What is a Mid-Latitude Cyclone?Also called an extratropical cycloneAn area of surface low pressureRequire upper-level lows/trough (at 300-500 mb level) to formAny cyclone is an area of low pressureCenter of cyclone is center of lowLifetime: Several days to a week+Scale: Several hundreds to 1000+ miles acrossWeather effects:Thunderstorms and tornadoesBlizzards and ice stormsWidespread snow and rainWarm and cold frontsUpper-Level Low or TroughFound on upper-air maps (300, 500 mb)Several km above the surfaceIdentify from height contoursSurface LowFound on surface mapsIdentify from surface isobarsFronts also shownSatellite AppearanceLook for classic comma-shaped cloud on satellite pictureComma head called wraparound regionExtra-Tropical CyclonesWhy are they important?Bring cold air southward and warm air northwardCool the Tropics, warm Polar RegionsProvide precipitation to many regions of worldProduce much of the severe weather across North AmericaWeatherShowers and thunderstorms (possibly severe) may form along cold frontLifting along cold frontTail of comma cloudMore on these after second exam!Heavy snow (possible blizzard) to northwest of surface lowLarge area of light to moderate precipitation to north of warm frontMixed precipitation types in winterGradual slope à Weaker ascentWhat Is a Blizzard?Visibility less than ¼ of a mile due to snowWinds greater than 35 mph (30 knots)Conditions must persist for 3 or more hoursGround blizzards – Blowing snow on ground onlyNo snow is actually fallingBlizzard IngredientsCold air – precipitation must be snowStrong windsIntense pressure gradientDeep low and strong Arctic high can create such a gradientLittle friction over flat plainsBlizzards are typically found to the NW of low pressure systemsNor’EastersA Nor’Easter is an intense mid-latitude cyclone that tracks along the northeastern coast of the United StatesCan produce heavy rain and winds along coast and heavy snowfall inlandPrecipitation types determined by track of surface lowHeavy snow typically found just northwest of low trackCoastal flooding possibleIn an average year, Nor’Easters cause more economic damage to the United States than any other type of storm1 inch rain=12-12 in snowMid-Latitude Cyclones: Weather 10/15/2012What is a Mid-Latitude Cyclone?•Also called an extratropical cyclone•An area of surface low pressure•Require upper-level lows/trough (at 300-500 mb level) to form•Any cyclone is an area of low pressure•Center of cyclone is center of low•Lifetime: Several days to a week+•Scale: Several hundreds to 1000+ miles across•Weather effects:•Thunderstorms and tornadoes•Blizzards and ice storms•Widespread snow and rain•Warm and cold fronts-Upper-Level Low or TroughoFound on upper-air maps (300, 500 mb)Several km above the surfaceoIdentify from height contours-Surface LowoFound on surface mapsoIdentify from surface isobarsoFronts also shown-Satellite AppearanceoLook for classic comma-shaped cloud on satellite pictureoComma head called wraparound region Extra-Tropical Cyclones-Why are they important?-Bring cold air southward and warm air northwardoCool the Tropics, warm Polar Regions-Provide precipitation to many regions of world-Produce much of the severe weather across North America Weather-Showers and thunderstorms (possibly severe) may form along cold frontoLifting along cold frontoTail of comma cloudoMore on these after second exam!-Heavy snow (possible blizzard) to northwest of surface low-Large area of light to moderate precipitation to north of warm frontoMixed precipitation types in winteroGradual slope à Weaker ascent What Is a Blizzard?-Visibility less than ¼ of a mile due to snow-Winds greater than 35 mph (30 knots)-Conditions must persist for 3 or more hours-Ground blizzards – Blowing snow on ground onlyoNo snow is actually falling-Blizzard IngredientsoCold air – precipitation must be snowoStrong windsIntense pressure gradientDeep low and strong Arctic high can create such a gradientLittle friction over flat plainsoBlizzards are typically found to the NW of low pressure systems Nor’Easters-A Nor’Easter is an intense mid-latitude cyclone that tracks along the northeastern coast of the United States-Can produce heavy rain and winds along coast and heavy snowfall inlandoPrecipitation types determined by track of surface lowoHeavy snow typically found just northwest of low trackoCoastal flooding possible-In an average year, Nor’Easters cause more economic damage to the United States than any other type of storm 1 inch rain=12-12 in