481 
 WTPA45 PHFO 240247
 TCDCP5
 
 TROPICAL STORM HILDA DISCUSSION NUMBER   7
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP112009
 500 PM HST SUN AUG 23 2009
 
 HILDA CONTINUES TO GRADUALLY INTENSIFY...DESPITE THE PRESENCE OF
 MODERATE...EASTERLY VERTICAL WIND SHEAR. AN ORGANIZED BAND OF DEEP
 CONVECTION ALONG THE SOUTHERN AND EASTERN SIDE OF HILDA HAS
 PERSISTED THROUGH THE DAY AND HAS RESULTED IN THE DVORAK CI NUMBERS
 FROM ALL THE FIX AGENCIES AND ADT TO INCREASE BY AT LEAST 0.5 IN
 THE PAST SIX HOURS. IN ADDITION...UW-CIMSS AMSU INTENSITY ALGORITHM
 HAS DETECTED A STRENGTHENING WARM CORE ALOFT. THUS...THE INITIAL
 INTENSITY HAS BEEN RAISED TO 50 KT.
 
 THE INITIAL MOTION IS 280/10...ESSENTIALLY UNCHANGED FROM SIX HOURS
 AGO. HILDA IS BEING STEERED IN A GENERAL WESTERLY DIRECTION WITHIN
 A DEEP EASTERLY FLOW CREATED BY AN UPPER LEVEL ANTICYCLONE TO THE
 NORTH ALONG 20N AND A STRONG SURFACE HIGH FARTHER NORTH. THE
 EASTERLY FLOW ALOFT IS CREATING MODERATE...EASTERLY VERTICAL WIND
 SHEAR AROUND 15 KT AND IS INHIBITING OUTFLOW ALONG THE NORTHEAST
 QUADRANT OF HILDA. IN SPITE OF THESE MARGINAL CONDITIONS...HILDA
 HAS MANAGED TO INTENSIFY TODAY.
 
 HILDA IS FORECAST TO INTENSIFY SLIGHTLY AND CONTINUE ON A TRACK THAT
 IS JUST NORTH OF DUE WEST THROUGH THE NEXT 48 HOURS AS RIDGING AT
 THE SURFACE AND ALOFT REMAINS TO THE NORTH. THE FORECAST TRACK IS
 ESSENTIALLY DOWN THE MIDDLE OF A TIGHTLY CLUSTERED GUIDANCE
 ENVELOPE DURING THE FIRST 36 HOURS AND IS ALONG THE NORTHERN
 PORTION OF THE ENVELOPE BY 48 HOURS. WITH SST VALUES HOVERING
 AROUND 27C AND WINDS ALOFT CHANGING LITTLE...A GRADUAL 
 INTENSIFICATION TREND IS FORECAST TO PERSIST THROUGH 48 HOURS. THE 
 FORECAST INTENSIFIES HILDA SLIGHTLY FASTER THAN THE PREVIOUS PACKAGE 
 AND FOLLOWS ICON RELATIVELY CLOSELY.
 
 BY 72 HOURS...THE TRACK OF HILDA SHIFTS TO THE DUE WEST AS RIDGING
 ALOFT STRENGTHENS OVER AND TO THE WEST OF THE HAWAIIAN ISLANDS AS A
 DEEP UPPER TROUGH DIGS FAR EAST OF THE ISLANDS BETWEEN 150W AND
 140W. THE DYNAMIC MODELS AND SHIPS FORECAST THE WIND SHEAR TO SHIFT
 MORE NORTHERLY BUT RELAX SLIGHTLY AT THIS TIME. DUE TO THE
 UNCERTAINTY OF THESE EFFECTS...THE FORECAST INTENSIFICATION HAS
 BEEN HALTED AFTER 48 HOURS...WITH HILDA REMAINING AT A HIGH END
 TROPICAL STORM. HOWEVER...IT WOULD NOT BE SURPRISING IF HILDA
 INTENSIFIES FURTHER AFTER 48 HOURS AND BECOMES A HURRICANE AS A
 GOOD NUMBER OF THE INTENSITY MODELS PREDICT. THE TRACK FORECAST AT
 72 HOURS AND BEYOND IS SLIGHTLY TO THE RIGHT OF AN INCREASINGLY
 DIVERGENT GUIDANCE ENVELOPE.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      24/0300Z 14.2N 143.2W    50 KT
  12HR VT     24/1200Z 14.6N 144.6W    50 KT
  24HR VT     25/0000Z 15.0N 146.7W    55 KT
  36HR VT     25/1200Z 15.3N 148.7W    55 KT
  48HR VT     26/0000Z 15.4N 150.7W    60 KT
  72HR VT     27/0000Z 15.3N 154.2W    60 KT
  96HR VT     28/0000Z 15.2N 156.9W    60 KT
 120HR VT     29/0000Z 15.0N 160.0W    60 KT
  
 $$
 FORECASTER WROE