JOHN: GOOD EVENING, I'M JOHN YANG.

A SECOND ROUND OF VIOLENT WEATHER IS BARRELLING ACROSS THE CENTRAL AND SOUTHERN UNITED STATES AFTER A DEADLY AND DESTRUCTIVE FRIDAY NIGHT.

THE STORMS HAVE SPAWNED VIOLENT TORNADOES AND FANNED WILDFIRES AND DUST STORMS THAT HAVE CLAIMED AT LEAST 17 LIVES AND DESTROYED SCORES OF HOMES.

MORE THAN 200,000 PEOPLE ARE WITHOUT POWER ACROSS FIVE STATES.

MANY OF THE FATALITIES HAVE BEEN IN MISSOURI, WHERE AT LEAST FOUR TORNADOES TOUCHED DOWN.

THE NATIONAL WEATHER SERVICE SAYS THERE'S A HEIGHTENED THREAT OF TORNADOES TONIGHT STRETCHING FROM THE DEEP SOUTH TO THE OHIO RIVER VALLEY.

EARLIER I SPOKE WITH MATTHEW CAPPUCCI, SENIOR METEOROLOGIST AT MYRADAR, WHO'S IN MISSISSIPPI TRACKING THE STORMS.

I ASKED HIM HOW UNUSUAL A MULTI-DAY TORNADO OUTBREAK LIKE THIS IS.

MATTHEW: EITHER OF THESE TWO DIFFERENT EVENTS WOULD IN AND OF THEMSELVES, BE VERY SIGNIFICANT.

LAST NIGHT, WE SAW ROUGHLY 140 TORNADO WARNINGS IN A 24 HOUR PERIOD WITH NUMEROUS FATALITIES AND AT LEAST 18 TORNADO WARNINGS SIMULTANEOUSLY READ LAST NIGHT WAS A BIG DEAL YET, THAT'S THE , APPETIZER FOR WHAT'S BEEN HAPPENING ALL DAY TODAY INTO THE EVENING WE HAVE A LEVEL FIVE OUT HOURS.

OF FIVE, A HIGH RISK, WHICH IS ISSUED LESS THAN 1% OF THE TIME.

IT IS A TOP TIER EVENT ANYWAY.

THE VERBIAGE THE NATIONAL WEATHER SERVICE IS USING IS DOWNRIGHT ALARMING WHEN THEY SAY THINGS LIKE VOLATILE, INTENSE LONG TRACK TORNADOES.

JOHN: EXPLAIN THAT AND WHY THEY ARE SO DANGEROUS.

MATTHEW: MOST TORNADOES ARE TOWARD THE LOWER END EF ZERO, ON OR TWO.

BUT WE ARE TALKING EF4, EF5, PLUS WINDS OF 160 MILES PER HOUR.

PLUS THESE SUPERCELLS, THE ROTATING STORMS, WILL BE SELF-SUSTAINED FOR A LONG TIME BECAUSE THE ATMOSPHERE IS SO FAVORABLE FOR THAT THAT THESE TORNADOES CAN STAY ON THE GROUND FOR 15, 20, 30 MINUTES, MAYBE CLOSE TO AN HOUR, AND IN A FEW INSTANCES LEADING TO VERY LONG DAMAGE TRACKS.

JOHN: WHAT ARE THE INGREDIENTS IN THE ATMOSPHERE, THE ENVIRONMENT, THAT MAKES THIS SO CONDUCIVE?

MATTHEW: YOU NEED TWO INGREDIENTS, PAINT OR JUICE, HOW WARM AND MOIST IS THE ATMOSPHERE, AND YOU NEED SPIN WHICH COMES FROM CHANGING WINDS WITH HEIGHT.

IT IS WARM AND HUMID WITH GULF MOISTURE WAFTING RIGHT NOW, SO THE ATMOSPHERE IS VERY JUICED UP AREA AT THE SAME TIME, THE WINDS AT THE SURFACE ARE OUT OF THE SOUTH OR SOUTHEAST, BUT ALOFT THEY ARE MORE OUT OF THE SOUTHWEST.

ANY STORM THAT GROWS TALL ENOUGH WILL FEEL THOSE CHANGING WINDS AND WILL ROTATE IN SOME CASES QUITE PROFUSELY.

JOHN: THIS INCREASE IN INTENSITY AND THTH LONG-LASTING STORMS, HW MUCH OF THIS IS DUE TO CLIMATE CHANGE, OR IS ANY OF IT?

MATTHEW: IT IS NOT THAT CLOSELY LINKED TO CLIMATE CHANGE.

YOU KNOW, THE SPRING MONTHS EVERY YEAR TEND TO BE A REALLY ROUGH TIME.

WE HAVE THE INSURGENCIES OF GULF MOISTURE AND A LITTLE BIT OF LEFTOVER COLD FROM WINTER.

THOSE TWO SEASONS KIND OF BATTLE IT OUT DURING MARCH, APRIL, MAY.

REALISTICALLY, IF YOU'RE GOING TO GET BIG TORNADOES, IT'LL BE OVER MISSISSIPPI OR ALABAMA THIS TIME OF YEAR.

THAT SAID, WE DO KNOW THAT WINTERTIME EVENTS, WHEN THE ATMOSPHERE IS WARMING A LITTLE BIT MORE, TEND TO BE OVER ACHIEVING A BIT MORE THANKS TO THE WARMING ADVANCE -- ATMOSPHERE SO THERE IS A LITTLE ROLE, BUT REALLY IT IS THE TIME OF YEAR.

JOHN: WHAT IS YOUR ADVICE TO THOSE LIVING IN THOSE AREAS WHO ARE UNDER TORNADO WATCHES OR WARNINGS?

MATTHEW: WE WANT PEOPLE TO TAKE ACTION AHEAD OF TIME.

ORDINARILY FOLKS WAIT UNTIL A TORNADO WARNING IS ISSUED BEFORE THEY SEEK SHELTER, BUT ON A DAY LIKE TODAY A NIGHT LIKE TONIGHT, , IF PEOPLE ARE IN A TORNADO WATCH, IT'S PROBABLY A GOOD IDEA TO GET TO A SITE FIELD LOCATION SOME PLACE WITH A BELOW GROUND SHELTER EVEN BEFORE ANY WARNINGS ARE ISSUED.

YOU NEVER WANT TO BE MORE THAN FIVE MINUTES AWAY FROM A SHELTER ON A NIGHT LIKE TONIGHT READ THAT WAY IF A WARNING IS ISSUED, YOU CAN JUST DUCK AND COVER REAL QUICK AND YOU DON'T HAVE TO WORRY ABOUT MOVING LOCATIONS.

IF YOU HAVE ELDERLY FAMILY, FRIENDS, LOVED ONES, CHECK IN WITH THEM.

MAKE SURE THEY HAVE A PLAN.

IT IS ONE OF THOSE NIGHTS YOU HAVE TO BE GOOD NEIGHBORS.

JOHN: TO HELP PEOPLE OUT WHEN THEY HEAR THESE WATCHES AND ALERTS, WHAT IS THE DIFFERENCE BETWEEN A WATCH AND A WARNING?

MATTHEW: A WATCH MEANS CONDITIONS ARE FAVORABLE FOR TORNADOES TO FORM.

A WARNING MEANS WE ARE SEEING ONE ON RADAR OR IN PERSON, ONE IS IMMINENT OR OCCURRING.

WATCH MEANS WATCH OUT.

A WARNING MEANS TAKE ACTION RIGHT NOW, SHELTER RIGHT NOW.

THE WARNINGS BUZZ ON YOUR PHONES.

NOW, THE NATIONAL WEATHER SERVICES CALLING THIS A PDS, OR PARTICULARLY DANGEROUS SITUATION.

THOSE TYPE OF WATCHES ARE ONLY ISSUED ABOUT 7% OF THE TIME, BUT YOU'RE THREE TIMES MORE LIKELY TO BE HIT BY A VIOLENT TORNADO.

JOHN: MATTHEW CAPPUCCI, SENIOR METEOROLOGIST AT MYRADAR, THANK YOU VERY MUCH AND BE SAFE.

MATTHEW: THANK YOU