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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

7000+ ships worldwide (600 US)

Weather Observations

Data is collected and formatted in

accordance with the Marine Observer’s

Handbook.

http://www.nws.noaa.gov/om/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

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

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

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