Advisories

WDPN31 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.7N 127.4E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 134 NM NORTH OF KADENA AB
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 22W HAS BEGUN ITS LONG-AWAITED PIVOT AND HAS
REVERSED COURSE, TRACKING EQUATORWARD AT 11 KTS. ANIMATED SHORTWAVE
INFRARED (SWIR) IMAGERY DEPICTS A FULLY EXPOSED LOW-LEVEL
CIRCULATION CENTER, WITH CONVECTION CONFINED TO THE NORTHEASTERN
PERIPHERY. THIS CONVECTION IS ENHANCED BY A STRONG POLEWARD OUTFLOW
CHANNEL INTO A 150-KT JET STREAK AHEAD OF THE AFOREMENTIONED
TROUGH. TO THE NORTH, A TROUGH IS RAPIDLY TRAVERSING THE SEA OF
JAPAN, AND BEHIND IT, A SURFACE RIDGE IS BUILDING SOUTHEASTWARD.
CONSEQUENTLY, VERY DRY, COOL AIR IS BEING ADVECTED EQUATORWARD AND
INTO THE LLCC. THUS, THE WESTERN SIDE HAS LARGELY BEEN DEVOID OF
CONVECTION. AN UPPER-LEVEL RIDGE IS ALSO IMPARTING MODERATE TO
HIGH, NORTHWESTERLY VERTICAL WIND SHEAR (VWS). WHILE THE OVERALL
ENVIRONMENT IS UNFAVORABLE, THE BROAD CIRCULATION IS PUSHED UP
AGAINST THE NORTHEASTERLY COOL SURGE, RESULTING IN A TIGHT PRESSURE
GRADIENT AND 40-KT MAXIMUM SUSTAINED WINDS ALONG THE NORTHERN
PERIPHERY. RECENT SHIP OBSERVATIONS CONTINUED TO REPORT 33-42 KT
WIND SPEEDS IN THE VICINITY OF TS 22W. AN EARLIER 040144Z ASCAT-C
PASS DEPICTED A LARGE AREA OF GALES ALONG THE NORTHERN PERIPHERY.
BASED ON THESE OBSERVATIONS AND THE VIRTUALLY UNCHANGED SATELLITE
PRESENTATION OF TS 22W, THE INITIAL INTENSITY HAS BEEN HELD AT 40
KTS WITH HIGH CONFIDENCE, WHICH IS A LITTLE HIGHER THAN THE
T2.0-2.5 SUBJECTIVE DVORAK CLASSIFICATIONS AND ON THE HIGHER END OF
THE CIMSS OBJECTIVE INTENSITY ESTIMATES. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE SWIR IMAGERY.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHEASTERN FLANK OF A RIDGE
POSITIONED OVER NORTHEAST CHINA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 33 KTS AT 040840Z
   CIMSS AIDT: 37 KTS AT 040840Z
   CIMSS D-PRINT: 33 KTS AT 041340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR

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: NOW THAT TS 22W HAS BEGUN TO TRAVEL SOUTHWARD,
THIS MOTION WILL CONTINUE THROUGH TAU 12. IT WILL THEN ENCOUNTER
WESTERLY TO SOUTHWESTERLY FLOW ALONG THE SOUTHERN PERIPHERY OF A
LARGE CYCLONIC CAULDRON OF THE MONSOON TROUGH AND TURN EASTWARD. BY
TAU 60, THE SYSTEM WILL ENCOUNTER THE WESTERN FLANK OF A STR
POSITIONED EAST OF HONSHU AND TURN POLEWARD. TROPICAL DISTURBANCE
97W HAS DEVELOPED INTO TS 23W, AND ITS STRONGER-THAN-PREDICTED
VORTEX WILL YANK THE EASTERN PERIPHERY OF THE CAULDRON MORE
STRONGLY NORTHWARD. THEREFORE, THE TRACK HAS SHIFTED MORE SHARPLY
POLEWARD THIS CYCLE. A FAST-MOVING TROUGH WILL APPROACH HONSHU BY
TAU 96 AND FLATTEN THE STR. THIS WILL ALLOW THE MID-LATITUDE
WESTERLIES TO DRIVE THE SYSTEM NORTHEASTWARD. THE INTENSITY
FORECAST HAS CHANGED LITTLE. THE STRONG SURFACE PRESSURE GRADIENT
RESPONSIBLE FOR THE TS INTENSITY WILL EASE OVER THE NEXT 24 HOURS,
ALLOWING THE INTENSITY TO DECREASE. WHILE THE SYSTEM WILL MOVE INTO
A MORE FAVORABLE ENVIRONMENT OF LOWER SHEAR AND HIGHER MOISTURE
CONTENT, THE BROAD CIRCULATION WILL NEED TIME TO RECOVER AND
CONSOLIDATE. AS TS 22W ACCELERATES IN THE LATTER PART OF THE
FORECAST PERIOD, IT WILL HAVE LITTLE TIME TO INTENSIFY PRIOR TO
INTERACTING WITH THE LANDMASS OF HONSHU.

MODEL DISCUSSION: THE ENTIRE MODEL GUIDANCE SUITE IN THE EARLY TAUS
HAS SHIFTED SIGNIFICANTLY WESTWARD, POTENTIALLY DUE TO THE
SIGNIFICANT AND UNEXPECTEDLY FAST EQUATORWARD MOTION OVER THE PAST
SIX HOURS. THE JTWC FORECAST TRACK DOES NOT JUMP SHARPLY TO THE
CORE GUIDANCE ENVELOPE AND INSTEAD IS A BLEND OF THE PREVIOUS
FORECAST WITH THE CURRENT GUIDANCE. THE OVERALL CURVE OF THE TRACK
HAS NOT CHANGED, BUT THE JTWC FORECAST TRACK HAS SHIFTED A BIT
WESTWARD AT TAU 96, OWING TO THE STRONGER INFLUENCE OF TS 23W ON
THE EASTERN SIDE OF THE CAULDRON. THE JTWC INTENSITY FORECAST IS
VERY SIMILAR TO THE PREVIOUS FORECAST AND IS WELL-ALIGNED WITH THE
CONSENSUS.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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