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Tropical Storm OPHELIA


ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM OPHELIA DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL162011
1100 PM AST FRI SEP 23 2011
 
EASY COME...EASY GO.  AFTER STRENGTHENING EARLIER THIS AFTERNOON...
OPHELIA NOW APPEARS TO BE ON A WEAKENING TREND.  AN AIR FORCE
HURRICANE HUNTER AIRCRAFT INVESTIGATING THE SYSTEM MEASURED A
MAXIMUM 925-MB FLIGHT-LEVEL WIND OF 47 KT AND HAS YET TO MEASURE
ANY TROPICAL-STORM-FORCE WINDS FROM THE SFMR.  IN ADDITION...THE
LAST CENTRAL PRESSURE MEASURED BY THE PLANE WAS 1006 MB. 
HOWEVER...THE PLANE IS JUST GETTING READ TO SAMPLE THE DEEP
CONVECTION LOCATED ABOUT 100-200 N MI NORTHEAST OF THE LOW-LEVEL
CENTER...AND THE INITIAL INTENSITY IS ONLY BEING LOWERED TO 45 KT
FOR NOW UNTIL WE CAN GET DATA FROM THAT PART OF THE STORM.  STRONG
SOUTHWESTERLY SHEAR IS EXPECTED TO CONTINUE AFFECTING OPHELIA FOR
AT LEAST THE NEXT 3 DAYS.  AFTER THAT...THE POSITION OF THE CYCLONE
RELATIVE TO THE UPPER-LEVEL TROUGH TO ITS NORTHWEST WILL MEAN THE
DIFFERENCE BETWEEN A HOSTILE OR FAVORABLE ENVIRONMENT FOR
STRENGTHENING.  GIVEN THE UNCERTAINTY...IT IS NOT WORTH HAGGLING
OVER 5 OR 10 KT FROM DAY TO DAY...AND THE OFFICIAL FORECAST HOLDS
THE INTENSITY CONSTANT THROUGH 5 DAYS WITH THE UNDERSTANDING THAT
FLUCTUATIONS ARE LIKELY.

BASED ON RECENT FIXES FROM THE PLANE...THE CENTER OF OPHELIA IS
EITHER JUMPING AROUND OR IS BECOMING LESS WELL DEFINED.  A 12-HOUR
AVERAGE GIVES A MOTION OF 300/12.  OPHELIA IS FORECAST TO TURN
NORTHWESTWARD IN THE NEXT 12 HOURS OR SO AND SHOULD BEGIN TO
DECREASE IN FORWARD SPEED AS IT BECOMES BLOCKED BY THE MID-LEVEL
HIGH TO ITS NORTH.  THE GUIDANCE ENVELOPE HAS SHIFTED SOMEWHAT
SIGNIFICANTLY TO THE EAST WITH A SLOWER MOTION AND IS BOUNDED BY
THE WESTERNMOST ECMWF AND THE EASTERNMOST HWRF AND GFDL.  THE NEW
OFFICIAL FORECAST HAS BEEN SHIFTED EASTWARD AND LIES ON THE WESTERN
EDGE OF THE MAIN CLUSTER OF MODELS...CLOSE TO THE ECMWF.  IT SHOULD
BE NOTED THAT SOME OF THE MODELS ARE SHOWING A SLOW NORTHEASTWARD
MOTION BY DAY 5...BUT THAT SCENARIO IS NOT YET INDICATED BY THE
OFFICIAL FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0300Z 16.0N  54.5W   45 KT  50 MPH
 12H  24/1200Z 16.9N  56.1W   45 KT  50 MPH
 24H  25/0000Z 18.2N  58.0W   45 KT  50 MPH
 36H  25/1200Z 19.4N  59.7W   45 KT  50 MPH
 48H  26/0000Z 20.3N  61.1W   45 KT  50 MPH
 72H  27/0000Z 22.0N  63.5W   45 KT  50 MPH
 96H  28/0000Z 24.0N  64.5W   45 KT  50 MPH
120H  29/0000Z 26.0N  65.0W   45 KT  50 MPH
 
$$
FORECASTER BERG
 
NNNN


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Page last modified: Tuesday, 17-Jul-2012 13:44:06 UTC