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JTWC/09W/#04/07-19 06Z Prognostic Reasoning
WDPN31 PGTW 190900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (WIPHA) WARNING NR
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 20.5N 118.9E
INITIAL INTENSITY: 50 KTS
GEOGRAPHIC REFERENCE: 284 NM EAST-SOUTHEAST OF HONG KONG
MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
SIGNIFICANT WAVE HEIGHT: 24 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A MAINLY
OBSCURED LOW-LEVEL CIRCULATION CENTER WITH SYNOPTIC SCALE SPIRAL BANDS
OF DEEP CONVECTION, ASSOCIATED WITH TROPICAL STORM (TS) 09W (WIPHA).
STRONG EQUATORWARD OUTFLOW CAN BE OBSERVED ON THE WATER VAPOR AND
VISIBLE SPECTRUM SATELLITE IMAGERY. THE INITIAL POSITION IS PLACED
WITH
MEDIUM CONFIDENCE DUE TO INTENSE CONVECTIVE OBSCURATION, AND IS BASED
ON 190552Z ATMS MICROWAVE IMAGE, IN CONJUNCTION WITH THE POSITION
EXTRAPOLATION FROM A 190211Z METOP-C UHR ASCAT PASS. THE INITIAL
INTENSITY OF 50 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A
COMBINATION OF AGENCY DVORAK FIXES AND OBJECTIVE ESTIMATES LISTED
BELOW, SUPPORTED BY THE AFOREMENTIONED UHR ASCAT PASS DATA. ADDITIONAL
ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS, INCLUDING DEEP-
LAYER MOISTURE AVAILABLE THROUGHOUT THE ATMOSPHERIC COLUMN, WARM (29-
30
C) SEA SURFACE TEMPERATURES AND STRONG UPPER-LEVEL OUTFLOW, OFFSET
ONLY
BY A MODERATE TO HIGH (20-25 KTS) VERTICAL WIND SHEAR (VWS).
INITIAL WIND RADII BASIS: A 190214Z METOP-C ASCAT PASS
CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) TO
THE NORTHEAST
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T3.0 - 45 KTS
RJTD: T3.0 - 45 KTS
RCTP: T3.5 - 55 KTS
KNES: T3.5 - 55 KTS
CIMSS SATCON: 51 KTS AT 190600Z
CIMSS ADT: 45 KTS AT 190530Z
CIMSS AIDT: 42 KTS AT 190600Z
CIMSS D-MINT: 47 KTS AT 190528Z
CIMSS D-PRINT: 47 KTS AT 190630Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 20-25 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG EQUATORWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: MEDIUM
INITIAL INTENSITY: HIGH
INITIAL WIND RADII: HIGH
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TS 09W IS FORECAST TO TRACK WEST-NORTHWESTWARD
ALONG THE SOUTHWESTERN PERIPHERY OF A STR LOCATED TO THE NORTHEAST
OF THE SYSTEM. AFTER TAU 24, THE RIDGING IS EXPECTED TO BUILD AND
EXTEND FURTHER WEST, RESULTING IN THE CIRCULATION MAKING A SLIGHT TURN
TOWARD THE WEST. DURING THAT TIME, THE SYSTEM WILL REMAIN WITHIN
MOSTLY
FAVORABLE ENVIRONMENT LEADING TO POTENTIAL INTENSIFICATION AND
REACHING
PEAK WIND SPEEDS OF 55-60 KTS BETWEEN TAUS 12 AND 24. AS THE RIDGING
BUILDS, THE TRACK IS EXPECTED TO SHIFT WEST-SOUTHWESTWARD AND CONTINUE
ALONG THE COASTLINE OF SOUTHERN CHINA, UNTIL THE SYSTEM REACHES
NORTHEASTERN VIETNAM, WHERE IT IS EXPECTED TO MAKE LANDFALL. TS 09W IS
FORECAST TO BEGIN WEAKENING AFTER TAU 24, AS A RESULT OF TERRAIN
INTERACTION AND SLIGHTLY INCREASING VWS, HOWEVER AS SOON AS THE TS
REACHES THE GULF OF TONKIN, IT WILL ENCOUNTER EXCEPTIONALLY WARM (30-
31
C) SEA SURFACE TEMPERATURES. THIS WILL RESULT IN MAINTAINED OR
POTENTIALLY SLIGHTLY INCREASED WIND SPEEDS MAXIMA. AFTERWARD HOWEVER,
THE SYSTEM IS EXPECTED TO BEGIN DISSIPATING, SHORTLY AFTER LANDFALL
EAST OF HANOI, VIETNAM. FULL DISSIPATION IS EXPECTED AROUND TAU 96.
MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT FOR THE SHORT TERM, AS WITNESSED BY A 65 NM CROSS-TRACK
SPREAD AT TAU 72, WITH MAJORITY OF THE MODELS ENCLOSED WITHIN A 30 NM
ENVELOPE. THE TWO OPPOSITE OUTLIERS ARE GALWEM, TAKING THE SYSTEM
ON A TRACK FURTHER NORTH, AND NAVGEM SUGGESTING A PASS CLOSER TO
HAINAN ISLAND. LONG TERM GUIDANCE IS NOT SIGNIFICANTLY WORSE, WITH
A CROSS-TRACK SPREAD OF JUST 110 NM AT TAU 96, HOWEVER THE FORECAST
CONFIDENCE IS REDUCED TO MEDIUM, DUE TO SOME MODELS (PAST RUNS OF
THE DETERMINISTIC GFS, AND GFS ENSEMBLE) INDICATING POTENTIAL FOR
THE SYSTEM TURNING AROUND AT OR SOON AFTER LANDFALL. INTENSITY
GUIDANCE
IS IN FAIR AGREEMENT, WITH MAJORITY OF THE MODELS SUGGESTING 45-55 KTS
FOR THE NEXT 24 HOURS, FOLLOWED BY WEAKENING AND EVENTUAL DISSIPATION.
JTWC FORECAST IS LAID CLOSE TO THE MULTI-MODEL CONSENSUS THROUGHOUT
THE
FORECAST. LOW INTENSITY PREDICTION CONFIDENCE IS ASSOCIATED WITH THE
SLIGHTLY INCREASED UNCERTAINTY IN REGARD TO THE TRACK OF THE SYSTEM
AROUND THE TIME OF LANDFALL.
FORECAST CONFIDENCE:
TRACK 0 - 72 HR: HIGH
TRACK 72-120 HR: MEDIUM
INTENSITY 0 - 72 HR: MEDIUM
INTENSITY 72-120 HR: LOW
NNNN
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发表于 2025-7-19 15:31
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