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Monday, October 29, 2012

Hurricane Sandy Developing Precipitation Eyewall

 
 
 
000
WTNT43 KNHC 291443
TCDAT3

HURRICANE SANDY DISCUSSION NUMBER  29
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL182012
1100 AM EDT MON OCT 29 2012

SANDY IS MAINTAINING A SMALL AREA OF DEEP CONVECTION NEAR THE
CENTER...WITH BOTH AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT DATA
AND VARIOUS MICROWAVE SATELLITE DATA INDICATING A 20 N MI DIAMETER
EYE HAS DEVELOPED SINCE THE PREVIOUS ADVISORY. MAXIMUM 700 MB
FLIGHT-LEVEL WINDS HAVE BEEN 94 KT IN THE SOUTHERN QUADRANT...AND
SFMR-ADJUSTED SURFACE WINDS OF 80-83 KT HAVE BEEN OBSERVED IN THE
SOUTHWESTERN QUADRANT MORE THAN 90 N MI FROM THE CENTER.  THE
AIRCRAFT DATA ALSO INDICATE THAT THE CENTRAL PRESSURE HAS FALLEN A
LITTLE...TO ABOUT 943 MB.  BASED ON THE LATEST RECONNAISSANCE
DATA...THE INITIAL INTENSITY HAS BEEN INCREASED TO 80 KT.

RECONNAISSANCE CENTER FIXES INDICATE THAT SANDY HAS BEEN GRADUALLY
TURNING TO THE LEFT AND IS NOW MOVING NORTH-NORTHWESTWARD OR ABOUT
330/16 KT. THE LATEST RECON FIXES HAVE BEEN FALLING ON THE PREVIOUS
FORECAST TRACK...AND SO HAVE THE LATEST 12Z NHC FORECAST MODELS.
THEREFORE...NO SIGNIFICANT CHANGES TO THE ADVISORY PREVIOUS TRACK
OR REASONING ARE REQUIRED. SANDY IS NOW LOCATED NORTH OF THE AXIS
OF A STRONG NEGATIVELY TILTED MID-/UPPER-LEVEL TROUGH...AND THE
HURRICANE SHOULD TURN NORTHWESTWARD VERY SOON. LANDFALL ALONG OR
JUST SOUTH OF THE SOUTHERN NEW JERSEY COAST IS EXPECTED LATE THIS
EVENING...AT WHICH TIME A TURN TO THE WEST-NORTHWEST IS EXPECTED.
AFTER MOVING INLAND OVER THE MID-ATLANTIC STATES A DECREASE IN
FORWARD SPEED IS EXPECTED. BY 48 HOURS...THE POST-TROPICAL CYCLONE
IS FORECAST TO MOVE NORTHWARD AND THEN NORTHEASTWARD. THE OFFICIAL
NHC FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY TRACK...AND
LIES CLOSE TO A BLEND OF THE CONSENSUS MODELS TV15 AND TVCN.

SANDY IS CURRENTLY TRAVERSING A NARROW RIDGE OF WARM SSTS AROUND
27C...WHICH ARE ASSOCIATED WITH THE GULF STREAM. THIS EXTRA
LOW-LEVEL HEAT INPUT HAS LIKELY CONTRIBUTED TO THE RECENT INCREASE
IN CONVECTION AROUND THE EYE. HOWEVER...SANDY WILL BE MOVING OVER
THE NORTH WALL OF THE GULFSTREAM WITHIN THE NEXT 3 HOURS...WHICH
WILL BRING A HALT TO ANY SIGNIFICANT INNER-CORE CONVECTIVE
DEVELOPMENT. HOWEVER...THIS SHOULD HAVE LITTLE IMPACT ON THE
OVERALL INTENSITY OR THE SIZE OF THE EXTREMELY LARGE WIND FIELD
THAT IS NOW MORE THAN 1000 N MI IN DIAMETER. AT THE MOMENT...
HURRICANE FORCE WINDS ARE ONLY OCCURRING IN THE SOUTHWEST
QUADRANT...BUT MODEL GUIDANCE SUGGESTS THAT THESE COULD SPREAD INTO
THE NORTHERN SEMICIRCLE BEFORE LANDFALL.

SURFACE DATA INDICATE THAT WELL-DEFINED WARM AND COLD FRONTS LIE
VERY NEAR THE CENTER OF SANDY...AND THE COMBINATION OF COLDER OCEAN
WATER AND NEARBY FRONTAL SYSTEMS ARE EXPECTED TO RESULT IN
EXTRATROPICAL TRANSITION BEFORE THE CENTER OF THE CYCLONE REACHES
THE COAST.  HOWEVER...THIS TRANSFORMATION WILL NOT DIMINISH THE
OVERALL IMPACTS FROM WINDS TO HURRICANE STRENGTH...LIFE-THREATENING
STORM SURGE... AND FLOODING RAINS ASSOCIATED WITH THIS DANGEROUS
WEATHER SYSTEM.  BASED ON THE GLOBAL MODELS...THE CYCLONE SHOULD
WEAKEN FAIRLY RAPIDLY AFTER LANDFALL.

INTERESTS ARE REMINDED NOT TO FOCUS ON THE CENTER OR THE EXACT
FORECAST TRACK OF THIS SYSTEM...SINCE STRONG WINDS COVER AN AREA
SEVERAL HUNDRED MILES ACROSS...AND THE HIGHEST WINDS WILL NOT
NECESSARILY BE NEAR THE CENTER...ESPECIALLY JUST A FEW HUNDRED FEET
ABOVE THE GROUND.

AS NOTED IN PREVIOUS ADVISORIES...TO AVOID A HIGHLY DISRUPTIVE
CHANGE FROM TROPICAL TO NON-TROPICAL WARNINGS WHEN SANDY BECOMES
POST-TROPICAL...THE WIND HAZARD NORTH OF THE TROPICAL STORM WARNING
AREA WILL CONTINUE TO BE CONVEYED THROUGH HIGH WIND WATCHES AND
WARNINGS ISSUED BY LOCAL NATIONAL WEATHER SERVICE OFFICES.

FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z 37.5N  71.5W   80 KT  90 MPH
 12H  30/0000Z 39.0N  74.0W   80 KT  90 MPH...POST-TROP/EXTRATROP
 24H  30/1200Z 39.9N  76.7W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  31/0000Z 40.4N  77.9W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  31/1200Z 41.5N  77.2W   35 KT  40 MPH...POST-TROP/EXTRATROP
 72H  01/1200Z 44.5N  75.6W   30 KT  35 MPH...POST-TROP/EXTRATROP
 96H  02/1200Z 45.9N  72.7W   25 KT  30 MPH...POST-TROP/EXTRATROP
120H  03/1200Z 47.5N  68.5W   20 KT  25 MPH...POST-TROP/EXTRATROP

$$
FORECASTER STEWART
 
 
For more coverage and commentary on Hurricane Sandy VISIT:
www,thenewsunit.com 

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