Advisories

WDPN31 PGTW 260900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0N 163.0E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 379 NM SOUTHWEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 30W HAS UNDERGONE VERY RAPID INTENSIFICATION (RI),
HAVING STRENGTHENED BY 35 KTS IN 12 HOURS AND 50 KTS IN 24 HOURS. A
15-NM WIDE EYE BEGAN TO APPEAR IN ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) AT 260100Z. SINCE THEN, THE EYE HAS CLEARED
SUBSTANTIALLY, AND THE SURROUNDING CLOUD-TOP TEMPERATURES HAVE
RAPIDLY COOLED. UPPER-LEVEL OUTFLOW APPEARS HEALTHY IN ALL
DIRECTIONS, AND VORTICAL HOT TOWERS ARE OBSERVED ROTATING ALONG THE
EYEWALL. A 260225Z GMI PASS INDICATED A SLIGHT VORTEX TILT TOWARD
THE NORTHEAST WITH HEIGHT, CONSISTENT WITH THE PERSISTENT 15-20 KTS
OF SOUTHWESTERLY MID-LEVEL SHEAR. THE ENVIRONMENT IS OTHERWISE
FAVORABLE, CHARACTERIZED BY MODERATE RADIAL OUTFLOW ALOFT, HIGH
OCEAN HEAT CONTENT (OHC), AND VERY WARM SEA SURFACE TEMPERATURES
(SST). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
THE WELL-DEFINED EYE IN MSI. THE INITIAL INTENSITY HAS BEEN RAISED
TO 115 KTS WITH LOW CONFIDENCE BASED ON THE T6.0 DVORAK
CLASSIFICATIONS FROM PGTW AND PHFO, WITH OTHER AGENCY ESTIMATES
RANGING FROM T5.0 TO T5.5. THIS ASSESSMENT IS MUCH HIGHER THAN THE
OBJECTIVE ESTIMATES FROM CIMSS, WHICH MAY BE UNDERESTIMATING THE
RAPIDLY INTENSIFYING, COMPACT STORM.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMPETING INFLUENCES BETWEEN A
DEEP-LAYER NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTH AND A
DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED SOUTH-SOUTHEAST OF
HONSHU

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.5 - 102 KTS
   PHFO: T6.0 - 115 KTS
   CIMSS SATCON: 82 KTS AT 260235Z
   CIMSS ADT: 107 KTS AT 260530Z
   CIMSS AIDT: 91 KTS AT 260530Z
   CIMSS D-MINT: 90 KTS AT 260235Z
   CIMSS D-PRINT: 99 KTS AT 260600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE INTENSITY FORECAST HAS BEEN
SIGNIFICANTLY INCREASED.

FORECAST DISCUSSION: TY 30W HAS BEEN QUASI-STATIONARY FOR THE PAST
THREE HOURS UNDER THE COMPETING INFLUENCES OF THE DEEP-LAYER
NEAR-EQUATORIAL RIDGE TO THE SOUTH AND THE SUBTROPICAL RIDGE TO THE
NORTH. AS THE STR SHIFTS EASTWARD, THE SYSTEM WILL SLOWLY TURN
WEST-NORTHWESTWARD ALONG ITS SOUTHERN PERIPHERY. WITH THE RIDGE
NEARLY DUE NORTH OF TY 30W BY TAU 24, THE VORTEX WILL GAIN FORWARD
SPEED. TOWARD THE END OF THE FORECAST PERIOD, THE SYSTEM WILL TURN
NORTHWESTWARD AND SLOW DOWN AS IT REACHES THE SOUTHWESTERN
PERIPHERY OF THE RIDGE. TY 30W HAS BEEN ABLE TO OVERCOME THE
DETRIMENTAL EFFECTS OF MODERATE MID-LEVEL SHEAR, WHICH WILL PERSIST
FOR THE NEXT 24 HOURS. THE FORECAST CALLS FOR ADDITIONAL
INTENSIFICATION THROUGH TAU 12 BEFORE UPWELLING OF COOLER
SUBSURFACE WATERS TAKES EFFECT AND LIMITS FURTHER STRENGTHENING.
THE ENVIRONMENT AFTER TAU 24 WILL IMPROVE, WITH SST AND OHC
REMAINING HIGH AND VERTICAL WIND SHEAR DECREASING TO 10-15 KTS.
BARRING INTERNAL STRUCTURAL CHANGES, WHICH ARE DIFFICULT TO
PREDICT, A SECOND ROUND OF INTENSIFICATION IS FORECAST. BY TAU 120,
THE CIRCULATION WILL MOVE OVER LOWER OHC, WHICH SHOULD INDUCE
WEAKENING.

MODEL DISCUSSION: TRACK GUIDANCE IS IN EXCELLENT AGREEMENT.
ALONG-TRACK SPREAD IS MINIMAL, WHILE THE CROSS-TRACK SPREAD REMAINS
LOW THROUGH TAU 120. THE PHYSICS-BASED AND AI MODELS ARE CLUSTERED
TOGETHER, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. THE
JTWC TRACK IS SIMILAR TO THE PREVIOUS FORECAST, PLACED NEAR THE
AI-MODEL MEAN, THE MULTI-MODEL CONSENSUS, AND ECMWF. GFS, HAFS-A,
AND NAVGEM ARE SLIGHTLY NORTH OF THE TRACK, WHILE DEEPMIND IS
SLIGHTLY SOUTH. AIFS IS THE SOLUTION CLOSEST TO TINIAN, PASSING 105
NM FROM THE ISLAND. INTENSITY GUIDANCE HAS TRENDED UPWARD GIVEN THE
OBSERVED RAPID INTENSIFICATION. THE JTWC INTENSITY FORECAST IS SET
SLIGHTLY HIGHER THAN THE CENTER OF THE GUIDANCE ENVELOPE BUT WELL
BELOW THE PEAKS OF 145 KTS FROM COAMPS-TC AND HAFS-A AND 155 KTS
FROM DEEPMIND. AT THE END OF THE FORECAST PERIOD, COAMPS-TC AND
HAFS-A DEPICT GRADUAL WEAKENING, WHILE DEEPMIND HOLDS THE INTENSITY
STEADY.

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