WDPN31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (NOUL) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.7N 123.5E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 285 NM NORTH-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
CONSOLIDATING VORTEX, CHARACTERIZED BY DEEP CONVECTIVE BANDING
ALONG THE WESTERN PERIPHERY THAT IS WRAPPING AROUND A FORMATIVE,
RAGGED CENTRAL DENSE OVERCAST (CDO). THE VORTEX IS STILL TILTED
WITH HEIGHT, WITH THE MID-LEVEL CIRCULATION DISPLACED APPROXIMATELY
50 NM TO THE SOUTHWEST OF THE LOW-LEVEL CIRCULATION CENTER (LLCC)
DUE TO LIGHT TO MODERATE VERTICAL WIND SHEAR (VWS). CONSEQUENTLY,
THE LLCC IS PARTIALLY EXPOSED WITHIN THE NORTHEAST QUADRANT.
UPPER-LEVEL OUTFLOW IS HEALTHY ON THE SOUTHWESTERN PERIPHERY BUT
REMAINS SOMEWHAT LIMITED ON THE EASTERN SIDE. A 231927Z GMI 37 GHZ
IMAGE REVEALED A NASCENT INNER CORE THAT WAS OPEN ON THE NORTHEAST
SIDE. SINCE THEN, THE CURVED BANDING FEATURES HAVE BECOME BETTER
DEFINED. ENVIRONMENTAL CONDITIONS ARE CONDUCIVE FOR FURTHER
DEVELOPMENT. THE SYSTEM IS TRAVERSING EXCEPTIONALLY WARM SEA
SURFACE TEMPERATURES (SST) OF 30-31 DEGREES CELSIUS, WITH HIGH
OCEAN HEAT CONTENT (OHC) OF 110 KJ PER CM2. THE SURROUNDING
ENVIRONMENT IS DEEPLY MOIST, AND THESE FACTORS ARE MODESTLY OFFSET
BY ONGOING EASTERLY VWS. WHILE THESE CONDITIONS STRONGLY FAVOR
INTENSIFICATION, THE SYSTEM IS NOW INTERACTING WITH THE TERRAIN OF
NORTHERN LUZON, WHICH MAY TEMPORARILY DISRUPT THE CONSOLIDATING
STORM STRUCTURE. THE INITIAL POSITION IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE PARTLY EXPOSED LLCC OBSERVED IN THE MSI.
THE INITIAL INTENSITY IS RAISED TO 40 KTS WITH MEDIUM CONFIDENCE
BASED ON A BLEND OF SUBJECTIVE DVORAK ESTIMATES RANGING FROM T2.5
TO T3.0.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A LOW- TO
MID-LEVEL SUBTROPICAL RIDGE (STR) CENTERED SOUTH OF HONSHU

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS D-PRINT: 39 KTS AT 240100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: LAND INTERACTION WITH NORTHERN LUZON

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) 11W CONTINUES ON A
NORTHWESTWARD TRAJECTORY, STEERED BY A LOW- TO MID-LEVEL STR
CENTERED SOUTH OF HONSHU. AS THE SYSTEM INTENSIFIES, A DEEP-LAYER
RIDGE WILL BECOME THE DOMINANT STEERING INFLUENCE, MAINTAINING A
SIMILAR NORTHWESTWARD MOTION THROUGH TAU 36. AROUND THAT TIME, THE
VORTEX WILL BEGIN TO ROUND THE SOUTHWESTERN PERIPHERY OF THE RIDGE
AND TURN POLEWARD FOR THE REMAINDER OF THE FORECAST PERIOD. THE
OVERALL ENVIRONMENT WILL BE FAVORABLE FOR INTENSIFICATION,
CHARACTERIZED BY WARM SST AND ABUNDANT DEEP-LAYER MOISTURE.
HOWEVER, THE CIRCULATION WILL BE POSITIONED ON THE SOUTHERN
PERIPHERY OF AN UPPER-LEVEL RIDGE, WHICH WILL IMPART PERIODS OF LOW
TO MODERATE EASTERLY SHEAR. FOR THE FIRST 12 HOURS, THIS PERSISTENT
VWS, COMBINED WITH THE TERRAIN OF LUZON, WILL TEMPER THE RATE OF
DEVELOPMENT. ONCE THE STORM PULLS AWAY FROM THE PHILIPPINES AND THE
INNER CORE BECOMES ESTABLISHED, A FASTER RATE OF INTENSIFICATION
WILL COMMENCE. THE JTWC FORECAST NOW CALLS FOR RAPID
INTENSIFICATION TO OCCUR FROM TAU 12 TO TAU 36, WITH THE SYSTEM
REACHING A PEAK INTENSITY OF 80 KTS PRIOR TO LANDFALL. IT IS
POSSIBLE THAT 11W COULD INTENSIFY MORE THAN FORECAST IF IT IS ABLE
TO COMPLETELY COUNTER THE EFFECTS OF VWS. UPON MOVING INLAND, THE
SYSTEM WILL RAPIDLY DECAY AND DISSIPATE BY TAU 72.

MODEL DISCUSSION: THE MODEL GUIDANCE REMAINS IN GOOD AGREEMENT,
EXHIBITING A TIGHT GUIDANCE ENVELOPE WITH A CROSS-TRACK SPREAD OF
110 NM AT THE TIME OF LANDFALL. THE ENVELOPE HAS SHIFTED SLIGHTLY
WESTWARD, WITH THE GFS BRINGING THE SYSTEM CENTER TO WITHIN 40 NM
OF HONG KONG. TO ACCOUNT FOR THE STORM'S RECENT, MORE WESTERLY
TREND, THE JTWC FORECAST TRACK IS INITIALLY HEDGED SLIGHTLY SOUTH
OF THE MULTI-MODEL CONSENSUS THROUGH TAU 24. BEYOND THAT POINT, THE
TRACK NUDGES POLEWARD OF THE CONSENSUS, ALIGNING MORE CLOSELY WITH
THE CLUSTER OF AI TRACKERS. THE POTENTIAL FOR RAPID INTENSIFICATION
(RI) IS NOW EXPLICITLY SUPPORTED BY THE TRIGGERING OF RIDE, RICN,
AND FRIA. WHILE GFS IS THE MOST CONSERVATIVE SOLUTION WITH A 70-KT
PEAK, THE MAJORITY OF THE OTHER MODELS DEPICT MORE AGGRESSIVE
STRENGTHENING. THE JTWC INTENSITY FORECAST IS SET ON THE HIGHER END
OF THE GUIDANCE ENVELOPE, CALLING FOR A 30 KT INCREASE BEGINNING AT
TAU 12. THIS FORECAST REMAINS BELOW THE MORE AGGRESSIVE PEAKS OF 85
KTS SHOWN BY THE EXPERIMENTAL GOOGLE DEEPMIND MODEL AND 100 KTS BY
COAMPS-TC. IN ALIGNMENT WITH THE INTENSITY AIDS, THE FORECAST SHOWS
RAPID WEAKENING AFTER LANDFALL.

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