Jet streams are fast moving air currents in the upper atmosphere. They were first discovered in the 1920s and knowledge of them increased during World War II. There are two main types: polar and subtropical jet streams. Weather features like storms can form when air rises due to low pressure caused by jet streaks. Other weather systems discussed include air masses, frontal systems like cold fronts and warm fronts, mid-latitude cyclones, thunderstorms, tornadoes, and hurricanes.

1. Weather cells & weather systems

2. Jet Streams & History
 In the upper troposphere “rivers” of rapidly moving air circle
around the Earth.
 First discovered in the 1920s by Wasaburo Ooishi.
 In 1934, Wiley Postan American pilot.
 1939 by a German meteorologist named H. Seilkopf when he used
it in a research paper
 Knowledge of the jet stream increased during World War II while
flying between Europe and North America.

3. Types of jet streams
 Polar jet streams
 Sub tropical jet streams
150 – 500 km wide
0.9-2.2 km thick
Speeds may exceed 300 km/h

4. Tropopause
height
Jet Stream Cross Section
18 000 m
12 000 m
6 000 m
“Rivers” of strong wind
where cold and warm meet
Discontinuity or step in tropopause
height
See: www.avsim.com/avwx/avsim_wxus_jetstream.html

5. Weather features associated
 Jet streaks cause air to rise, lowering the air pressure at the
Earth's surface.
 When surface pressures are low, the rising air can form clouds,
precipitation and storms.

6. Jet streams & Indian monsoon

7. Sub tropical jet during Summer seasons

8. Weather systems
1. Air Masses
2. Frontal Systems
3. Mid-latitude Cyclones
4. Thunderstorms
5. Tornadoes
6. Hurricanes

9. Air mass
Air mass an extremely large body of air (thousands of square
kilometers) whose properties of temperature and moisture are fairly
similar in any horizontal direction at any given altitude.

10. AIR MASS CLASSIFICATION
SOURCE REGIONS
 Maritime (m) – originates over oceans or large bodies of water
 Continental (c) – originates over land
THERMAL TYPES
 Tropical (T) – from low latitudes
 Polar (P) – from mid-high latitudes
 Arctic (A) – from high latitudes (> 65°N)

11. Classification of air masses

12. Fronts

13.  Front:
Front is the transition zone between air masses with distinctly
different properties.
 Frontogenesis:
A formation, strengthening or generation of a front. This is due to
increased contrast of temperature conditions between two air
masses.
 Frontolysis:
The weakening or dissipation of a front this is due to decreased
in temperature contrast between two air masses.

14. How to identify a front on a surface weather map
 Sharp temperature changes over a relatively short distance
 Change in moisture content
 Rapid shifts in wind direction
 Pressure changes
 Clouds and precipitation patterns

15. Types of fronts
WARM FRONT COLD FRONT
STATIONARY FRONT OCCLUDED FRONT

16. Cold fronts
Cold front
symbol
Heavy precipitation

17. Clouds associated with a cold front
Cloud types occur
ahead of a cold front.
Cirrus
Cumulonimbus
Stratocumulus
Altocumulus

18. Identifying a cold front’s passage
Precipitation generally falls in the vicinity of the
cold front.
PPaarraammeetteerrss BBeeffoorree DDuurriinngg AAfftteerr
TTeemmppeerraattuurree WWaarrmm SShhaarrpp ffaallll SSlliigghhtt ffaallll
DDeeww PPooiinntt HHiigghh SShhaarrpp ffaallll SSlliigghhtt ffaallll
WWiinnddss SSSSWW SShhiifftt WW ttoo NN
PPrreessssuurree FFaallll LLoowweesstt RRiissee

19. Warm fronts Warm front symbol

20. Clouds associated with a warm front
Cirrus Nimbostratus
Altostratus
Cirrostratus

22. STATIONARY FRONT

23. EXTRA TROPICAL/ MID-LATITUDE CYCLONES

24. Synoptic scale low pressure weather systems that occur
in the middle latitudes, connected with fronts and
horizontal gradients in temperature and dew point
along anticyclones.
Capable of producing
Cloudiness
Mild showers
heavy gales
Thunderstorms.

25. Life cycle of a mid-latitude cyclone
Cyclogenesis
Open stage
Occluded stage
Dissolving stage

26. Cyclogenesis

27. Open stage

28. Occluded stage

29. Dissolving stage

30. THUNDERSTORMS

31. THUNDER STORMS
It is a type of storm characterized by the presence of lightening and
its acoustic effect on the earths atmosphere known as thunder.
Congenial conditions to form:
Moisture
Unstable Air
Upward drift

32. Stages of development

33. Weather phenomena associated
 Down burst of winds
 Lightening & Acoustic sounds
 Hail storms
 Heavy precipitation & flash floods

34. TORNADOES

35.  Tornadoes are narrow, funnel-shaped spiraling wind that rotate at
speeds of up to 500 km/hr because of extreme pressure gradients.
 Tornadoes are ranked from F0 (weakest) to F5 (strongest) using
the Fujita Intensity scale.
 Most tornadoes move to the east or northeast at an average speed
of approximately 50 km/hr.
 Tornadoes are associated with thunderstorms and develop in
association with mesocyclones within the thunderstorm cell.

36. Tornado formation:
• Early stage:
Contrasting vertical wind speeds generate local winds that rotate
about a horizontal axis.
• Updraft stage:
Mesocyclones may be up to 10 km in diameter.
•Tornado stage:
More intense spiraling winds within a tornado that extend
downward from a cloud base toward the ground surface .

37. Tornado

38. Management of tornado
 Warning in advance
 Precautions to protect the agricultural produce
 Quick removal of debris

39. Water sprouts

41. HURRICANES / TROPICAL CYCLONES

42. HURRICANES/ TYPHOONS/CYCLONES/WILLY WILLY:
It is a rapidly rotating storm system characterized by a low
pressure center, strong winds, and a spiral arrangement of
thunder storm that produce heavy rain.
Chief characteristics:
 High winds (more than 119 km/hr)
 Heavy rainfall (10-25 cm)
 Storm surges (sudden rise in sea level) along coastlines.

43. Anatomy of hurricane

45. Factors favor to form:
 Water temperature of at least 26.5 °C to a depth of at least 50 m
 Heat of condensation energy
 pre-existing system of disturbed weather
 High humidity in lower-to-mid troposphere
 Low amounts of wind shear

46. Saffir-Simpson hurricane intensity scale