WDPN32 PGTW 052100

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//

SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (KUJIRA) WARNING NR

005//

RMKS/

1. FOR METEOROLOGISTS.

2. 6 HOUR SUMMARY AND ANALYSIS.



SUMMARY:

   INITIAL POSITION: 17.7N 120.2E

   INITIAL INTENSITY: 35 KTS

   GEOGRAPHIC REFERENCE: 192 NM NORTH-NORTHWEST OF MANILA,

PHILIPPINES

   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 04 KTS

   SIGNIFICANT WAVE HEIGHT: 12 FEET



SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:

ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS POORLY

ORGANIZED CONVECTION OBSCURING THE PREVIOUSLY EXPOSED LOW-LEVEL

CIRCULATION CENTER OF TROPICAL STORM 13W. ALTHOUGGH POORLY

ORGANIZED, THE CONVECTION HAS MANAGED TO PERSIST NEAR THE SYSTEM

CENTER AND SUSTAINED THE CIRCULATION AS IT APPROACHES NORTHERN

LUZON, WHERE LANDFALL IS IMMINENT. THE INITIAL POSITION IS PLACED

WITH MEDIUM CONFIDENCE BASED ON THE ROTATION OF THE CONVECTIVE

ELEMENTS, BUT THERE HAS BEEN A LACK OF MICROWAVE OR SCATTEROMETR

DATA TO CONFIRM THE POSITION OF THE LLCC. THE INITIAL INTENSITY OF

35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PERSISTENT

STRUCTURE OF THE SYSTEM AND ACKNOWLEDGING THE PRESENCE OF

SOUTHWESTERLY MONSOONAL FLOW ALONG THE COAST OF LUZON. THE

ENVIRONMENT IS CHARACTERIZED AS MARGINAL WITH MODERATE VERTICAL

WIND SHEAR AND PROXIMITY TO LUZON LIMITING THE POTENTIAL FOR

FURTHER INTENSIFICATION.



INITIAL WIND RADII BASIS: PERSISTENCE



CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT, DOMINATED BY

THE LOWER-LEVEL SOUTHWESTERLY MONSOONAL SURGE FLOW



AGENCY DVORAK AND AUTOMATED FIXES:

   PGTW: NO CURRENT ESTIMATE

   RJTD: T2.0 - 30 KTS

   RCTP: T1.5 - 25 KTS

   KNES: T2.0 - 30 KTS

   CIMSS ADT: 33 KTS AT 051730Z

   CIMSS AIDT: 32 KTS AT 051730Z

   CIMSS D-MINT: 28 KTS AT 051811Z

   CIMSS D-PRINT: 33 KTS AT 052010Z



FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL

   VWS: 15-20 KTS

   SST: 29-30 CELSIUS

   OUTFLOW: STRONG EQUATORWARD

   OTHER FACTORS: LAND INTERACTION



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) 13W HAS SLOWLY MADE ITS

WAY SOUTHEASTWARD TOWARD NORTHERN LUZON OVER THE PAST SIX HOURS.

LANDFALL OVER THE ISLAND IS IMMINENT, AFTER WHICH THE SOUTHWESTERLY

MONSOONAL FLOW (ENHANCED BY TY 12W TO THE NORTHEAST) IS EXPECTED TO

CAPTURE THE REMNANT VORTEX AND EJECT IT INTO THE PHILIPPINE SEA

SHORTLY AFTER TAU 12. THE REMNANTS ARE THEN FORECAST TO RAPIDLY

TRACK WITHIN THE SOUTHWESTERY FLOW BEFORE EVENTUALLY BEING ABSORBED

INTO THE WINDFIELD SURROUNDING TY 12W BY TAU 36. THE INTENSITY IS

EXPECTED TO WEAKEN APPRECIABLY AS THE SYSTEM TRACKS OVER LUZON,

THEN MORE SLOWLY AS THE VORTEX OPENS INTO A TROUGHING FEATURE OF

THE SOUTHWESTERLY FLOW OVER THE PHILIPPINE SEA. THE REMNANTS WILL

LOSE TROPICAL CHARACTERISTICS IN THIS PROCESS AND DISSIPATION UNDER

THESE CONDITIONS IS EXPECTED BY TAU 36.



MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT ABOUT

THE TRACK MOTION DOMINATED BY THE SOUTHWESTERLY MONSOON FLOW, WITH

PREVIOUS TRACK SPEED DISPARITIES NO LONGER PRESENT IN THE LATEST

MODEL SUITE. THE JTWC TRACK IS PLACED CLOSE TO THE MULTI-MODEL

CONSENSUS WITH MEDIUM CONFIDENCE, OWING TO THE UNCERTAINTY

ASSOCIATED WITH CROSSING OVER LUZON. MODEL INTENSITY GUIDANCE DOES

NOT APPEAR TO ACCURATLEY DEPICT THE WEAKENING OVER LAND, AND THE

JTWC INTENSITY FORECAST IS PLACED BELOW THE CONSENSUS TO ACCOUNT

FOR THIS.



FORECAST CONFIDENCE:

   TRACK 00-72 HR: MEDIUM

   INTENSITY 00-72 HR: MEDIUM//

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