Tropical Storm OMAR

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TROPICAL STORM OMAR DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL152008
1100 PM EDT FRI OCT 17 2008

THE CONVECTION ASSOCIATED WITH OMAR HAS DECREASED AGAIN THIS
EVENING...WITH THE REMAINING CONVECTION IN A RAGGED BAND WELL
SOUTHEAST OF THE CENTER.  HOWEVER...AN AMSU OVERPASS NEAR 20Z SHOWS
THAT THE CYCLONE HAS A DEEP-LAYER WARM CORE...WHICH SSM/I IMAGERY
SHOWS IS SURROUNDED BY MID/UPPER-LEVEL DRY/COOL AIR.  A QUIKSCAT
OVERPASS NEAR 22Z SHOWS A SIGNIFICANT DECREASE IN THE WINDS FROM
THE EARLIER OVERPASS...WITH NO RELIABLE-LOOKING VECTORS SHOWING
WINDS OF MORE THAN 45 TO 50 KT.  AMSU INTENSITY ESTIMATES AT 20Z
WERE 55 TO 60 KT...WHILE REGULAR SATELLITE INTENSITY ESTIMATES WERE
TROPICAL 65 KT FROM TAFB AND SUBTROPICAL 35-40 KT FROM SAB.  THE
INITIAL INTENSITY IS DECREASED TO 55 KT BASED ON AN AVERAGE OF
THESE ESTIMATES...AND THIS MIGHT BE A BIT GENEROUS.  THE INITIAL
WIND RADII HAVE BEEN REVISED BASED ON THE QUIKSCAT DATA.

OMAR HAS SLOWED ITS FORWARD MOTION DURING THE PAST FEW HOURS AND THE
INITIAL MOTION IS NOW 040/14.  IN THE SHORT TERM...OMAR SHOULD
CONTINUE A GENERAL NORTHEASTWARD MOTION BETWEEN A DEEP-LAYER RIDGE
OVER THE EAST CENTRAL ATLANTIC AND THE MID-LATITUDE WESTERLIES TO
THE NORTH.  THE FIRST 48 HR OF THE FORECAST IS DOWN THE MIDDLE OF
THE FAIRLY TIGHTLY CLUSTERED GUIDANCE.  AFTER 48 HR...THE GFS...
ECMWF...UKMET..AND HWRF SHOW OMAR BEING ABSORBED INTO A BAROCLINIC
LOW MOVING EASTWARD FROM THE WESTERN ATLANTIC...THIS AFTER OMAR
TURNS MORE NORTHWARD IN ADVANCE OF THE LOW.  THE NOGAPS...THE
BAMD...THE BAMM...AND THE LBAR FORECAST OMAR TO TURN EASTWARD AND
EVENTUALLY SOUTHWARD AROUND THE EASTERN ATLANTIC RIDGE.  THE NEW
FORECAST TRACK WILL LEAN MORE TOWARD THE GFS/UKMET/ECMWF/HWRF
SOLUTION...CALLING FOR OMAR TO TURN MORE NORTHWARD AFTER 72 HR. 
HOWEVER...OUT OF DEFERENCE TO THE OTHER MODELS AND THE PREVIOUS
FORECAST...THE NEW FORECAST IS NOT AS FAR NORTH AS THAT OF THOSE
MODELS.
 
OMAR IS MOVING OVER SEA SURFACE TEMPERATURES OF LESS THAN 26C...AND
IS LIKELY TO ENCOUNTER INCREASING WESTERLY VERTICAL WIND SHEAR
AFTER 24 HR.  WHILE ANOTHER CONVECTIVE FLARE-UP CANNOT BE RULED
OUT...THESE CONDITIONS INDICATE THE STORM SHOULD GENERALLY WEAKEN
THROUGH THE FORECAST PERIOD.  THIS IS SUPPORTED BY ALL THE
INTENSITY GUIDANCE.  OMAR SHOULD BECOME EXTRATROPICAL IN 48-72 HR
AS IT MERGES WITH A FRONTAL SYSTEM OVER THE NORTH ATLANTIC.  IF THE
GFS/UKMET/ECMWF/HWRF SCENARIO VERIFIES...OMAR WILL BE ABSORBED BY
THE WARM FRONT OF THE ONCOMING BAROCLINIC LOW...WITH THE FORMER
TROPICAL CYCLONE SHOWING LITTLE RE-INTENSIFICATION AS AN
EXTRATROPICAL LOW. THIS IS REFLECTED IN THE 48-96 HR PORTION OF THE
INTENSITY FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0300Z 31.5N  52.8W    55 KT
 12HR VT     18/1200Z 33.3N  51.1W    50 KT
 24HR VT     19/0000Z 35.1N  48.7W    45 KT
 36HR VT     19/1200Z 36.7N  46.2W    40 KT
 48HR VT     20/0000Z 38.3N  43.2W    35 KT...BECOMING EXTRATROPICAL
 72HR VT     21/0000Z 39.5N  39.0W    35 KT...EXTRATROPICAL
 96HR VT     22/0000Z 42.0N  36.0W    35 KT...EXTRATROPICAL
120HR VT     23/0000Z...ABSORBED BY FRONTAL SYSTEM
 
$$
FORECASTER BEVEN
 
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