WTPQ30 RJTD 201800
RSMC TROPICAL CYCLONE PROGNOSTIC REASONING
REASONING NO.10 FOR TS 2023 KROVANH (2023)
1.GENERAL COMMENTS
TS KROVANH IS LOCATED AT 9.2N, 113.8E. INFORMATION ON THE CURRENT
POSITION IS BASED ON ANIMATED MSI AND SURFACE OBSERVATIONS.
POSITIONAL ACCURACY IS FAIR. CENTRAL PRESSURE IS 1002HPA AND
MAXIMUM SUSTAINED WINDS ARE 35KNOTS. THE SYSTEM IS IN A NEUTRAL
ENVIRONMENT FOR DEVELOPMENT UNDER THE INFLUENCE OF HIGH SSTS, GOOD
UPPER-LEVEL OUTFLOW AND INCREASED VWS. THIS HAS CAUSED THE SYSTEM
TO MAINTAIN ITS INTENSITY OVER THE LAST SIX HOURS. INFORMATION ON
THE CURRENT INTENSITY IS BASED ON SURFACE WINDS DATA ESTIMATED
FROM SATELLITE SCATTEROMETERS AND DVORAK INTENSITY ANALYSES.
2.SYNOPTIC SITUATION
THE SYSTEM IS MOVING SOUTHWESTWARD DUE TO WEAK STEERING FLOW.
ANIMATED MSI SHOWS THE SEPARATION OF ACTIVE CONVECTIVE CLOUD
CLUSTERS FROM THE CSC, INDICATING INTERFERENCE FROM
INTENSIFICATION. ANIMATED MSI SHOWS GOOD CLOUD CHARACTERISTICS OF
ANTICYCLONIC OUTFLOW.
3.TRACK FORECAST
THE SYSTEM WILL MOVE WEST-SOUTHWESTWARD DUE TO WEAK STEERING FLOW
UNTIL FT48. THE TRACK FORECAST IS BASED ON GSM PREDICTIONS, AND
REFERENCE TO OTHER NWP MODELS. TRACK FORECAST CONFIDENCE IS LOW
DUE TO SIGNIFICANT DIFFERENCES AMONG NWP MODEL OUTPUTS.
4.INTENSITY FORECAST
THE SYSTEM WILL MAINTAIN ITS INTENSITY UNTIL FT24 DUE TO THE
INFLUENCE OF INTERACTION WITH GOOD UPPER LEVEL OUTFLOW, LOWER SSTS
AND REDUCED TCHP. THE SYSTEM WILL THEN WEAKEN DUE TO THE INFLUENCE
OF INTERACTION WITH LOW TCHP AND LOWER SSTS. THE SYSTEM WILL
WEAKEN TO TD INTENSITY BY FT48. THE INTENSITY FORECAST IS BASED ON
GUIDANCE DATA.
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WDPN31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 26W (KROVANH)
WARNING NR 010//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 26W (KROVANH), LOCATED APPROXIMATELY
287 NM SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-
SOUTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS WEAK, FRAGMENTED, AND
FLARING CONVECTION SHEARED APPROXIMATELY 100NM NORTHWEST OF A RAGGED
AND FULLY EXPOSED LOW LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS
PLACED WITH FAIR CONFIDENCE BASED ON THE LLC IN THE MSI LOOP. THE
INITIAL INTENSITY OF 25KTS, CLASSIFIED AS TOO WEAK BY PGTW, IS BASED ON
SURFACE WIND OBSERVATIONS FROM HUYEN TRAN ISLAND, 20NM TO THE NORTH.
RECENT SCATTEROMETER DATA INDICATE A NARROW SWATH OF ELEVATED 30-35KT
WINDS TO THE NORTHWEST ASSOCIATED WITH CONVERGENCE INDUCED BY A WIND
SURGE IN THE SOUTH CHINA SEA AND COMPRESSED ALONG THE VIETNAMESE COAST. UPPER-LEVEL ANALYSIS REVEALS A MARGINAL ENVIRONMENT WITH MODERATE
(15-20KT) VERTICAL WIND SHEAR (VWS) OFFSET BY STRONG POLEWARD OUTFLOW.
SST VALUES (27-28C) REMAIN CONDUCIVE. THE SYSTEM IS TRACKING WEST- SOUTHWESTWARD ALONG THE SOUTHEAST PERIPHERY OF A LOW-LEVEL
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHWEST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TD KROVANH IS EXPECTED TO TRACK WESTWARD ALONG THE SOUTHERN
PERIPHERY OF THE LOW-LEVEL STR THROUGH TAU 24. THE SYSTEM IS FORECAST
TO HOLD ITS CURRENT INTENSITY UNDER THE MARGINAL CONDITIONS FOR 12HRS
THEN WEAKEN STEADILY AS IT TRACKS INTO INCREASING VWS AND DIMINISHING
UPPER LEVEL OUTFLOW. THE SYSTEM IS FORECAST TO DISSIPATE SOUTH OF
VIETNAM BY TAU 24. NUMERICAL MODELS ARE IN GOOD AGREEMENT LENDING FAIR CONFIDENCE IN THE JTWC TRACK FORECAST.//
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