WDPN32 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (HIGOS) WARNING 
NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.1N 141.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 194 NM WEST-NORTHWEST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SHALLOW
LOW LEVEL CIRCULATION CENTER (LLCC) PARTIALLY OBSCURED BY FLARING,
DEEP CONVECTION ON THE NORTHERN PERIPHERY. CONVECTION REMAINS
ABSENT IN THE SOUTHERN SEMICIRCLE AS MODERATE SOUTHEASTERLY
VERTICAL WIND SHEAR (VWS) INHIBITS DEVELOPMENT. A 232058Z WSF-M MWI
89 GHZ IMAGE SHOWS RATHER DISORGANIZED LOW LEVEL CLOUDS OUTLINING
AN ELONGATED LLCC. A 232359Z PARTIAL ASCAT-C PASS REVEALED 25-30 KT
WINDS IN THE NORTHERN SEMICIRCLE AND 5 KT WESTERLIES TO THE SOUTH,
INDICATING THAT THE WIND FIELD IS HIGHLY ASYMMETRIC. THE
ENVIRONMENT IS MARGINALLY FAVORABLE FOR DEVELOPMENT, CHARACTERIZED
BY WARM SEA SURFACE TEMPERATURE (SST) OF 29-30 DEGREES CELSIUS
OFFSET BY AN INTRUSION OF DRY AIR FROM THE SOUTH AND MODERATE VWS.
THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
THE CENTER BEING PARTIALLY EXPOSED. THE INITIAL INTENSITY REMAINS
AT 30 KTS WITH HIGH CONFIDENCE GIVEN ASCAT PASS AND THE LITTLE
CHANGE IN APPEARANCE FROM 6-12 HOURS AGO, WHICH ALIGNS WITH THE
PGTW AND RJTD SUBJECTIVE DVORAK ESTIMATES OF T2.0.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 34 KTS AT 231710Z
   CIMSS ADT: 37 KTS AT 232330Z
   CIMSS AIDT: 36 KTS AT 232330Z
   CIMSS D-MINT: 25 KTS AT 232059Z
   CIMSS D-PRINT: 23 KTS AT 232330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: DRY AIR IN THE MID-UPPER TROPOSPHERE

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: LOCATED ON THE SOUTHWESTERN PERIPHERY OF A
LOWER LEVEL STR, TROPICAL DEPRESSION 08W WILL MAINTAIN A
WEST-NORTHWESTWARD TRAJECTORY FOR THE FIRST 24 HOURS. BY TAU 36,
THE LARGER CIRCULATION OF TYPHOON 07W WILL BEGIN TO INTERACT WITH
08W. THE DEEP-LAYER SOUTHERLY FLOW ASSOCIATED WITH THE CIRCULATION
WILL WORK IN CONJUNCTION WITH THE STR TO ACCELERATE 08W POLEWARD.
THE TRACK WILL GAIN AN EASTWARD COMPONENT BY TAU 72 AS THE
MID-LATITUDE WESTERLIES EXERT STRONGER STEERING CONTROL OF HIGOS AS
IT RAPIDLY UNDERGOES EXTRATROPICAL TRANSITION. THE CIRCULATION WILL
BECOME FULLY EXTRATROPICAL BY TAU 96 AND MERGE WITH A BAROCLINIC
SYSTEM SHORTLY THEREAFTER. THE INTENSITY FORECAST IS QUITE
CHALLENGING. THE VWS CURRENTLY IMPEDING INTENSIFICATION WILL EASE
WITHIN THE NEXT 12 HOURS, WHILE HIGOS TRAVERSES OVER VERY WARM SST.
THIS ENVIRONMENT WILL GIVE 08W A BRIEF WINDOW OF OPPORTUNITY TO
INTENSIFY BEFORE IT INTERACTS WITH 07W. GIVEN THE INITIAL
CONDITIONS AND THE DISORGANIZED NATURE OF THE LLCC, THE FORECAST
CALLS FOR LITTLE DEVELOPMENT FOR THE FIRST 12 HOURS AND MODEST
INTENSIFICATION FROM TAU 12 TO TAU 48. ONCE THE INTERACTION UNFOLDS
IN EARNEST, THE SYSTEM WILL LEVEL OFF IN INTENSITY. IF 08W IS ABLE
TO ESCAPE THE GRASP OF 07W TOWARDS TAU 72, IT WILL PHASE WELL WITH
A 140 KT JET STREAK OVER NORTHERN HONSHU, PROVIDING ENHANCING
DIVERGENCE ALOFT AND KEEPING THE INTENSITY ELEVATED TO THE END OF
THE FORECAST PERIOD.

MODEL DISCUSSION: MODELS ARE IN GOOD AGREEMENT IN DEPICTING A
WEST-NORTHWEST MOTION THROUGH TAU 12 AND A MORE POLEWARD TRAJECTORY
THEREAFTER. THE JTWC TRACK FORECAST FOLLOWS THE TIGHT GROUPING OF
TRACKERS UP TO TAU 48. THERE REMAINS SIGNIFICANT UNCERTAINTY AS TO
HOW MUCH INTERACTION WILL OCCUR, OWING TO THE 150 NM CROSS-TRACK
SPREAD OF 07W AT TAU 72. THE ECMWF, NAVGEM, AND VARIOUS AI MODELS
SHOW 08W BEING COMPLETELY ABSORBED BY TAU 72. THE GFS SOLUTION
DEVOLVES THE SYSTEM INTO A WAVE FROM TAU 60 TO TAU 72, AFTER WHICH
TIME THE WAVE PINCHES OFF INTO A CLOSED CIRCULATION SOUTH OF THE
KANTO PLAIN AS IT SPEEDS NORTHEASTWARD. BECAUSE OF THESE
UNCERTAINTIES, THE TRACK AND INTENSITY FORECAST IS ASSESSED WITH
LOW CONFIDENCE. FOR NOW, THE FORECAST CONTINUES TO KEEP 08W AS A
DISCRETE CIRCULATION UNTIL IT MERGES WITH A FRONTAL SYSTEM TOWARDS
TAU 96. IT IS ENTIRELY POSSIBLE THAT SUBSEQUENT FORECASTS MAY SHOW
A DISSIPATION OR MERGER SCENARIO WITH 07W PRIOR TO TAU 72 IF THE
MODEL GUIDANCE CONTINUES TO TREND IN THAT DIRECTION.

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