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JTWC/34W/#08/11-28 18Z Prognostic Reasoning
WDPN32 PGTW 282100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 34W (THIRTYFOUR)
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 4.5N 105.1E
INITIAL INTENSITY: 30 KTS
GEOGRAPHIC REFERENCE: 390 NM SOUTH-SOUTHWEST OF HO CHI MINH
CITY, VIETNAM
MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 06 KTS
SIGNIFICANT WAVE HEIGHT: 10 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND ANIMATED
RADAR DATA FROM MALAYSIA SHOWS THAT THE REMNANTS OF TC 04B RAPIDLY
MOVED OVER THE MALAYSIAN PENINSULA AND EMERGED INTO THE SOUTH CHINA
SEA AROUND 280600Z LAST NIGHT, WITH A VERY WELL-DEFINED LOW LEVEL
CIRCULATION CENTER (LLCC). REANALYSIS OF THE AVAILABLE DATA RESULTS
IN A 30-KNOT INTENSITY AS EARLY AS 12-HOURS AGO, AS THE SYSTEM
MOVED OFFSHORE. UNFORTUNATELY, AS THE SYSTEM HAS TRACKED FURTHER
AWAY FROM THE COAST, IT HAS BECOME LESS DEFINED IN THE RADAR DATA,
BUT A VERY TIMELY 281744Z GMI COLOR-ENHANCED 37GHZ MICROWAVE IMAGE
REVEALS A MICROWAVE EYE-LIKE FEATURE OR LOW EMISSIVITY REGION (LER)
SURROUNDED BY SHALLOW, WARM RAIN BANDS AND A SMALL REGION OF
INTENSE CONVECTION ARRAYED ALONG THE WESTERN PERIPHERY. THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE MICROWAVE
IMAGERY AS WELL AS THE LAST FEW FRAMES OF DECENT RADAR DATA. THE
INITIAL INTENSITY IS ASSESSED WITH LOW CONFIDENCE DUE TO THE LACK
OF OBJECTIVE OR SCATTEROMETER DATA, AND PLACED IN LINE WITH THE
AGENCY DVORAK INTENSITY ESTIMATES NOTED BELOW. ENVIRONMENTAL
CONDITIONS ARE MARGINALLY FAVORABLE, WITH WARM SSTS, LOW TO
MODERATE SOUTHERLY SHEAR AND WEAK POLEWARD OUTFLOW ALOFT.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A SHALLOW
NEAR EQUATORIAL RIDGE (NER) TO THE SOUTHEAST AND ALONG THE WESTERN
EDGE OF A BAND OF MONSOONAL SOUTHWESTERLIES WHICH EXTENDS FROM
SINGAPORE TO PALAWAN ISLAND.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.0 - 30 KTS
RJTD: T2.0 - 30 KTS
KNES: T1.5 - 25 KTS
CIMSS D-PRINT: 29 KTS AT 281800Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
VWS: 15-20 KTS
SST: 28-29 CELSIUS
OUTFLOW: WEAK POLEWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: LOW
INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: WHILE THIS WARNING IS A REGENERATION
OF TC 04B, BEING THE FIRST WARNING IN THE SOUTH CHINA SEA, THIS IS
THE INITIAL PROGNOSTIC REASONING MESSAGE FOR TD 34W AND ESTABLISHES
THE REGENERATED FORECAST PHILOSOPHY.
FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 34W IS TRACKING
NORTHEASTWARD ALONG THE WESTERN SIDE OF A BELT OF SOUTHWESTERLY
MONSOONAL FLOW. THERE ARE NO SIGNIFICANT CHANGES EXPECTED IN THE
OVERALL STEERING PATTERN FOR THE DURATION OF THE FORECAST PERIOD.
IF ANYTHING, THE SYSTEM WILL SPEED UP AS A NER BUILDS OVER NORTHERN
BORNEO AND STRENGTHENS THE STEERING GRADIENT. IN THE NEAR-TERM,
OVERALL FAVORABLE ENVIRONMENTAL CONDITIONS WILL SUPPORT A SLIGHT
INTENSIFICATION TREND, THOUGH THE VORTEX WILL REMAIN VERY SHALLOW
THROUGH THE FORECAST PERIOD AND THUS WILL BE UNABLE TO SUPPORT OR
MAINTAIN MORE THAN A TRIVIAL AMOUNT OF INTENSIFICATION. BY TAU 24,
AS THE SYSTEM CLOSES IN ON TS 33W, NORTH-NORTHEASTERLY SHEAR
ASSOCIATED WITH THE OUTFLOW FROM TS 33W IS FORECAST TO INCREASE
SHARPLY, WHICH ALONG WITH SOME DRY AIR INTRUDING INTO THE CORE OF
THE SYSTEM, WILL BEGIN A RAPID WEAKENING TREND. BY TAU 48,
POTENTIALLY AS EARLY AS TAU 36, THE SYSTEM WILL DISSIPATE AS A
TROPICAL CYCLONE TO THE EAST OF HO CHI MINH CITY.
MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD
AGREEMENT, WITH ALL AVAILABLE GUIDANCE SUPPORTING A NORTHEASTWARD
TRACK THROUGH THE FORECAST PERIOD. CROSS-TRACK SPREAD OPENS UP TO A
MODEST 120NM BY TAU 36, AS THE NAVGEM AND ECWMF ENSEMBLE MEAN TRY
TO PULL THE SYSTEM ONTO A MORE NORTHWARD TRACK, WHILE THE GFS, GEFS
MEAN AND REMAINDER OF THE GUIDANCE PACKAGE CONTINUE THE TRACK
STRAIGHT NORTHEASTWARD. THE JTWC FORECAST IS POSITIONED NEAR, BUT
SLIGHTLY AHEAD OF, THE MULTI-MODEL CONSENSUS MEAN THROUGH THE
FORECAST PERIOD, WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS IN
GOOD AGREEMENT, WITH ALL AVAILABLE GUIDANCE SUPPORTING A SLIGHT
INTENSIFICATION THROUGH TAU 12, FOLLOWED BY A STEADY WEAKENING
AFTER TAU 24.
FORECAST CONFIDENCE:
TRACK 00-72 HR: HIGH
INTENSITY 00-72 HR: HIGH//
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发表于 2025-11-29 04:08
