WDPN31 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (TWENTYSEVEN) 
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.2N 126.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 321 NM EAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEVELOPING
AND CONSOLIDATING SPIRAL BANDS OF DEEP CONVECTION WRAPPING INTO THE
LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL STORM (TS) 27W. THE
SYSTEM IS BENEFITING FROM FAVORABLE ENVIRONMENT, CHARACTERIZED BY
STRONG EQUATORWARD OUTFLOW, WARM (29-30 C) SEA SURFACE TEMPERATURES
(SST), LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS) AND DEEP-LAYER
MOISTURE AVAILABLE THROUGHOUT THE ATMOSPHERIC COLUMN. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE FOCAL POINT
OF CONVECTIVE WRAPPING. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON THE DVORAK FIXES AND OBJECTIVE
ESTIMATES LISTED BELOW, WHICH ALL ARE IN GOOD AGREEMENT.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTH-NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 44 KTS AT 020522Z
   CIMSS ADT: 43 KTS AT 020530Z
   CIMSS AIDT: 39 KTS AT 020530Z
   CIMSS D-MINT: 39 KTS AT 020454Z
   CIMSS D-PRINT: 36 KTS AT 020630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 27W IS FORECAST TO CONTINUE TRACKING
NORTHWESTWARD AND TOWARDS THE NORTHERN PHILIPPINES ALONG THE
SOUTHERN PERIPHERY OF A DEEP STR TO THE NORTH. THE SYSTEM IS
EXPECTED TO MAKE LANDFALL OVER LUZON, JUST PRIOR TO TAU 24,
REACHING 65-75 KTS JUST PRIOR TO THAT, WHILE TAKING ADVANTAGE OF
THE FAVORABLE ENVIRONMENT. AFTER LANDFALL, FRICTIONAL EFFECTS OF
LAND INTERACTION WILL RESULT IN WEAKENING OF THE STORM TO
SUB-TYPHOON MAXIMUM WIND SPEEDS. PRIOR TO TAU 36, THE SYSTEM IS 
EXPECTED TO RE-EMERGE OVER SLIGHTLY COOLER, BUT STILL VERY WARM (28-
29 C) WATERS OF THE SOUTH CHINA SEA. AS THE SUBTROPICAL RIDGE SHIFTS
EASTWARD OVER THE NEXT FEW DAYS, TS 27W WILL CONTINUE ALONG ITS
SOUTHWESTERN PERIPHERY AND TOWARDS THE COAST OF CHINA. FAVORABLE
CONDITIONS WILL RESULT IN RE-INTENSIFICATION, LIKELY TO 75-80 KTS.
CURRENT TRACK FORECAST PREDICTS LANDFALL JUST NORTH OF THE HAINAN
ISLAND AND OVER THE LEIZHOU PENINSULA. AFTERWARDS, ANOTHER LANDFALL
IS EXPECTED AROUND TAU 96, NEAR THE BORDER OF CHINA WITH NORTHERN
VIETNAM. THE SYSTEM WILL THEN BEGIN WEAKENING AND EVENTUALLY
DISSIPATE PRIOR TO THE END OF THE CURRENT FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GENERALLY
GOOD AGREEMENT IN REGARD TO THE STEERING MECHANISM AND PREDICTED
TRACK THROUGHOUT THE CYCLE OF THE STORM. CROSS-TRACK SPREAD PRIOR
AND AFTER THE LANDFALL OVER LUZON IS APPROXIMATELY 25-35 NM. GUIDANCE 
STARTS TO DIVERGE AS THE SYSTEM NEARS THE COAST OF CHINA, BUT IS 
STILL IN FAIR AGREEMENT, AS WITNESSED BY A CROSS-TRACK SPREAD SMALLER 
THAN 60 NM AROUND TAU 72. JTWC OFFICIAL TRACK FORECAST CLOSELY 
FOLLOWS THE MULTI-MODEL CONSENSUS AND IS LAID ON ITS NORTHERN SIDE. 
IN REGARD TO INTENSITY, JTWC FORECAST IS ASSESSED WITH MEDIUM 
CONFIDENCE, DUE TO UNCERTAINTY ASSOCIATED WITH THE TIMELINE OF LAND 
INTERACTION AND THE AMOUNT OF TIME THE SYSTEM WILL SPEND OVER WARM 
WATERS AND IN GENERALLY FAVORABLE CONDITIONS, PRIOR TO SUFFERING FROM 
LAND-RELATED FRICTIONAL EFFECTS. OTHERWISE, THE SEA SURFACE 
TEMPERATURES, OUTFLOW AND VERTICAL WIND SHEAR ARE EXPECTED TO REMAIN 
FAVORABLE OVER THE NEXT 5 DAYS AND ALONG THE PATH OF THE STORM. 
ADDITIONALLY, NUMEROUS RAPID INTENSIFICATION (RI) AIDS ARE CURRENTLY 
TRIGGERING, INDICATING THAT THE SYSTEM MAY REACH INTENSITY 
SIGNIFICANTLY HIGHER THAN THE CURRENT PEAK OF 60 KTS. AFTER TAU 12, 
BUT PRIOR TO LANDFALL, MAXIMUM WIND SPEEDS ARE EXPECTED TO REACH 65-
75 KTS.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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