PNSHOU

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX 
530 PM CDT SAT JUL 12 2003

...HURRICANE/TROPICAL STORM PROBABILITIES...

NATIONAL HURRICANE CENTER ISSUES HURRICANE/TROPICAL STORM
PROBABILITIES /MIASPFAT(X)/ TO REALISTICALLY ASSESS THE THREAT OF
A PARTICULAR STORM AFFECTING YOUR COMMUNITY.  PROBABILITIES ARE 
DEFINED AS THE CHANCE IN PERCENT THAT THE CENTER OF THE STORM WILL 
PASS WITHIN 65 MILES OF SELECTED LOCATIONS.

FOR THE TEXAS COAST...PROBABILITIES WILL BE ISSUED FOR BROWNSVILLE...
CORPUS CHRISTI...PORT O CONNOR...GALVESTON...AND PORT ARTHUR.  NEARBY
LOUISIANA LOCATIONS ARE NEW IBERIA AND NEW ORLEANS.  ADDITIONALLY... 
IF THE STORM TRACK IS EXPECTED TO PARALLEL THE COAST...PROBABILITIES 
WILL BE ISSUED FOR POINTS OVER THE GULF.  OVER THE TEXAS COASTAL 
AREAS GULF POINTS WILL BE:  28N 93W /SOUTHEAST OF PORT ARTHUR...28N 
95W /SOUTHEAST OF FREEPORT/...27N 96W /SOUTHEAST OF CORPUS 
CHRISTI/...AND 25N 97W/SOUTHEAST OF BROWNSVILLE.  PROBABILITIES ARE 
PRIMARILY FOR LOCAL GOVERMENT DECISION MAKERS AND THOSE IN PRIVATE 
INDUSTRY WHO MUST TAKE EARLY PREVENTATIVE ACTION.  LOCAL EMERGENCY 
MANAGEMENT OFFICIALS USE THEM TO MAKE DECISIONS ON WHEN TO OPEN 
SHELTERS AND/OR BEGIN EVACUATION.  

PROBABILITIES ARE ISSUED FOUR TIMES DAILY...WHEN STORMS ARE IN
EXISTENCE...AROUND 5 AM...11 AM...5 PM...AND 930 PM AND ARE IN
A TABULAR FORM.

REMEMBER THE FOLLOWING POINTS WHEN USING THE PROBABILITIES...

  A.  IF YOU LIVE BETWEEN TWO LISTED POINTS...YOU MAY ESTIMATE YOUR
PROBABILITY BY AVERAGING THE TWO.

  B.  TO ASSESS YOUR THREAT...COMPARE YOUR PROBABILITY WITH THOSE OF
NEIGHBORING LOCATIONS...IF YOU HAVE THE HIGHEST VALUE...YOUR THREAT 
IS THE GREATEST.

  C.  YOU SHOULD BE SENSITIVE TO INCREASING VALUES FROM ONE ADVISORY 
TO THE NEXT.  INCREASING VALUES INDICATE A GREATER RISK THAN THOSE 
THAT REMAIN THE SAME OR DECREASE.

WHEN A HURRICANE/TROPICAL STORM IS 36-72 HOURS FROM LANDFALL
PROBABILITIES ARE QUITE LOW.  VALUES INCREASE RAPIDLY AS THE STORM
GETS CLOSER THAN 36 HOURS.  IF A STORM IS FORECAST TO BE DIRECTLY
OVER YOUR LOCATION IN 72 HOURS THE MAXIMUM PROBABILITY IS ONLY 10
PERCENT.  PROBABILITIES ARE LOW OUT TO 72 HOURS DUE TO FORECAST
ERRORS WHICH MAY OCCUR THROUGH A LONG PERIOD OF TIME.  AT 48 HOURS
FROM PREDICTED LANDFALL THE MAXIMUM IS 13 TO 18 PERCENT.  AT 36 HOURS
MAXIMUM IS 20 TO 25 PERCENT.  AT 24 HOURS THE MAXIMUM PROBABILITY IS
35 TO 45 PERCENT. AT 12 HOURS...THE MAXIMUM PROBABILITY IS 60 TO 70 
PERCENT.

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