Tuesday, June 23, 2009

50,000 Degrees

...THE SCIENCE OF LIGHTNING...

THIS WEEK IS NATIONAL LIGHTNING SAFETY AWARENESS WEEK. LIGHTNING
KILLS--PLAY IT SAFE!

ALL THUNDERSTORMS CONTAIN THUNDER AND LIGHTNING. AS LIGHTNING
PASSES THROUGH THE AIR, IT RAPIDLY HEATS THE AIR TO 50,000 DEGREES
FAHRENHEIT, MUCH HOTTER THAN THE SURFACE OF THE SUN. DURING A
LIGHTNING DISCHARGE, THE SUDDEN HEATING OF THE AIR CAUSES IT TO
RAPIDLY EXPAND AND CONTRACT. THIS IN TURN CAUSES A SHOCK WAVE THAT
WE HEAR AS THUNDER.

LIGHTNING CAN OCCUR COMPLETELY WITHIN THE THUNDERSTORM CLOUD, BETWEEN
CLOUDS, OR BETWEEN THE CLOUD AND THE GROUND. CLOUD-TO-GROUND
LIGHTNING CAN BE CATEGORIZED AS NEGATIVE FLASHES AND POSITIVE
FLASHES. PRIOR TO A NEGATIVE FLASH, AN ALMOST INVISIBLE NEGATIVELY
CHARGED CHANNEL OF AIR FORMS NEAR THE CLOUD BASE AND SURGES DOWNWARD
NEAR THE GROUND. AT THE SAME TIME, STREAMERS OF POSITIVE CHARGES
SHOOT UP FROM TREES, BUILDINGS, AND OTHER HIGH OBJECTS ON THE
GROUND. WHEN THESE MEET, THE CONNECTION IS COMPLETE, AND A SURGE OF
ELECTRICAL CURRENT MOVES FROM THE GROUND TO THE CLOUD CAUSING THE
VISIBLE RETURN STROKE CALLED LIGHTNING.

POSITIVE FLASHES USUALLY OCCUR BETWEEN THE POSITIVELY CHARGED UPPER
LEVEL OF THE STORM AND THE NEGATIVELY CHARGED AREAS UNDER THE
STORM. THE PROCESS OF A POSITIVE FLASH IS SIMILAR TO THAT OF THE
NEGATIVE FLASH. HOWEVER, BECAUSE THE DISTANCE BETWEEN THE GROUND
AND THE STORM TOP ANVIL IS MUCH GREATER, A SIGNIFICANTLY LARGER
ELECTRIC POTENTIAL IS NEEDED TO INITIATE A POSITIVE FLASH OF
LIGHTNING. FOR THIS REASON, POSITIVE FLASHES ARE INFREQUENT AND
WIDELY SCATTERED AROUND THE STORM, BUT THEY GENERALLY INVOLVE THE
EXCHANGE OF MUCH GREATER CHARGE AND ARE MUCH MORE DESTRUCTIVE.

THE GREATEST DANGER ASSOCIATED WITH POSITIVE CHARGES, HOWEVER, IS
THAT THEY STRIKE IN AREAS WHERE MOST PEOPLE THINK THEY ARE SAFE FROM
THE STORM. THEY CAN STRIKE WELL BEYOND THE AREA WHERE RAIN IS
FALLING AND WELL BEYOND THE AREA WHERE LIGHTNING AND THUNDER ARE
OCCURRING--AS MUCH AS 10 MILES AWAY! CONSEQUENTLY, MANY VICTIMS ARE
CAUGHT COMPLETELY OFF GUARD. DO NOT BECOME A LIGHTNING VICTIM--GET
TO A SAFE PLACE SOONER AND STAY THERE LONGER. REMEMBER, IF YOU CAN
HEAR THUNDER, YOU ARE CLOSE ENOUGH TO GET STRUCK! FOR MORE ON
LIGHTNING SAFETY, GO TO WWW.LIGHTNINGSAFETY.NOAA.GOV.

$$

Sent from my Verizon Wireless BlackBerry

3 comments:

Anjelina said...

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Jaine said...

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Piterson said...

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