Answer to Question 1
ANSWER: A radar transmitter sends out microwave pulses and when this energy strikes an object, a small fraction of it is reflected and scattered back to the antenna. Precipitation particles are large enough to bounce microwaves back to the antenna. Consequently, a colorful area on the radar screen represents the amount of reflected microwave energy translated into precipitation intensity inside a supercell thunderstorm. Doppler radar can do more than measure rainfall intensity; it can actually measure the speed at which precipitation is moving horizontally toward or away from the radar antenna. Because precipitation particles are carried by the wind, Doppler radar can peer into a severe storm and unveil its winds. Doppler radar works on the principle that, as precipitation moves toward or away from the antenna, the returning radar pulse will change in frequency when compared to the transmitted frequency.
Answer to Question 2
ANSWER: If the precipitation in the cloud is swept too far away from the updraft, or if too much precipitation wraps around the mesocyclone, the necessary interactions that produce the rear-flank downdraft are disrupted, and a tornado is not likely to form. Moreover, tornadoes are not likely to form if the supercell is fed warm, moist air that is elevated above a deep layer of cooler surface air. And tornadoes usually will not form when the rain-chilled air of the rear-flank downdraft is too cold. Even among supercells that have mesocyclones evident on radar, only about 25 percent produce tornadoes.
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