Storm of the Century. Severe Blizzards from Cyclonic Storm

Transcription

1 FRONTS & CYCLONES

2 Storm of the Century Severe Blizzards from Cyclonic Storm

3 Polar Front Theory Norwegian Cyclone Model (1921) Weather for Middle Latitudes Between South Florida & Alaska Storms driven across U.S.A. by Westerlies

4 Polar Front Theory Fronts between Air Masses Stronger during Cold Winter Colder Polar (Continental) Warmer Tropical (Maritime)

5 Fronts Boundaries separating Air Masses Different Densities Temperature Warm Cold Moisture (Humidity)

6 Fronts Air Mass collision similar to Battlefronts One Air Mass is displaced over another Warm over Cold Fronts are Mid-Latitude source for Precipitation Severe Weather

7 Fronts 4 Types Warm Front Cold Front Stationary Front Occluded Front

8 Fronts on Weather Map

9 Warm Fronts Ground Air movement Warm Air occupies where Formerly Colder Air Red Line with Half-Circles on Map... Facing into displaced Cold Air

10 Warm Fronts Warm Air Less Dense than Cold Air & cannot displace it Rises gently over Cold Air (wedges) Gradual Slope Lower Height

11 Warm Fronts Warm Air Cools Adiabatically as rises over Cold Air Moisture condenses into Stratus Clouds Precipitation for large area in advance of edge Wind shifts from East Southwest

12 Warm Fronts Hot Summer Season Warm Air Mass is very Moist Unstable Warm Air is forced aloft Becomes Buoyant & Rises Cumulonimbus Clouds & Thunderstorms

13 Warm Fronts Where? East of Rockies Maritime Tropical (mt) from Gulf of Mexico Overruns receding Cool Air Raises Air Temp. of area displaced

14 Cold Fronts Cold Air Area with Warmer Air Blue Line with Triangles on Map... Facing into displaced Warm Air

15 Cold Fronts Subsiding dense Cold Polar Air Pushes into Warm Air Steep Slope Greater Height = 2 X Warm Front

16 Cold Fronts Move faster than Warm Fronts Cold = mph Warm = mph Wind shifts from Southwest Northwest

17 Cold Fronts Cumulonimbus Clouds Heavier Precipitation Shorter distance/area & duration at edge Narrow Width due to steeper slope

18 Cold Fronts More Violent Weather

19 Stationary Fronts Neither Cold nor Warm Air is aggressive Air flows parallel to line of front Front does not advance Line on Map with opposite side Red Half-Circles Ahead of Warm Air Blue Triangles Ahead of Cold Air

20 Occluded Fronts Involves 3 Air Masses Fast Cold Air Slower Warm Air Cool Air Purple Line with Alternating Half-Circles & Triangles

21 Occluded Fronts Rapidly moving Cold Front Overtakes slower Warm Front

22 Occluded Fronts Warm Air wedged upwards New Front between Slower Cool Air Faster Cold Front

23 Occluded Fronts Warm Air forced Aloft Rain with Warm Front Heavy at first Lightens with Occlusion

24 Occluded Fronts Cold Type Polar Cold Air Cool Air East of Rockies Warm Type Maritime Cool Air Polar Cold Air Pacific Coast

25 Drylines Fronts between Humidity differences Denser Dry Air displaces lighter Moist Air Moist Air is forced Aloft Advancing Front brings drop in Humidity Little change in Temperature

26 Drylines Occurs in Summer Great Plains lower Mississippi Southwest (ct) Gulf of Mexico (mt)

27 Mid-Latitude Cyclones Storm Track along Polar Front Propelled West East by Jet Stream aloft

28 Mid-Latitude Cyclones Cyclogenesis Cyclone formation Waves form as Jet Stream moves East

29 Mid-Latitude Cyclones Waves reflect competing Cold Air from North Warm Air from South

30 Mid-Latitude Cyclones Waves caused by surface irregularities Topography (Mountains) Sea-Land contrasts in Temperature Ocean currents Cyclone has 6 Stages in Life Cycle

31 Cyclone Life Cycle Stationary Front develops Parallel opposing winds Invading Cold Polar Air South Warm Air North

32 Cyclone Life Cycle Wave develops Front bends to opposing winds

33 Cyclone Life Cycle Cyclone develops Around Low Pressure center Updraft of Warm Moist Air Clouds & Rain

34 Cyclone Life Cycle Occlusion begins Cold Air begins to overtake Warm Air

35 Cyclone Life Cycle Occluded Front develops Low Pressure Center Forces Warm Air aloft

36 Cyclone Life Cycle Occlusion exhausts energy Low Pressure weakens Cyclone & Storms dissipate Warm Air above Cold Air below Fronts gone

37 Cyclone Life Cycle 6 Stages proceed from West East Along Storm Track Propelled Eastward by Westerlies

38 Cyclone on Weather Map

39 Cyclonic Storm Weather Warm Front mt from South Falling Air Pressure Cirrus Stratus... Light Rain Temperature rises Winds change From East South

40 Cyclonic Storm Weather Between Storms Maritime Tropical Clear skies Wind from South

41 Cyclonic Storm Weather Cold Front cp from North Rising Air Pressure Cumulonimbus Heavy Rain Temperature drops Winds change From S N

42 Cyclonic Storm Weather Occlusion Center of Cyclone Warm Air aloft Temperature remains cool at surface Air Pressure continues to fall

43 Cyclonic Storm Weather Occlusion Farther North Nimbostratus Winter Snow & Ice Moves slowly Cold Weather remains longer

44 Aloft Cyclones & Anticyclones Ground

45 Cyclones & Anticyclones Wind circulation propelled by Winds aloft Surface Convergence Convergence Aloft Divergence Aloft Surface Divergence Also Wind blows High Low

46 Cyclones & Jet Stream Divergence Aloft not in all directions Flow from West East due to Jet Stream Mechanisms Speed Divergence Acceleration Directional Divergence Horizontal Spread Vorticity Rotation

47 Cyclones & Jet Stream Low Pressure continues at Ground When Divergence Aloft Exceeds Convergence at Ground

48 Cyclones & Jet Stream Convergence Aloft into Anticyclone Downwind from Ridge Divergence Aloft out of Cyclone Downwind from Trough

49 Cyclone Formation Areas Leeward of Mountains East of Rocky Mtns Where great Temperature differences Coastal Regions Southeast USA

50 Cyclonic Storm Tracks Cyclones travel East Northeast Most Storms Great Lakes Northeast

51 Cyclonic Storms Alberta Clipper Wind & Snow Nor-easter Perfect Storm movie

52 Cyclone Migration Cyclone migration Southeast North

53 Anticyclones Polar High Blocking Highs = Stagnant Anticyclone Blocks Cyclone migration Frigid Cold Gulf of Mexico

54 Anticyclones Subtropical Inversions Subsiding Air Traps Pollution Los Angeles Mexico City

55 Conveyor Belt Model Modern view Circulation

56 Conveyor Belt Model 3 Interacting Airstreams 2 Surface that Rise Warm Conveyor Belt (Humid) Most Rain with rise Cold Conveyor Belt (Dry) Saturates with rise 1 Aloft Dry Conveyor Belt (Cold)

57 Mature Cyclone Mid-Latitude Cyclone Comma shape Dry slot from South center (Low) Comma Tail

58 Weather Forecasting Indicators for Weather Forecasting Barometric Pressure High = Clear Low = Rain Wind Direction Air Mass source