Lecture 12Outline of Last Lecture I. Upper-Level Winds ReviewII. The Geostroph WindIII. The Geostrophic WindIV. Analyzing Upper-Air MapsV. Circular MotionVI. Curved Flow Around Lows Curved Flow Around HighsVII. Curved Flow Aloft: Gradient Wind BalanceVIII. Upper-Level MapsIX. NomenclatureX. Surface WindsOutline of Current Lecture XI. Mid-Latitude CycloneXII. Upper-Level Low or TroughXIII. Surface lowXIV. Satellite AppearanceXV.Extratropical CyclonesXVI. Air Mass MovementXVII. WeatherXVIII. BlizzardXIX. Blizzard IngredientsXX.Chicago Blizzard 2011XXI. Nor’EastersATMS 100 1st EditionXXII. Coastal FloodingXXIII. Northeast Blizzard (2013)Current LectureXXIV. Mid-Latitude Cyclonea. Also called a extratropical cyclonei. an area of surface low pressureii. requires upper-level low/trough (at 300-500 mb level) to formb. any cyclone is an area of low pressurei. center of cyclone is center of low (lowest pressure)c. lifetiem: several days to a week +d. scale: several hundreds to 1000+ miles acrosse. Possible Weather:i. thunderstorms and tornadoesii. blizzards and ice stormsiii. widespread snow and rainiv. warm and cold frontsXXV. Upper-Level Low or Trougha. Found on upper-air maps (300-500 mb)i. several km above the surfaceb. Identify from height contoursc. generally found west of the surface lowXXVI. Surface lowa. Found on surface mapsb. identify from surface isobardsc. fronts also shownXXVII. Satellite Appearancea. Looks for classic-comma shaped cloud on satellite pictureb. comma head called wraparound regionXXVIII. Extratropical Cyclonesa. Why are they important?i. bring most of the precipitationb. Bring cold air southward and warm air northwardi. cool the tropics, warm polar regionsc. provide precipitation to many regions of the worldd. produce much of the severe weather across North AmericaXXIX. Extratropical Cyclones Circulationa. Cold to the eastb. Warm from the southXXX. Air Mass Movementa. Clockwise Circulation moves air masses aroundXXXI. ***Weather***a. Showers and thunderstorms (possibly severe) may form along cold fronti. strong lifting along cold frontii. tail of comma cloudb. Heavy snow (possible blizzard) to northwest of surface flowc. Large area of light to moderate precipitation to north or warm fronti. mix precipitation types in winter ii. gradual slope=weaker ascentd. Snow/Blizzard= Northwest of lowe. Ice= Northeast of Low (most common ahead of warm front)f. Rain=East of lowg. Thunderstorms=South/Southeast of low frontXXXII. Blizzarda. Visibility less than 1/4 of a mile due to snowb. Winds greater than 35 mph (30 knots)c. conditions must persist for 3 or more hoursd. Ground Blizzardi. blowing snow on ground only1. no snow is actually fallinge. Where do they occur?i. North Dakota/South Dakota/MinnesotaXXXIII. Blizzard Ingredientsd. Cold Air-Precipitation must be snowe. Strong Windsi. intense pressure gradientii. Deep low and strong arctic high can create such a gradientiii. little friction over flat plainsf. Blizzards are typically found to the Northwest of low pressure systemsXXXIV. Chicago Blizzard 2011d. Impacted central US from Oklahoma to Michigan on February 1-3, 2011i. at least 36 deathsii. produced tornadoes acorss Texas, Louisiana, and Alabamaiii. Very cold temperatures followed storm, especially over SW Us and Northern Mexicoe. 20 inches of snow in Chicagof. 12 inches of snow in Oklahoma Cityg. 7 inches (mostly sleet) in ChampaignXXXV. Nor’Eastersd. an intense mid-latitude cyclone that tracks along the northeastern coast of the United Statese. Can produce heavy rain and winds along the coast and heavy snowfallinlandi. precipitation types determined by track of surface lowii. heavy snow typically found just northwest of low trackiii. coast flooding possiblef. in an average year, Nor’Easters cause more economic damage to theUS than any other type of stormXXXVI. Northeast Blizzard (2013)d. occurred february 8-8, 2013i. 18 US deaths (hypothermia, traffic accidents)ii. 1 inch rain=10-12 inches of