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JTWC/05W/#17/07-08 00Z Prognostic Reasoning
WDPN32 PGTW 080300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (DANAS) WARNING NR
017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 28.1N 122.3E
INITIAL INTENSITY: 40 KTS
GEOGRAPHIC REFERENCE: 185 NM NORTH-NORTHEAST OF TAIPEI, TAIWAN
MOVEMENT PAST 6 HOURS: NORTHWARD AT 05 KTS
SIGNIFICANT WAVE HEIGHT: 22 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND REGIONAL RADAR
LOOPS VERIFY THAT TROPICAL STORM DANAS (05W) HAS FINISHED THE TURN
TO THE WEST AND IS MAKING A RUN FOR THE CHINESE COAST. CURRENT
MOMENTUM IS POINTING THE VORTEX AT ZHANTAI TOWN, BUT THE WINDFIELDS
ARE BROAD ENOUGH TO BRING EFFECTS FROM TAIZHOU THROUGH PINGYANG
COUNTY. THE LATEST FRAMES OF THE VISUAL ANIMATION SHOW A BROAD
SWATH OF VIGOROUS CONVECTION OVER THE SOUTHERN SEMICIRCLE AS THE
SYSTEM THROWS ONE LAST PUNCH. WATER VAPOR ANIMATION SHOWS
IMPINGEMENT OVER THE POLEWARD SEMICIRCLE BUT EQUATORIAL OUTFLOW IS
EXCELLENT. OTHERWISE, THE ENVIRONMENT IS IDEAL FOR INTENSIFICATION
AND TS 05W IS PEAKING JUST PRIOR TO ENCOUNTERING THE DEGRADING
EFFECTS OF LAND INTERACTION. AN EXPOSED LOW LEVEL CIRCULATION CENTER
MADE FOR IDENTICAL FIXES AND DVORAK ASSESSMENTS FROM RJTD AND PGTW.
THE INTENSITY IS SET JUST ABOVE THE AGENCY T2.5 DVORAKS DUE TO CIMSS
OBJECTIVE ASSESSMENTS OF 45KTS FROM ADT, AIDT, AND SATCON.
INITIAL WIND RADII BASIS: PERSISTENCE FROM A 071232Z ASCAT.
CURRENT STEERING MECHANISM: A WEAK MID-LEVEL ANTICYCLONE ANCHORED
OVER THE GULF OF BOHAI THAT EXTENDS OVER THE EAST CHINA SEA TO
SOUTH OF SHANGHAI.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.5 - 35 KTS
RJTD: T2.5 - 35 KTS
KNES: T3.0 - 45 KTS
DEMS: T2.5 - 35 KTS
CIMSS SATCON: 44 KTS AT 0100Z
CIMSS ADT: 45 KTS AT 080100Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 5-10 KTS
SST: 26-27 CELSIUS
OUTFLOW: STRONG EQUATORWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TROPICAL STORM DANAS HAS ENTERED ITS TERMINAL
LEG AND WILL NOT INTENSIFY ANY FURTHER DUE TO THE EFFECTS OF LAND
INTERACTION. ONCE INLAND, THE SYSTEM WILL STEADILY DECAY ALONG A
SOUTHWESTWARD BEARING, DECAYING TO UNDER 25KTS WITHIN 36 HOURS FROM
NOW. IN ADDITION TO THE RAINFALL AND STORM SURGE HAZARDS ALONG THE
COAST, TROPICAL STORM 05W HAS SET UP THE SOUTHWEST MONSOON THROUGH
THE ENTIRE SOUTH CHINA SEA, WITH STRAIGHT AND STEADY SOUTHWESTERLIES
EXTENDING FROM SINGAPORE THORUGH THE TAIWAN STRAIT, INDICATING A 6 TO
10 WEEK RESPITE FROM TROPICAL CYCLONE ACTIVITY IN THE SOUTH CHINA SEA
BASIN AND NARROWING THE POTENTIAL AREA OF FUTURE STORM GENESIS TO THE
EAST
CHINA AND PHILIPPINE SEAS. AS 05W TRACKS INLAND, A VERY HIGH
LATITUDE MONSOON TROF WILL BECOME ESTABLISHED, WITH THE AXIS OF THE
SEASONAL TROF EXPECTED TO SETTLE IN FROM NORTH OF TAIWAN THROUGH
SOUTH OF OKINAWA BETWEEN THE 25TH AND 26TH LATITUDES.
MODEL DISCUSSION: AT THIS LATE-STAGE MODEL GUIDANCE HAS ALMOST
BECOME A NON-FACTOR. AS PER EXPECTATION THE MODELS STRUGGLE WITH
THE RATE OF DECAY OVER LAND, SO THE INTENSITY FORECAST IS BASED ON
A CLIMATOLOGICAL RATE OF DECAY ALONG THE OVERLAND TRACK. IN
RETROSPECT THE ECMWF-AIFS PERFORMED EXCEPTIONALLY WELL DURING THIS
STORM, AND ALL GUIDANCE WAS CONSISTENT AND PERFORMED QUITE WELL,
PARTICULARLY DURING THE EARLY STAGE OF THE STORM WHEN THE DIFFICULT
ISSUE OF WHETHER OR NOT THE SYSTEM WOULD TRACK THROUGH THE TAIWAN
STRAIT OR MOVE OVER THE ISLAND.
FORECAST CONFIDENCE:
TRACK 0 - 72 HR: MEDIUM
INTENSITY 0 - 72 HR: MEDIUM//
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