Weather ForecastingWeather Forecasting

Persistence MethodPersistence Method

Assumes that the conditions that exist Assumes that the conditions that exist today will be the conditions that exist today will be the conditions that exist tomorrow.tomorrow.

New York City receives precipitation on New York City receives precipitation on avg. 121 days each year. If you predict the avg. 121 days each year. If you predict the weather will be good every day you will be weather will be good every day you will be right 67% of the time. In LA rain only falls right 67% of the time. In LA rain only falls 10% of the time so if you predict no rain 10% of the time so if you predict no rain you will be right 90% of the time. you will be right 90% of the time.

Folk LoreFolk Lore

Red sky at night, sailor’s delightRed sky at night, sailor’s delight red sky at morning sailor take warningred sky at morning sailor take warning

Red skies in the west (sunset) indicate clear skies and Red skies in the west (sunset) indicate clear skies and our weather usually comes from the west. our weather usually comes from the west.

When the wind blows from the west, the weather is at it’s When the wind blows from the west, the weather is at it’s best. Wind from the east is good for neither man nor best. Wind from the east is good for neither man nor beast. beast. West wind comes from land areas and is usually dry West wind comes from land areas and is usually dry while wind from the east off the ocean is full of moisture while wind from the east off the ocean is full of moisture and brings rain.and brings rain.

A Halo around the moon means a storm is coming.A Halo around the moon means a storm is coming.Halos are formed by ice crystals in high, thin, cirrus Halos are formed by ice crystals in high, thin, cirrus clouds which usually precede a storm by 24 hours.clouds which usually precede a storm by 24 hours.

RadarRadar

Radar works by sending out microwave Radar works by sending out microwave pulses which bounce back when they pulses which bounce back when they encounter a an object. encounter a an object.

The object then shows up as a pattern on The object then shows up as a pattern on the radar screen. The presence of the radar screen. The presence of precipitation and it’s distance show up as precipitation and it’s distance show up as an echo on the radar screen. an echo on the radar screen.

The strength of the signal is determined by The strength of the signal is determined by the amount of precipitation and can be the amount of precipitation and can be color coded. Red is heaviest rain.color coded. Red is heaviest rain.

Doppler Radar or NEXRAD Doppler Radar or NEXRAD Next generation RadarNext generation Radar

The Doppler shift works with light waves as well The Doppler shift works with light waves as well as sound waves and causes a shift in frequency as sound waves and causes a shift in frequency as an object moves towards or away from an as an object moves towards or away from an observer.observer.

Microwaves used in Doppler radar indicate if Microwaves used in Doppler radar indicate if raindrops are moving toward or away from raindrops are moving toward or away from the radar.the radar.

Doppler radar is more sensitive than Doppler radar is more sensitive than traditional radar and different levels of traditional radar and different levels of precipitation can be detected flowing in precipitation can be detected flowing in different directions. different directions.

The different motions are color coded so The different motions are color coded so When there is sharp change in direction it When there is sharp change in direction it shows up as a sharply contrasting color.shows up as a sharply contrasting color.

This contrast can indicate a severe storm is This contrast can indicate a severe storm is present, even a tornado.present, even a tornado.

Satellite ImagesSatellite Images