1. Question of the Day What are cyclones?
What does “cyclone” mean to you?
119

2. Questions
high
low
1) Winds blow from _____ to ___.
2) Due to the Coriolis effect, winds in the N. Hemi. are deflected to the ____.
3) High pressure systems bring happy or lousy weather?
4) Low pressure systems bring happy or lousy weather?
right
Happy
Lousy

3. Cyclone
Low-pressure system
Wind toward center
Rotates counter- clockwise in N. Hemi.
Warm, moist, less dense air rises
Lousy weather: hurricanes, tornadoes

5. Anticyclone
High-pressure
Wind away center
Rotates clockwise
Cool, dry, dense air sinks
Happy weather

6. Is a hurricane a high-pressure or low-pressure region?

12. 1 3 2 4

13. In the N. Hemisphere, in which direction does surface wind circulate in a low-pressure air mass?
1) clockwise & toward the center
2) clockwise & away from the center
3) counterclockwise, toward center
4) counterclockwise, away from center

14. In the N. Hemisphere, in which direction does surface wind circulate in a high-pressure air mass?
1) clockwise & toward the center
2) clockwise & away from the center
3) counterclockwise, toward center
4) counterclockwise, away from center

16. Question of the Day What causes storms? High or Low Pressure System?
Name That Front! A
High or Low Pressure System? B C D ? ?
120

17. Storms
Violent or severe disturbance of atmosphere
Dangerous conditions
Injuries, loss of life or property

18. Mid-Latitude Cyclones (Cyclonic Storms)
Large low-pressure storm
Brings much precipitation to U.S.
Caused by movement of air along Polar Fronts - N. edge of Prevailing Westerlies

20. Life Cycle
A. Polar Front - Stationary
● Opposite winds create eddies
B. Cold & Warm Fronts develop
● Warm air starts to rise

21. C. Occluded Front
● Warm air completely above front
D. Stationary Front ( → 1st stage)
● Warm air mixes with surrounding air

24. Classic Midlatitude Cyclone

25. Jet Stream moves cyclone W → E

26. The most likely location for heavy precipitation is at A, B, C or D?

28. Question of the Day How are hurricanes formed?
Which way do prevailing winds blow between:
0º & 30º N?
30º N & 60º N?
60º N
30º N 0º
121

30. Hurricane (Tropical Cyclone)
Also typhoon or tropical cyclone
Large (100’s of miles wide)
Strong (sustained winds 74 mph +)
Lasts weeks

31. Birth
Tropical waters in E. Atlantic, Gulf of Mexico or Caribbean
Evaporating water condenses & provides energy (latent heat released)

32. Structure
Large pressure gradient = strong winds
Eye: calm, very low center

33. Growth
Tropical Depression: mild low-press.
Tropical Storm: sustained winds > 39 mph
Hurricane: winds > 74 mph

34. Saffir-Simpson Scale
Classification by sustained wind speed

35. Official Season
June 1 - Nov. 30

36. Typical Track
Affected by N.E. then S.W. winds

38. Flooding from torrential rains
Destruction
High winds (>74 mph)
Flooding from torrential rains
Storm surge - 90% of all deaths from hurricanes
Hurricane Katrina damage, New Orleans

39. Storm Surge
Wall of water - low pressure, high winds

40. Death
Loses strength over:
1. Cold ocean water - loses energy source of warm water
2. Land - friction + no water
Becomes mid-latitude cyclone

41. Safety
Listen to weather alerts!
Evacuate area
Move to higher ground
Prepare survival kit
Backup electric power

43. Question of the Day How are thunderstorms & tornadoes formed?
Which is the fastest-moving front?
122

44. Heavy rainstorm with thunder, lightning
Sometimes flash floods, hail, tornadoes
Formed by rapidly moving cold front

46. Lightning & Thunder
Friction in cloud results in electrical charges (+ -)
Discharge = lightning
Heated air expands explosively = thunder

47. Squall Line
Thunderstorms along cold front

48. Supercell
Giant thunderstorm w/ strong updrafts

49. Safety
Listen to weather alerts!
Seek indoor shelter
Don’t touch electrical outlets or plumbing
Stay in car
Avoid high ground

50. Narrow (100-foot-wide) funnel of spiraling winds
Most violent storm: winds 300+ mph
Lasts minutes to an hour

51. Formation 2. U P D R A F T 1. Winds converge 3. Tornado Descends
Tornado in Supercell

52. Formation
Warm, moist air rises
Air flows in & counter- clockwise

53. Occurences
Usually forms over land, but also over water = waterspout

54. Most common in spring & summer
Prime region - flat terrain, and clash of cP & mT air masses

55. Fujita Intensity Scale
Classification by wind speed & damage

56. Safety
Listen to weather alerts!
Get indoors to strongest structure
Lowest level or safest interior room
Stay away from windows
Open windows if time
Cover body with coat or blanket

58. Question of the Day How is a weather map made?
This station model shows all the key information needed to predict the weather. How many factors can you list?
124 A,B,C

59. Station Model
Weather variables at a particular site.

60. Synoptic Map
Summary of weather variables.
Used to predict the weather.

61. ESRT p. 13

62. Air Temperature
Recorded in ºF.

63. Present Weather
Use symbols in box below

64. Visibility
Greatest distance (miles) at which objects can be identified.

65. Dewpoint
Temp. air is saturated if cooled. ºF.

66. Wind Direction (From!)
Circle = head of an arrow.

67. Wind Speed
Whole feather = 10 knots
Half feather = 5 knots
Total
1- 4

68. Cloud Cover
% circle dark = % covered by clouds

69. Precipitation
Inches over past 6 hours
Liquid water equivalent

70. Barometric Pressure
3-digit code

71. Do what brings you closer to 1000 mb
Barometric Pressure
Cracking the Code (Converting to mb)
Do what brings you closer to 1000 mb
< 500, place 10 in front and decimal between last 2 digits.
> 500, place 9 in front and decimal between last 2 digits.

72. Cracking the Code
Coded
320
999
499
Decoded mb
999.9 mb mb

73. Barometric Trend
What pressure did over past 3 hours
Before the number
+ Pressure now higher than 3 hrs. ago
- Pressure now lower than 3 hrs. ago

74. Add a decimal inside the number (mb rounded to nearest 1/10th)
Barometric Trend
Decoding the Number
Add a decimal inside the number
(mb rounded to nearest 1/10th)

75. After the number / Increasing \ Decreasing Stable Barometric Trend
What pressure did over past 3 hours
After the number
/ Increasing
\ Decreasing
Stable

77. This station model shows weather conditions at Massena, NY, 9 a. m
This station model shows weather conditions at Massena, NY, 9 a.m. on a June day.
What was the barometric pressure 3 hours earlier that day?
1) mb 3) mb
2) mb 4) mb

78. Draw a station model to indicate a temperature of 20º C, a dewpoint of 11º C, and clear skies. (Be sure the numbers are in the proper position!)

80. Question of the Day How can we use synoptic maps to predict the weather?
How will temperature & barometric pressure change at X as this front passes?
125

81. How does station data become a weather map?

82. 4 Principles of Weather Predictions
1. Air temp. increases ↑, air pressure decreases ↓
2. Air temp. closer to dew point, chance of precip. increases ↑
3. Greater air pressure gradient = greater wind speeds
4. Rapidly falling air press. → low press. system coming (lousy weather)

83. Where would the isobar for 1008.0 mb be drawn?
Barometric Pressure
Where would the isobar for mb be drawn?

84. Barometric Pressure

85. Where would the isotherm for 60º F be drawn?
Temperature
Where would the isotherm for 60º F be drawn?

86. Temperature

87. Barometric Pressure
Temperature +
Wind Direction
Precipitation