1. Clouds, Cyclones/Anticyclones & Precipitation
Cloud Types & Characteristics
Rolfie rule(s) of anti-cyclones and cyclones
Rossby waves (depressions)
Cyclogenesis
Who is Stan Hatfield and Ken Pinzke

2. Cloud Types and Precipitation
Types of Clouds
Cloud Types and Precipitation
 Clouds are classified on the basis of their form and height.
• Cirrus (cirrus = curl of hair) are clouds that are high, white, and thin.
• Cumulus (cumulus = a pile) are clouds that consist of rounded individual cloud masses.
• Stratus (stratus = a layer) are clouds best described as sheets or layers that cover much or all of the sky.
Nimbus (

3. Cirrus Clouds
Makes no sense without caption in book

4. Cloud Types and Precipitation
Types of Clouds
Cloud Types and Precipitation
 High Clouds
• Cirrus clouds are high, white, and thin.
• Cirrostratus clouds are flat layers of clouds.
• Cirrocumulus clouds consist of fluffy masses.
 Middle Clouds
• Altocumulus clouds are composed of rounded masses that differ from cirrocumulus clouds in that altocumulus clouds are larger and denser.
• Altostratus clouds create a uniform white to gray sheet covering the sky with the sun or moon visible as a bright spot.

5. 18.3 Cloud Types and Precipitation
Types of Clouds
18.3 Cloud Types and Precipitation
 Low Clouds
• Stratus clouds are best described as sheets or layers that cover much or all of the sky.
• Stratocumulus clouds have a scalloped bottom that appears as long parallel rolls or broken rounded patches.
• Nimbostratus clouds are the main precipitation makers.

6. Cloud Classification
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7. Cloud Types and Precipitation
Types of Clouds
Cloud Types and Precipitation
 Clouds of Vertical Development
• Some clouds do not fit into any one of the three height categories mentioned. Such clouds have their bases in the low height range but often extend upward into the middle or high altitudes.

8. Cloud Types and Precipitation
Fog
Cloud Types and Precipitation
 Fog is defined as a cloud with its base at or very near the ground.
 Fog Caused by Cooling
• As the air cools, it becomes denser and drains into low areas such as river valleys, where thick fog accumulations may occur.
 Fog Caused by Evaporation
• When cool air moves over warm water, enough moisture may evaporate from the water surface to produce saturation.

9. Isobars and Cyclonic Systems
Cyclone vs. Anticyclone
Wind direction affected by friction (surface), pressure gradient (H-L) and Coriolis Force

10. Isobars and Cyclonic Systems

11. Isobars and Cyclonic Systems

12. Rossby Waves and Depressions
Jet streams = the fast moving air
Rossby waves = long wave moving around the world – bends and turns as the wind changes speed
When the Rossby wave ‘meanders’ it can control and influence surface level cyclonic systems
Opposite air pressure
Surface vs. upper level ( mb pressure)

13. Movements of Air: 7-12km altitude
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14. Mid-Latitude Cyclones (cyclonic depressions – LOW PRESSURE)
Rolfie rule:
A FRONT is the leading edge of an air mass (cold/warm)
i.e. cold FRONT (cold air)
warm FRONT (warm air)
Air is being pulled in and around the low pressure system
Below 1013mb pressure level

15. Mid-Latitude Cyclones (cyclonic depressions)
Occurs at the mid-latitudes (30-60 degrees north and south)
Difference in air masses (cold air and warm air)
Instability in the atmosphere, cold air moves FASTER than WARM air

16. Mid-Latitude Cyclones (MLC’s)
Who is Stan Hatfield and Ken Pinzke

17. Mid-Latitude Cyclones (MLC’s)
Discovered by a Norwegian University (1920’s)
1st stage – Initial Wave – Stationary
North – Cold
South – Warm
2nd stage - Cyclogenesis Stage
Beginning of cold air moving south – moving faster than the warm air!
COUNTER-CLOCKWISE WINDS
Who is Stan Hatfield and Ken Pinzke

18. 3rd Stage - Mature Stage:
mT is brought north
cP increasingly develops and moves faster into the warm front
Occlusion starts to appear at the center of the low pressure system
Who is Stan Hatfield and Ken Pinzke

19. Who is Stan Hatfield and Ken Pinzke

23. Warm and Cold Front Overview
A warm front forms when warm air moves into an area formerly covered by cooler air.
Weather conditions:
Clouds persisting for a long period of time
Light winds
Light precipitation
Longer persisting pattern of weather
A cold front forms when cold, dense air moves into a region occupied by warmer air. Warm air is then forcible lifted (frontal lifting)
Weather conditions:
Shorter more intensified clouds, larger updrafts and cloud formation
Increased precipitation and wind gusts (stormier weather)
Production of cumulonimbus clouds and severe weather during certain times and locations
Shorter duration of weather pattern

24. Stationary & Occluded Front Overview
 Stationary Fronts
Weather –
Potential for ‘stormy’ weather (unstable air mass and missing of air mass temps)
Low cloud base and precipitation is steady
Temp – warm or cool
Wind changes direction as the occluded front passes over
Clear skies and dry air occur after the occluded front has past
• Occasionally, the flow of air on either side of a front is neither toward the cold air mass nor toward the warm air mass, but almost parallel to the line of the front. In such cases, the surface position of the front does not move, and a stationary front forms.
 Occluded Fronts
• When an active cold front overtakes a warm front, an occluded front forms.
Cold front eventually will ‘catch’ the warm front and become ‘joined’ for a short period of time.