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JTWC/05W/#01/07-04 00Z Prognostic Reasoning
WDPN32 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (FIVE) WARNING
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 19.7N 118.7E
INITIAL INTENSITY: 25 KTS
GEOGRAPHIC REFERENCE: 296 NM EAST-SOUTHEAST OF HONG KONG
MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS
SIGNIFICANT WAVE HEIGHT: 12 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY
CONSOLIDATING, ALTHOUGH STILL SOMEWHAT DISORGANIZED CIRCULATION,
WITH POCKETS OF DISORGANIZED CONVECTIVE ACTIVITY ACROSS THE
SOUTHERN PORTION OF THE CIRCULATION. CONVECTION HAS MANAGED TO
PERSIST THROUGH THE DIURNAL MAXIMUM AND IS IN FACT, STRENGTHENING
AFTER SUNRISE, A SURE SIGN OF STEADY CONSOLIDATION OF THE SYSTEM.
THE LATEST MICROWAVE PASS, A 032042Z SSMIS 37GHZ IMAGE, REVEALED
THAT THE LLCC REMAINS SOMEWHAT BROAD, WITH CURVED BANDS OF
CONVECTION BEGINNING TO DEVELOP TO THE SOUTH OF THE ASSESSED
CENTER, THOUGH CONVECTIVE ACTIVITY ON THE NORTH SIDE REMAINS BENIGN
DUE TO SOME LINGERING DRY AIR. ANIMATED MSI SUGGESTS A POSSIBLE
NASCENT VORTEX ABOUT 60NM TO THE SOUTHEAST OF THE ASSESSED
POSITION. THIS IS LIKELY THE MID-LEVEL VORTEX, WHICH MULTIPLE
MESOSCALE MODELS SHOW AS PRECESSING AROUND THE EASTERN SIDE OF THE
LLCC AND THEN EVENTUALLY MERGING INTO IT. THE INITIAL POSITION IS
ASSESSED WITH LOW CONFIDENCE BASED ON THE DISORGANIZED NATURE OF
THE LLCC AND THE LACK OF CONSISTENT HIGH-RESOLUTION MICROWAVE OR
SCATTEROMETER DATA. THE INITIAL INTENSITY IS ALSO ASSESSED WITH LOW
CONFIDENCE, CONSISTENT WITH THE PGTW DVORAK AND DPRINT ESTIMATES.
THE ENVIRONMENT IS FAVORABLE FOR INTENSIFICATION, ONCE THE VORTEX
ALIGNS, WITH WARM SSTS, AND LOW VWS. CURRENTLY, THE SYSTEM IS
TAPPING INTO DUAL OUTFLOW CHANNELS, ONE TOWARDS THE EQUATOR AND
ANOTHER TOWARDS THE EAST, ALONG THE SOUTHERN PART OF AN EAST-WEST
ORIENTED TUTT OVER TAIWAN EXTENDING TO A TUTT-CELL SOUTHEAST OF
OKINAWA.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED NEAR SHANGHAI.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T1.5 - 25 KTS
RJTD: T1.0 - 25 KTS
KNES: T2.5 - 35 KTS
CIMSS D-PRINT: 26 KTS AT 040000Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 5-10 KTS
SST: 29-30 CELSIUS
OUTFLOW: MODERATE DUAL-CHANNEL
OTHER FACTORS: DUAL-CHANNEL OUTFLOW EQUATORWARD AND EASTWARD.
ANALYSIS CONFIDENCE:
INITIAL POSITION: LOW
INITIAL INTENSITY: LOW
INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.
FORECAST DISCUSSION: TD 05W IS CURRENTLY DRIFTING SLOWLY ON A
GENERAL WESTWARD TRACK ALONG THE SOUTH SIDE OF A LARGE STR CENTERED
NEAR SHANGHAI. OVER THE NEXT 12 TO 24 HOURS, THE LOW-LEVEL VORTEX
IS LIKELY TO TRACE AND ERRATIC TRACK, LOOPING TO THE SOUTH AS IT
PRECESSES AND UNDERGOES AN AXISYMMETRIZATION WITH THE MID-LEVEL
VORTEX. HOWEVER, IN THE AGGREGATE, THE CENTER WILL CONTINUE TO
TRACK TOWARDS THE WEST-NORTHWEST AT A SLOW RATE OF SPEED. AFTER TAU
24, THE SYSTEM WILL TAKE A HARD RIGHT TURN AS THE STR TO THE NORTH
PUSHES NORTHEASTWARD INTO THE YELLOW SEA AND THE STR CENTERED IN
THE PHILIPPINE SEA BECOMES THE DOMINANT STEERING MECHANISM. OVER
THE REMAINDER OF THE FORECAST PERIOD, THE STR TO THE SOUTHEAST
MOVES WEST, WHILE THE RIDGE TO THE NORTH PUSHES EAST OVER KOREA
RESULTING IN A NORTH-SOUTH ORIENTED RIDGE AXIS EXTENDING FROM KOREA
TO EAST OF THE PHILIPPINES. TD 05W WILL TRACK NORTH-NORTHEASTWARD
ALONG THE WEST SIDE OF THIS RIDGE COMPLEX THROUGH TAU 96. AROUND
THE TIME THE SYSTEM MAKES LANDFALL ALONG THE EAST COAST OF MAINLAND
CHINA (NEAR TAU 96), THE PRIMARY STEERING INFLUENCE SHIFTS ONCE
MORE TO THE STR OVER KOREA AND THE SYSTEM WILL PUSH INLAND OVER
EASTERN CHINA THROUGH TAU 120. TD 05W IS FORECAST TO INTENSIFY AT
ROUGHLY THE CLIMATOLOGICAL RATE FOR THE FIRST 24 HOURS, AS THE
VORTEX BECOMES VERTICALLY ALIGNED. THE PACE OF INTENSIFICATION
INCREASES FROM TAU 24 AS THE TUTT STRENGTHENS TO THE NORTHEAST OF
TAIWAN, ENHANCING THE POLEWARD OUTFLOW CHANNEL. WHILE THE FORECAST
CALLS FOR A PEAK OF 75 KNOTS AT TAU 48, THE ACTUAL PEAK IS LIKELY
TO OCCUR AROUND TAU 60, AND COULD BE 10-15 KNOTS HIGHER, AS THE
SYSTEM MOVES INTO THE SOUTHERN ENTRANCE TO THE TAIWAN STRAIT. WHILE
PASSING THROUGH THE STRAIT, EASTERLY DOWNSLOPE WINDS OFF TAIWAN
WILL DISRUPT THE VORTEX, LEADING TO A GENERAL WEAKENING TREND PASS
THROUGH THE TAIWAN STRAIT. BY THE TIME IT LEAVES THE STRAIT, THE
SYSTEM WILL HAVE WEAKENED BELOW TYPHOON STRENGTH AS IT EXPERIENCES
INCREASED SHEAR AND DECREASED OUTFLOW ALOFT. AFTER LANDFALL, THE
SYSTEM WILL RAPID WEAKEN WHILE MOVING FURTHER INLAND.
MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS
SPLIT, WITH ROUGHLY HALF OF THE GUIDANCE SUPPORTING A WEST OF
TAIWAN TRACK AND HALF SUPPORTING AN EAST OF TAIWAN SCENARIO. ECMWF,
ECEPS, EC-AIFS, GALWEM AND THE CONSENSUS MEAN ALL SUPPORT THE JTWC
TRACK UP THE WEST SIDE OF TAIWAN AND THROUGH THE TAIWAN STRAIT. THE
GFS AND GEFS MEANWHILE CLIP THE SOUTHERN TIP OF TAIWAN AND TRACK
INTO THE SOUTHERN EAST CHINA SEA TO THE WEST OF OKINAWA. ENSEMBLE
SPREAD IS SIGNIFICANT, THOUGH ALL MEMBERS OF THE GEFS TRACK EAST OF
TAIWAN AND ALL BUT FIVE MEMBERS OF THE ECEPS TRACK WEST OF TAIWAN,
WITH SOME STRONG MEMBERS PUSHING INLAND EAST OF HONG KONG. THE JTWC
FORECAST IS POSITIONED CLOSE TO THE EC-AIFS TRACK THROUGH THE
FORECAST PERIOD WITH LOW CONFIDENCE. INTENSITY GUIDANCE IS SOMEWHAT
SURPRISINGLY IN GOOD AGREEMENT, AS THE MAJORITY OF THE MESOSCALE
GUIDANCE FAVORS THE WEST OF TAIWAN TRACK. THE HWRF TAKES THE SYSTEM
OVER TAIWAN AND THUS SHOWS RAPID WEAKENING AFTER TAU 48, BUT THE
REMAINDER OF THE GUIDANCE ALL SHOW A PEAK OCCURRING AT TAU 48, WITH
A RANGE BETWEEN 60 AND 95 KNOTS. THE HIGHER-END MODELS INCLUDE THE
RIDE AND RICN RAPID INTENSIFICATION (RI) MODELS, BOTH OF WHICH ARE
TRIPPED. THE JTWC FORECAST IS POSITIONED ON TOP OF THE CONSENSUS
THROUGH TAU 24 THEN INCREASES AT A FASTER RATE THROUGH THE PEAK.
FORECAST CONFIDENCE:
TRACK 0 - 72 HR: LOW
TRACK 72-120 HR: LOW
INTENSITY 0 - 72 HR: LOW
INTENSITY 72-120 HR: LOW//
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