Approved by DC-E USCG AuxA, Inc

BOATING SKILLS AND SEAMANSHIP

BOATING SKILLS AND SEAMANSHIP

Lesson 12

Weather & Boating

2

Lesson Objective

• What Causes Weather

• Wind, Waves, And Weather

• Recognizing Signs Of Change

• Weather And Clouds

• The Signs Of Bad Weather & What To Avoid

• Where To Get Weather Info

3

• Sun Heats Earth & Air• Warm Air Rises

– Creates Low Pressure

• Cooler Upper Air Falls– Creates High Pressure

• Air Flows From Highs Toward Lows– Creates Wind

• Greater The Pressure Difference– Stronger The Wind

Weather & HeatWeather & Heat

4

• Warm Air Can Hold More Moisture Than Cold Air

• Relative Humidity– The Amount Of Moisture In Air, Compared To

The Maximum Amount It Could Hold At That Temperature

• Cooling Air To Its Dew Point Creates 100% Relative Humidity And Moisture Condenses Out

Heat & HumidityHeat & Humidity

5

• Water Gains Heat Slower Than Land• Water Loses Heat Slower Than Land• Daytime

– Land Warmer Than Water• Air Warms, Rises Over Land And Air Flows In From Sea –

Sea Breeze

• Nighttime– Water Warmer Than Land

• Air Warms, Rises Over Water And Air Flows From Land to Sea – Land Breeze

Land & WaterLand & Water

6

Equator

North Pole

Wind PatternsWind Patterns

7

Present Surface Wind

Stand with back to surface wind Turn Right 45o

Low Pressure is on left

Buys-Ballot’s LawBuys-Ballot’s Law

8

• Northern Hemisphere– Earth’s Rotation Causes Any Air Motion To

Bend To The Right– Air Moving Down & Out Of A High

Pressure Area• Bends To The Right Causing A Clockwise

Motion

– Air Rushing Into A Low Pressure Area• Rises, Bends To The Left

Coriolis ForceCoriolis Force

9

Circulation Of Air

Down, Out & Clockwise around High

Toward & Up Counterclockwise around lows

Circulation of AirCirculation of Air

10

• Swells– Dying Waves A Long Way From

Source

• Breakers– Waves Nearing Shore– Caused By:

• Shallow Water Slowing Bottom Of Wave, Top Then Spills Over & Breaks

Wind & WavesWind & Waves

11

• Wave Height Depends On– Wind Strength– Wind Duration– Fetch (Long & Short)

Toledo

Buffalo

Lake Erie

Wind & WavesWind & Waves

12

• Seas 3 to 5 Feet Means– 15% Of Waves Over 5’– 15% Of Waves Under 3’– 70% Of Waves 3’ to 5’

Wave HeightWave Height

13

• Defined As Zone Between Two Different Air Masses

• Differences In:– Temperature– Humidity– Wind – Direction & Speed– Air Pressure

FrontsFronts

14

• Air Cooler Behind Than Ahead• Fast Moving• Can Create Violent Weather• When Passes

– Pressure Rises Abruptly– Temperature Falls– Relative Humidity Decreases– Wind Shifts Direction

Cold FrontsCold Fronts

15

Cold FrontsCold Fronts

16

• Air Warmer Behind Than Ahead

• Slow Moving

• Non-Violent Weather

• Nighttime Fog Frequent

• Can Have Long Periods Of Rain

• When Passes• Little Pressure Change• Little Temperature Change

Warm FrontsWarm Fronts

17

Warm FrontWarm Front

18

• Cumulus– Fluffy, White, Fair Weather Clouds– May Grow To Cumulonimbus

• Stratus– Layered

• Nimbo/Nimbus– Rain Clouds

Cloud IdentificationCloud Identification

19

• High - Cirriform– Cirrus, Cirrocumulus, Cirrostratus

• Mostly Ice – No Precipitation

• Middle - Alto– Altostratus, Altocumulus, Nimbostratus

• Mostly Water

• Low– Stratus, Stratocumulus, Cumulus

• Mostly Water

Cloud FamiliesCloud Families

20

• Cirrus– Mares’ Tails

• Cirrocumulus– Mackerel Scales

• Cirrostratus– Like A Sheet Or Veil

High CloudsHigh Clouds

21“Mare’s tails “

Cirrus (Ci)Cirrus (Ci)

22

Cirrocumulus (Cc)Cirrocumulus (Cc)

23

• Altostratus– Mid-level, Layered

• Altocumulus– Cumulus Clouds Gathered In Layers

• Cumulonimbus– Rain Clouds– May Develop Into Thunderheads

(Towering Cumulus)

Middle CloudsMiddle Clouds

24

• Cumulus– Summer Afternoon Cotton Balls– Generally No Precipitation Unless Building

• Towering Cumulus– Building Cumulus– Deep Layer Of Unstable Air– Thundershowers Can Result

• Cumulonimbus– Thunderhead/Thunderstorm Cloud

Cumulus FamilyCumulus Family

25

CumulusCumulus

26

Towering Cumulus (Tcu)

Towering Cumulus (Tcu)

27

Cumulonimbus (Cb)Cumulonimbus (Cb)

28

Altocumulus (Ac)Altocumulus (Ac)

29

• Stratus– Low Layers Of Solid Cloud Cover

• Nimbostratus– Rain Clouds– Intermittent Or Steady Rain

Low CloudsLow Clouds

30

Stratocumulus (Sc)Stratocumulus (Sc)

31

Stratus (St)Stratus (St)

32

Turbulence In Cumulonimbus Cloud

Turbulence In Cumulonimbus Cloud

33

Stages Of A ThunderstormStages Of A Thunderstorm

34

Thunderstorms In A Squall Line

Thunderstorms In A Squall Line

35

• Cause– Friction Of Raindrops & Ice Particles In

Thunderstorms Creates Electrical Charge

• Distant Lightning– Heard As Static In AM Radios– More Frequent The Static, The More Severe

The Storm

LightningLightning

36

TornadoTornado

37

Funnel CloudsFunnel Clouds

38

WaterspoutWaterspout

39

• Radiation– Clear Sky– Little Or No Wind– Small Temp – Dew Point Spread– Burns Off In Morning

• Advection– Sea Fog– Needs Light Winds – Up To 15 MPH– Warm Moist Air Moving Over A Colder Body– Long Lasting

FogFog

40

FogFog

41

• Radio

• Television

• Newspapers

• Telephone

• NOAA Weather Radio Stations

• Pennants, Flags, Lights

Weather InformationWeather Information

42

• Classifications– Tropical Depression

• Wind Up To 34 Knots– Tropical Storm

• Wind 35 - 64 Knots– Hurricane

• Wind 65 Knots Or More

• Other Names For Hurricanes– Typhoon– Cyclone– Willy-Willy

Tropical WeatherTropical Weather

43

Hurricane TracksHurricane Tracks

44

• Heat & Weather

• Global Air Circulation

• Wind & Boating

• Highs & Lows

• Frontal Weather

SUMMARY (1)SUMMARY (1)

45

• Clouds & Weather

• Thunderstorms

• Fog

• Tropical Weather

• Sources Of Weather Information

SUMMARY (2)SUMMARY (2)