Unformatted text preview: Weather Patterns Weather Air masses Air Air mass: Large body of air Air masses are about 1000 miles or Air across and about 2 miles thick across Types of air masses Types Polar and arctic air masses: Air masses Air that originate at high latitudes, usually towards the poles towards Tropical air masses: Air masses that Air originate low latitudes, mainly around the tropics tropics Continental air masses: Form over land Maritime air masses: Form over water Air masses (cont.) Air Types 1) 1) 2) 2) 3) 3) 4) 4) 5) 5) based on classification: continental polar (cP) continental tropical (cT) maritime polar (mP) maritime tropical (mT) continental arctic (cA) Continental polar (cP) air masses masses Continental Continental polar and maritime tropical air masses influence weather in North America the most America cP air masses originate in northern cP Canada, Alaska, and the Arctic Canada, These air masses are responsible for “lake These effect” snows effect” cP air masses bring heavy snow in most cP of North America of Maritime tropical (mT) air masses masses mT mT air masses affecting North America originate over the warm waters of the Gulf of Mexico, Caribbean Sea, and the Atlantic Ocean Atlantic These air masses are warm, moist, and These usually unstable usually mT air is responsible for most of our mT precipitation precipitation In summer, these air masses bring about In high temperatures and oppressive humidity Continental tropical (cT) Continental This This air mass is definitely prevalent in the Southwest and Mexico, especially during the summer months the Fronts Fronts These These are boundaries that separate different air masses different Fronts can form between any two Fronts any contrasting air masses contrasting Fronts are relatively narrow, basically 9120 mile bands of discontinuity Ideally, air masses on both sides of a front Ideally, move in the same direction at the same speed speed Types of fronts Types Warm fronts Cold fronts Stationary fronts Occluded fronts Warm front Warm
A front along which a warm air mass front overrides a retreating mass of cooler air overrides On a weather map, warm front is shown On with a red line and semicircles protruding into the cooler air into The first sign of the approach of a warm The front is the appearance of cirrus clouds ahead ahead Warm front (cont.) Warm As As the front nears, lower clouds and then thicker stratus and nimbostratus clouds form, bringing moderate or light precipitation precipitation As warm front passes, gradual increase in As temperature occurs temperature Cold front Cold Front Front in which dense, cold air occupies territory formerly taken by warm air territory Cold fronts are about twice as steep as Cold warm fronts warm Cold fronts advance faster than warm Cold fronts fronts As cold front approaches, towering As cumulonimbus clouds form, which account for most of our violent weather for Cold fronts (cont.) Cold In In a cold front, intense precipitation over a shorter time duration results shorter As this front passes, a temperature drop As and a wind shift results and Stationary front Stationary Front Front in which the surface position does not move not Neither the cold air mass or the warm air Neither mass overtake each other mass The front can remain over an area for The several days several Stationary fronts give weather conditions Stationary similar to that of a warm front (light to moderate precipitation) moderate Occluded front Occluded Front Front in which an active cold front overtakes a warm front overtakes Precipitation occurs along both frontal Precipitation boundaries, combining the narrow band of heavy precipitation of a cold front with a wider band of precipitation of a warm front wider Middle latitude cyclones Middle Usually Usually shown on weather maps depicting an “L”, meaning low pressure system an Large centers of low pressure that travel Large from west to east from Weather conditions usually last from a few Weather days up to a week days These systems bring precipitation and These severe weather severe Thunderstorms Thunderstorms
A storm that generates lightning and storm thunder thunder Produced in cumulonimbus clouds Thunderstorms are formed when warm, Thunderstorms humid air rises in an unstable environment humid Thunderstorms (cont.) Thunderstorms An An estimated 16 million thunderstorms occur every year occur At any given moment, about 2000 At thunderstorms are in progress over different parts of the earth different All thunderstorms require warm, moist air Thunderstorms (cont.) Thunderstorms Most Most thunderstorms take place in the early evening, when surface temperatures are high high Tornadoes These These are violent windstorms that take on the form of a rotating column of air (vortex) that extends from a cumulonimbus cloud that Tornadoes form in association with Tornadoes thunderstorms that produce high winds, and torrential rainfall and Tornadoes (cont.) Tornadoes The The most intense tornadoes are the ones which form in association with huge thunderstorms thunderstorms General atmospheric conditions for General tornadoes usually involve the encounter of a cold air mass with a moist warm air mass mass Most tornado activity occurs in the central Most part of the U.S. part Tornadoes (cont.) Tornadoes Tornadoes Tornadoes can occur any month of the year, April-June is the period of greatest tornado activity tornado Hurricanes Hurricanes
A tropical cyclonic storm with winds in tropical excess of 74 miles per hour excess Hurricanes are the largest and most Hurricanes destructive storms on earth destructive Hurricanes can impose damage in the Hurricanes billions of dollars and cause great loss of life life Hurricanes (cont.) Hurricanes Hurricanes Hurricanes form in all the tropical oceans, except for the South Atlantic and South Pacific Oceans Pacific In the western Pacific Ocean, they are In called typhoons, iin the Indian Ocean, they typhoons n are called cyclones cyclones Profile of a Hurricane Profile Hurricanes average 375 miles across Hurricanes are low pressure systems Lowest barometric pressures ever Lowest recorded in the Western hemisphere are associated with hurricanes associated Eye Eye Eye: Calmest portion of the storm In the eye, precipitation ceases and winds In subside subside The eye is the warmest part of the storm The eye is characterized by clear, blue The skies skies Eyewall Eyewall Most intense portion of the storm In the eyewall, the greatest windspeeds In and heaviest rainfall occur and Hurricanes (cont.) Hurricanes Hurricanes Hurricanes are fueled by the heat liberated when huge quantities of water vapor condense condense Hurricanes most often in late summer, Hurricanes when ocean waters have reached temperatures of 80oF or higher temperatures Hurricanes (cont.) Hurricanes When When a cyclone’s strongest winds do not exceed 38 miles per hour, it is called a tropical depression tropical When winds are between 38-74 miles per When hour, it is called a tropical storm hour, When a tropical storm is produced, it is When then assigned a name then Saffir-Simpson scale Saffir-Simpson This This scale ranks the relative intensity of hurricanes: hurricanes: 75-96 mph: Category 1 75-96 97-111 mph: Category 2 112-131 mph: Category 3 132-155 mph: Category 4 >155 mph Category 5 Hurricane destruction Hurricane Hurricane Hurricane damage is divided into three categories: 1) wind damage 2) storm surge and 3) inland freshwater flooding 3) Hurricane damage (cont.) Hurricane Storm Storm surge is responsible for 90 percent of hurricane deaths of Storm surge: An abnormal rise of the sea An along a shore as a result of strong winds along Forecasting tornadoes Forecasting Tornado Tornado watch: Alerts the public of the possibility of tornadoes in a specified area possibility Tornado warning: Issued when a tornado Tornado has actually been sighted and is indicated by radar by Accuracies of tornado warning by the use Accuracies of Doppler radar of ...
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This note was uploaded on 12/25/2010 for the course ESC 1000 taught by Professor Faculty during the Fall '10 term at FAU.
- Fall '10