WDPN31 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (NOUL) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.3N 125.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 324 NM NORTHEAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTIVE BANDING ON THE WESTERN PERIPHERY WRAPPING AROUND A
NASCENT, RAGGED CENTRAL DENSE OVERCAST (CDO). THE VORTEX HAS BECOME
SIGNIFICANTLY LESS TILTED WITH HEIGHT AS THE VERTICAL WIND SHEAR
(VWS) HAS EASED. THESE INDICATORS, ALONG WITH INCREASING CURVATURE
IN THE CONVECTIVE STRUCTURE AND EXPANDING OUTFLOW ALOFT, POINT TO A
DEVELOPING TREND. ENVIRONMENTAL CONDITIONS ARE FAVORABLE FOR
INTENSIFICATION. THE SYSTEM IS TRAVERSING VERY WARM SEA SURFACE
TEMPERATURES (SST) OF 30-31 DEGREES CELSIUS WITH HIGH OCEAN HEAT
CONTENT (OHC) NEAR 120 KJ PER CM2, AND IS SUPPORTED BY INCREASING
UPPER-LEVEL DIVERGENCE AND RICH DEEP-LAYER MOISTURE. THESE POSITIVE
FACTORS ARE SLIGHTLY TEMPERED BY MODEST, ONGOING VWS. THE
ASSESSMENT OF INTENSITY AND INTERNAL STRUCTURE HAS BEEN MADE MORE
CHALLENGING BY A LACK OF HIGH-RESOLUTION MICROWAVE IMAGERY SINCE
231036Z AND RELIABLE OCEAN SURFACE VECTOR WIND DATA SINCE 230138Z.
THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
THE PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) AND THE
CLUSTER OF AGENCY FIXES. THE IMPROVED CONVECTIVE STRUCTURE
JUSTIFIES RAISING THE INITIAL INTENSITY TO 35 KTS WITH MEDIUM
CONFIDENCE, WHICH IS SUPPORTED BY THE SUBJECTIVE DVORAK ESTIMATES
OF T2.5 FROM PGTW AND KNES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS D-PRINT: 28 KTS AT 231800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 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 11W IS BEING DRIVEN
WEST-NORTHWESTWARD BY A LOW- TO MID-LEVEL RIDGE CENTERED SOUTH OF
HONSHU. AS THE SYSTEM INTENSIFIES, THE DEEPER-LAYER RIDGE WILL
BECOME THE DOMINANT STEERING MECHANISM BY TAU 12, MAINTAINING THE
GENERAL NORTHWEST MOTION. AT TAU 36, THE STORM WILL BEGIN TO ROUND
THE WESTERN PERIPHERY OF THE STR, TURN POLEWARD INTO SOUTHEAST
CHINA, AND MAINTAIN THIS TRAJECTORY UNTIL IT DISSIPATES INLAND. THE
ENVIRONMENT WILL BE FAVORABLE FOR INTENSIFICATION, WITH THE VERY
WARM WATERS OF THE PHILIPPINE SEA AND THE SOUTH CHINA SEA SUPPLYING
AMPLE ENERGY TO THE CIRCULATION. HOWEVER, THE SYSTEM'S POSITION
ALONG THE SOUTHERN EDGE OF AN UPPER-LEVEL RIDGE WILL IMPART
PERSISTENT, LOW-TO-MODERATE EASTERLY VWS THROUGHOUT ITS LIFECYCLE.
DESPITE THE VWS, THE IMPROVING VERTICAL ALIGNMENT OF THE VORTEX
WILL SUPPORT A NEAR-RAPID RATE OF INTENSIFICATION OVER THE NEXT 12
HOURS. THIS STRENGTHENING WILL BE MODESTLY TEMPERED BY INTERACTION
WITH THE TERRAIN OF NORTHERN LUZON. AFTER TAU 24, AS 11W PULLS AWAY
FROM LAND, A HIGHER RATE OF INTENSIFICATION WILL COMMENCE. THE
FORECAST CALLS FOR 11W TO PEAK AT 80 KTS AT LANDFALL AROUND TAU 48.
ONCE INLAND, THE SYSTEM WILL RAPIDLY DECAY, LEADING TO DISSIPATION
BY TAU 96.

MODEL DISCUSSION: THE MODEL TRACKERS PRESENT A TIGHT ENVELOPE UP TO
THE POINT OF LANDFALL, WITH EXCELLENT ALONG-TRACK CONSENSUS.
NAVGEM IS THE POLEWARD OUTLIER. EXCLUDING THIS SOLUTION, THE
CROSS-TRACK SPREAD AMONG THE REMAINING GUIDANCE IS 100 NM AT TAU
48. THIS SPREAD IS HIGHLIGHTED BY GFS, WHICH BRINGS THE SYSTEM
CENTER TO WITHIN 25 NM OF HONG KONG, WHILE ECMWF IS 100 NM FURTHER
EAST. THE JTWC TRACK FORECAST LARGELY FOLLOWS THE MULTI-MODEL
CONSENSUS WITH HIGH CONFIDENCE, HEDGED SLIGHTLY TOWARDS THE MORE
SOUTHERN SOLUTIONS OF HAFS-A AND THE EXPERIMENTAL GOOGLE DEEPMIND
THROUGH TAU 72. VIRTUALLY ALL RELIABLE INTENSITY AIDS SHOW STEADY
TO RAPID INTENSIFICATION THROUGH TAU 48. TAKING RECENT SATELLITE
TRENDS INTO ACCOUNT, THE JTWC INTENSITY FORECAST CALLS FOR A 15-KT
INCREASE OVER THE NEXT 12 HOURS, FOLLOWED BY SLIGHTLY SLOWER
DEVELOPMENT FROM TAU 12 TO TAU 24 DUE TO LAND INTERACTION AND A
FASTER RATE THEREAFTER. THE FORECAST IS SET ON THE HIGHER END OF
THE GUIDANCE ENVELOPE BUT IS BELOW THE 85-90 KT PEAK PREDICTED BY
DEEPMIND AND COAMPS-TC. THE GUIDANCE SUITE RAPIDLY WEAKENS THE
SYSTEM AFTER LANDFALL, SHOWING COMPLETE DISSIPATION NO LATER THAN
TAU 96.

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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