WDPN31 PGTW 172100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (RAI) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.7N 117.3E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 319 NM SOUTHWEST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TY RAI IS NOW BACK OVER WATER AND SHOWING SIGNS OF STRENGTHENING AS
IT TRANSITS TO THE WEST-NORTHWEST. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS PERSISTENT CONVECTION ROTATING OVER AN
ASSESSED LOW LEVEL CIRCULATION CENTER. A 171802Z AMSR2 36GHZ IMAGE 
SHOWS A WELL-DEFINED MICROWAVE EYE WITH THE STRONGEST CONVECTION 
SEEN IN THE SOUTHERN AND EASTERN PERIPHERIES. TY RAI IS IN AN AREA 
FAVORABLE CONDITIONS FOR FURTHER DEVELOPMENT WITH STRONG WESTWARD 
AND POLEWARD OUTFLOW ALOFT, LOW (10-15 KT) VERTICAL WIND SHEAR 
(VWS), AND WARM (28-29 C)SEA SURFACE TEMPERATURES. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED 
MICROWAVE IMAGERY. THE INITIAL INTENSITY OF 100 KTS IS ASSESSED WITH 
MEDIUM CONFIDENCE BASED ON ANALYSIS OF MICROWAVE STRUCTURE AND 
HEDGED HIGHER THAN MUTLI-AGENCY AND AUTOMATED DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 93 KTS AT 171722Z
   CIMSS ADT: 90 KTS AT 171740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG WESTWARD

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: TY RAI IS EXPECTED TO INCREASE IN SURFACE
SPEED AS IT APPROACHES THE STR AXIS OVER THE NEXT 24 HOURS. AS IT 
DOES SO, THE SYSTEM WILL CONTINUE TO BE IN A FAVORABLE ENVIRONMENT 
AND WILL STRENGTHEN TO ITS MAX INTENSITY OF 110 KTS BY TAU 12. AFTER 
TAU 36, TY RAI WILL CROSS THE 25C ISOTHERM AND WILL REMAIN OVER 
RELATIVELY COOLER WATERS FOR THE REMAINDER OF THE FORECAST PERIOD. 
IN ADDITION, TY 28W WILL MAKE ITS TURN NORTHWARD AS IT ROUNDS THE 
RIDGE AXIS AND WILL ALSO BEGIN TO APPROACH A BROAD AREA OF INCREASED 
VWS THAT WILL ONLY INCREASE IN SHEAR OVER THE DURATION OF THE 
FORECAST PERIOD. BY TAU 48, TY RAI WILL MAKES ITS TURN NORTHEASTWARD 
TO THE OPEN WATERS OF THE NORTHERN SOUTH CHINA SEA. AT TAU 72, TY 
28W WILL BEGIN TO LOSE ITS MOISTURE AS DRIER AIR FROM THE WEST 
BEGINS TO GET WRAPPED INTO THE CENTER THROUGH THE SOUTHERN 
PERIPHERY. AT THIS TIME, THE SYSTEM WILL FALL UNDER THE INFLUENCE OF 
STRONG WESTERLIES AND BEGIN DISSIPATION. TY RAI IS FORECAST TO BE 
COMPLETELY DISSIPATED BY TAU 96, WITH THE POSSIBILITY OF DISSIPATION 
OCCURRING SOONER.

MODEL DISCUSSION: MODEL CONSENSUS (CONW) FOR TRACK GUIDANCE
CONTINUES TO BE IN VERY TIGHT AGREEMENT WITH A 34 NM SPREAD AT TAU
24, GRADUALLY INCREASING TO AN 85 NM SPREAD AT TAU 72, LENDING HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK THROUGH TAU 72. CONFIDENCE
DROPS TO MEDIUM AFTERWARDS DUE TO SPORADIC TRACK POSITION, POSSIBLY
DUE TO THE MODELS HAVING A HARD TIME WITH DISSIPATION. THE JGSM
TRACK IS THE OUTLIER SHOWING A MORE WESTERLY TRACK AND MAKING
LANDFALL OVER SOUTHERN HAINAN BY TAU 72. INTENSITY GUIDANCE IS IN
FAIRLY GOOD AGREEMENT THROUGH TAU 72, LENDING MEDIUM CONFIDENCE IN
THE JTWC INTENSITY FORECAST UP UNTIL THAT TIME. AFTER 72,
CONFIDENCE DROPS TO LOW DUE TO A HIGHER SPREAD IN INTENSITY
PLACEMENT. THE JTWC INTENSITY FORECAST IS SET HIGHER THAN CONSENSUS
THROUGH TAU 24 DUE TO THE POSSIBILITY OF RE-INTENSIFICATION IN THE
SHORT TERM. AFTERWARDS, THE JTWC INTENSITY IS IN AGREEMENT WITH
CONSENSUS THROUGHOUT THE FORECAST PERIOD.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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