Weather Measure
Thursday, May 24, 2007
Weather Sayings of the Old Sailors
 
Weather Sayings of the Old Sailors

• Dew indicates a good day ahead; a dry morning is sign of showers.
• Distant shores loom up "nearer" before rain because of thinning of the air.
• Large halo around the moon indicates cirrus cloudform and warm front rain.
• A veering wind is sign of fair weather; backing wind means rain.
• Falling barometer indicates nearing "low" area, with winds and rain.
• Rain is most frequent at the turn of the tide (if air is humid).
• Rainbow to windward, rain ahead. Rainbow to leeward, rains end.
• Higher the clouds, finer the weather. Lowering ceilings foretell a rain.
• Smoke that curls downward and lingers, means a nearing storm.
• Thinning air is harder to fly in. Birds "sit it out" before a storm.
• Sky full of webby cirrus foretells disturbance and rain's on its way.
• Lightning from the west or northwest will reach you; from south or southeast will pass.

Illustrations by Eric Sloane.

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Friday, May 4, 2007
Finding True North
 
Hints about orienting a wind vane to TRUE NORTH for accurate wind direction measurements

No matter how precise your electronic wind vane is, if the zero point of the wind vane's base is not oriented to north the readings will be in error.

There are some easy ways to find north. Once it gets dark look up into the sky and find the north star. When you have done that you are looking in the direction of true north.

Another aid can be our streets and roads. Many city streets are laid out in a north-south grid pattern. Just line the zero point of the anemometer so it points parallel to the north-south running streets.

The use of a compass to locate true north requires a little extra work. Magnet compass needles point to the magnetic north pole which is not at the same place as the geographic north pole. A correction must be applied to convert the magnetic north direction to the true north direction. The magnitude of the correction depends on where you are located. The following URL will take you to a U.S. government site that takes you through some very simple steps to convert magnetic compass readings to true direction readings for your location: http://www.ngdc.noaa.gov/geomag/faqgeom.shtml

Once you have successfully aligned the anemometer to true north, your wind direction readings will report true wind directions within the limit of the errors of the anemometer.

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