Lightning Awareness Week

| June 22, 2010 @ 7:31 am | 1 Reply

This is Lightning Safety Awareness Week and check out today’s story below by Jim Stefkovich, Meteorologist in Charge of NWS/Birmingham.

I have had three close calls with lightning in my lifetime, so until this day, lightning is my most feared of all weather-related events! –JBE
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PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BIRMINGHAM AL
421 AM CDT TUE JUN 22 2010

..THIS WEEK IS NATIONAL LIGHTNING SAFETY AWARENESS WEEK

TODAY’S TOPIC IS THE SCIENCE OF LIGHTNING. 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!

WEDNESDAY’S TOPIC WILL BE OUTDOOR LIGHTNING SAFETY.

FOR MORE ON
LIGHTNING SAFETY, GO TO WWW.LIGHTNINGSAFETY.NOAA.GOV.

FOR FURTHER INFORMATION, PLEASE CONTACT

JIM STEFKOVICH
METEOROLOGIST IN CHARGE
NATIONAL WEATHER SERVICE
BIRMINGHAM, AL
205-664-3010

Category: Pre-November 2010 Posts

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