WDPN32 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (HIGOS) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.8N 144.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 66 NM NORTH OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 08W (HIGOS) WITH A HIGHLY COMPACT, PARTIALLY EXPOSED
LOW-LEVEL CIRCULATION CENTER (LLCC) AND ASSOCIATED DEEP CONVECTION
OFFSET TO THE NORTH OF THE CENTER. THE BURSTS OF CONVECTION HAVE
BECOME MORE VIGOROUS OVER THE PAST 6 HOURS WITH SIGNIFICANT AMOUNTS
OF LIGHTNING ACTIVITY. A PARTIAL 230313Z AMSR2 89 GHZ MICROWAVE
IMAGE CONFIRMED THAT THE CONVECTION IS CONFINED TO THE NORTHERN
SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON THE PARTIALLY EXPOSED LLCC IN THE ANIMATED MSI AND
AFOREMENTIONED AMSR2 IMAGE. THE INITIAL INTENSITY OF 35 KTS IS ALSO
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL
ANALYSIS INDICATES THAT 08W IS IN A MARGINALLY FAVORABLE ENVIRONMENT 
CHARACTERIZED BY WEAK OUTFLOW ALOFT, LOW TO MODERATE (15-20 KTS) 
VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES

INITIAL WIND RADII BASIS: PERSISTENCE

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 38 KTS AT 230600Z
   CIMSS ADT: 41 KTS AT 230600Z
   CIMSS AIDT: 37 KTS AT 230600Z
   CIMSS D-MINT: 32 KTS AT 230404Z
   CIMSS D-PRINT: 29 KTS AT 230600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 08W IS FORECAST TO TRACK NORTHWESTWARD,
ALONG THE SOUTHWESTERN PERIPHERY OF THE ELONGATED STR THROUGH TAU
48. NEAR TAU 48, THE STR IS EXPECTED TO BUILD AND BECOME MORE
SYMMETRIC. 08W WILL THEN BEGIN TO ROUND THE WESTERN EXTENT OF THE
STR WITH A NORTHWARD TURN. THE TRACK WILL THEN BECOME NORTHEASTWARD
AS 08W ACCELERATES ALONG THE NORTHWESTERN PERIPHERY OF THE STR. THE
SYSTEM IS EXPECTED TO REMAIN WELL OFF THE COAST OF HONSHU AS IT
COMMENCES ITS RECURVE, THOUGH THE TRACK HAS SHIFTED TO THE WEST
COMPARED TO THE PERVIOUS FORECAST. EXTRATROPICAL TRANSITION IS
FORECAST TO BEGIN AT TAU 72 WITH COMPLETION AROUND TAU 96 AS THE
SYSTEM BECOMES EMBEDDED WITHIN THE STRONG MID-LATITUDE WESTERLY
FLOW. IN TERMS OF INTENSITY, 08W IS FORECAST TO GRADUALLY INTENSIFY
OVER THE NEXT 48 HOURS AS THE VORTEX BECOMES MORE VERTICALLY
ALIGNED AND SHEAR REMAINS LOW. HOWEVER, DRY AIR AND INTERACTION
WITH THE WIND FIELD OF 07W WILL LIMIT THE INTENSIFICATION RATE.
NEAR TAU 72, SEA SURFACE TEMPERATURES WILL QUICKLY DROP AND SHEAR
WILL INCREASE, CAUSING 08W TO WEAKEN. BY TAU 96, SHEAR WILL
INCREASE TO OVER 60 KTS AND SEA SURFACE TEMPERATURES WILL DROP
BELOW 20 C AS 08W TRANSITIONS INTO A COLD-CORE CYCLONE. THERE STILL
REMAINS A CHANCE THAT THE VORTEX INTERACTS MORE WITH THE WIND FIELD
OF TY 07W (MEKKHALA) THAN IS CURRENTLY FORECAST, WHICH WOULD LEAD
TO A MUCH MORE RAPID RATE OF WEAKENING AND A POTENTIAL ABSORPTION
SCENARIO SOUTH OF HONSHU. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT THROUGH TAU 72 WITH TWO DISTINCT GROUPINGS IN THE
GUIDANCE. ONE GROUP CONSISTS OF NAVGEM, UKMET, GALWEM, AND JGSM,
WHICH IS SIGNIFICANTLY SLOWER AND TO THE WEST OF THE OTHER GROUP.
THE SECOND GROUP, WHICH CONSISTS OF GFS, ECMWF, AND THE
EXPERIMENTAL GOOGLE DEEPMIND, IS FASTER AND TO THE EAST OF THE
FIRST GROUP. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MEAN OF
THE SECOND GROUP WITH MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW
CONFIDENCE THEREAFTER. INTENSITY GUIDANCE GENERALLY AGREES ON
INTENSIFICATION THROUGH TAU 48-60 FOLLOWED BY WEAKENING. HAFS-A AND
COAMPS-TC (GFS BASED) ARE THE MOST AGGRESSIVE MODELS, SUGGESTING A
PEAK INTENSITY OF 65 KTS AND 75 KTS RESPECTIVELY. THE JTWC
INTENSITY FORECAST IS PLACED CLOSE TO THE HAFS-A MODEL THROUGH TAU
72 AND THEN SLIGHTLY HIGHER THAN IT THROUGH TAU 96 DUE TO THE
EXPECTED BAROCLINIC FORCING ALLOWING FOR 08W TO MAINTAIN INTENSITY.

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