908 
ABUS34 KBHM 092240
PNSBHM

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BIRMINGHAM AL
540 PM CDT THU APR 9 1998

...PRELIMINARY TORNADO SURVEY FOR THE APRIL 8, 1998 TORNADO ACROSS
WESTERN JEFFERSON COUNTY ALABAMA, JUST WEST OF DOWNTOWN BIRMINGHAM...

     THE MOST SIGNIFICANT TORNADO TO IMPACT ALABAMA SINCE 1977,
TOUCHED DOWN IN WESTERN JEFFERSON COUNTY AT APPROXIMATELY 7:53 PM CDT. 
THE TORNADO WAS PRODUCED BY AN INTENSE THUNDERSTORM REFERRED TO BY
METEOROLOGISTS AS A SUPERCELL, A LONG-LIVED THUNDERSTORM THAT
FREQUENTLY PRODUCES MULTIPLE TORNADOES.

     IN AN AERIAL SURVEY CONDUCTED BY NATIONAL WEATHER SERVICE
METEOROLOGIST WITH THE HELP OF THE ALABAMA STATE TROOPERS AVIATION
UNIT HAVE DETERMINED THAT THE TORNADO THAT RIPPED ACROSS WEST
JEFFERSON COUNTY LAST NIGHT WAS AN F5 TORNADO, THE MOST VIOLENT
TORNADO THAT OCCURS.  F5 TORNADOES HAVE WINDS IN EXCESS OF 260 MILES
PER HOUR.  THE F5 TORNADO IS HIGHEST RATING FOR THE MOST VIOLENT
TORNADO.  THE FUJITA SCALE RUNS FROM F0 FOR THE WEAKEST TO F5 FOR THE
MOST INTENSE.

     THE TORNADO TRACK WAS APPROXIMATELY 21 MILES LONG AND AT IT'S
WIDEST POINT WAS ONE-HALF A MILE WIDE.  THE TOUCH DOWN WAS JUST SOUTH
OF THE TOWN OF SCRAP, JUST INSIDE JEFFERSON COUNTY.  IT TRAVELED EAST-
NORTHEAST IMPACTING OAK GROVE, CONCORD, PLEASANT GROVE, EDGEWATER,
MCDONALD'S CHAPEL, AND ENDED IN PRATT CITY.  THE STORM REACHED IT'S
STRONGEST POINT NEAR THE EDGEWATER/MCDONALD'S CHAPEL AREA.

     INTERESTINGLY, THE TORNADO WAS ON A TRAJECTORY THAT IF IT HAD
STAYED ON THE GROUND FOR AN ADDITIONAL TWO MILES THE HIGH RISES IN
DOWNTOWN BIRMINGHAM WOULD HAVE BEEN HIT; FOUR MORE MILES AND THE
BIRMINGHAM AIRPORT WOULD HAVE SEEN THE DESTRUCTION AS WELL.

     THE LATEST DEATH TOLL WITH THIS STORM WAS IN THE UPPER 20S, WITH
MORE THAN 160 INJURIES.  MORE THAN 100 HOMES WERE DESTROYED AND MORE
THAN 500 HOMES WITH SIGNIFICANT DAMAGE.

     A TORNADO WARNING WAS ISSUED FOR JEFFERSON COUNTY AT 7:45 PM,
GIVING RESIDENTS IN THE INITIAL TOUCHDOWN AREA 8 MINUTES WARNING AND
PEOPLE TOWARD THE END OF THE 21 MILE TRACK 37 MINUTES LEAD TIME.

     IN ST. CLAIR COUNTY, THE TORNADO BEGAN JUST NORTH OF MOODY AND
CONTINUED ON A EAST-NORTHEAST TRACK FOR APPROXIMATELY 10 MILES.  THIS
TORNADO WAS RATED AS AN F2 ON THE FUJITA SCALE.

     THERE WERE TWO TORNADOES IN TUSCALOOSA COUNTY.  DUE TO TIME
CONSTRAINTS, THOSE HAVE NOT YET BEEN SURVEYED.  AN AERIAL SURVEY WILL
BE CONDUCTED ON THOSE TWO TORNADOES ON FRIDAY.

     BRIAN E. PETERS
     WARNING COORDINATION METEOROLOGIST
     205-664-3010

This is a textbook wind profile for supercells - winds in the lowest 1-3km veer strongly with height and increase in speed rapidly with height. Also note how strong the upper-level winds are.

Notice the very obvious hook echo in west-central Alabama.

Again, look at the small appendage of higher reflectivity on the southwest edge.

Notice the Tornado Vortex Signature (TVS) with high gate-to-gate shear couplet north-northwest of the WSR-88d antenna.

Notice the mesoscale inflow which is larger than the TVS in the previous image.

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