WDPN32 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (HALONG) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.8N 137.0E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 413 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 48 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
28W (HALONG) WITH A CLEAR AND EVIDENT EYE-FEATURE, SURROUNDED BY A
RELATIVELY UNIFORM CIRRUS CANOPY. WITHIN THE OBSERVABLE
EYE-FEATURE, TEMPERATURES ARE OBSERVED BETWEEN 17 C TO 19 C, WHILE
THE ROBUST CONVECTION IMMEDIATELY WEST OF THE EYEWALL SHOWS A SHARP
TEMPERATURE GRADIENT RANGING FROM -77 C TO -79 C ON ANIMATED GOES
INFRARED SATELLITE IMAGERY. ALOFT, STRONG RADIAL OUTFLOW HAS BEEN
OBSERVED OVER THE LAST FEW HOURS ON ANIMATED WATER VAPOR IMAGERY,
INDICATED BY BURSTING CIRRIFORM STRIATIONS AWAY FROM THE SYSTEM,
WHICH INDICATES A CONTINUED HIGHLY FAVORABLE ENVIRONMENT.
ADDITIONALLY, ENVIRONMENTAL CONDITIONS REMAIN CONDUCIVE, WITH WARM
SEA SURFACE TEMPERATURES BETWEEN 28-29 C AND LOW VERTICAL WIND
SHEAR (VWS) BETWEEN 5-10 KTS. A 071630Z 89 GHZ MICROWAVE IMAGE HAS
ALSO REVEALED ONE DISTINCT CONVECTIVE BANDING FEATURE, WRAPPING
FROM THE NORTHERN QUADRANT ALONG THE EASTERN FLANK, AND INTO THE
SOUTHERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON ANIMATED EIR SATELLITE IMAGERY. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF
SUBJECTIVE AGENCY DVORAK ESTIMATES RANGING BETWEEN 115-127 KTS AND
CIMSS OBJECTIVE INTENSITY ESTIMATES HOLDING STEADY BETWEEN 119-122
KTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE DIRECTLY
TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.5 - 127 KTS
   RCTP: T6.5 - 127 KTS
   CIMSS SATCON: 118 KTS AT 071530Z
   CIMSS ADT: 119 KTS AT 071900Z
   CIMSS AIDT: 115 KTS AT 071900Z
   CIMSS D-MINT: 114 KTS AT 071636Z
   CIMSS D-PRINT: 122 KTS AT 071900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 28W IS FORECASTED TO CONTINUE TRACKING
ALONG THE WESTERN-MOST EXTENT OF THE SUBTROPICAL RIDGE AXIS LOCATED
DIRECTLY TO THE EAST OVER THE NEXT 36 HOURS. AT TAU 36, TYPHOON
HALONG IS EXPECTED TO START INTERACTING WITH THE SOUTHERN EXTENT OF
THE MID-LATITUDE WESTERLIES TO THE NORTH AND BEGIN AN
EAST-NORTHEAST TRACK THROUGH TAU 72. DURING THIS PHASE OF THE
FORECAST, TRACK SPEED WILL BEGIN TO INCREASE SIGNIFICANTLY AS TY
28W UNDERGOES EXTRATROPICAL TRANSITION INTO THE END OF THE FORECAST
PERIOD. WITH REGARD TO INTENSITY, TY 28W IS FORECASTED TO INTENSIFY
TO 125 KTS OVER THE NEXT 12 HOURS AS THE ENVIRONMENT REMAINS
LARGELY CONDUCIVE WITH WARM SEA SURFACE TEMPERATURES (28-29 C) AND
RELATIVELY LOW VWS AT LESS THAN 15 KTS. AFTER TAU 12, VWS WILL
BEGIN TO STEADILY INCREASE WHILE DRY AIR STARTS WRAPPING INTO THE
SOUTHERN QUADRANT. AS THE SYSTEM BEGINS APPROACHING THE
AFOREMENTIONED SOUTHERN EXTENT OF THE MID-LATITUDE WESTERLIES TO
THE NORTH AFTER TAU 12, TY 28W WILL BEGIN ITS INITIAL WEAKENING
PHASE INTO TAU 36. AFTER TAU 36, VWS IS FORECASTED TO INCREASE
ABOVE 30 KTS AT THE SAME TIME DRY AIR BEGINS ENVELOPING THE ENTIRE
SOUTHERN HALF OF THE SYSTEM, INITIATING THE TERMINAL WEAKENING
PHASE AND THE TRANSITION INTO AN EXTRATROPICAL CYCLONE. BY TAU 72,
TY 28W IS FORECASTED TO BECOME FULLY EXTRATROPICAL, WHILE
MAINTAINING SURFACE INTENSITIES OF 60 KTS UNDER SIGNIFICANT
INFLUENCE FROM THE UPPER-LEVEL JET. 

MODEL DISCUSSION: NUMERICAL WEATHER PREDICTION (NWP) GUIDANCE IS IN
VERY STRONG AGREEMENT THAT TY 28W WILL CONTINUE TO ROUND THE
WESTERN EXTENT OF THE SUBTROPICAL STEERING RIDGE TO THE EAST AND
BEGIN ITS TERMINAL WEAKENING PHASE THEREAFTER. THE CROSS-TRACK
SPREAD AT TAU 36 IS JUST 41 NM WITH THE TAU 72 CROSS-TRACK SPREAD
IMPROVING TO 39 NM. THEREFORE, THE JTWC FORECAST TRACK IS PLACED
WITH HIGH CONFIDENCE DURING THE ENTIRETY OF THE FORECAST PERIOD.
WITH REGARD TO INTENSITY, MOST JTWC INTENSITY CONSENSUS MEMBERS ARE
IN AGREEMENT WITH AN INITIAL WEAKENING PHASE AFTER TAU 12. HAFS AND
COAMPS-TC CONTINUE TO SHOW SLIGHT PROLONGED AND SUSTAINED
INTENSITIES BETWEEN 120-125 KTS BETWEEN TAU 12 AND TAU 24, HOWEVER,
A SHARP DECAYING PHASE IS ILLUSTRATED BY ALL INTENSITY GUIDANCE
MEMBERS BETWEEN TAU 24 AND TAU 72. THE JTWC INTENSITY FORECAST IS
ASSESSED WITH MEDIUM CONFIDENCE DUE TO THE SYSTEMS FORECASTED
TRANSITION INTO AN EXTRATROPICAL CYCLONE BETWEEN TAU 36 AND TAU 72.


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