[http://www.srh.noaa.gov/ewx/html/wxevent/2001/hurricane/hw2001-wed-ewx.htm]
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO, TX
300 PM CDT WED MAY 23 2001
...HURRICANE FLOODING...
CLIMATOLOGY AND THE HISTORY OF TEXAS TROPICAL SYSTEMS INDICATE THAT
ON AVERAGE HURRICANES STRIKE THE TEXAS COAST ONCE EVERY 3 TO 4 YEARS.
THEY BRING DEVASTATING SURGE...WIDESPREAD DAMAGING WINDS AND
TROPICAL TORNADOES. BUT THE MOST DEADLY EFFECT OF THESE STORMS
IS THE FLOODING ASSOCIATED WITH THEIR RAINFALL.
ALTHOUGH EACH HURRICANE HAS ITS OWN UNIQUE FEATURES...ALL PRODUCE
HEAVY RAINFALL ALTHOUGH THE RAIN TOTALS MAY VARY GREATLY. HEAVY RAIN
DEVELOPS OUTWARD FROM NEAR THE HURRICANE EYE THROUGH THE SPIRAL RAIN
BANDS UP TO 200 MILES AWAY. HEAVY RAINFALL IS USUALLY CONCENTRATED
IN THE RIGHT FRONT QUADRANT OF THE STORM AND IS MOST PRONOUNCED IN
THE DAYTIME HOURS WHEN THE HEATING OF THE SUN ENHANCES THE ACTIVITY.
A FIRST ESTIMATE OF THE MAXIMUM RAINFALL IN A HURRICANE IS OBTAINED
BY DIVIDING THE STORMS FORWARD SPEED INTO 100. FOR EXAMPLE...A
HURRICANE WITH A FORWARD SPEED OF 10 MPH WOULD YIELD A MAXIMUM
RAINFALL AMOUNT OF 10 INCHES. ONE MOVING AT 20 MPH WOULD YIELD A
MAXIMUM RAINFALL AMOUNT OF 5 INCHES.
HISTORICALLY...NINE OUT OF 10 DEATHS IN HURRICANES IN THE
UNITED STATES WERE ATTRIBUTED TO STORM SURGE...BUT WITH IMPROVED
WARNING THAT IS NO LONGER THE CASE. ACCORDING TO ED RAPPAPORT...
DEPUTY DIRECTOR OF THE HURRICANE CENTER IN MIAMI...INLAND FLOODING
IN THE PAST 30 YEARS HAS BEEN RESPONSIBLE FOR MORE THAN HALF THE
DEATHS ASSOCIATED WITH TROPICAL SYSTEMS IN THE UNITED STATES.
OFTEN THE GREATEST DAMAGE IS ASSOCIATED WITH FLASH FLOODING OR
RIVER FLOODING WHICH OCCUR DAYS AFTER THE HURRICANE HAS PASSED.
IN SPITE OF THE FACT THAT HURRICANE BEULAH IN 1967 PRODUCED A
RECORD-SETTING TOTAL OF 115 TORNADOES...MOST OF BEULAHS DAMAGE
WAS CAUSED BY THE FLOODING RESULTING FROM RAINFALL OF 10 TO 20
INCHES OVER MUCH OF DEEP SOUTH TEXAS...WITH ISOLATED TOTALS NEAR
30 INCHES.
AND DON'T UNDERESTIMATE A TROPICAL STORM. EVEN THOUGH ITS WINDS
ARE WEAKER THAN THOSE IN A HURRICANE...ITS RAINFALL CAN BE FAR
MORE DEADLY. THE LAST HURRICANES TO STRIKE THE UPPER COAST WERE
JERRY AND CHANTAL IN 1989...BUT TROPICAL STORM CLAUDETTE IN 1979
CAUSED GREATER DEVASTATION THAN BOTH OF THESE. OVER A PERIOD OF
THREE DAYS...CLAUDETTE PRODUCED UP TO 45 INCHES OF RAIN...CAUSING
MASSIVE FLOODING IN AREAS SOUTH OF HOUSTON.
A DEVASTATING EFFECT KNOWN AS "CORE RAINS" CAN DEVELOP AT NIGHT...
AND RECUR FOR UP TO FOUR DAYS AFTER A HURRICANE OR TROPICAL SYSTEM
HAS MOVED INLAND. UNLIKE THE WIDESPREAD DAYTIME RAIN BANDS THAT
MAY COVER AN AREA HALF THE SIZE OF TEXAS...CORE RAINS FORM AT NIGHT
IN AN AREA OFTEN NO LARGER THAN A SINGLE COUNTY. ALL THE ABILITY
OF THE DYING TROPICAL SYSTEM TO PRODUCE RAIN IS CONCENTRATED INTO
THIS SMALL AREA...AND RAINFALL CONTINUES HOUR AFTER HOUR AT RATES
OF 4 TO 6 INCHES PER HOUR BENEATH THE CENTER OF THE SYSTEM. IT WAS
IN THIS MANNER THAT TROPICAL STORM AMELIA...IN AUGUST OF 1978...SET
THE RAINFALL RECORD FOR TROPICAL SYSTEMS STRIKING TEXAS. AFTER
MOVING INLAND ALONG THE LOWER COAST AND PASSING WEST OF
SAN ANTONIO... AMELIA SAT FOR TWO DAYS AND NIGHTS IN A CORE RAIN
EVENT OVER THE TEXAS HILL COUNTRY... PRODUCING AN ASTOUNDING
48 INCHES OF RAIN.
BE PREPARED...IF YOU LIVE IN A FLOOD PRONE AREA OR IN AN AREA WHERE
ROADS FREQUENTLY ARE FLOODED YOU SHOULD PLAN TO EVACUATE YOUR HOME
IN ADVANCE OF THE STORM. ONCE THE STORM IS UPON YOU... EVACUATION
ROUTES COULD EASILY BE FLOODED AND HIGH WINDS WILL MAKE TRAVEL
DANGEROUS IF NOT IMPOSSIBLE.
HURRICANES AND TROPICAL STORMS DELIVER A VARIETY OF DESTRUCTIVE
ELEMENTS THAT THREATEN BOTH LIFE AND PROPERTY. FOR THIS REASON
THE 2001 TEXAS HURRICANE AWARENESS WEEK IS ESTABLISHED TO EDUCATE
RESIDENTS AND PROMOTE TROPICAL WEATHER PREPAREDNESS.
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