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 599 
 WTNT42 KNHC 130248
 TCDAT2
 TROPICAL STORM JULIA DISCUSSION NUMBER   3
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL122010
 1100 PM AST SUN SEP 12 2010
  
 INFRARED AND MICROWAVE SATELLITE IMAGERY SHOW THAT THE CENTER OF
 THE CYCLONE IS LOCATED NEAR THE EASTERN EDGE OF A CURVED BAND OF
 CONVECTION THAT WRAPS AROUND THE WESTERN SEMICIRCLE OF THE SYSTEM.
 SUBJECTIVE DVORAK INTENSITY ESTIMATES ARE 35 KT FROM TAFB AND 30 KT
 FROM SAB.  OBJECTIVE DVORAK ESTIMATES FROM UW/CIMMS ARE SLIGHTLY
 HIGHER.  A BLEND OF THESE ESTIMATES SUPPORT AN UPGRADE OF THE
 DEPRESSION TO A 35-KT TROPICAL STORM...THE TENTH OF THE 2010 
 ATLANTIC HURRICANE SEASON.
  
 THE EASTERLY SHEAR IS EXPECTED TO WEAKEN DURING THE NEXT 12 HOURS
 AND IS FORECAST TO REMAIN LIGHT OVER THE NEXT COUPLE OF DAYS.
 DURING THAT TIME JULIA WILL BE TRAVERSING WARM WATER AND AS A
 RESULT...STEADY STRENGTHENING IS ANTICIPATED.  THE SHIPS...LGEM...
 AND GFDL MODELS ALL BRING JULIA TO HURRICANE STATUS WITHIN TWO DAYS
 AND THE NHC FORECAST IS IN GOOD AGREEMENT.  THEREAFTER...JULIA WILL
 BE MOVING OVER SLIGHTLY COOLER SEA SURFACE TEMPERATURES AND INTO AN
 AREA OF INCREASING SOUTHWESTERLY SHEAR TO THE EAST OF AN
 UPPER-LEVEL LOW/TROUGH BETWEEN 30W AND 40W.  IT IS A BIT SURPRISING
 GIVEN THESE NEGATIVE FACTORS THAT THE INTENSITY GUIDANCE SHOWS
 LITTLE...IF ANY...WEAKENING.  BECAUSE OF THAT...THE OFFICIAL
 FORECAST WILL KEEP JULIA AT 65 KT AT DAYS 3-5 FOR NOW.
  
 THE CENTER OF JULIA WAS RELOCATED A LITTLE EAST OF THE PREVIOUS
 ADVISORY POSITION BASED ON THE EARLIER MICROWAVE DATA.  THE INITIAL
 MOTION ESTIMATE IS 285/10.  THE TRACK FORECAST REASONING REMAINS
 THE SAME AS THE PREVIOUS ADVISORY.  JULIA IS FORECAST TO MOVE
 WEST-NORTHWESTWARD AROUND THE SOUTHWESTERN SIDE OF A MID-LEVEL
 RIDGE THAT EXTENDS FROM AFRICA WESTWARD INTO THE EASTERN ATLANTIC. 
 IN A COUPLE OF DAYS...THE CYCLONE IS FORECAST TO TURN NORTHWESTWARD
 TOWARD A WEAKNESS IN THE RIDGE.  MOST OF THE GUIDANCE INDICATES A
 TURN BACK TOWARD THE WEST-NORTHWEST LATE IN THE PERIOD AS JULIA
 MOVES AROUND THE NORTH SIDE OF AN UPPER-LEVEL LOW THAT CUTS OFF
 NEAR 40W.  THE OFFICIAL FORECAST TRACK IS GOOD AGREEMENT WITH THE
 PREVIOUS ADVISORY AND A BLEND OF THE LATEST RUNS OF THE GFS...
 UKMET...GFDL...HWRF...AND ECMWF MODELS.
   
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      13/0300Z 13.5N  23.5W    35 KT
  12HR VT     13/1200Z 14.0N  25.3W    45 KT
  24HR VT     14/0000Z 14.9N  27.6W    50 KT
  36HR VT     14/1200Z 15.9N  29.5W    55 KT
  48HR VT     15/0000Z 17.1N  31.1W    65 KT
  72HR VT     16/0000Z 20.9N  35.1W    65 KT
  96HR VT     17/0000Z 24.5N  41.0W    65 KT
 120HR VT     18/0000Z 27.5N  46.5W    65 KT
  
 $$
 FORECASTER BROWN
  
 
 
 069 
 WTNT41 KNHC 130248
 TCDAT1
 HURRICANE IGOR DISCUSSION NUMBER  20
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
 1100 PM AST SUN SEP 12 2010
  
 IGOR HAS CONTINUED TO INTENSIFY WITH VERY COLD CLOUD TOPS...LOWER
 THAN -70C...WRAPPING AROUND THE SLOWLY-SHRINKING EYE DURING THE
 PAST SEVERAL HOURS.  ALTHOUGH THE TOPS HAVE RECENTLY WARMED A
 LITTLE OVER THE SOUTHWEST QUADRANT...SUBJECTIVE DVORAK ESTIMATES
 FROM TAFB AND SAB ARE T6.5/127 KT AND OBJECTIVE ESTIMATES FROM THE
 ADT AND HIE ALGORITHMS ARE T6.6/130 KT AND T6.9/137 KT...
 RESPECTIVELY.  AS A COMPROMISE...THE INITIAL INTENSITY IS SET AT
 130 KT.  AN EXPERIMENTAL PRODUCT FROM UW-CIMSS RUN AT NHC INDICATES
 THAT THERE IS A 42 PERCENT CHANCE OF SECONDARY EYEWALL FORMATION
 WITHIN THE NEXT 12 HOURS...AND A 90 PERCENT CHANCE WITHIN 24 HOURS.
 THE PERIOD OF RAPID INTENSIFICATION IS LIKELY TO END SOON...BUT THE
 OFFICIAL FORECAST FOLLOWS THE SHIPS/LGEM MODELS BY SHOWING IGOR
 REACHING THE THRESHOLD OF CATEGORY 5 STRENGTH BEFORE THAT HAPPENS.
 SOME WEAKENING IS THEN INDICATED AFTER EYEWALL REPLACEMENT
 OCCURS...BUT IGOR IS EXPECTED TO REMAIN A POWERFUL HURRICANE FOR
 SEVERAL DAYS.  AS IS ALWAYS THE CASE WITH STRONG HURRICANES LIKE
 IGOR...FLUCTUATIONS IN INTENSITY ARE LIKELY BUT ARE ALSO DIFFICULT
 TO FORECAST.
  
 THE MEAN MOTION IS 270/11...BUT IGOR HAS BEEN WOBBLING A LITTLE TO
 THE SOUTH OF THAT VECTOR.  IGOR IS MOVING INTO AN ENVIRONMENT WHERE
 THE STEERING FLOW IS BECOMING INCREASINGLY DICTATED BY A LARGE
 LONGWAVE TROUGH OVER THE WESTERN ATLANTIC...AND THE HURRICANE IS
 EXPECTED TO RESPOND BY TURNING TOWARD THE WEST-NORTHWEST WITHIN THE
 NEXT 24-48 HOURS.  SOME OF THE GLOBAL MODELS INDICATE THAT THE
 TROUGH COULD FLATTEN A LITTLE BY DAY 3 AND ALLOW THE SUBTROPICAL
 RIDGE TO BUILD WESTWARD...BUT AT THIS TIME THERE IS TOO MUCH
 DISAGREEMENT TO INDICATE A WESTWARD TURN IN THE FORECAST.  THE
 TRACK GUIDANCE HAS SHIFTED A LITTLE TO THE NORTH...BUT THE NEW
 OFFICIAL FORECAST STILL LIES ON THE SOUTHERN SIDE OF THE GUIDANCE
 ENVELOPE UNTIL IT BECOMES CLEAR THAT IGOR IS READY TO TURN.  THIS
 SOLUTION ALSO GIVES CREDENCE TO THE MORE SOUTHERN ECMWF AND UKMET
 MODELS.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      13/0300Z 17.6N  47.8W   130 KT
  12HR VT     13/1200Z 17.8N  49.5W   140 KT
  24HR VT     14/0000Z 18.2N  51.3W   135 KT
  36HR VT     14/1200Z 18.9N  53.0W   130 KT
  48HR VT     15/0000Z 19.8N  54.6W   125 KT
  72HR VT     16/0000Z 22.0N  57.5W   125 KT
  96HR VT     17/0000Z 24.0N  60.0W   120 KT
 120HR VT     18/0000Z 27.0N  63.0W   110 KT
  
 $$
 FORECASTER BERG
  
 
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