The Journey of Flight.pdf - Valkyrie Cadet

Chapter Chapter Chapter 20 20 - - A AAviation
A viation W WWeather
W eather
Weather Occurring with an Easterly Wave
One of the major factors influencing tropical weather is the easterly wave. This is a common
tropical weather disturbance that normally occurs in the trade-wind belt. Easterly waves of the Northern
Hemisphere have advance winds blowing somewhat more northerly than the usual trade-wind
direction. As the wave line approaches, the atmospheric pressure falls.
The wind shifts to the east as the line passes. The typical wave is preceded by fair weather, but
followed by much cloudiness, low cloud ceilings, rain, and usually, thunderstorms.
Easterly waves are more numerous and stronger during summer and early fall. Their effects occasionally
reach as far north as the Gulf Coast area of the United States. They frequently affect Hawaii
and are commonly observed in the West Indies. A wave that is hardly noticeable on the weather chart
may one day deepen rapidly and, by the next day, become the spawning ground of a tropical cyclone
(hurricane).
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