Approved by DC-E USCG AuxA, Inc 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 & 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 & 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 & Water

6 Equator North Pole Wind Patterns

7 Present Surface Wind Stand with back to surface wind Turn Right 45 o Low Pressure is on left Buys-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 Force

9 Circulation Of Air Down, Out & Clockwise around High Toward & Up Counterclockwise around lows Circulation 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 & Waves

11 Wave Height Depends On –Wind Strength –Wind Duration –Fetch (Long & Short) Toledo Buffalo Lake Erie Wind & 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 Height

13 Defined As Zone Between Two Different Air Masses Differences In: –Temperature –Humidity –Wind – Direction & Speed –Air Pressure Fronts

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 Fronts

15 Cold 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 Fronts

17 Warm Front

18 Cumulus –Fluffy, White, Fair Weather Clouds –May Grow To Cumulonimbus Stratus –Layered Nimbo/Nimbus –Rain Clouds Cloud 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 Families

20 Cirrus –Mares’ Tails Cirrocumulus –Mackerel Scales Cirrostratus –Like A Sheet Or Veil High Clouds

21 “Mare’s tails “ Cirrus (Ci)

22 Cirrocumulus (Cc)

23 Altostratus –Mid-level, Layered Altocumulus –Cumulus Clouds Gathered In Layers Cumulonimbus –Rain Clouds –May Develop Into Thunderheads (Towering Cumulus) Middle 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 Family

25 Cumulus

26 Towering Cumulus (Tcu)

27 Cumulonimbus (Cb)

28 Altocumulus (Ac)

29 Stratus –Low Layers Of Solid Cloud Cover Nimbostratus –Rain Clouds –Intermittent Or Steady Rain Low Clouds

30 Stratocumulus (Sc)

31 Stratus (St)

32 Turbulence In Cumulonimbus Cloud

33 Stages Of A Thunderstorm

34 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 Lightning

36 Tornado

37 Funnel Clouds

38 Waterspout

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 Fog

40 Fog

41 Radio Television Newspapers Telephone NOAA Weather Radio Stations Pennants, Flags, Lights Weather Information

42 Classifications –Tropical Depression Wind Up To 34 Knots –Tropical Storm Wind Knots –Hurricane Wind 65 Knots Or More Other Names For Hurricanes –Typhoon –Cyclone –Willy-Willy Tropical Weather

43 Hurricane Tracks

44 Heat & Weather Global Air Circulation Wind & Boating Highs & Lows Frontal Weather SUMMARY (1)

45 Clouds & Weather Thunderstorms Fog Tropical Weather Sources Of Weather Information SUMMARY (2)