ACUS41 KWBC 191042 
SCCNS1 
STORM SUMMARY NUMBER 52 FOR THE HISTORY OF "ALLISON" 
NATIONAL CENTERS FOR ENVIRONMENTAL PREDICTION 
HYDROMETEOROLOGICAL PREDICTION CENTER...NWS...CAMP SPRINGS MD 
630 AM EDT TUE JUN 19 2001 

...EXTRAORDINARY FLOODS FROM A TYPICAL TROPICAL STORM... 

AS THE LOW THAT WAS ONCE ALLISON PASSES SOUTH OF CAPE RACE 
NEWFOUNDLAND...IT IS TIME TO REFLECT ON THE GREAT IMPACT ALLISON 
HAD ON THE SOUTHERN AND EASTERN UNITED STATES OVER THE TWO WEEK 
PERIOD FROM JUNE 4TH THROUGH THE 18TH. WHILE THE CYCLONE WAS 
FAIRLY SMALL IN AREAL COVERAGE...IT REMAINED CLOSE ENOUGH TO THE 
GULF OF MEXICO AND ATLANTIC TO FEED OFF THE MOISTURE AND WARMTH 
OF THOSE WATER BODIES...ALLOWING THE SYSTEM TO SURVIVE LARGE 
PERIODS OF TIME OVER LAND...AND MORE IMPORTANTLY...TO BECOME AN 
EFFICIENT RAIN PRODUCER. 

THE LIFE CYCLE OF ALLISON WAS SPURRED BY A TROPICAL WAVE THAT HAD 
MOVED OFF THE COAST OF AFRICA ON MAY 21ST. IT TRACKED WESTWARD 
ACROSS THE ATLANTIC OCEAN...REACHING THE WESTERN CARIBBEAN ON THE 
29TH... THEN CROSSED INTO THE NORTHEAST PACIFIC JUNE 1ST. A LOW 
LEVEL CIRCULATION FORMED ALONG THE TROPICAL WAVE SOUTH-SOUTHEAST 
OF VERA CRUZ ON THE 3RD...THEN MOVED QUICKLY INTO SOUTHEAST 
MEXICO STEERED BY DEEP SOUTHWESTERLY FLOW. IT MOVED INTO THE BAY 
OF CAMPECHE LATE ON THE 4TH AS AN AREA OF THUNDERSTORMS...AND WAS 
GUIDED BY A NEARBY UPPER LEVEL LOW TOWARDS THE NORTH-NORTHWEST 
THROUGH THE WESTERN GULF OF MEXICO. 

THE AREA OF THUNDERSTORMS BECAME INCREASINGLY ORGANIZED...SO MUCH 
SO THAT RECONNAISANCE AIRCRAFT ALONG WITH SHIP AND BUOY REPORTS 
INDICATED THE FORMATION OF A TROPICAL STORM WHILE ONLY 80 MILES 
OFF THE COAST OF GALVESTON DURING THE AFTERNOON OF THE 5TH. THIS 
PROMPTED EVACUATIONS OF THE WEST END OF GALVESTON ISLAND...AN 
AREA NOT PROTECTED BY THE LEGENDARY SEAWALL WHICH WAS BUILT AFTER 
THE GALVESTON HURRICANE OF 1900. 

INITIALLY STEERED BY THE SUBTROPICAL RIDGE CENTERED EAST OF 
FLORIDA...THE CYCLONE MOVED NORTHWARD...MAKING LANDFALL ON THE 
EAST END OF GALVESTON ISLAND TEXAS DURING THE EVENING OF THE 5TH. 
THE HIGHEST WINDS REPORTED ON LAND WERE TO THE NORTHEAST OF THE 
CENTER IN THE AREA WITH THE TIGHTEST PRESSURE GRADIENT. AT SEA 
RIM STATE PARK...NEAR THE COAST OF WESTERN JEFFERSON COUNTY IN 
SOUTHEAST TEXAS... SUSTAINED WINDS REACHED 48 MPH AT 9:50 AM CDT 
ON THE 6TH...AND GUSTS PEAKED AT 61 MPH AT 9:42 AM CDT. TROPICAL 
STORM FORCE WINDS WERE REPORTED FROM GALVESTON EASTWARD TO THE 
SABINE RIVER DURING THE NIGHT OF THE 5TH AND THE MORNING OF THE 
6TH. THEREAFTER... THE CYCLONE WEAKENED TO A TROPICAL DEPRESSION 
...AND THE HURRICANE CENTER HANDED THE RESPONSIBILITY OF THE 
ADVISORIES OVER TO THE HYDROMETEOROLOGICAL PREDICTION CENTER IN 
CAMP SPRINGS MARYLAND IN THE FORM OF STORM SUMMARIES... STANDARD 
PROCEDURE WHEN A DEPRESSION DRIFTS INLAND. 

ALLISON DRIFTED AS FAR INLAND AS LUFKIN TEXAS DURING THE MORNING 
OF THE 7TH...DROPPING LARGE QUANTITIES OF RAIN ALONG AND EAST OF 
ITS PATH. MUCH OF SOUTHEAST TEXAS AND SOUTH CENTRAL LOUISIANA HAD 
ALREADY RECEIVED OVER 10 INCHES OF RAIN BY THE MORNING OF THE 
8TH. IN SOUTH CENTRAL LOUISIANA...MUCH OF THIS RAIN FELL WITHIN A 
TWELVE HOUR PERIOD ON THE 6TH...FLOODING MANY HOMES IN 
LAFAYETTE... IBERIA... ST MARY... AND VERMILLION PARISHES. DEEP 
WATER SUBSEQUENTLY SUBMERGED US HIGHWAY 90 IN THIS REGION FOR 
OVER TWELVE HOURS. THIBODAUX LOUISIANA WENT UNDERWATER WHEN 15.16 
INCHES OF RAIN FELL IN THE 24 HOUR PERIOD ENDING THE MORNING OF 
THE 7TH. 

DURING THE NIGHT OF THE 6TH/ 7TH...HEAVY RAINS DELUGED NORTHWEST 
JEFFERSON AND ORANGE COUNTIES IN SOUTHEAST TEXAS WHEN 6-10 INCHES 
OF RAIN FELL IN LESS THAN FIVE HOURS. SEVERAL HOMES IN 
CHINA...BEAUMONT...NOME...AND VIDOR TEXAS SAW FLOOD WATERS INVADE 
WHILE NUMEROUS STREETS WERE CLOSED DUE TO FLOOD WATERS THAT 
STALLED HUNDREDS OF CARS IN THE REGION. FLOODING HAD ALREADY 
BEGUN IN HOUSTON ...BUT THE WORST WAS YET TO COME. 

ON THE MORNING OF THE 7TH...THE SUBTROPICAL HIGH OFF FLORIDA 
WEAKENED AND DRIFTED TO THE SOUTH...WHILE A HIGH PRESSURE RIDGE 
OVER NEW MEXICO WAS INTENSIFYING. THIS CAUSED THE CYCLONE TO 
TRANSCRIBE A CLOCKWISE LOOP THAT MORNING...AND THEN MOVE TO THE 
SOUTHWEST. THIS BROUGHT MORE RAINFALL TO LOUISIANA AND TEXAS OVER 
THE NEXT COUPLE DAYS WHILE THE DEPRESSION AMBLED BACK TOWARDS THE 
COAST. ALTHOUGH THE MAIN THREAT FROM ALLISON WAS HEAVY RAINS... 
TORNADOES DID TOUCHDOWN NORTHWEST OF ZACHARY IN EAST BATON ROUGE 
PARISH DURING THE EARLY MORNING OF THE 7TH... WELL TO THE EAST OF 
THE CENTER. ONE PERSON WAS KILLED WHEN A TREE FELL ONTO HIS 
VEHICLE. 

AS THE CENTER APPROACHED HOUSTON FOR A SECOND TIME ON THE 8TH... 
RAIN INTENSIFIED ACROSS SOUTHEAST TEXAS. CONROE MEASURED 8.23 
INCHES DURING A SIX HOUR PERIOD ON THE AFTERNOON OF THE 8TH. 
STILL HEAVIER RAINS WERE MOVING ACROSS THE HOUSTON AREA...OVER 20 
INCHES OF RAIN FELL WITHIN A TWELVE HOUR PERIOD. A VAST AREA OF 
HOUSTON WAS SUBMERGED BY A SECOND ONSLAUGHT OF HEAVY RAIN WITHIN 
SIX DAYS...BUFFALO BAYOU AND GREENS BAYOU FLOODED SEVERELY. 
ALLISON TURNED OUT TO BE THE FLOOD OF RECORD FOR THE HOUSTON 
METROPOLITAN AREA. PORTIONS OF US HIGHWAY 59 AND INTERSTATE 10 
WERE DEEPLY SUBMERGED...ONLY THE TOPS OF SEMI-TRACTOR TRAILERS 
WERE VISIBLE ON THOSE MAJOR ROADWAYS. FLOODING OF SIMILAR 
MAGNITUDE WAS OCCURRING IN THE BEAUMONT AREA AS WELL. THE LATEST 
COUNT OF THOSE THAT PERISHED IN THE FLOOD WAS 22 FROM THE HOUSTON 
AREA. 

THE HIGHEST STORM TOTAL REPORTED FROM TEXAS WAS 36.99 INCHES AT 
THE PORT OF HOUSTON. AMELIA (1978)...CLAUDETTE (1979)...AND THE 
UNNAMED HURRICANE OF SEPTEMBER 1921 REMAIN THE THREE WETTEST 
TROPICAL CYCLONES IN TEXAS HISTORY. BELOW IS A LIST OF THE TOP 
TEN AMOUNTS: 

     AMOUNT    LOCATION          STORM NAME    DATES 
     46.00"    BLUFF             AMELIA        8/01-04/1978 
     45.00"    ALVIN COOP SITE   CLAUDETTE     7/24-27/1979 
     40.00"    THRALL            UNNAMED HU    9/07-11/1921 
     36.99"    PORT OF HOUSTON   ALLISON       6/05-11/2001 
     36.40"    WILLIAMSON CTY    UNNAMED HU    9/09/1921 
     35.67"    GREENS BAYOU      ALLISON       6/05-11/2001 
              (HOUSTON) 
     33.00"    WESTHEIMER &      ALLISON       6/05-11/2001 
               KIRBY (HOUSTON) 
     32.99"    HUNTING BAYOU AT  ALLISON       6/05-11/2001 
               I-10 (HOUSTON) 
     32.00"    ALBANY            AMELIA        8/01-04/1978 
     30.07"    ALVIN NWS SITE    CLAUDETTE     7/24-27/1979 

THE SITUATION WAS NOT MUCH BETTER FOR THE BAYOU STATE. HEAVY 
RAINS BEGAN ON THE 5TH AND CONTINUED THROUGH THE 11TH. THE CENTER 
FINALLY EXITED THE TEXAS COAST NEAR PALACIOS ON THE EVENING OF 
THE 9TH. WHEN IT EMERGED BACK INTO THE GULF OF MEXICO...IT BECAME 
THE FIRST KNOWN TROPICAL CYCLONE TO MAKE LANDFALL IN TEXAS...ONLY 
TO EMERGE BACK INTO THE GULF. UPPER LEVEL WESTERLIES ASSOCIATED 
WITH THE SOUTHERN FRINGE OF THE SUBTROPICAL JET STREAM GUIDED THE 
LOW EAST-NORTHEASTWARD... MOVING INTO THE MARSHES/BAYOUS OF 
SOUTHEAST LOUISIANA ON THE MORNING OF THE 11TH. THE MAXIMUM 
AMOUNTS OCCURRED IN THE VERMILION AND ATCHAFALAYA BASINS OF SOUTH 
CENTRAL LOUISIANA WHICH SAW HEAVY RAINS EACH DAY FROM THE 5TH 
THROUGH THE 11TH. THE HIGHEST AMOUNT REPORTED FROM LOUISIANA WAS 
27.55 INCHES AT SALT POINT...IN ST. MARY PARISH. 

BELOW IS A LIST OF THE TOP TEN TROPICAL CYCLONE-RELATED RAINFALL 
AMOUNTS IN LOUISIANA HISTORY...NOTE THE AMOUNTS ARE LOWER THAN 
THEY ARE FOR TEXAS. THE HURRICANE OF 1940 REMAINS THE WETTEST 
TROPICAL CYCLONE IN LOUISIANA HISTORY... VIRTUALLY FLOODING THE 
ENTIRE RICE COUNTRY...INCLUDING MANY TOWNS...IN SOUTHWEST AND 
SOUTH CENTRAL LOUISIANA. 

     AMOUNT    LOCATION          STORM NAME    DATES 
     33.71"    CROWLEY           UNNAMED HU    8/6-10/1940 
     31.66"    ABBEVILLE         UNNAMED HU    8/6-10/1940 
     29.86"    THIBODAUX         ALLISON       6/05-11/2001 
     29.65"    LAFAYETTE         UNNAMED HU    8/6-10/1940 
     27.55"    SALT POINT        ALLISON       6/05-11/2001 
     22.30"    LOGANSPORT        UNNAMED TS    7/22-26/1933 
     21.35"    SLIDELL WFO       ALLISON       6/05-11/2001 
     21.10"    TERRYTOWN         FRANCES       9/10-14/1998 
     20.96"    MORGAN CITY       ALLISON       6/05-11/2001 
     20.62"    RESERVE           ALLISON       6/05-11/2001 

IN SOUTHEAST LOUISIANA...THE COMITE RIVER RECORDED ITS THIRD 
HIGHEST RIVER STAGE ON RECORD ON THE 9TH...CRESTING AT 29.1 FEET 
AT COMITE. IN THE AMITE RIVER BASIN AT PORT VINCENT AND FRENCH 
SETTLEMENT...THE RIVER PEAKED AT ITS THIRD HIGHEST STAGE ON 
RECORD. AMONG ALL RAIN EVENTS THAT HAVE PLAGUED SOUTHEAST 
LOUISIANA IN THE PAST...ALLISON IS COMPARABLE TO THE MAY 1995 AND 
APRIL 1983 FLOOD EVENTS. 

ON THE 11TH THE LOW THAT WAS ONCE ALLISON ACCOMPLISHED A RARE 
TASK...DEVELOPMENT OVER LAND. THIS WAS MAINLY DUE TO A JET STREAK 
RIDING ALONG THE SUBTROPICAL JET TO ITS NORTH AND NORTHEAST 
ENHANCING ITS OUTFLOW...WHICH IN TURN LED TO A STRONGER SURFACE 
LOW. BY 1 AM CDT ON THE 11TH... THE CYCLONE REGAINED GALE-FORCE 
WINDS WHICH WERE OVERSPREADING THE MOUTH OF THE MISSISSIPPI RIVER 
AND THE BARRIER ISLANDS OF THE MISSISSIPPI COAST. BY 7 AM 
CDT...AN EYE-LIKE FEATURE DEVELOPED ON RADAR WHILE THE SYSTEM 
ENTERED SOUTHWEST MISSISSIPPI. SUSTAINED WINDS INCREASED TO 45 
MPH...WITH GUSTS TOWARDS 60 MPH IN ITS MAIN INFLOW BAND EAST OF 
THE CENTER. AS IT EDGED FARTHER INLAND THAT AFTERNOON...IT 
FINALLY WEAKENED AND LOST THE EYE. 

SEVERE WEATHER BECOME MORE FREQUENT IN THE VICINITY OF ALLISON 
DUE TO STRONGER WINDS ALOFT INTERACTING WITH ITS CIRCULATION. TWO 
TORNADO TOUCHDOWNS WERE REPORTED BY THE BILOXI POLICE DEPARTMENT 
AT 5:35 AM CDT ON THE 11TH. AN F1 TORNADO TOUCHED DOWN IN GEORGE 
COUNTY MISSISSIPPI AROUND 7 AM CDT THE 11TH...DESTROYING A 
MANUFACTURED HOME AND CAUSING MAJOR DAMAGE TO A TWO-STORY HOME. 

AN F0 TORNADO TOUCHED DOWN IN MOBILE COUNTY ALABAMA AROUND 7:30 
AM CDT ON THE 11TH...AND REMAINED ON THE GROUND FOR 2.5 MILES. 
SEVERAL HOMES SAW DAMAGE WHEN TREES FELL UPON THEM WHILE OTHER 
HOUSES SUFFERED ROOF DAMAGE FROM HIGH WINDS. TWO TORNADOES WERE 
SPOTTED IN MADISON COUNTY FLORIDA BETWEEN 7:56 AND 9:38 PM EDT ON 
THE 11TH...WITH A THIRD TOUCHING DOWN 3 MILES EAST OF TALLAHASSEE 
AT 11:05 PM EDT. ON THE AFTERNOON OF THE 12TH...WITNESSES 
REPORTED SEEING A FUNNEL CLOUD TOUCH DOWN IN HEPHZIBAH GEORGIA. 

HEAVY RAINS FELL ACROSS THE EASTERN GULF COAST AS WELL...BUT WITH 
MUCH LESS SEVERITY AS THE LOW WAS MOVING WITH A 13 MPH FORWARD 
MOVEMENT.  EVEN SO...GULFPORT MISSISSIPPI RECORDED 11.99 INCHES 
OF RAIN BY 1 PM ON THE 11TH...MUCH OF IT IN THE PRECEDING 24 
HOURS. BEFORE THE CENTER EMERGED OUT OF MISSISSIPPI...ALLISON'S 
MAIN RAIN BAND HAD MOVED EASTWARD TO NEAR TALLAHASSEE FLORIDA... 
AND THEN STALLED. DOPPLER RADAR ESTIMATES EXCEEDED TEN INCHES 
JUST TO THE WEST OF THE FLORIDA CAPITAL...WITH TALLAHASSEE 
NETTING 9.86 INCHES BETWEEN THE MORNING OF THE 11TH AND 12TH. 

ALLISON TRACKED OUT OF MISSISSIPPI INTO SOUTHERN ALABAMA ON THE 
AFTERNOON ON THE 11TH...CONTINUING ITS QUICK EAST-NORTHEAST 
MOVEMENT. ITS FORWARD MOTION BEGAN TO SLOW AS A BLOCKING RIDGE OF 
HIGH PRESSURE WAS SITTING OFF THE COAST OF NEW ENGLAND...BRINGING 
THE SYSTEM TO A HALT AS IT WAS NEARING THE ATLANTIC COAST NEAR 
WILMINGTON ON THE MORNING OF THE 14TH. 

THE HEAVIEST RAINFALL WITH THE LOW WAS SHIFTING TO ITS NORTHWEST 
QUADRANT EACH NIGHT AS IT TRACKED THROUGH THE SOUTHEAST. HEAVY 
RAINS FELL IN GEORGIA... WHERE SILOAM PICKED UP 5.75 INCHES IN 
THE 24 HOUR PERIOD ENDING ON THE MORNING OF THE 13TH. ON THE 
13TH...A LOCAL FIRE DEPARTMENT REPORTED ITS RAIN GAGE OVERFLOWED 
WITH OVER 12 INCHES OF RAIN IN 14 HOURS JUST TO THE EAST OF 
COLUMBIA SOUTH CAROLINA. 

SEVERE WEATHER BROKE OUT IN GEORGIA...SOUTH CAROLINA...AND 
SOUTHERN NORTH CAROLINA ON THE 13TH AND 14TH. HAIL FELL IN 
MOUNTAIN REST... LANDRUM...AND ANDERSON SOUTH CAROLINA. SQUALLY 
WINDS DOWNED TREES AND POWER LINES THROUGHOUT THE REGION. 
DANGEROUS RIP CURRENTS DEVELOPED IN THE OUTER BANKS OF NORTH 
CAROLINA AS THE WINDS BECAME PERPENDICULAR TO THE SHORE. 

AS THE SYSTEM SLOWED TO A CRAWL IN NORTH CAROLINA...FLOODING 
BECAME A MAJOR PROBLEM IN THAT STATE. EVEN AFTER ALLISON BEGAN 
MOVING NORTH-NORTHEAST AROUND THE HIGH PRESSURE RIDGE TO ITS 
EAST...INTO VIRGINIA...THE RAIN KEPT ON FALLING ACROSS NORTHEAST 
NORTH CAROLINA IN ITS SOUTHWESTERN QUADRANT ...PROLONGING THE 
FLOOD EVENT INTO THE 16TH. ASKEWVILLE REPORTED 8.50 INCHES OF 
RAIN WITHIN A 16 HOUR PERIOD ON THE 15TH. FLOODED ROADS WERE 
REPORTED IN ITS VICINITY...ALONG WITH WATER INVADING CARS AND 
AREA HOMES. BETWEEN THE 12TH AND THE 16TH...THE DOPPLER RADAR IN 
MOREHEAD CITY ESTIMATED UP TO 21 INCHES OF RAIN FELL ACROSS THE 
BERTIE/HERTFORD COUNTY BORDER...AS WELL AS HALIFAX AND MARTIN 
COUNTIES IN NORTH CAROLINA. 

AS THE CENTER MOVED NORTH-NORTHWEST ALONG THE EASTERN EDGE OF THE 
DELMARVA PENINSULA...A COLD FRONT MOVED IN FROM THE WEST. THIS 
ALLOWED MOISTURE FROM ALLISON TO POOL ALONG THE FRONT TO THE 
NORTH OF THE CENTER...SETTING THE STAGE FOR HEAVY RAINS ACROSS 
THE NORTHERN MID-ATLANTIC AND SOUTHERN NEW ENGLAND. SOUTHEAST 
PENNSYLVANIA SAW TORRENTS OF RAIN DURING THE AFTERNOON AND 
EVENING OF THE 16TH...WILLOW GROVE NAVAL AIR STATION RECORDED 
8.47 INCHES OF RAIN MAINLY IN THE EIGHT HOUR PERIOD BETWEEN 2 AND 
10 PM EDT. ULTIMATELY...WILLOW GROVE RECEIVED 10.16 INCHES WHILE 
CHANFONT RECORDED 10.17 INCHES FOR THE 24 HOUR PERIOD ENDING THE 
MORNING OF THE 17TH. 

AS THE SYSTEM PARALLELED THE COAST OFF THE NORTHEAST...RAINFALL 
AMOUNTS OF 2 TO 3 INCHES SOAKED PORTIONS OF NEW JERSEY...SOUTHERN 
NEW YORK...CONNECTICUT...MASSACHUSETTS...AND RHODE ISLAND. THE 
LAST OF THE RAIN ASSOCIATED WITH ALLISON LEFT EASTERN MAINE 
DURING THE EARLY MORNING OF THE 18TH AS THE CYCLONE ACCELERATED 
OFF TO THE EAST-NORTHEAST. ACCORDING TO PRESS REPORTS...43 PEOPLE 
PERISHED DURING ALLISON...MAINLY DUE TO FLOODING. DAMAGE TO THE 
HOUSTON AREA ALONE TOTALED 2.14 BILLION DOLLARS. 

THE INFORMATION IN THIS FINAL STORM SUMMARY WAS MADE UP OF A 
COMPILATION OF STORM AND RAINFALL SUMMARIES FROM THE HOUSTON/ 
GALVESTON...LAKE CHARLES...SLIDELL...MOBILE...WAKEFIELD... AND 
MOUNT HOLLY OFFICES...IN ADDITION TO THE PREVIOUS 47 STORM 
SUMMARIES ISSUED BY THIS OFFICE. THE NATIONAL HURRICANE CENTER 
PROVIDED AN EARLY VERSION OF ITS PRELIMINARY STORM REPORT FOR 
REFERENCE IN PROVIDING A HISTORY OF ALLISON'S FORMATION. 

THIS WILL BE THE LAST STORM SUMMARY TO BE ISSUED ON ALLISON FROM 
THE HYDROMETEOROLOGICAL PREDICTION CENTER. 
  

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