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发表于 2025-10-19 17:00
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JTWC/30W/#06/10-19 06Z Prognostic Reasoning
WDPN31 PGTW 190900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 30W (FENGSHEN) WARNING NR
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 14.8N 119.7E
INITIAL INTENSITY: 35 KTS
GEOGRAPHIC REFERENCE: 76 NM WEST OF MANILA, PHILIPPINES
MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 16 KTS
SIGNIFICANT WAVE HEIGHT: 17 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 30W HAS NOW MOVED OFFSHORE INTO THE SOUTH CHINA
SEA AFTER PASSING SOUTH OF MANILA AND IS PRIMED FOR RAPID
INTENSIFICATION. TRACKING OF THE LOW LEVEL CIRCULATION CENTER
(LLCC) HAS BEEN A CHALLENGE AS THE SYSTEM PASSED ACROSS LUZON AND
LOST A WELL-DEFINED LLCC. SURFACE OBSERVATIONS FROM THE MANILA
REGION, SUBIC BAY, CLARK AB AND IBA HAVE PROVEN TO BE HIGHLY
BENEFICIAL TO PLACEMENT OF THE LLCC. SURFACE WINDS AT THE LAST
THREE ABOVE ARE NOW SOUTHERLY OR SOUTHWESTERLY, PROVIDING HIGH
CONFIDENCE THAT THE LLCC IS SOMEWHERE TO THE WEST OF ALL THREE.
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
FAST-DEVELOPING LLCC WITH DEEP CONVECTION AND VORTICAL HOT TOWERS
CONGEALING INTO BANDING FEATURES ALONG THE SOUTHERN AND EASTERN
FLANKS OF THE LLCC. RADAR DATA HAS BEEN INCONCLUSIVE ALL DAY BUT IS
NOW BEGINNING TO TIGHTEN UP AND SHOWING WHAT COULD BE A MID-LEVEL
VORTEX BEGINNING TO TAKE SHAPE JUST WEST OF IBA. SOME OF THE
MESOSCALE MODELS SUGGESTED THIS VERY SCENARIO, WITH A MID-LEVEL
ROTATION DISPLACED NORTH OF THE LLCC DUE TO SOME MODERATE SOUTHERLY
MID-LEVEL SHEAR. THE INITIAL POSITION IS ASSESSED WITH LOW
CONFIDENCE DUE TO THE LACK OF RECENT MICROWAVE IMAGERY OR RELIABLE
SCATTEROMETER DATA AND IS BASED MOSTLY ON THE SURFACE OBSERVATIONS
AND MSI LOOP. THE INITIAL INTENSITY IS ASSESSED WITH LOW CONFIDENCE
AS WELL AND COULD BE A BIT HIGHER, WITH THE BULK OF AGENCY FIXES
RIDING ABOUT 10 KNOTS HIGHER AND THE AVAILABLE OBJECTIVE ESTIMATES
AVERAGING RIGHT AROUND 35 KNOTS. THE ENVIRONMENT HAS IMPROVED NOW
THAT THE SYSTEM IS MOVING OFFSHORE, WITH ZESTY WATERS TO FEED OFF,
STRONG RADIAL OUTFLOW AND LOW DEEP-LAYER SHEAR.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T3.0 - 45 KTS
RJTD: T2.0 - 30 KTS
RCTP: T3.0 - 45 KTS
KNES: T3.0 - 45 KTS
DEMS: T3.0 - 45 KTS
CIMSS SATCON: 38 KTS AT 190400Z
CIMSS D-MINT: 32 KTS AT 190524Z
CIMSS D-PRINT: 32 KTS AT 190600Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 0-5 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG RADIAL
ANALYSIS CONFIDENCE:
INITIAL POSITION: LOW
INITIAL INTENSITY: LOW
INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TS 30W IS FORECAST TO TRACK RELATIVELY QUICKLY
TOWARDS THE NORTHWEST ALONG THE SOUTHWESTERN SIDE OF THE STR TO THE
NORTHEAST. THE SYSTEM WILL CONTINUE TRACKING NORTHWESTWARD FOR
ABOUT 36 HOURS, BEFORE IT MOVES INTO A WEAK STEERING ENVIRONMENT,
CAUGHT BETWEEN COMPETING RIDGES TO THE NORTHEAST AND THE WEST. AT
THE SAME TIME, THE SYSTEM WILL SMACK HEADLONG INTO STRONG
NORTHEASTERLY FLOW FUNNELING SOUTH OUT OF THE TAIWAN STRAIT. AS THE
SYSTEM CONTINUES TO PUSH SLOWLY WESTWARD, THESE NORTHEASTERLY WINDS
WILL STRENGTHEN AS THEY ARE TRAPPED BETWEEN TS 30W AND COASTAL
CHINA, AND AS THEY DO SO, WILL EFFECTIVELY BLOCK TS 30W FROM
PROGRESSING FURTHER TO THE NORTHWEST. BY TAU 48, THE SYSTEM WILL
HAVE REACHED ITS FURTHER NORTHWESTWARD POINT AND QUICKLY TURN
SOUTHWESTWARD, AHEAD OF THE LOW-LEVEL NORTHEASTERLY FLOW PUSHING
OUT OF CHINA. THE SYSTEM IS EXPECTED TO MAKE LANDFALL ALONG THE
COAST OF CENTRAL VIETNAM PRIOR TO TAU 96, BEFORE PROGRESSING INTO
EASTERN CAMBODIA BY THE END OF THE FORECAST PERIOD. NOW THAT THE
SYSTEM HAS MOVED OVER WATER AND MOVING FURTHER AWAY FROM LUZON,
STRONG RADIAL OUTFLOW ALOFT, WARM WATERS AND LOW SHEAR WILL ALLOW
FOR RAPID VORTEX SYMMETRIZATION AND INTENSIFICATION OVER THE NEXT
24 HOURS. THE FORECAST CALLS FOR THE SYSTEM TO REACH PEAK INTENSITY
WITHIN 36 HOURS, THOUGH A FASTER RATE OF INTENSIFICATION AND A
HIGHER PEAK INTENSITY ARE CERTAINLY A POSSIBILITY IF THE SYSTEM CAN
QUICKLY ORGANIZE. AFTER TAU 48 HOWEVER, SHEAR IS EXPECTED TO
INCREASE AND THE INFLUX OF RELATIVELY COOL, DRY AND STABLE AIR
ASSOCIATED WITH THE NORTHEASTERLY FLOW INTO THE WESTERN FLANK OF
THE SYSTEM WILL MARK THE ONSET OF A RAPID WEAKENING PHASE. BY THE
TIME IT MAKES LANDFALL ALONG THE COAST OF VIETNAM THE SYSTEM WILL
BE A MINIMAL TROPICAL STORM, WITH A RELATIVELY SHALLOW VORTEX,
HAVING BEEN ENGULFED BY DRY AIR AND SHATTERED BY MODERATE EASTERLY
SHEAR. AFTER LANDFALL, THE SYSTEM WILL RAPID WEAKEN AND DISSIPATE
NO LATER THAN TAU 120 AND LIKELY MUCH EARLIER.
MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH HAS BEEN
DISCARDED FROM THE CONSENSUS DUE TO ITS HIGHLY UNLIKELY WESTWARD
TRACK, THE REMAINDER OF THE GUIDANCE PACKAGE IS IN RELATIVELY GOOD
AGREEMENT, AT LEAST THROUGH TAU 48. AT THAT POINT IN THE FORECAST,
CROSS-TRACK SPREAD IS JUST 75NM BETWEEN THE JGSM AND GOOGLE DEEP
MIND (FNV3) MODEL ON THE NORTHERN EDGE, AND THE GEFS MEAN ON THE
SOUTH. ALONG-TRACK SPREAD UP TO THIS POINT IN THE FORECAST IS
MINIMAL. BUT THINGS GET HAIRY AFTER TAU 48, WITH SIGNIFICANT AND
RAPID ALONG- AND CROSS-TRACK DISPERSION IN THE MODEL GUIDANCE. AT
TAU 72, THERE IS A 250NM ALONG-TRACK SPREAD BETWEEN THE JGSM WHICH
SHOWS LANDFALL IN VIETNAM AT THIS POINT AND THE EC-AIFS WHICH LAGS
FAR BEHIND, LINGERING IN THE SCS. THE SITUATION ONLY GETS WORSE
GOING FORWARD, SUCH THAT BY TAU 120, THERE IS OVER 500NM OF
ALONG-TRACK SPREAD BETWEEN THE GALWEM IN THE GULF OF THAILAND AND
THE ECMWF JUST ONSHORE IN SOUTHERN VIETNAM. ENSEMBLE MODELS ALL
SHOW SIMILAR TRACK SHAPES BUT ALSO DIFFER FAIRLY WIDELY ON THE
SPEED OF THE TRACK AFTER TAU 48, LEADING TO SIGNIFICANT ALONG-TRACK
SPREAD AFTER THAT POINT IN THE FORECAST. THE JTWC FORECAST IS
POSITIONED ON THE NORTHERN SIDE OF THE GUIDANCE ENVELOPE, CLOSE TO
THE FNV3 TRACKER TO TAU 48, THEN CLOSER TO THE ECMWF DETERMINISTIC
THEREAFTER. CONFIDENCE IS HIGH TO TAU 48, BUT LOW THEREAFTER DUE TO
THE LARGE AMOUNT OF UNCERTAINTY IN THE MODEL GUIDANCE AFTER TAU 72.
INTENSITY GUIDANCE IS IN GOOD AGREEMENT, WITH ALL CONSENSUS MEMBERS
INDICATING THE PEAK INTENSITY OCCURRING AT TAU 48, WITH A RANGE
BETWEEN 50 AND 65 KNOTS, FOLLOWED BY RAPID WEAKENING. TWO RAPID
INTENSIFICATION (RI) AIDS (RIPA AND FRIA) ARE TRIPPED, AND THE JTWC
FORECAST IS PLACED NEAR THE RIPA FORECAST TO TAU 24, THEN NEAR THE
CONSENSUS MEAN THEREAFTER. CONFIDENCE IS MEDIUM IN THE NEAR-TERM
AND LOW IN THE LONG-TERM.
FORECAST CONFIDENCE:
TRACK 00-72 HR: MEDIUM
TRACK 72-120 HR: LOW
INTENSITY 00-72 HR: MEDIUM
INTENSITY 72-120 HR: LOW//
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楼主: ygsj24
发表于 2025-10-19 14:56
