Chapter 15 Weather and Boating Sailing Skills And
Chapter 15 Weather and Boating Sailing Skills And Seamanship
Lesson Objectives Sailing Skills And Seamanship • • • Weather information sources Basic storm patterns Storm forecasting and precautions Go/no go decision making Personal weather equipment and equipment check list SSSppt. Chpt 15 Weather 040609. ppt 2
Weather Information Sailing Skills And Seamanship Sources of weather information: • NOAA • Private wx services • Intellicast, etc. • USCG Broadcasts • Local sources • Personal observation SSSppt. Chpt 15 Weather 040609. ppt Courtesy of NOAA 3
Wind and Boating Sailing Skills And Seamanship • What can happen to a vessel caught in a storm? SSSppt. Chpt 15 Weather 040609. ppt Courtesy of FEMA 4
Winds and Boating Sailing Skills And Seamanship • • • Storm surge Swells Breaking waves Wave height and period Waves in shallow water Seamanship vs. seaworthyness SSSppt. Chpt 15 Weather 040609. ppt 5
Winds and Boating Sailing Skills And Seamanship Beaufort Wind Scale Table 12 -1 Beaufort Number Wind Description Mean Wind Speed Equivalent (knots) Mean Wave Height meters feet Sea Conditions 0 Calm ≤ 1 Sea is like a mirror. - - 1 Light air 1 -3 Ripples without foam crests. 0 -0. 1 0 -0. 3 5 Fresh breeze 17 -21 moderate waves with a more pronounced long form; many whitecaps. A little spray. 2 6. 6 41 -47 High waves; crests begin to tumbler; dense streaks of form. Spray affects visibility. 7 23 64 + Seas tumultuous. The air is filled with foam. The ocean is totally white with driving spray. Visibility seriously reduced. 14 46 9 12 Strong gale Hurricane SSSppt. Chpt 15 Weather 040609. ppt Copyright Hal Roth, 2006 Reprinted with permission 6
Understanding Weather Sailing Skills And Seamanship • Sea breeze • Daytime: Land warms, warm air rises, cooler sea air flows in • Land breeze • Nighttime: Land cools, cool dense air flows out to sea SSSppt. Chpt 15 Weather 040609. ppt Reprinted with permission from Gary Jobson’s Championship Sailing by Gary Jobson 7
Understanding Weather Sailing Skills And Seamanship • Coriolis Force • Causes rotation of pressure systems SSSppt. Chpt 15 Weather 040609. ppt 8
Understanding Weather Sailing Skills And Seamanship • Temperature and humidity • Moisture and energy • Air masses • High pressure system • Low pressure system SSSppt. Chpt 15 Weather 040609. ppt 9
Understanding Weather Sailing Skills And Seamanship • Low pressure systems • High pressure systems SSSppt. Chpt 15 Weather 040609. ppt Adopted from Boater’s Bowditch by Richard K. Hubbard 10
Understanding Weather Sailing Skills And Seamanship • Why do we have inclement weather with a low pressure system? • Cold, dense air mass flows under warm, moist air mass • Warm, moist air rises, cools, and water vapor condenses into precipitation • Closing isobars mean increasing winds, as air flows from high to low pressure area • Rapid vertical development: thunderstorms SSSppt. Chpt 15 Weather 040609. ppt 11
Understanding Weather Sailing Skills And Seamanship • Buys Ballot’s Law SSSppt. Chpt 15 Weather 040609. ppt 12
Understanding Weather Sailing Skills And Seamanship • Symbols: Fronts • Warm front: Leading edge of warm air mass • Cold front: Leading edge of cold air mass • Occluded front: Cold air mass underlying warm air mass SSSppt. Chpt 15 Weather 040609. ppt warm front cold front occluded front 13
Understanding Weather Sailing Skills And Seamanship • Clouds and Fronts • What are three types of clouds and characteristics of each that accompany fronts? SSSppt. Chpt 15 Weather 040609. ppt 14
Understanding Weather Sailing Skills And Seamanship • • High, mid-level, and low clouds Cirrus: (high): “locks of hair” Cumulus: (low-, mid-level) “pile or accumulation” Stratus: (low-, mid-, high-level) “solid layer” Alto: (mid- to high-level) “high, upper” Nimbus: low-, mid-level “rainy” Typical types: Cumulonimbus, cirrostratus, altocumulus, etc. • Generally avoid: Cumulonimbus, cumulus SSSppt. Chpt 15 Weather 040609. ppt 15
Understanding Weather Sailing Skills And Seamanship • • • Approaching a low Approaching a warm front Passing warm front Within warm sector Approaching cold front Passing cold front SSSppt. Chpt 15 Weather 040609. ppt 16
Understanding Weather Sailing Skills And Seamanship • Fog: a cloud touching the earth • Radiation fog: Land-based, caused by surface cooling and subsequent condensation • Advection fog: Warm, moist air flows over cooler surface, causing condensation • Haze: Dust or salt particles in the air • Mist: Particles of liquid water in the air • Smog: Fog and smoke mixed SSSppt. Chpt 15 Weather 040609. ppt 17
Fog Precautions Sailing Skills And Seamanship • What precautions must be taken in fog? • Navigate, Communicate, Mitigate • Navigate: (avoid danger) • Communicate: (with proper fog signal) • Mitigate: (slow down) • Look and listen SSSppt. Chpt 15 Weather 040609. ppt 18
Non-Frontal Weather Sailing Skills And Seamanship Thunderstorms! From least to most dangerous: • • Single-cell Multicell cluster Multicell lines Supercell SSSppt. Chpt 15 Weather 040609. ppt 19
Thunderstorms Sailing Skills And Seamanship Tornadoes Lightening Microbursts • Waterspouts SSSppt. Chpt 15 Weather 040609. ppt Courtesy of NOAA 20
Non-Frontal Weather Sailing Skills And Seamanship • In sight of a thunderstorm? • Determine its path and steer to avoid if possible • Get a weather report, check radar picture • If you cannot avoid: • • Prepare for heavy weather Reduce sail Close hatches and secure loose gear Put on foul weather clothing, life jackets, tethers SSSppt. Chpt 15 Weather 040609. ppt Courtesy of NOAA 21
Non-Frontal Weather Sailing Skills And Seamanship • Tropical Storms • Tropical wave • Circulation begins with wave in isobars • Tropical cyclone • Closed isobars, winds <64 knots • Hurricanes • Intense circulation, winds >64 knots SSSppt. Chpt 15 Weather 040609. ppt Courtesy of NOAA 22
The Go/No-Go Decision Sailing Skills And Seamanship • Making Go/No Go decision: • Vessel seaworthiness • Crew experience • Weather forecast • Wind direction and speed, temperature, precipitation, waves • Purpose and length of voyage • Crossing a harbor or an ocean? SSSppt. Chpt 15 Weather 040609. ppt Courtesy of NOAA 23
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