Advisories

WDPN31 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (SURIGAE) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.2N 136.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 728 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL 
STORM (TS) 25W (SURIGAE) SLOWLY IMPROVING ITS CONVECTIVE STRUCTURE AS 
THE LOW LEVEL CIRCULATION CENTER (LLCC) BECOMES FURTHER TUCKED 
UNDERNEATH THE SOUTHEASTERN PORTION OF THE LARGER CENTRAL DENSE 
OVERCAST (CDO) EXTENDING TO THE NORTHWEST. THE LLCC IS ASSESSED TO 
STILL BE SLIGHTLY ELONGATED ALONG THE SOUTHEAST TO NORTHWEST AXIS 
BASED ON THE EXPOSED LOW LEVEL CLOUD BANDING ON THE SOUTHERN 
SEMICIRCLE. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS OF 
WARM (29-30 C) SEA SURFACE TEMPERATURES, MODERATE RADIAL OUTFLOW 
ALOFT, AND LOW TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS). THE 
INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON THE OBSCURED 
LLCC IN EIR IMAGERY. THE INITIAL INTENSITY IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON THE AGREEMENT ACROSS AGENCY DVORAK FIXES AND CIMSS 
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 33 KTS AT 231740Z
   CIMSS AIDT: 34 KTS AT 231740Z
   CIMSS D-MINT: 30 KTS AT 231556Z
   CIMSS D-PRINT: 34 KTS AT 231810Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 25W IS FORECAST TO CONTINUE
WEST-NORTHWESTWARD AT A STEADY PACE FOR THE NEXT 48 HOURS UNDER THE 
INFLUENCE OF THE SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTH 
NORTHEAST OF THE SYSTEM. BETWEEN TAUS 48 AND 60, TS 25W IS EXPECTED TO 
SLOW IN TRACK SPEED AND TURN NORTHWARD AS IT NEARS A WEAKNESS BETWEEN 
THE STR TO THE NORTHEAST AND A WEAKER STR CENTERED TO THE NORTHWEST 
OVER CHINA. WHILE THIS WEAK STEERING ENVIRONMENT WILL CAUSE A SLOW IN 
TRACK SPEED, THE STR TO THE NORTHEAST IS EXPECTED TO REMAIN THE 
PRIMARY STEERING MECHANISM FOR THE ENTIRETY OF THE FORECAST PERIOD, 
CAUSING 25W TO BEGIN RECURVING TO THE NORTHEAST AT THE END OF THE 
FORECAST PERIOD AS IT ROUNDS THE STR AXIS. REGARDING INTENSITY, 25W IS 
EXPECTED TO GRADUALLY INTENSIFY OUT TO TAU 48 AS VWS ABATES AND ALL 
OTHER ENVIRONMENTAL FACTORS REMAIN FAVORABLE. A PERIOD OF RAPID 
INTENSIFICATION IS FORECAST BETWEEN TAU 48 AND 72 AS THE RIDGING TO 
THE NORTHEAST IS EXPECTED TO PROVIDE ENHANCED POLEWARD OUTFLOW. AFTER 
THIS PERIOD OF RI, INTENSITY IS FORECAST TO GRADUALLY INCREASE TO A 
PEAK OF 105 KTS, WITH INTENSIFICATION SLOWING AS OUTFLOW DECREASES; 
HOWEVER, THERE REMAINS POTENTIAL FOR 25W TO PEAK AT A HIGHER 
INTENSITY.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN IMPROVING AGREEMENT ON
THE RECURVATURE SCENARIO; HOWEVER, ROUGHLY HALF OF THE INDIVIDUAL 
ENSEMBLE MEMBERS OF GEFS AND ECENS STILL PORTRAY A DIRECT 
NORTHWESTWARD TRACK, AS DOES THE UKMET ENSEMBLE MEAN. MOST NOTABLY, 
THE GFS DETERMINISTIC SOLUTION NOW DEPICTS A NEW TRACK IN LINE WITH 
THE RECURVATURE SCENARIO OUT TO TAU 96 BUT THEN TURNS SHARPLY WESTWARD 
TO TRANSIT TOWARDS NORTHERN TAIWAN AS THE GFS MODEL FIELD DEPICTS THE 
STR CENTERED OVER CHINA BUILDING SOUTHEASTWARD INTO THE SOUTH CHINA 
SEA AROUND TAU 96 AND BECOMING THE PRIMARY STEERING MECHANISM OF 25W 
THEREAFTER. THE OFFICIAL JTWC FORECAST TRACK IS PLACED WITH MEDIUM 
CONFIDENCE OUT TO TAU 72 AND LOW CONFIDENCE THEREAFTER DUE TO THE 
CONTINUED DISAGREEMENT ON THE TIMING AND SPEED OF RECURVATURE, 
DISREGARDING THE OUTCOME DEPICTED BY GFS AND MORE IN LINE WITH THE 
MULTI-MODEL CONSENSUS, AND MARKEDLY SLOWER IN TRACK SPEED THAN ALL AI 
MODELS. MODEL INTENSITY GUIDANCE IS IN GENERAL AGREEMENT ON A STEADY 
INTENSIFICATION OUT TO A PEAK OCCURRING BY TAU 96, WITH HAFS-A AND 
COAMPS-TC DEPICTING RI BEGINNING AT TAU 48 AND PEAKING AT TAU 84 ON 
THE HIGHER END OF THE GUIDANCE PACKAGE, WITH A TOTAL SPREAD AT THIS 
POINT OF PEAK INTENSITY OF 60 KTS. THE OFFICIAL JTWC INTENSITY 
FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE OUT TO TAU 72 AND LOW 
THEREAFTER DUE TO THIS SPREAD, CLOSELY IN LINE WITH THE MULTI-MODEL 
CONSENSUS OUT TO TAU 72 AND SLIGHTLY ABOVE IT THEREAFTER TO ACCOUNT 
FOR THE PEAKS DEPICTED BY MESOSCALE MODELS.

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