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JTWC/01W/#03/06-11 00Z Prognostic Reasoning
WDPN31 PGTW 110300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (WUTIP) WARNING
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 16.2N 113.9E
INITIAL INTENSITY: 30 KTS
GEOGRAPHIC REFERENCE: 323 NM EAST OF DA NANG, VIETNAM
MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 11 KTS
SIGNIFICANT WAVE HEIGHT: 12 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SMALL AND
FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH CONVECTION
BEGINNING TO FLARE UP ONCE MORE NEAR THE CENTER. ANIMATED WATER
VAPOR IMAGERY, AS WELL AS CIRA TC-SCALE ATMOSPHERIC MOTION VECTORS
INDICATE RELATIVELY STRONG NORTH-NORTHEASTERLY UPPER-LEVEL WINDS
PUSHING SOUTH FROM AN ANTICYCLONE OVER THE TAIWAN STRAIT, IMPARTING
MODERATE TO HIGH SHEAR OVER THE SYSTEM AT THE PRESENT TIME. A
120110Z ASCAT-B PASS INDICATED 25-30 KNOT WINDS AROUND THE MAJORITY
OF THE CIRCULATION, WITH A RADIUS OF MAXIMUM WINDS AROUND 45NM.
SHIP OBSERVATIONS INDICATE THE ELEVATED WINDS EXTEND OVER 150NM
AWAY FROM THE CENTER, PRIMARILY FOCUSED IN THE EASTERN HEMISPHERE
OF THE CIRCULATION. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE EXPOSED LLCC IN THE MSI. THE INITIAL
INTENSITY IS ALSO ASSESSED WITH HIGH CONFIDENCE, BASED ON THE
OVERALL AGREEMENT OF THE SUBJECTIVE AND OBJECTIVE FIXES WITH THE
SCATTEROMETER DATA. ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY
FAVORABLE CONDITIONS, WITH STRONG EQUATORWARD OUTFLOW AND WARM SSTS
OFFSET BY MODERATE NORTH-NORTHEASTERLY WIND SHEAR. AS DEPICTED WELL
BY THE HAFS-A AND HWRF, A REGION OF RELATIVELY DRIER MID-LEVEL AIR
REMAINS IN PLACE ACROSS THE NORTHERN PORTION OF THE CIRCULATION,
BUT WEAK CONVECTION IN THE AREA SUGGESTS THE ATMOSPHERE IS
MOISTENING.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) FAR TO THE NORTHEAST.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.0 - 30 KTS
RJTD: T2.0 - 30 KTS
KNES: T1.5 - 25 KTS
CIMSS ADT: 33 KTS AT 110020Z
CIMSS AIDT: 31 KTS AT 110020Z
CIMSS DPRINT: 25 KTS AT 110000Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
VWS: 15-20 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG EQUATORWARD
OTHER FACTORS: DRY MID-LEVEL AIR ACROSS THE NORTHERN PERIPHERY
OF THE CIRCULATION.
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: HIGH
INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: AFTER COMPLETING A COUNTER-CLOCKWISE LOOP
BETWEEN 12Z-18Z, TROPICAL DEPRESSION (TD) 01W (WUTIP) KICKED OUT TO
THE NORTH, PUTTING THE PEDAL DOWN AND INCREASING SPEED FROM 02
KNOTS TO 11 KNOTS IN THE LAST SIX HOURS. THE MOST RECENT MOTION
VECTOR LOOKS TO BE ABOUT 320DEG, HEADING TOWARDS HAINAN ISLAND. TD
01W IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD THROUGH TAU 48,
ALONG THE SOUTHWESTERN SIDE OF THE STEERING RIDGE. LANDFALL ALONG
THE SOUTHEASTERN COAST OF HAINAN ISLAND IS EXPECTED SHORTLY AFTER
TAU 36. THE MAJORITY OF THE TRACK GUIDANCE INDICATES THE SYSTEM
SHOULD SLOW DOWN A BIT OVER THE NEXT 12 HOURS AS THE RIDGE IS
EXPECTED TO WEAKEN AND BREAK DOWN A BIT DUE TO THE PRESENCE OF
INVEST 94W IN THE PHILIPPINE SEA. HOWEVER, IF THE SYSTEM MAINTAINS
ITS CURRENT SPEED, LANDFALL COULD OCCUR UP TO 6-12 HOURS EARLIER
THAN CURRENTLY ANTICIPATED. THE CURRENT FORECAST SHOWS TD 01W
ROUNDING THE RIDGE AXIS BY TAU 48 AS IT CROSSES OVER HAINAN ISLAND,
THEN ACCELERATING NORTHEASTWARD THROUGH THE REMAINDER OF THE
FORECAST PERIOD AS THE SYSTEM GETS CAUGHT UP IN THE ENHANCED
GRADIENT FLOW AHEAD OF A MID-LATITUDE TROF MOVING IN FROM THE WEST.
UPPER-LEVEL CONDITIONS ARE FORECAST TO IMPROVE, WITH SHEAR
DECREASING AND OUTFLOW BECOMING MORE ORGANIZED, WHICH WILL ALLOW
THE SYSTEM TO SYMMETRIZE AND THE VORTEX TO ALIGN VERTICALLY,
ENABLING STEADY INTENSIFICATION THROUGH LANDFALL. WHILE THE PEAK OF
55 KNOTS IS SHOWN TO OCCUR AT TAU 36, THE SYSTEM MAY INTENSIFY AN
ADDITIONAL 5-10 KNOTS IN THE PERIOD BETWEEN TAU 36 AND LANDFALL BUT
CANNOT BE CAPTURED IN THE FORECAST TIME STEPS. AFTER MAKING
LANDFALL, THE LOSS OF A OCEANIC HEAT SOURCE AND TERRAIN INTERACTION
WILL STEADILY ERODE THE VORTEX, LEADING TO DISSIPATION BY TAU 96 TO
THE NORTH OF HONG KONG.
MODEL DISCUSSION: DETERMINISTIC GUIDANCE HAS COME INTO SLIGHTLY
BETTER AGREEMENT SINCE THE LAST RUN, PARTICULARLY IN THE EXTENDED
FORECAST. AT LANDFALL, CROSS-TRACK SPREAD IS 110NM, BETWEEN THE
ECMWF-AIFS ON THE LEFT AND THE UKMET ON THE RIGHT SIDE OF THE
ENVELOPE. CROSS-TRACK SPREAD INCREASES TO 200NM BY TAU 72 AND
REMAINS STEADY THROUGH TAU 96. ALONG-TRACK SPREAD IS ABOUT 100NM AT
LANDFALL BETWEEN THE ECMWF AND THE NAVGEM. MODELS CONTINUE TO SHOW
ENHANCED ALONG-TRACK SPREAD DUE TO LARGE DISCREPANCIES IN HOW THEY
ARE HANDLING THE STRENGTH OF THE MID-LATITUDE TROF MOVING IN FROM
NORTH-CENTRAL CHINA. GFS IS STARTING TO MOVE INTO BETTER AGREEMENT
TO THE FASTER MODELS, BUT STILL LAGS FAR BEHIND, WITH THE TROF
BEING WEAKER, WHILE ECMWF AND THE UKMET SHOW A DEEPER TROF WHICH
PICKS UP THE SYSTEM EARLIER. AFTER THE SYSTEM ROUNDS THE RIDGE
AXIS, ALONG-TRACK INCREASES TO 460NM BY THE END OF THE FORECAST.
THE JTWC FORECAST IS SITUATED TO THE WEST OF THE CONSENSUS MEAN AND
CONSISTENT WITH THE ECWMF DETERMINISTIC MODEL THROUGH THE FORECAST
PERIOD. INTENSITY GUIDANCE CONTINUES TO SHOW A FAIR AMOUNT OF
UNCERTAINTY. SOMEWHAT SURPRISINGLY, THREE RAPID INTENSIFICATION (RI)
AIDS ARE NOW BEING TRIPPED (CTR1, RIDE, RICN), AND THE COAMPS-TC
(BOTH VERSIONS) ARE STICKING TO THEIR GUNS IN INDICATING A PEAK
INTENSITY OF 65 KNOTS OR GREATER PRIOR TO LANDFALL. THE HAFS AND
HWRF MEANWHILE HAVE COME DOWN ABOUT 10 KNOTS FROM THE PREVIOUS RUN,
NOW PEAKING AROUND 50-60 KNOTS. THE SHIPS PACKAGE CONTINUES TO BE
QUITE BEARISH, WITH A PEAK BETWEEN 35-40 KNOTS. THE JTWC FORECAST
PEAKS AT 55 KNOTS, WITH THE CAVEAT THAT SOME ADDITIONAL
INTENSIFICATION COULD OCCUR IN THE PERIOD AFTER TAU 36 AND
LANDFALL. AFTER LANDFALL, THE SYSTEM WILL RAPIDLY WEAKEN AND
DISSIPATE BY TAU 96, IN LINE WITH THE BULK OF THE GUIDANCE PACKAGE.
FORECAST CONFIDENCE:
TRACK 0 - 72 HR: MEDIUM
TRACK 72-120 HR: LOW
INTENSITY 0 - 72 HR: MEDIUM
INTENSITY 72-120 HR: MEDIUM//
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楼主: ygsj24
发表于 2025-6-11 09:35
