WDPN31 PGTW 252100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 33W (KOTO) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.1N 119.3E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 180 NM SOUTHWEST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SMALL
AND DEVELOPING CENTRAL DENSE OVERCAST (CDO) FEATURE WITH
OVERSHOOTING VERTICAL HOT TOWERS, WITH CLOUD TOP TEMPS APPROACHING
-100C ACCOMPANIED BY A STRONG INNER-CORE LIGHTNING BURST. A 251718Z
AMSR2 89GHZ MICROWAVE IMAGE DEPICTED A WEAK UPPER-LEVEL LOW
EMISSIVITY REGION OR NASCENT MICROWAVE EYE, WHILE THE 36GHZ IMAGE
REVEALED A LESS-ORGANIZED STRUCTURE BUT WITH HINTS OF SOME STRONG
LOW-LEVEL BANDING WRAPPING INTO A DEVELOPING LOW LEVEL CIRCULATION
CENTER (LLCC). THE INITIAL POSITION IS ASSESSED WITH MEDIUM
CONFIDENCE, EVEN WITH THE AMSR2 IMAGERY, DUE TO LARGE DISPERSAL IN
THE AGENCY FIXES AND THE INCONCLUSIVE NATURE OF THE MICROWAVE
IMAGERY. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED
BELOW. ENVIRONMENTAL CONDITIONS ARE FAVORABLE, WITH LOW DEEP-LAYER
SHEAR, GOOD POLEWARD AND EQUATORWARD OUTFLOW ALOFT AND WARM SSTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 48 KTS AT 251715Z
   CIMSS ADT: 57 KTS AT 251730Z
   CIMSS AIDT: 44 KTS AT 251730Z
   CIMSS D-PRINT: 47 KTS AT 251800Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM (TS) 33W IS FORECAST TO
CONTINUE TRACK WEST-NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY
OF THE STEERING RIDGE FOR THE NEXT 24 HOURS, BEFORE IT WILL BEGIN
TO SLOW DOWN PRECIPITOUSLY AS IT SLAMS INTO THE STRONG
NORTHEASTERLY FLOW ASSOCIATED WITH A COLD SURGE EVENT PUSHING SOUTH
INTO THE SOUTH CHINA SEA (SCS). THE SYSTEM WILL SLAM ON THE BRAKES
SHORTLY AFTER TAU 24, AND SLOWLY DRIFT GENERALLY WESTWARD THROUGH
TAU 72, WHERE AFTER IT BECOMES ALMOST QUASI-STATIONARY AS IT MOVES
INTO A WEAK STEERING PATTERN IN THE DEEP-LAYER SENSE AND IS BLOCKED
FROM FURTHER WESTWARD MOTION DUE TO THE STRONG NORTH EASTERLIES
TRAPPED BETWEEN THE STORM AND THE COAST OF VIETNAM. THERE IS
SIGNIFICANT UNCERTAINTY IN THE LONG-RANGE FORECAST TRACK, AS THE
SYSTEM WILL REMAIN IN THE WEAK STEERING PATTERN, CAUGHT BETWEEN
RIDGING EXTENDING FROM THAILAND SOUTH TO INDONESIA AND THEN INTO
THE WESTERN PACIFIC. THE GFS SHOWS A STRONGER SOUTHWESTERLY FLOW IN
THE SCS TO THE SOUTH OF THE SYSTEM AND A WEAKER RIDGE OF THAILAND,
WHILE THE ECMWF IS THE OPPOSITE, REPRESENTING THE TWO MAIN OUTLIERS
IN TERMS OF THE OVERALL STEERING PATTERN. THE TRACK SHOULD DRIFT
NORTHWESTWARD AT A SNAILS PACE, AS THE SYSTEM SEPARATES FROM THE
WEAKENING COLD SURGE FLOW AND TRENDS TOWARDS A WEAKNESS IN RIDGE TO
THE NORTH. HOWEVER, A MORE ERRATIC TRACK IS DEFINITELY A
POSSIBILITY. THE SYSTEM IS FORECAST TO STEADILY INTENSIFY UNDER
FAVORABLE CONDITIONS, TO A PEAK OF 70 KNOTS BY TAU 24, BEFORE IT IS
CONFRONTED BY RAPIDLY INCREASING DEEP-LAYER SHEAR BEGINNING SHORTLY
AFTER TAU 24. THE SYSTEM WEAKENS SHARPLY UNDER THE INFLUENCE OF
THIS HIGH SOUTHERLY SHEAR THROUGH TAU 96, BUT ONCE THE SYSTEM
SEPARATES FROM THE COLD SURGE FLOW, SHEAR WILL DECREASE ONCE MORE
BEGINNING AROUND TAU 96, WHICH WILL ALLOW FOR THE SYSTEM TO START
INTENSIFYING ONCE AGAIN THROUGH TAU 120 AND BEYOND. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN POOR
AGREEMENT, PARTICULARLY AFTER TAU 48, AS THE GLOBAL MODELS BEGIN TO
DIVERGE IN THEIR HANDLING OF THE OVERALL STEERING ENVIRONMENT. THE
JTWC CONSENSUS HAS BEEN MODIFIED TO ELIMINATE LESS RELIABLE MODELS
FROM THE CONSENSUS, AND THE RESULTING CONSENSUS IS COMPARED CLOSELY
WITH THE ENSEMBLES AND THE AI MODEL GUIDANCE TO GENERATE THE
FORECAST TRACK. THE JTWC FORECAST TRACK IS CONSISTENT WITH THE
MODIFIED CONSENSUS THROUGH TAU 48, THEN IS PLACED ROUGHLY AT THE
AVERAGE BETWEEN IT AND THE ECMWF AIFS AND GDM TRACKS. CONFIDENCE IS
LOW AFTER TAU 48 DUE TO EXTREME SPREAD ACROSS THE MODEL PACKAGE.
INTENSITY GUIDANCE IS IN GENERAL AGREEMENT ON INTENSIFICATION TO
TAU 24, FOLLOWED BY A GENERAL WEAKENING THEREAFTER. MODELS DISAGREE
ON THE PEAK INTENSITY, RANGING BETWEEN CTCX ON THE LOW END AT ABOUT
60 KNOTS, AND HAFS-A ON THE HIGHER END NEAR 75 KNOTS. SEVERAL RI
AIDS HAVE BEEN TRIPPED ON THIS RUN, SUPPORTING PEAK INTENSITIES
BETWEEN 75 TO 105 KNOTS WITHIN THE NEXT 24 TO 36 HOURS. THE JTWC
FORECAST IS PLACED BETWEEN THE HAFS-A AND CONSENSUS MEAN THROUGH
THE FORECAST PERIOD. 

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