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January 2012

Forecasting fundamentals

Learn to read the weather

Once you know the basics of onboard forecasting, you’ll be able to understand what your observations are telling you. Then you can use this information to modify and refine the official forecast. First, let’s look at the signs of weather stability and change:

 

Continuing good weather

Indicators of a change

Skies

Clear, light to dark blue, bright moon; contrails dissipate

Hazy; halo around the sun or moon; thick, lingering jet contrails

Clouds

Few puffy cumulus or high thin clouds, the higher the better

Veil of clouds; clouds at multilayers and  directions; cirrus

Winds

Generally steady, little change over the day

Strong winds in early morning; wind shift to south

Seas

Sea swells same direction

Seas confused; varying directions

Temperatures

Stable; heavy dew or frost at night

Marked changes; increased humidity

Dew Point

Marked spread between dew point and temperature = no fog

Close spread; probable fog if temperature drops

Barometer

Steady; rising slowly

Falling slowly

Sunrise

Gray sky at dawn or sun rising from clear horizon

Red sky; sun rises above horizon because of cloud cover

Sunset

Red sky; sun “ball of fire” or sets on a clear horizon

Sun sets high above horizon, color purplish or pale yellow

Approaching low

Clouds: high cirrus, gradually lowering and thickening
Wind: backing to southeast, possibly increasing
Barometer: begins to fall 2 to 10 millibars in three hours
Seas: Offshore swells increase, with decreasing period
What to expect: Rain within 15 to 24 hours. If low is west to northwest passing to your north, you will see fronts. If low is west to southwest passing to your south, you will not see distinct fronts.

Approaching warm front

Cirrus or mackerel clouds: Front is more than 24 hours away.
Lowering and thickening clouds (altostratus, nimbostratus): Front is less than 24 hours away.
Rain: begins lightly, becoming steady and persistent
Barometer: falls steadily; the faster it falls, the stronger the winds.
Winds: increase steadily, stay southeast
Visibility: deteriorates, especially in rain

Passing warm front

Sky: lightens toward western horizon
Rain: breaks
Wind: veers from south to southwest, may decrease
Barometer: stops falling
Temperature: rises

Within warm front

Wind: steady, typically southwest; will strengthen ahead of cold front Barometer: steady, may drop shortly ahead of cold front
Precipitation: mist, possible drizzle

Approaching cold front

Wind: southwest, increases; line squalls possible more than 100 miles ahead of front
Barometer: begins brief fall, could be rapid
Clouds: cumulonimbus builds to west
Temperature: steady
Rain: begins and intensifies, but duration short, one to two hours

Passing cold front

Wind: veers rapidly to northwest; gusty behind front
Barometer: begins to rise, often quickly
Clouds: cumulonimbus to nimbostratus and then clearing
Temperature: drops suddenly, followed by a slow decline

Rain: ends, gives way to rapidly clearing skies, possibly with leftover altocumulus clouds

To learn more about predicting the weather, take the Onboard Weather Forecasting seminar at a squadron near you.

 

 

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Short splice

Splicing is an art, and the final appearance is your reward. Done correctly, the short splice is aesthetically pleasing and strong.

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