Thermal Flying snippet

[THER THERM M ALFLYING]

THERMAL FLYI N G

PART 5: THE WIND

 A series of choice cuts from Burkhard Martens’ new t echnique book on everything you need to know about cross country flying air. The clear spell is drawing to an end and the cloud base sinks.  From south to west means the air is coming from the Atlantic again. Humid air and rain.  Strengthening wind from the west tell of the arrival of the next frontal system.  If during prolonged periods of rain the wind suddenly increases, the weather is just about to improve.

H

ortherrn Alps indicate Sustained gusty winds from the east in the northe

a

prol rolonged high pressure situation

WHAT CAN WE LEARN ABOUT THE WEATHER FROM OBSERVING THE WIND?  As a supplement to personal weather forecasting the winds can give important hints as well.  In the Alps, low clouds coming from the south and high clouds from the northwest indicate a warm-weather spell.  The opposite situation, with low clouds from the northwest and high from southwest, indicate a cold spell.  During high-pressure spells along the northern perimeter of the Alps it is common to have winds gusting with variable strength from the east. If these winds prevail during the entire day the high-pressure will remain in place, but if the wind direction turns to west a period of changeable conditions ensue. A decreasing easterly wind at night is a good sign.  During high-pressure days the valley winds will characterise the mountain regions and the sea breeze the coast.  If the wind in the northern hemisphere turns left during the day the weather is about to change to the worse. If the skies clear during this process the situation is defined as an intermediary highpressure, which rarely lasts very long.

much as 30-40 degrees in the mountains and 15-20 degrees in the flats.  So when the wind is turning right, from west to northwest, it means that there is drier air arriving and the skies are about to clear.  If the wind turns even further, from northwest to north to northeast, we get cool dry air from the Russian steppes. Prolonged periods of nice, flyable weather!  Further turning to the right, from east to south, means the intrusion of humid Mediterranean

ections The high pressure travels from west to east, and the wind direct foll follo ow clockwise aroun round the centr centre e of the high pressure. In the Dol Dolomi omites for instance the winds start aroun round the north orth turning first rocess takes a couple of days east, then south. This ent entire proce

NOTE: All these tips are for Alpine pilots. There is a  good chance that something similar is observable at  your home sites, all you need to do is pay attention, take notes and maybe discuss things with more experienced pilots.

WHEN WE KNOW WHERE THE WIND IS COMING FROM WE CAN ALSO FORM AN OPINION ABOUT WHERE THE AIRMASS IS COMING FROM AND USE IT FOR OUR OWN FORECAST  The wind strength increases with altitude due to wind gradient. The Coriolis effect causes the wind to turn to the right (northern Hemisphere), by as

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CROSS COUNTRY | EDITION 116

It will be bette tter for this pilot ome up from the fron front ilot, when the valle lley wind reaches up to take off. He is waiting for the wind to come

 THERMAL FLYING FLYING