Advisories

WDPN31 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 30W (IN-FA) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.6N 166.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 144 NM NORTHWEST OF KWAJALEIN
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TS 30W HAS BECOME INCREASINGLY ORGANIZED OVER THE PAST SIX HOURS.
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEVELOPING
DEEP CONVECTIVE BANDING AND A FLARE OF CENTRAL CONVECTION OVER A
TIGHTLY WRAPPED LOW-LEVEL CIRCULATION CENTER EVIDENT IN A 231843Z
WSF-M PASS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE 37 GHZ IMAGERY FROM THE WSF-M PASS. THE INITIAL
INTENSITY OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A
CONSENSUS OF SUBJECTIVE DVORAK AND AUTOMATED INTENSITY ESTIMATES
LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS ADT: 32 KTS AT 231740Z
   CIMSS AIDT: 32 KTS AT 231740Z
   CIMSS D-MINT: 34 KTS AT 231508Z
   CIMSS D-PRINT: 37 KTS AT 232010Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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: TS 30W IS EXPECTED TO REMAIN QUASI-STATIONARY
OVER THE NEXT SIX HOURS IN A COMPETING STEERING ENVIRONMENT BETWEEN
NEAR-EQUATORIAL RIDGING TO THE SOUTHEAST AND A SOUTHWARD EXTENSION
OF SUBTROPICAL RIDGING TO THE WEST. THE NEAR-EQUATORIAL RIDGE WILL
BUILD OVER THIS PERIOD AND, BY TAU 12, GRADUALLY BECOME THE
DOMINANT STEERING MECHANISM. TS 30W WILL FOLLOW THE FLOW ASSOCIATED
WITH THIS RIDGE POLEWARD THROUGH TAU 72. A SUBTROPICAL RIDGE
BUILDING TO THE NORTH WILL EXERT AN INCREASING INFLUENCE ON STORM
MOTION AFTER TAU 48, INDUCING A TEMPORARY SLOWDOWN BEFORE TAKING
OVER AS THE DOMINANT STEERING MECHANISM AND PUSHING THE SYSTEM
WESTWARD. STEADY TO RAPID NEAR-TERM INTENSIFICATION IS HIGHLY
LIKELY GIVEN THE PRESENCE OF LOW VERTICAL WIND SHEAR AND SUPPORTIVE
POLEWARD AND EQUATORWARD UPPER-LEVEL OUTFLOW AND A TROPICAL
UPPER-TROPOSPHERIC TROUGH ENHANCING OUTFLOW ON THE POLEWARD SIDE. IN
THE EXTENDED RANGE, ADDITIONAL INTENSIFICATION IS EXPECTED BUT THE
RATE SHOULD DROP AS THE OUTFLOW PATTERN BECOMES LESS FAVORABLE. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE HAS COME INTO BETTER
ALIGNMENT REGARDING THE SYNOPTIC STEERING PATTERN AND OVERALL
FORECAST SCENARIO, WITH ALL AI AND PHYSICS-BASED MODEL CONSENSUS
MEMBERS SUPPORTING SLOW NEAR-TERM MOTION FOLLOWED BY A POLEWARD
TRACK THROUGH TAU 72 AND A WESTWARD TURN THEREAFTER. THE PRECISE
TRACK AND TIMING ARE STILL UNCERTAIN, ALTHOUGH ALL BUT TWO OUTLIERS
(NAVGEM AND JGSM, SITUATED SLIGHTLY TO THE EAST) FALL WITH A NARROW
ENVELOPE AROUND THE CURRENT FORECAST, WHICH IS LARGELY CONSISTENT
WITH THE PREVIOUS JTWC TRACK FORECAST. INTENSITY FORECAST GUIDANCE
IS IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD REGARDING
NEAR-TERM STEADY TO RAPID AND LATER STEADY INTENSIFICATION. HAFS IS
A BIT LOWER THAN THE REMAINDER OF THE GUIDANCE THROUGH TAU 60, BUT
SEVERAL RAPID INTENSIFICATION AIDS HAVE TRIGGERED ON THE CURRENT
CYCLE AND THE ENVIRONMENT IS QUITE FAVORABLE, MAKING SLOW
INTENSIFICATION UNLIKELY.

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