shirley murillo: at the upper atmosphere. you could see indications of ice crystals, and those ice crystals are snow. eric jay dolin: hurricane sandy was the first time, and i think still the only time that a national hurricane forecast had both wind, waves, as well as snow. [thunder crashes] about 60% of the hurricanes start in the southern flanks of the sahara desert, where the hot air rising off the desert meets with the moist air coming from the indian ocean. they're called african easterly waves. jack parrish: these are waves in the atmosphere over central africa. they come out over the ocean, and then when they start to hit the warmer water, they get stronger. derek van dam: now, because our planet rotates, we have a spinning effect on our storms. it's called the coriolis effect. you start rotating faster and faster and faster until it's a perfect, perfect cylindrical eye, and then all of a sudden, you got yourself a monster. and that's the hurricane. robert campbell : i had my last conversation with my sister. you need