Mission: 2009 United States/Canada Pacific Hake Acoustic Survey
Geographical area of cruise: North Pacific Ocean from Monterey, CA to British Columbia, CA.
Date: July 28, 2009
Weather Data from the Bridge
Wind speed: 17 knots
Wind direction: 345° from the north
Visibility: 8 nautical miles /clear
Temperature: 16.8°C (dry bulb); 11.6°C (wet bulb)
Sea water temperature: 15.5°C
Wave height: 3-5 ft.
Air pressure: 1012.9 millibars
Weather note: Millibars is a metric unit used to measure the pressure of the air.
Science and Technology Log
Weather Instruments and Predicting Weather
Everything that happens out at sea is dependent upon the weather forecasts. Throughout history man has used a variety of instruments to acquire accurate weather information. The Miller Freeman is equipped with state of art weather reporting instruments. Every 3 hours weather data is sent to the National Weather Service to help predict the weather at sea. Once again accuracy in reporting data is paramount.
Global Position: The Miller Freeman has several methods by which to determine longitude and latitude, which is our position in the ocean or on land. There are 2 G.P.S. systems on the bridge, a magnetic compass, a gyro compass, and radar. These instruments help determine the ship’s position.
True north: The actual location of a point on the earth related to the north pole.
Magnetic north: Caused by the magnetic pull on the earth. Magnetic north heading is different depending on where you are on the earth, for instance, Magnetic north in Oregon has a variation of 16.45°east from true north. Southern California has a variation of 13.3° east from true north.
Temperature: Measured by a thermometer, units used are Celsius. Dry bulb: Measures air temperature. Wet bulb: Uses a thermometer wrapped in a wet cloth. The dry and wet temperatures together give the dew point and help to determine humidity.
Wind Speed: Measured in knots using an anemometer, or estimated by using the Beaufort scale. The Beaufort scale uses observations of the sea surface, and the effects of wind on people or objects aboard ship to estimate the wind speed.
Wind Direction: Is measured by what direction in which the wind is coming.
Cloud Height/Type: Is measured visually.
Cloud Type: Is measured visually using a variety of names of clouds depending on their patterning and altitude.
Visibility: Is measured by estimating how much of the horizon can be seen.
Wave Direction: measured visually from the direction the wave comes.
Wave Height: The vertical distance between trough (bottom of the wave) and crest (top of the wave) and is usually measured in feet.
Swell Direction/ Height: Measured visually usually in feet.
I have enjoyed my time on the bridge of the Miller Freeman immensely. I have a better understanding of the weather instruments used onboard and am getting better at spotting whales and identifying birds. I want to thank the entire NOAA Corps Officers who have taught me so much about how navigation and weather work aboard the Miller Freeman.