Advisories

WDPN31 PGTW 252100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (SURIGAE) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.9N 127.8E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 276 NM SOUTH OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 25W (SURIGAE) CONTINUING TO IMPROVE ITS CONVECTIVE
STRUCTURE AS THE LOW LEVEL CIRCULATION CENTER (LLCC) REMAINS TUCKED
UNDERNEATH THE PERSISTENT CENTRAL DENSE OVERCAST (CDO), AS WELL AS
BEGINNING TO DEVELOP A BAND OF CONVECTION ON THE NORTHERN QUADRANT.
A 251658 AMSR3 37 GHZ MICROWAVE IMAGE DEPICTS AN ALMOST FULLY
CLOSED MICROWAVE EYE FEATURE WITH A PARTIALLY CLOSED AND SLIGHTLY
OFFSET RING OF CONVECTION REFLECTED IN THE 89 GHZ IMAGE, INDICATING
A SLIGHT BUT LESSENING NORTHWESTWARD TILT WITH HEIGHT.
ENVIRONMENTAL CONDITIONS ARE ASSESSED TO BE HIGHLY FAVORABLE, WITH
VERTICAL WIND SHEAR (VWS) ASSESSED TO BE LOW (5-10 KTS), WARM
(29-30 C) SEA SURFACE TEMPERATURES (SSTS), AND IMPROVED OUTFLOW
ALOFT, BOTH IMPROVING RADIALLY AS UPPER LEVEL SHEAR HAS ABATED, AS
WELL AS MAINTAINING A ROBUST POLEWARD OUTFLOW CHANNEL. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AMSR3 DATA.
THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON
AGREEMENT ACROSS AGENCY DVORAK FIXES AND CIMSS OBJECTIVE ESTIMATES
LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE CENTERED TO THE
NORTHEAST 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   CIMSS SATCON: 54 KTS AT 251712Z
   CIMSS ADT: 51 KTS AT 251750Z
   CIMSS AIDT: 49 KTS AT 251750Z
   CIMSS D-MINT: 59 KTS AT 251713Z
   CIMSS D-PRINT: 59 KTS AT 251710Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: ADDITIONAL POLEWARD OUTFLOW CHANNEL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 HAS BEGUN TO SLOW IN TRACK SPEED AND
TURN POLEWARD AS IT APPROACHES THE AXIS OF THE SUBTROPICAL RIDGE
(STR) CENTERED TO THE NORTHEAST. TRACK SPEED IS FORECAST TO REMAIN
SLOWER OUT TO TAU 36 AS 25W ENTERS THE COL BETWEEN THE STR TO THE
NORTHEAST AND THE WEAKER STR CENTERED FARTHER TO THE WEST OVER
SOUTHERN CHINA. BY TAU 36, THE STRONGER STEERING INFLUENCE OF THE
EASTERN STR AS WELL AS THE PASSAGE OF A MID-LATITUDE SHORTWAVE
TROUGH WILL BOTH AID IN THE RECURVATURE AND NORTHEASTWARD TURN OF
25W. ONCE POLEWARD OF THE STEERING STR, TRACK SPEED IS FORECAST TO
ACCELERATE AS 25W NEARS THE STRONG WESTERLIES ASSOCIATED WITH THE
UPPER-LEVEL JET, CAUSING THE ONSET OF EXTRATROPICAL TRANSITION
(ETT) AT TAU 120. REGARDING INTENSITY, TS 25W IS FORECAST TO
INTENSIFY 25 KTS OVER THE NEXT 24 HOURS, JUST SHORT OF THE TRUE
RATE OF RI AS THE SYSTEM NEARS THE AXIS OF THE STR AND AN AREA OF
ENHANCED OUTFLOW ALOFT WHILE ALL OTHER ENVIRONMENTAL CONDITIONS ARE
EXPECTED TO REMAIN FAVORABLE. 25W IS FORECAST TO PEAK AT 85 KTS
BETWEEN TAUS 36 AND 48 IN CONJUNCTION WITH THE TIME OF CPA TO
KADENA AS IT PASSES TO THE SOUTHEAST OF OKINAWA. AFTER THIS POINT,
25W IS EXPECTED TO BEGIN A WEAKENING TREND FOR THE REMAINDER OF THE
FORECAST PERIOD AS NORTHWESTERLY VWS INCREASES AND SSTS COOL. THERE
REMAINS A POSSIBILITY FOR 25W TO INTENSIFY MORE RAPIDLY THAN
FORECAST IN THE SHORT TERM DEPENDING HOW QUICKLY 25W VERTICALLY
ALIGNS ITS INNER CORE AS WELL AS HOW LONG IT WILL BE IN THE
FORECAST AREA OF ENHANCED OUTFLOW. THE LATTER IS HIGHLY DEPENDENT
ON THE SPEED AT WHICH 25W MAKES ITS RECURVATURE OF THE STR, WHICH
REMAINS AN AREA OF UNCERTAINTY IN THE FORECAST TRACK.

MODEL DISCUSSION: TRACK MODEL GUIDANCE REMAINS SPREAD IN TRACK AND
TRACK SPEED IN LATER TAUS, HOWEVER ALL MEMBERS OF THE MULTI-MODEL
CONSENSUS NOW AGREE ON A POLEWARD TO NORTH-NORTHEASTWARD TURN OUT
TO TAU 60. AFTER THIS POINT, GFS CONTINUES TO FULLY STALL THE
SYSTEM IN THE COL BETWEEN STRS, WHILE THE REMAINDER CONTINUE A
NORTHEASTWARD TRACK, BIFURCATING IN TRACK SPEED FROM THE AI
GUIDANCE WHICH PUT 25W SOUTHEAST OF TOKYO BY TAU 120 WHILE
PHYSICS-BASED MODELS LARGELY KEEP 25W SOUTH OF KYOTO AT TAU 120.
THE OFFICIAL JTWC FORECAST TRACK IS THUS PLACED WITH MEDIUM
CONFIDENCE OUT TO TAU 72, IN LINE WITH THE MULTI-MODEL AND AI
CONSENSUS, AND LOW CONFIDENCE THEREAFTER, IN LINE WITH THE TRACK
SPEED OF THE AI CONSENSUS. MODEL INTENSITY GUIDANCE IS IN GOOD
AGREEMENT ON A SHORT TERM INTENSIFICATION AND PEAK BETWEEN TAUS 36
AND 48, ALTHOUGH THE OUTCOMES DEPICTED BY COAMPS-TC AND HAFS-A ARE
BASED ON A TRACK THAT STALLS NEAR THE SOUTHERN RYUKYU ISLANDS,
WHICH IS NOT REFLECTED IN THE JTWC FORECAST. SEVERAL RI AIDS HAVE
POPULATED, LENDING CONFIDENCE TO THE SHORT TERM INTENSITY FORECAST,
WITH THE AFOREMENTIONED UNCERTAINTY IN EXACT RATE OF RI. THE
OFFICIAL JTWC FORECAST INTENSITY IS ASSESSED WITH LOW CONFIDENCE
THROUGHOUT THE FORECAST PERIOD, IN GOOD AGREEMENT WITH GOOGLE
DEEPMIND OUT TO TAU 60 AND HIGHER THAN THE GOOGLE DEEPMIND DURING
THE LATER TAUS AS THE JTWC FORECAST TRACK LAGS BEHIND THE DEEPMIND
TRACK, AND THUS WILL BE SLOWER TO MEET THE INCREASINGLY HOSTILE
ENVIRONMENTAL CONDITIONS.

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