Advisories

WDPN31 PGTW 231500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (SURIGAE) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.5N 137.6E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 413 NM NORTH-NORTHWEST OF ULITHI
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION (TD) 25W (SURIGAE) AS A COMPLETELY OBSCURED LOW-LEVEL
CIRCULATION CENTER WITH PERIPHERY LOW-LEVEL CLOUD BANDING VISIBLE
FROM UNDER THE EXPANDING CANOPY. THE 231101Z PARTIAL ASCAT PASS
REVEALS THE EASTERN SEMICIRCLE AND AN ASYMMETRIC WIND FIELD. THE
HIGHEST 30 KT WIND SPEEDS ARE A RESPECTABLY SIZED SWATH CONFINED TO
THE NORTHEASTERN QUADRANT, WHILE THE SOUTHEASTERN QUADRANT IS
RELEGATED TO A SMALL STRIP OF 15-20 KT WINDS. ENVIRONMENTAL
ANALYSIS REVEALS A HIGHLY FAVORABLE ENVIRONMENT, CHARACTERIZED BY
LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), VERY WARM (29-30 C) SEA
SURFACE TEMPERATURES (SST), HIGH (100-120 KJ PER CM SQUARED) OCEAN
HEAT CONTENT (OHC), STRONG POLEWARD OUTFLOW, AND AMPLE MOISTURE
THROUGHOUT THE AIR COLUMN. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE PARTIAL ASCAT PASS FROM 231101Z. THE
INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE CIMSS AUTOMATED INTENSITY ESTIMATES AND THE AGENCY
DVORAK FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: A DEEP-LAYER SUBTROPICAL RIDGE CENTERED
TO THE NORTH-NORTHEAST OF THE SYSTEM

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS ADT: 28 KTS AT 231140Z
   CIMSS AIDT: 30 KTS AT 231140Z
   CIMSS D-MINT: 30 KTS AT 230945Z
   CIMSS D-PRINT: 30 KTS AT 231140Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 25W (SURIGAE) IS FORECAST TO CONTINUE TRACKING 
NORTHWESTWARD WHILE IT REMAINS UNDER THE STEERING INFLUENCE OF THE 
DEEP-LAYER STR CURRENTLY CENTERED TO ITS NORTH-NORTHEAST. 25W IS 
EXPECTED TO MAINTAIN A RELATIVELY CONSISTENT TRACK SPEED THROUGH TAU 
48-60, AT WHICH POINT, THE STORM IS FORECAST TO SLOW SLIGHTLY AS IT 
APPROACHES A WEAKNESS BETWEEN THE STEERING RIDGE AND A WEAKER MID-
LAYER STR CURRENTLY CENTERED OVER CHINA. AROUND TAU 60-72, SURIGAE 
WILL CONTINUE TO SLOW ITS SPEED OF ADVANCE AND TURN NORTH-
NORTHWESTWARD INTO THE WEAKNESS AND BEGIN TO TRACK AROUND THE 
SOUTHWESTERN PERIPHERY OF THE STEERING RIDGE TOWARDS THE RIDGE AXIS. 
BETWEEN TAU 72-96, 25W IS FORECAST TO RECURVE ABOUT THE STEERING RIDGE 
WHILE TRACKING CONSIDERABLY SLOWER. FROM TAU 96 THROUGH THE END OF THE 
FORECAST PERIOD, 25W WILL BEGIN TO ACCELERATE TO THE NORTH-NORTHEAST 
WHILE THE DEEP-LAYER STR MAINTAINS STEERING AUTHORITY OVER THE SYSTEM.
REGARDING INTENSITY, 25W IS FORECAST TO STEADILY INTENSIFY WHILE IT
CONTINUES TO CONSOLIDATE THROUGH TAU 48. AT THAT POINT, 25W MAY
UNDERGO A PERIOD OF RAPID INTENSIFICATION. THE ENVIRONMENT IS
EXPECTED TO BE HIGHLY FAVORABLE THROUGH THE ENTIRE FORECAST PERIOD,
ESPECIALLY BETWEEN TAU 48-96. DURING THAT TIME, SURIGAE IS EXPECTED
TO DEVELOP A ROBUST POLEWARD OUTFLOW CHANNEL, IN ADDITION TO
DECREASING VWS AND SLOWER TRACK SPEEDS OVER HIGH OHC VALUES. 25W IS
CURRENTLY FORECAST TO PEAK AT TAU 120, WITH ADDITIONAL
INTENSIFICATION POSSIBLE OUTSIDE THE FORECAST PERIOD.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE CONTINUES TO DEPICT
A BIFURCATION SCENARIO BEGINNING AROUND TAU 72 AS 25W ENCOUNTERS THE 
WEAKNESS BETWEEN THE TWO SUBTROPICAL RIDGES. THE BIFURCATION IS SPLIT 
GENERALLY BETWEEN THE PHYSICS-BASED MODELS AND EXPERIMENTAL AI-BASED 
MODELS. SOME GLOBAL PHYSICS-BASED MODELS INDICATE 25W COULD FAIL TO 
RECURVE AND INSTEAD TRANSITION STEERING INFLUENCES TO THE WEAKER STR 
OVER CHINA AND TRACK NORTHWESTWARD INTO TAIWAN; HOWEVER, GFS, ECMWF, 
AND NAVGEM NOW LIE AMONGST THE AI MODELS THAT DEPICT A RECURVE 
SCENARIO. ALL EXPERIMENTAL AI-BASED MODELS SUPPORT THE RECURVE 
SCENARIO. DUE TO THE CHARACTERIZATION OF THE ENVIRONMENTAL SETUP IN 
GLOBAL MODELS AND THE INCREASED MODEL AGREEMENT BETWEEN AI-BASED 
MODELS AND THE MOST RELIABLE PHYSICS-BASED MODELS, THE RECURVE 
SCENARIO REMAINS THE MOST LIKELY OUTCOME. THE TRACK FORECAST 
CONFIDENCE IS PLACED WITH MEDIUM CONFIDENCE FROM TAU 0-72 AND LOW 
CONFIDENCE FROM TAU 72-120 DUE TO THE REMAINING UNCERTAINTY 
SURROUNDING THE RECURVE SCENARIO. RELIABLE INTENSITY GUIDANCE IS IN 
STRONG AGREEMENT IN A STEADY RATE OF INTENSIFICATION THROUGH TAU 48 
WHILE 25W CONTINUES TO CONSOLIDATE, FOLLOWED BY AN INCREASED RATE OF 
INTENSIFICATION BETWEEN TAU 48-96. THE GUIDANCE DIVERGES WITH RESPECT 
TO PEAK INTENSITY, RANGING ANYWHERE FROM 80 KTS (GFS) TO 130-135 KTS
(COAMPS-TC AND HAFS-A) AT TAU 120. THE JTWC INTENSITY FORECAST LIES
VERY CLOSE TO THE HAFS-A SOLUTION AND THE MULTI-MODEL CONSENSUS
FROM TAU 0-48, AND HEDGED SLIGHTLY HIGHER THAN THE CONSENSUS
TOWARDS THE MESOSCALE MODELS FROM TAU 48-120. AS A RESULT, THE JTWC
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE FROM TAU 0-72
AND LOW CONFIDENCE FROM TAU 72-120.

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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