Navigation NAU 102 Lesson 32

Weather Instruments The safety of crew, passengers, cargo and the ship itself is dependent on making good weather decisions. Weather has a significant impact on every voyage.

Weather Instruments We are our own weather station at sea. We must develop an accurate forecast using data received from shore and that we collect ourselves. You’ll learn how to make a forecast in Meteorology.

Duties of the Mate At all times, be knowledgeable of the current weather. Wind direction and speed Wave direction and height Visibility Trend of the barometer

Duties of the Mate At all times, be knowledgeable of the weather forecast. Obtain 24 hour forecast from weather fax, messages, etc. Interpret the forecast for your area. When necessary, make your own forecast.

Weather Instruments Satellites Meteorological data is collected by: Buoys Ships (that’s you)

Duties of the Mate Conduct marine surface weather observations. Make observations Log observations Transmit observations to National Weather Service

Duties of the Mate Conduct marine surface weather observations. 4 times each day 0000, 0600, 1200, 1800 GMT Voluntary program ships worldwide (600 US)

Weather Observations Data is collected and formatted in accordance with the Marine Observer’s Handbook. /marine/handbk1.pdf

Weather Instruments Aneroid Barometer Measures atmospheric pressure. Air pressure exerts a crushing force on a thin metal element. Linkages move to a pointer to indicate the pressure on a scale.

Aneroid Barometer

Must be properly adjusted. (Usually done by a professional, often for free.) Reading must be adjusted for elevation to give pressure at sea level. (Note: Mercurial Barometers must also be corrected for latitude and temperature.)

Barometers

Weather Instruments Barograph A recording barometer.

Weather Instruments Thermometer Measures air temperature. You must be able to convert between Celsius and Fahrenheit scales.

Temperature Conversions

Weather Instruments Hygrometer Measures Relative Humidity and Dew Point.

Weather Instruments Relative Humidity – ratio of amount of water vapor in the air to the amount it could hold at the current temperature. Dew Point – the temperature at which water vapor will condense.

Weather Instruments Hygrometer Most common type: sling psychrometer.

Sling Psychrometer Two Thermometers: 1 wet, 1 dry Temperature difference is noted.

Sling Psychrometer

Psychrometer

Introduction to Navigation Questions?