WDPN31 PGTW 190900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (RAI) WARNING NR 026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0N 110.7E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 184 NM SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE LATEST FIX CYCLE CONFIRMS THAT TYPHOON RAI IS PAST ITS PEAK AND
EMBARKING ON A PERMANENT WEAKENING TREND. RAPIDLY WARMING TOPS AND
INCREASING ASYMMETRY ARE APPARENT IN ANIMATED WATER VAPOR IMAGERY
AND VISUAL IMAGERY SHOWS IRREGULARITIES AND FRAGMENTATION IN THE
EYEWALL. A 190535Z AMRS2 COLOR COMPOSITE VERIFIES THAT DRY AIR IS
MAKING IT INTO THE CORE, AND THE SYSTEM HAS LOST A SUBSTANTIAL
AMOUNT OF CONVECTION OVER THE SOUTHEAST QUADRANT. ALTHOUGH THE EYE
HAS BECOME CLOUD FILLED AND FRAGMENTED, VIGOROUS DEEP CONVECTION
PERSISTS OVER THREE FOURTHS OF THE STORM AND OVERSHOOTING TOPS ARE
STILL OCCURRING IN THE SOUTHWEST QUADRANT. THE CURRENT POSITION LIES
IN THE CENTER OF A TIGHT TRIANGLE OF AGENCY FIXES FROM JTWC, RJTD,
AND KNES. DATA T VALUES ARE PLUNGING BUT SUBJECTIVE DVORAKS ARE
HELD HIGH BY CONSTRAINTS, AND THE RECENT POSTING OF A SATCON RATING
OF 118 KNOTS FOR THE 190600Z FIX SHOWS THE WISDOM IN THAT. THE 
CURRENT INTENSITY ASSESSMENT BALANCES SATCON, ADT AND THE AGENCY
CURRENT INTENSITY VALUES. THE 6 HOUR MOVEMENT CLOCKED OVER ANOTHER
20 DEGREES TO THE NORTH, PROVIDING WELCOME VERIFICATION THAT THE
STORM IS INDEED ROLLING OVER AND CURLING TO THE NORTH AND WILL STAY 
OVER WATER RATHER THAN INFLICTING ANOTHER LAND STRIKE. AS IT TRACKS 
POLEWARD, IT IS MOVING INTO A REGION WHERE OCEAN HEAT CONTENT PLUNGES
PRECIPITOUSLY AND VERTICAL WIND SHEAR INCREASES STEADILY. THE
SYSTEM IS ALSO HEADING DIRECTLY INTO A RIVER OF BRISK NORTHEASTERLIES
FLOWING OUT OF A 1027MB HIGH OF CONTINENTAL POLAR AIR JUST SOUTH OF
SHANGHAI. THE EXTREMELY DRY AND COOL AIR HAS BROUGHT TEMPERATURES
ALL THE WAY DOWN TO BELOW 70F IN DA NANG. YET ALTHOUGH THE
NORTHEASTERLIES ARE PUMPING DRY AIR INTO THE CORE, THEY ARE ALSO
PROVIDING LOW LEVEL VORTICITY THAT WILL SUSTAIN THE VORTEX DESPITE 
ALL 
THE NEGATIVE ENVIRONMENTAL FACTORS WORKING TO KILL IT. NONETHELESS, 
THE PARTY IS OVER FOR 28W.

INITIAL WIND RADII BASIS: WINDFIELDS OVER THE EASTERN SEMICIRCLE
WERE REDUCED DUE TO A PARTIAL 190227Z ASCAT PASS.

CURRENT STEERING MECHANISM: THE EXTREME WESTERN FLANK OF THE
SUBTROPICAL RIDGE, WITH IS ANCHORED BY AN ANTICYCLONE NORTHEAST OF
LUZON. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T7.0 - 140 KTS 
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 117 KTS AT 190550Z
   CIMSS ADT: 127 KTS AT 190540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TYPHOON 28W IS ON A PERMANENT DECLINE. LOW
OCEAN HEAT CONTENT, INCREASING VERTICAL WIND SHEAR, AND SUBSTANTIAL
DRY AIR ENTRAINMENT WILL KILL THE SYSTEM AS IT ROLLS OVER AND ARCS
AROUND THE WESTERN FLANK OF THE SUBTROPICAL RIDGE. THE SAME
NORTHEASTERLIES SURGING OFF THE CONTINENT THAT WILL WEAKEN THE CORE
CONVECTION AND BE THE PRIMARY FACTOR IN THE SYSTEM'S DEMISE WILL
ALSO INDUCE ENOUGH SPIN TO KEEP THE VORTEX ALIVE FOR ANOTHER 72
HOURS, PROLONGING THE PROCESS. THE SYSTEM WILL ALSO ACT AS A SINK
FOR A RECENT VIGOROUS SURGE IN THE NORTHEAST MONSOON, DRAWING
SEVERE GALE TO STORM FORCE NORTHEASTERILES ALONG THE VIETNAMESE
COAST. THE SEVERELY HOSTILE ENVIRONMENT ALONG THE TRACK OF TYPHOON 
28W 
WILL PREVENT THE SYSTEM FROM EVEN REACHING TAIWAN. 
NNNN