992 
 WTNT45 KNHC 172032
 TCDAT5
 HURRICANE OMAR DISCUSSION NUMBER  18
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL152008
 500 PM EDT FRI OCT 17 2008
  
 OMAR HAS EXHIBITED A DISTINCT EYE FEATURE...ALBEIT EMBEDDED IN WEAK
 CONVECTION...IN BOTH CONVENTIONAL AND TRMM MICROWAVE IMAGERY. A
 SATELLITE INTENSITY ESTIMATE OF T4.0/65 KT SUPPORTS MAKING OMAR A
 HURRICANE AGAIN. THE 1601Z TRMM OVERPASS THAT DEPICTED A
 WELL-DEFINED CLOSED LOW- AND MID-LEVEL EYE FEATURE SUGGESTS THAT
 OMAR WAS LIKELY A HURRICANE AT 12Z AS WELL.
 
 THE INITIAL MOTION VECTOR IS 030/25. NOW THAT CONVECTION HAS STARTED
 TO WEAKEN...MAKING THE VERTICAL CIRCULATION MORE SHALLOW...THE
 FORWARD SPEED IS EXPECTED TO GRADUALLY DECREASE AS THE
 CORRESPONDING STEERING FLOW ALSO WEAKENS. AN UPPER-LEVEL SHORTWAVE
 TROUGH IS NOW PASSING DIRECTLY OVER OMAR...AND THIS FEATURE IS
 FORECAST TO CONTINUE LIFTING OUT QUICKLY TO THE NORTHEAST. BEHIND
 THE TROUGH...THE STEERING FLOW IS EXPECTED TO WEAKEN...WHICH SHOULD
 RESULT IN A CONTINUED GRADUAL DECREASE IN FORWARD SPEED FOR THE
 NEXT 48 HOURS. BY 72 HOURS...OMAR IS FORECAST TO TURN MORE EASTWARD
 WITHIN DEEP-LAYER WESTERLY FLOW IN ADVANCE OF THE NEXT EXTRATROPICAL
 STORM SYSTEM THAT IS EXPECTED TO EMERGE OFF OF THE U.S. EAST COAST
 ON SUNDAY-MONDAY. THIS LATTER SYSTEM IS FORECAST BY MOST OF THE
 GLOBAL MODELS TO MOVE EASTWARD AND GRADUALLY ABSORB OMAR IN 96 TO
 120 HOURS. THE OFFICIAL TRACK FORECAST IS SIMILAR IN FORWARD SPEED
 TO THE NHC MODEL CONSENSUS...BUT LIES TO THE LEFT OF THE MODEL
 CONSENSUS DUE TO A PERCEIVED SHARP SOUTHWARD TRACK BIAS AND TURN BY
 THE NOGAPS MODEL...ESPECIALLY AFTER 72 HOURS.
  
 THE 65-KT INTENSITY RECENTLY ACHIEVED BY OMAR IS EXPECTED TO BE
 SHORT-LIVED DUE TO THE LACK OF DEEP CONVECTION AND THE FACT THAT
 THE CYCLONE WILL BE MOVING OVER SUB-26C SSTS IN 12 HOURS...IF NOT
 SOONER. ALTHOUGH THE DEEP CONVECTION HAS BEEN DECAPITATED BY AN
 UPPER-LEVEL SHORTWAVE TROUGH THAT IS CURRENTLY PASSING OVER THE
 CYCLONE...ONCE THAT FEATURE MOVES AWAY FROM OMAR...A RE-FIRING OF
 SIGNIFICANT CONVECTION IS EXPECTED TO OCCUR LATER TONIGHT. FOR THAT
 REASON...THE INTENSITY IS NOT BEING FORECAST TO DECREASE TOO
 QUICKLY SIMPLY BASED ON THE CURRENT POOR SATELLITE SIGNATURE. IN
 THE LONGER TERM...HOWEVER...STEADY WEAKENING THROUGHOUT THE
 FORECAST PERIOD APPEARS LIKELY DUE TO DECREASING SSTS BENEATH THE
 CYCLONE AND INCREASING VERTICAL WIND SHEAR...ESPECIALLY BY 36 TO 48
 HOURS. THE OFFICIAL INTENSITY FORECAST IS IN BEST AGREEMENT WITH
 THE LGEM STATISTICAL MODEL AND THE HWRF DYNAMICAL MODEL.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      17/2100Z 31.2N  53.6W    65 KT
  12HR VT     18/0600Z 32.9N  52.2W    60 KT
  24HR VT     18/1800Z 34.9N  49.9W    55 KT
  36HR VT     19/0600Z 36.5N  47.3W    50 KT
  48HR VT     19/1800Z 38.0N  44.5W    45 KT...BECOMING EXTRATROPICAL
  72HR VT     20/1800Z 39.5N  39.0W    40 KT...EXTRATROPICAL
  96HR VT     21/1800Z 39.5N  34.0W    35 KT...EXTRATROPICAL
 120HR VT     22/1800Z...ABSORBED BY LARGER EXTRATROPICAL LOW
  
 $$
 FORECASTER STEWART