WDPN32 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 28W (HALONG) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.9N 142.3E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 55 NM EAST OF IWO TO
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 28W WITH DEEP CONVECTIVE BURSTS STILL SLIGHTLY OFFSET TO THE
EAST OF THE PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC).
THE VORTEX APPEARS TO BE IN BETTER ALIGNMENT WITH THE CONVECTION
INCHING CLOSER TO THE CENTER OF THE SYSTEM. ENVIRONMENTAL ANALYSIS
INDICATES THAT 28W IS IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY
STRONG EASTWARD OUTFLOW ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR,
AND WARM (29-30 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION
IS PLACED WITH MEDIUM CONFIDENCE BASED ON LOW-LEVEL CLOUD TRACING
OF THE PARTIALLY EXPOSED LLCC IN ANIMATED MSI. THE INITIAL
INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AGENCY DVORAK FIXES AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED
BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE FROM THE 042330Z METOP-B
ASCAT PASS

CURRENT STEERING MECHANISM: COMPETING STEERING PATTERN WITH A
SUBTROPICAL RIDGE (STR) TO BOTH THE EAST AND WEST. A NARROW BREAK
IN THE STR IS PRESENT TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 44 KTS AT 050610Z
   CIMSS ADT: 39 KTS AT 050610Z
   CIMSS AIDT: 37 KTS AT 050610Z
   CIMSS D-MINT: 38 KTS AT 050626Z
   CIMSS D-PRINT: 41 KTS AT 050610Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EASTWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: 28W IS NOW FORECAST TO RECURVE MUCH
EARLIER COMPARED TO THE PREVIOUS FORECAST. 

FORECAST DISCUSSION: 28W IS FORECAST TO TRACK WEST-NORTHWESTWARD,
ALONG THE SOUTHERN PORTION OF AN EXTENSION OF THE STR CENTERED TO
THE NORTHEAST THROUGH TAU 48. AROUND TAU 48, 28W IS FORECAST TO
BEGIN ROUNDING THE SOUTHWESTERN PERIPHERY OF THE STR TO THE EAST.
NEAR TAU 72, A TURN TO THE NORTHEAST IS EXPECTED AS THE SYSTEM
CONTINUES TO ROUND THE STR. TRACK SPEEDS WILL THEN INCREASE AS THE
SYSTEM BEGINS TO INTERACT WITH THE STRONG MIDLATITUDE WESTERLIES TO
THE NORTH. EXTRATROPICAL TRANSITION IS NOT EXPECTED TO START WITHIN
THE FORECAST PERIOD AS THE UPPER-LEVEL FLOW REMAINS ZONAL. THERE
CONTINUES TO BE VERY LOW CONFIDENCE IN THE TIMING OF THE RECURVE,
HOWEVER, MODELS ARE IN FAR BETTER AGREEMENT ON A RECURVE WELL
BEFORE INTERACTING WITH THE NORTHERN RYUKYU ISLANDS. REGARDING
INTENSITY, 28W IS FORECAST TO RAPIDLY INTENSIFY FROM TAU 24 (60
KTS) TO 48 (110 KTS). THE VORTEX IS EXPECTED TO BE COMPLETELY
ALIGNED IN AROUND 18 HOURS AND THE POLEWARD OUTFLOW CHANNEL IS
EXPECTED TO SIGNIFICANTLY IMPROVE, AIDING IN THE RAPID
INTENSIFICATION (RI). AFTER TAU 72, WESTERLY SHEAR IS EXPECTED TO
QUICKLY INCREASE, CAUSING THE SYSTEM TO WEAKEN THROUGH THE
REMAINDER OF THE FORECAST PERIOD. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE CONTINUES TO BE IN
POOR AGREEMENT, THOUGH IT IS GETTING BETTER. THE PRIMARY OUTLIERS
ARE NOW THE ECMWF ENSEMBLE MEAN, GALWEM, AND UKMET. THESE MODELS
SHOW A LATER, AND SHALLOWER RECURVE, INTERACTING WITH THE NORTHERN
RYUKYU ISLANDS AND SOUTHERN KYUSHU. THE REMAINDER OF GUIDANCE HAS
AN EARLEIR RECURVE, BEGINNING FAR SOUTHEAST OF KYUSHU. THE JTWC
TRACK FORECAST HAS SIGNIFICANTLY CHANGED AND FOLLOWS MORE CLOSELY
TO THE BULK OF RELIABLE GUIDANCE. INTENSITY GUIDANCE IS IN MODERATE
AGREEMENT WITH ALL MODELS SHOWING INTENSIFICATION THROUGH TAU 72.
PEAK INTENSITIES RANGE FROM 85 KTS (GFS) TO 135 KTS (COAMPS-TC).
THE JTWC INTENSITY FORECAST IS PLACED SLIGHTLY HIGHER THAN
CONSENSUS WITH OVERALL MEDIUM CONFIDENCE. 

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