Lesson 15A: Weather

1
Lesson 15A Weather
2
Lesson 21 Weather

• AGENDA
• Causes of Weather
• Weather Elements
• Basic Weather Phenomena (Fronts, Systems)
• Hurricanes/Typhoons
• Marine Weather Prediction
• Applicable reading Hobbs WB, App A

3
Overview

• Weather the state of the Earths atmosphere
• SPECIFICALLY
• Air Flow The circulation of air about the
  planet caused by temperature differentials.
• Pressure Areas The relationship between
  temperature and pressure and wind.
• Fronts The transition zone or interface between
  two air masses of different densities.

4
Weather Elements
TEMPERATURE
PRESSURE
WINDS
HUMIDITY
CLOUDS
PRECIPITATION
5
Temperature

• Temperature the amount heat in the atmosphere.
• Causes
• The Earths daily rotation about its axis
• The Earths annual revolution about the sun
• Effects
• The uneven heating and cooling of the Earths
  surface results in air flow about the planet.

6
Wind

• Wind The horizontal movement of the atmosphere
• Causes
• Temperature differentials
• Coriolis Effect
• Maritime significance
• Result in areas of High and Low pressure.

7
Air Flow

• Forces that define air flow
• 1. Pressure
• 2. Earths Rotation
• 3. Friction from the surface of the earth

8
(No Transcript)
9
Pressure

• Atmospheric Pressure The weight of the
  atmosphere.
• Causes
• Divergence and convergence of air
• Changes in Altitude/Depth
• Maritime significance
• High/Low pressure systems
• Low (L) - caused by converging winds rotate
  counter-clockwise
• High (H) - caused by diverging winds rotate
  clockwise

10
Low Pressure System Air Flow
11
High Pressure System Air Flow
12
(No Transcript)
13
Weather Fronts

• High and Low pressure systems travel from the
  areas where they are created.
• When air masses meet, they compete for
  dominance.
• The boundary zone between these two masses is
  known as a front.

14
Weather Fronts

• Fronts a zone of transition between air masses
• Cold Front - when a cold air mass displaces a
  warm air mass by vigorously forcing it up.
• move fast, 20-35 kts
• weather deteriorates rapidly
• Warm Front - when a warm air mass displaces a
  cold air mass.
• warm air slides over cold air
• move slowly, 19-15 kts
• weather deteriorates gradually

15
Frontal Passage
16
(No Transcript)
17
Basic Weather Phenomena

• Clouds
• Fog
• Tropical storms/hurricanes/typhoons

18
Heavy Weather
1. Closed Cyclonic - Rotary circulation
storms. 2. Noncyclonic - Storms produced by
prevailing winds are identified by their
accompanying winds - predictable.
19
Closed Cyclonic
1. Tornadoes - Violent, whirling storm of small
diameter that travels across land. Appear as
funnel shaped cloud, with a vortex that may or
may not touch the earth. Winds blow spirally
upwards from 150 - 300 mph. 2. Waterspouts -
Similar to tornadoes, occurring over oceans or
inland waters. Usually less destructive than
tornadoes.
20
Closed Cyclonic
3. Squall - A wind of considerable intensity
caused by atmospheric instability. Comes up
dies quickly, sometimes accompanied by thunder,
lightning and precipitation. 4. Monsoons -
Steady winds somewhat similar to trade winds.
Can reach moderate gale proportions and are
accompanied by heavy squalls and thunderstorms
during the summer.
21
Closed Cyclonic
5. Hurricanes - Tropical storm with continuous
winds greater than 75 mph (64 kts). 6.
Tropical Storms - Categorized based on wind
speed
- Tropical Depression lt 34 kts
- Tropical Storm 34 - 63 kts
- Hurricane gt 63 kts
22
Noncyclonic
ie gale - with winds from 34 - 47 mph
storm - with winds of 48 mph or greater.
23
(No Transcript)
24
Weather Elements(Review)
TEMPERATURE
PRESSURE
WINDS
HUMIDITY
CLOUDS
PRECIPITATION
25
Clouds

• Clouds condensed water droplets or ice
  crystals suspended over the
  surface of the earth
• Causes of clouds
• Clouds are formed by the cooling of saturated air
  by the ocean of land surface beneath.
• Basic Types of Clouds
• Cirrus
• Cumulus
• Stratus

26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
Coastal Fog

• Fog a cloud that touches the surface of the
  earth.
• Causes of clouds/fog
• Clouds are formed by the cooling of saturated air
  by the ocean of land surface beneath.
• Prediction of fog
• If the difference between air temperature and dew
  point is less than 2F, fog may result.

30
Hurricanes/Typhoons

• Hurricanes violent storms with no associated
  weather front.
• Causes
• Storms begin in a low-pressure area, lifting of
  the air, and a counter-clockwise inward wind
  flow.
• Heat released by condensation of water vapor
  from the surface below aggravates the process and
  the storm builds in intensity.

31
(No Transcript)
32
Review/Summary

• What 3 elements cause weather?
• Name 4 of the 6 basic weather elements
• What is a front?
• Describe the following types of clouds
• Cirrus
• Stratus
• Cumulus

33
Questions?