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发表于 2025-8-9 10:51
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JTWC/16W/#09/08-09 00Z Prognostic Reasoning
WDPN32 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (PODUL) WARNING NR
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 21.5N 142.9E
INITIAL INTENSITY: 50 KTS
GEOGRAPHIC REFERENCE: 880 NM EAST-SOUTHEAST OF KADENA AB
MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 06 KTS
SIGNIFICANT WAVE HEIGHT: 22 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS ONLY MILD
WEAKENING SINCE THE DIRURNAL MAX PERIOD WANED AFTER SUNRISE. THE
CONVECTIVE SHIELD HAS BEEN SHOVED EQUATORWARD, PARTIALLY EXPOSING
THE LOW LEVEL CIRCULATION CENTER (LLCC) OVER THE POLEWARD
HEMISPHERE OF THE STORM. CLOUD TOPS HAVE WARMED ONLY SLIGHTLY
DURING THE PAST SIX HOURS AND LIGHTNING STRIKES HAVE DECREASED
MODERATELY, BUT NOT AS MUCH AS IS TYPICAL FOR THIS TIME PHASE. THIS
INDICATES THAT THE SYSTEM IS HOLDING ITS OWN AGAINST THE
NORTHEASTERLY VERTICAL WINDSHEAR AND STILL ON AN UPTREND. MAXIMUM
SHEAR IS ASSESSED AT 16-20KTS AT 10,000 FT. THE RCTP DVORAK HAS
RISEN TO MATCH THE JTWC T3.5 AND ADT IS NOW UP TO 53KTS WHILE AIDT
HAS STEPPED UP TO 48KTS. 50KTS IS A GOOD MEAN BETWEEN THE AGENCY
DVORAKS AND CIMSS OBJECTIVE ASSESSMENTS. THE SYSTEM LIES IS AN
ENVIRONMENT WITH A STARK CONTRAST BETWEEN THE POLEWARD AND
EQUATORWARD SIDES, WITH DRY AIR AND A SUBSIDENT ATMOSPHERE ON THE
POLEWARD SIDE AND DEEP TROPICAL MOISTURE AND AMPLE LOW LEVEL
CONVERGENCE OVER THE EQUATORWARD SIDE, ESPECIALLY IN THE SOUTHEAST
QUADRANT. MODEL GUIDANCE INDICATES THE ALONG TRACK ENVIRONMENT IS
ABOUT AS GOOD AS IT WILL EVER GET FOR THE NEXT 24 HOURS, WITH AN
INCREASINGLY HOSTILE ENVIRONMENT CHARACTERIZED BY EVEN MORE VWS AND
DRY AIR FURTHER DOWNSTREAM. THE ENVIRONMENT REALLY BEGINS TO
DETERIORATE WEST OF THE 135TH MERIDIAN. THE LLCC HAS MAINTAINED A
CONSTANT BEARING WHILE SLOWING SLIGHTLY DURING THE PAST SIX HOURS.
A 082359Z ASCAT HOT OFF THE PRESS DURING THE PRODUCTION OF THIS
BULLETIN VERIFIES BOTH POSITION AND INTENSITY.
INITIAL WIND RADII BASIS: A 082359Z ASCAT.
CURRENT STEERING MECHANISM: A MID-LEVEL RIDGE EXTENDING FROM AN
ANTICYCLONE ANCHORED NEAR 35N 165E THROUGH THE RYUKUS. THE RIDGE IS
BUILDING AND SINKING TOWARDS TAIWAN.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T3.5 - 55 KTS
RJTD: T2.5 - 35 KTS
RCTP: T3.5 - 55 KTS
KNES: T3.5 - 55 KTS
CIMSS ADT: 53 KTS AT 082030Z
CIMSS AIDT: 48 KTS AT 082030Z
CIMSS D-MINT: 39 KTS AT 081903Z
CIMSS D-PRINT: 54 KTS AT 090020Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
VWS: 10-15 KTS
SST: 29-30 CELSIUS
OUTFLOW: MODERATE EQUATORWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: HIGH
INITIAL WIND RADII: MEDIUM
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TS 16W WILL CONTINUE TRACKING WEST-NORTHWEST
FOR ANOTHER 24 HOURS AND REACH LOW TYPHOON STRENGTH BEFORE BENDING
TO A MORE WESTWARD TRACK AND REACHING PEAK STRENGTH OVER THE SECOND
24 HOUR PERIOD. A MID-TO-HIGH LEVEL RIDGE BUILDING ALONG 160E WILL
EXTEND TOWARDS THE RYUKUS, KEEPING THE SYSTEM WELL SOUTH OF OKINAWA.
THE HARSH ENVIRONMENT WILL SLOW DEVELOPMENT TO A LOWER THAN
CLIMATOLOGICAL RATE BUT THE SYSTEM WILL STILL MANAGE TO ATTAIN
TYPHOON STRENGTH. RAPID INTENSIFICATION AND TRIPLE DIGIT INTENSITY IS
LOOKING HIGHLY UNLIKELY DUE TO THE HIGH VWS AND DRY AIR NORTH OF
20N. OKINAWA AND THE NORTHERN SENKAKUS ARE NOT QUITE OFF THE HOOK
YET AS A POLEWARD BEND TO THE TRACK STILL REMAINS A POSSIBILITY, BUT
NOT A PROBABILITY. IN FACT, THE AMERICAN ENSEMBLE (GFS) HAS JOINED
SOME OF THE TRADITIONALLY WEAKER TRACKERS SUCH AS EGRR AND AGUM,
BUT EVEN IN THE UNLIKELY EVENT OF A TRACK TOWARDS OKINAWA, THE
ENVIRONMENT ALONG THAT TRACK IS SO HARSH THAT THE STORM WOULD
LIKELY BE DRIED OUT AND SHEARED APART WELL BEFORE IT MADE IT THAT
FAR. THE TAIWAN-SOUTHERN SENKAKUS SCENARIO REMAINS MUCH MORE LIKELY,
AS THE DEEP SHORT WAVE CURRENTLY TRACKING OVER JAPAN PASSES HELPS
AMPLIFY THE LONG WAVE PATTERN OVER THE WESTERN PACIFIC. AS THE
PATTERN AMPLIFIES THE BONIN HIGH WILL BUILD A HIGH AMPLITUDE RIDGE
ALONG THE 165TH MERIDIAN AND EXPAND TOWARDS TAIWAN, WITH H500 HEIGHTS
EXCEEDING 5900 METERS ALL THE WAY ACROSS TAIWAN AND INTO MAINLAND
CHINA. THE POINT OF DIVERGENCE IN THE TRACKERS COMES AFTER 135E, AND
UNTIL THAT ISSUE IS CLARIFIED, A MINOR THREAT EXISTS TO OKINAWA. TS
16W IS EXPECTED TO BEGIN A DOWNTREND AS IT APPROACHES 130E AND DECAY
RAPIDLY DUE TO HIGH SHEAR WHEN IT TRACKS INTO THE EAST CHINA SEA.
MODEL DISCUSSION: THE JTWC TRACK FORECAST RUNS EQUATORWARD OF THE
MULTI MODEL CONSENSUS FAVORING THE ECMWF ENSEMBLE AND SOME OF THE
NEW, BUT IMPRESSIVE-SO-FAR AI TRACKERS. ALTHOUGH CROSS-TRACK SPREAD
INCREASES AFTER TAU 72, ALL TRACKERS FOLLOW THE GENERAL TREND OF A
WESTWARD RUN THROUGH 135E, THEN VARYING DEGREES OF A POLEWARD BEND
AND A WEAKENING TREND THEREAFTER. INTENSITY GUIDANCE IS ALSO IN
GOOD AGREEMENT SHOWING A GRADUAL UPTREND THROUGH THE NEXT 48 HOURS
FOLLOWED BY A SLOW DECLINE, THEN A RAPID DECLINE OVER THE EAST
CHINA SEA. THE JTWC INTENSITY FORECAST STAYS ABOVE THE MID-LINE OF
GUIDANCE IN ANTICIPATION OF ANOTHER SURGE DURING THE PRE-DAWN HOURS
TOMORROW.
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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