.  Modern equipment and forecasting allows for maybe 2-3 days' warning before a hurricane may hit an area.  Even that is not always certain because the track of the hurricane can vary up until almost the last minute.\n\nI live in a coastal area that has been hit by hurricanes before.  People make the choices they make about evacuating or not evacuating for a variety of reasons.  Some have no way to get out.  Some people are frightened of leaving their homes.  Some people are gone the minute the evacuation order is issued.  Other than physically removing people, going house to house, there is no way in the world that a government can ensure that everyone leaves.  Some people simply will NOT leave.  Unless you live in an area that gets hurricanes, you won't understand.  I'm not condoning it.  I'm simply telling you that it happens.
910309
There is no such thing.  The Saffir-Simpson scale is not open ended.  Despite the TV movie "Category 6" and its sequel "Category 7," these terms have no meaning.  The Saffir-Simpson scale could be extended some day, if significantly stronger storms require it, but as of now, 5 is the highest value.  A tropical system with sustained winds of 156 mph or greater is a Category 5, even if the winds are at 190 mph (the highest ever recorded).  No matter how intense a storm becomes, it is still a Category 5.\n\nRegardless of the classification, it is true that global warming may be leading to stronger tropical storms, due to warmer ocean waters.
537331
There are so many online resources for this, why would you ask here?\n\nFind these sites or ask at your library about: National Weather Service; National Hurricane Tracking Center; www.weather.com.
39653
its a giant storm  like a hurricane thats been going on for a logn time bout size of earth i think