PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Characteristics of the extra-tropical cycloneWinds and clouds circulate in a CCW direction1000s of milescommaDry Slott-stormsrainfreezing rainsleetsnowKey features of the extra-tropical cyclone: A review slideWarm, MoistCool, MoistCold, Dry * * * * * * * *Origin and tracks of extra-tropical cyclones affecting North AmericaAlberta Clipper:Move quickly along the US/Canada BoarderColorado Low:Track across the central US from CO  Chicago  NEArk-La-Tex Low:Name tells us where they startGulf Low: Very powerful because they extract heat and moisture directly from Gulf of MexicoHatteras Low:  Very powerful and rack up the east coast (100 million+ people)Typical track: Time to cross the US:Why do the winds in a ETC circulate CCW?2 Primary Forces that control the wind:Pressure gradient force:Coriolis Force:Change in pressureChange in distance= PGFAlways directed from H  L Acts perpendicularly to isobarsSpacing of the isobars ≈ wind speedAir crosses isobars into the low-pressure center  spirals inwardHHHHHHLDevelopment of High- and Low-pressure systemsMain Idea: To increase the surface pressure, put more air molecules in the column To decrease the surface pressure, remove some of the air molecules in the column.This is accomplished by Convergence and Divergence.For a low-pressure system to strengthen _________ aloft must be _________ than ___________ at the surfaceFor a high-pressure system to strengthen _________ aloft must be _________ than ___________ at the surfaceSinking air above a highclear skies, nice weatherRising air above a lowclouds and precipitationThe Jet StreamDefinitionSizeLocationJet streaks Band of strong winds that encircle the earth in a wave-like pattern that moves from the west to the east.200-300 miles wide1 mile thick1000s of miles longcoldwarmwarmwarm30°N – 80°N~9 km above the sfc (300 mb) regions of the jet stream with exceptionally fast windsConstant Pressure Maps: Sloping Pressure Surfaces300mb map  look for jet streamWinds: color coded (with arrows)Heights: contoured (white)TROUGHRIDGEReal WorldTROUGHRIDGECOLDWARMKey Idea: The thickness of a layer in atmosphere is governed by the mean air temperature between the top and bottom of the layerHow Do Meteorologists View the Jet Stream – another example Mainjetof theaxisstreamJet Streaks*** Air flow  parallel to isoheights (same as isobars)  faster when the isoheights are close togetherMain ridge axis  warm air under the ridgeMain trough axis  cold air under the troughAir Flow Aloftsurface300 mb 300 mb Map (height contours only) Key Feature: _____________________________________FAST FASTSLOWthe air flow in the jet stream slows down and piles up here(________________)the air flow in the jet stream speeds up and spreads apart here(___________________)Div.Conv.CCDDHow does the jet stream create low-pressure – Curvature Effects300 mbSurfaceJet StreamDCSurface high-pressure forms hereSurface low-pressure forms heretop down viewside viewPutting it all