Weather Forecasting Powerpoint Presentation

Weather Forecasting Persistence Method  Assumes that the conditions that exist today will be the conditions that exist tomorrow.  New York City receives precipitation on avg. 121 days each year. If you predict the weather will be good every day you will be right 67% of the time. In LA rain only falls 10% of the time so if you predict no rain you will be right 90% of the time. Folk Lore Red sky at night, sailor’s delight red sky at morning sailor take warning Red skies in the west (sunset) indicate clear skies and our weather usually comes from the west. When the wind blows from the west, the weather is at it’s best. Wind from the east is good for neither man nor beast. West wind comes from land areas and is usually dry while wind from the east off the ocean is full of moisture and brings rain. A Halo around the moon means a storm is coming. Halos are formed by ice crystals in high, thin, cirrus clouds which usually precede a storm by 24 hours. Radar  Radar works by sending out microwave pulses which bounce back when they encounter a an object.  The object then shows up as a pattern on the radar screen. The presence of precipitation and it’s distance show up as an echo on the radar screen.  The strength of the signal is determined by the amount of precipitation and can be color coded. Red is heaviest rain. Doppler Radar or NEXRAD Next generation Radar  The Doppler shift works with light waves as well as sound waves and causes a shift in frequency as an object moves towards or away from an observer.     Microwaves used in Doppler radar indicate if raindrops are moving toward or away from the radar. Doppler radar is more sensitive than traditional radar and different levels of precipitation can be detected flowing in different directions. The different motions are color coded so When there is sharp change in direction it shows up as a sharply contrasting color. This contrast can indicate a severe storm is present, even a tornado. Satellite Images