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Hurricane OMAR (Text)

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HURRICANE OMAR DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL152008
1100 AM EDT WED OCT 15 2008
 
ON ITS FINAL LEG AROUND 11Z...AN AIR FORCE HURRICANE HUNTER AIRCRAFT
REPORTED A PEAK SFMR SURFACE WIND OF 70 KT IN THE NORTHWEST
QUADRANT OF OMAR'S EYEWALL. THIS WAS COINCIDENT WITH A NEARBY
DROPSONDE SURFACE WIND VALUE OF 68 KT...SO THE INTENSITY AT THE 12Z
SYNOPTIC TIME WAS INCREASED TO 70 KT. HOWEVER...SINCE THE LAST
RECON FLIGHT...THE EYE HAS BECOME EVIDENT IN VISIBLE SATELLITE
IMAGERY...AND ALSO IN THE SAN JUAN DOPPLER WEATHER RADAR DATA AT A
RANGE OF MORE THAN 200 NMI. SATELLITE INTENSITY ESTIMATES ARE A
CONSENSUS T4.5/77 KT FROM TAFB AND SAB...SO THE ADVISORY INTENSITY
HAS BEEN INCREASED TO 75 KT BASED ON THE IMPROVED SATELLITE AND
RADAR SIGNATURES.

THE INITIAL MOTION ESTIMATE IS 045/08. THERE IS NO SIGNIFICANT
CHANGE TO THE PREVIOUS TRACK FORECAST OR PHILOSOPHY. OMAR IS
BASICALLY ON THE PREVIOUS ADVISORY TRACK...AND THE NHC MODEL
GUIDANCE REMAINS TIGHTLY CLUSTERED ABOUT A NORTHEASTWARD MOTION
THROUGH THE NORTHERN LEEWARD ISLANDS AND THE VIRGIN ISLANDS IN
ABOUT 24 HOURS. AFTER THAT...OMAR IS EXPECTED TO ACCELERATE AS IT
GETS CAUGHT UP IN THE STRONG SOUTHWESTERLY FLOW ON THE EAST SIDE OF
A LARGE DEEPENING MID-TROPOSPHERIC TROUGH LOCATED OVER THE WESTERN
ATLANTIC. A PIECE OF THE TROUGH BREAKS OFF AND LIFTS OUT TO THE
NORTHEAST IN 72-96 HOURS...WHICH BRIEFLY WEAKENS THE STEERING FLOW.
AFTER THAT...HOWEVER...THE MID-LATITUDE WESTERLIES ARE FORECAST TO
INCREASE AHEAD OF A STRONGER LOW PRESSURE SYSTEM...WHICH IS
EXPECTED TO ACCELERATE OMAR TO THE EAST-NORTHEAST AT 35-40 KT. THE
OFFICIAL FORECAST TRACK WAS NUDGED A LITTLE TO THE LEFT OF THE
PREVIOUS TRACK AND REMAINS SLOWER THAN THE NHC MODEL CONSENSUS.
 
NOW THAT A DISTINCT EYE AND EYEWALL HAVE DEVELOPED...A GOOD CHIMNEY
EFFECT CAN BE ESTABLISHED AND OMAR COULD GO THROUGH A BRIEF PERIOD
OF RAPID INTENSIFICATION AGAIN. ONLY THE GFDL MODEL IS CALLING FOR
OMAR TO STRENGTHEN TO AT LEAST 90 KT. THE REMAINDER OF THE
INTENSITY GUIDANCE HOLDS OMAR BELOW 80 KT. BASED ON THE BETTER
DEFINED EYE FEATURE...AND THE FACT THAT OMAR IS A RELATIVELY LOW
SHEAR ENVIRONMENT AND OVER 29C AND WARMER SSTS...ADDITIONAL
INTENSIFICATION SIMILAR TO THE GFDL MODEL SEEMS QUITE REASONABLE.
IT ALSO ISN'T OUT OF THE QUESTION THAT OMAR COULD ACHIEVE MAJOR
HURRICANE STATUS JUST BEFORE THE CYCLONE REACHES THE NORTHERN
LEEWARD ISLANDS. HOWEVER...THE RAPID ENCROACHMENT OF DRY MID-LEVEL
AIR FROM THE NORTHWEST AS NOTED IN WATER VAPOR SATELLITE IMAGERY
PRECLUDES EXPLICITLY FORECASTING THAT INTENSITY AT THIS TIME SINCE
THAT DRY AIR COULD MAKE IT INTO THE INNER CORE REGION IN 12-18
HOURS AND WEAKEN THE HURRICANE.
 
ALTHOUGH THE OFFICIAL FORECAST KEEPS THE CENTER EAST OF PUERTO
RICO...ONLY A SLIGHT DEVIATION TO THE LEFT OF THE CURRENT MOTION
COULD REQUIRE CHANGING THE HURRICANE WATCH TO A HURRICANE WARNING
FOR THAT ISLAND.  ALSO...STRONGER WINDS...POSSIBLY ONE CATEGORY
HIGHER...CAN BE EXPECTED OVER HIGHER TERRAIN...ESPECIALLY ABOVE 500
FT ELEVATION.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/1500Z 15.2N  67.2W    75 KT
 12HR VT     16/0000Z 16.6N  65.9W    80 KT
 24HR VT     16/1200Z 19.1N  63.9W    90 KT...NRN LEEWARD ISLANDS
 36HR VT     17/0000Z 22.0N  61.8W    90 KT
 48HR VT     17/1200Z 24.7N  60.2W    85 KT
 72HR VT     18/1200Z 30.0N  56.5W    75 KT
 96HR VT     19/1200Z 37.0N  48.5W    65 KT
120HR VT     20/1200Z 45.0N  32.5W    55 KT...EXTRATROPICAL
 
$$
FORECASTER STEWART
 
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