Advisories

WDPN31 PGTW 030300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 043//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.1N 139.3E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 150 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP
CONVECTION WRAPPING INTO A RAGGED EYE. THE SYSTEM MAINTAINS A
STRONG POLEWARD OUTFLOW CHANNEL INTO A JET STREAK TO THE NORTH. A
022042Z SSMIS PASS REVEALED THAT THE VORTEX WAS LIKELY TILTED DUE
TO 20 KTS OF PERSISTENT NORTHEASTERLY SHEAR, AND IT IS UNCLEAR IF
THE CIRCULATION HAS BECOME MORE VERTICALLY ALIGNED SINCE THEN. TY
30W IS TRAVERSING A GENERALLY FAVORABLE ENVIRONMENT OF WARM SEA
SURFACE TEMPERATURES (SST) OF 27-28 DEGREES CELSIUS, STRONG
UPPER-LEVEL DIVERGENCE, AND MODERATE VERTICAL WIND SHEAR (VWS). THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
RAGGED EYE IN MSI. BASED ON THE IMPROVED CONVECTIVE SIGNATURE, THE
INITIAL INTENSITY IS SET AT 70 KTS WITH LOW CONFIDENCE, ABOVE THE
SUBJECTIVE AND OBJECTIVE ESTIMATES. THE WIND RADII ARE ASSESSED
WITH LOW CONFIDENCE BECAUSE THE LAST FULL ASCAT OVERPASS TOOK PLACE
AT 012345Z.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT
CHARACTERIZED BY A DEEP-LAYER STR TO THE WEST AND ANOTHER
DEEP-LAYER STR TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.5 - 55 KTS
   CIMSS SATCON: 54 KTS AT 022330Z
   CIMSS ADT: 35 KTS AT 030000Z
   CIMSS AIDT: 65 KTS AT 030000Z
   CIMSS D-MINT: 57 KTS AT 022042Z
   CIMSS D-PRINT: 54 KTS AT 030000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST HAS BEEN TRUNCATED TO 72
HOURS.

FORECAST DISCUSSION: TY 30W REMAINS TRAPPED IN A COL REGION BETWEEN
TWO RIDGES THAT HAVE BEEN SHIFTING WESTWARD GRADUALLY.
CONSEQUENTLY, THE SYSTEM HAS BEEN MOVING SLOWLY WEST-NORTHWESTWARD
TO NORTHWESTWARD. A MID-LEVEL SHORTWAVE TROUGH PASSING TO THE NORTH
WILL SOON ERODE THE STR TO THE WEST, ALLOWING THE STR TO THE EAST
TO BECOME THE MORE DOMINANT STEERING MECHANISM. THIS EVOLUTION WILL
CAUSE TY 30W TO TURN POLEWARD OVER THE NEXT 24 HOURS. THEREAFTER,
THE SYSTEM WILL GRADUALLY ROUND THE NORTHWESTERN PERIPHERY OF THE
STR AND ACCELERATE TOWARD THE NORTH-NORTHEAST TO NORTHEAST FOR THE
REMAINDER OF THE FORECAST PERIOD. ADDITIONAL INTENSIFICATION
APPEARS LIKELY. THE WATERS WILL REMAIN WARM, WHILE MODERATE VWS AND
STRONG UPPER-LEVEL DIVERGENCE WILL PERSIST. THE FORECAST CALLS FOR
INTENSIFICATION TO 75 KTS PRIOR TO EXTRATROPICAL TRANSITION (ETT).
BEYOND TAU 36, PROGRESSIVELY COOLER SST AND INCREASING VWS WILL
PROMOTE WEAKENING. ETT WILL COMMENCE NEAR TAU 60 AS THE SYSTEM
MOVES BENEATH THE SOUTHERN PERIPHERY OF THE JET STREAM AND THERMAL
ADVECTION INCREASES. THE SYSTEM WILL THEN UNDERGO BAROCLINIC
REINTENSIFICATION TO TYPHOON FORCE AND COMPLETE ETT BY TAU 72.

MODEL DISCUSSION: CROSS-TRACK SPREAD AMONG THE TRACK GUIDANCE IS
LOW THROUGH TAU 72, BUT THE ALONG-TRACK SPREAD INCREASES TO 650 NM.
NAVGEM AND HWRF ARE THE SLOWEST SOLUTIONS, WHILE AIFS AND DEEPMIND
ARE THE FASTEST. THE JTWC TRACK FORECAST IS POSITIONED NEAR THE
AI-MODEL MEAN (AICN) THROUGH TAU 48 AND THEN LEANS AWAY FROM AICN
AND TOWARD THE MULTI-MODEL CONSENSUS THEREAFTER. MODERATE SPREAD
EXISTS AMONG THE INTENSITY GUIDANCE. MOST AIDS DEPICT VARYING
LEVELS OF INTENSIFICATION. DEEPMIND KEEPS THE INTENSITY FLAT
THROUGH TAU 36, WHILE HAFS-A IS THE MOST AGGRESSIVE SOLUTION AND
BRINGS THE SYSTEM UP TO 90 KTS. IF SATELLITE AND MODEL TRENDS
CONTINUE, SUBSEQUENT FORECASTS MAY NEED TO INCREASE THE AMOUNT OF
NEAR-TERM INTENSIFICATION. GUIDANCE DEPICTS A PERIOD OF WEAKENING
AFTER TAU 36. AT TAU 72, HAFS-A, GFS, AND ECMWF DEPICT
REINTENSIFICATION TO TYPHOON STRENGTH. DEEPMIND HOLDS THE INTENSITY
AT 55 KTS. THE JTWC INTENSITY FORECAST IS SET NEAR THE MULTI-MODEL
CONSENSUS THROUGH TAU 36, HEDGES CLOSER TO DEEPMIND FROM TAU 36 TO
TAU 60, AND ALIGNS WITH GFS AND ECMWF AT TAU 72.

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