WDPN33 PGTW 300900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (HAIKUI) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.4N 135.6E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 411 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS THE
PREVIOUSLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) HAS MOVED
ONCE MORE UNDER AN AREA OF DEEP CONVECTION AND IS NOW OBSCURED.
VORTICAL HOT TOWERS CONTINUE TO FIRE ALONG THE SOUTHERN SIDE OF THE
TILTED VORTEX BUT HAVE YET TO BE ABLE TO ROTATE UPSHEAR, AND HENCE
THE SYSTEM HAS YET TO INTENSIFY. A LACK OF RECENT MICROWAVE IMAGERY
MAKES ANALYSIS OF THE VORTEX TILT AND THE INITIAL POSITION A LOW
CONFIDENCE AFFAIR. REANALYSIS OF PREVIOUS INTENSITY DATA INCLUDING
A 292116Z SMAP PASS RESULTED IN A DOWNGRADE OF THE INTENSITY OF
BOTH THE 291800Z AND 300000Z INTENSITIES TO 45 KNOTS. THE INITIAL
POSITION REMAINS SET AT 45 KNOTS, WITH MEDIUM CONFIDENCE, HEDGED
LOWER THAN THE AGENCY CURRENT INTENSITY ESTIMATES BASED ON THE
EARLIER SMAP DATA, AS WELL AS A T3.0 ADT, 42 KNOT AIDT, AND SATCON
OF 48 KNOTS. THE SYSTEM IS MOVING TOWARDS THE NORTHWEST ALONG THE
SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO
THE NORTHEAST. ENVIRONMENTAL CONDITIONS ARE MARGINALLY FAVORABLE
WITH WARM SSTS, MODERATE EQUATORWARD OUTFLOW AND A DEVELOPING
POLEWARD OUTFLOW CHANNEL TEMPERED BY LOW TO MODERATE NORTHERLY WIND
SHEAR.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 48 KTS AT 300530Z
   CIMSS ADT: 43 KTS AT 300530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: SIGNIFICANT VORTEX TILT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM (TS) 10W (HAIKUI) IS FORECAST
TO CONTINUE TRACKING WEST-NORTHWEST ALONG THE SOUTHWEST SIDE OF THE
STEERING RIDGE THROUGH THE BULK OF THE FORECAST PERIOD. GLOBAL
MODEL FIELDS HAVE COME INTO MUCH BETTER AGREEMENT ON THE EVOLUTION
OF THE UPPER-LEVEL PATTERN OVER THE LAST COUPLE OF RUNS, PROVIDING
INCREASED CONFIDENCE IN THE TRACK GUIDANCE. OVER THE COURSE OF THE
FIRST 72 HOURS OF THE FORECAST, THE SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST IS EXPECTED TO EXTEND SOUTHWESTWARD, WITH A SHARP RIDGE
AXIS DEVELOPING ALONG A LINE EXTENDING FROM WEST OF SHANGHAI TO
TOKYO. THIS WILL SERVE TO KEEP THE TRACK OF 10W ON A MORE DEPRESSED
TRAJECTORY, PASSING SOUTH OF OKINAWA AROUND TAU 48 AND MOVING INTO
THE EAST CHINA SEA. AFTER TAU 72, THE MODELS DO BEGIN TO DIVERGE ON
HOW THEY HANDLE A SHARP MID-LATITUDE TROUGH MOVING EAST OUT OF
MONGOLIA; HOW DEEP WILL IT BE AND HOW FAST WILL IT ERODE THE RIDGE.
THE GFS AND NAVGEM MODELS SHOW A WEAKER TROUGH, WHICH DOES NOT
BREAK DOWN THE RIDGE AS MUCH, FORCING THE SYSTEM ONTO A FLATTER
TRACK, MAKING LANDFALL IN THE VICINITY OF WENZHOU, CHINA BY TAU 96.
THE ECMWF ON THE OTHER HAND, AND THE GFS ENSEMBLE INTERESTINGLY
ENOUGH, SHOW A STRONGER TROUGH WHICH ERODES THE RIDGE ALLOWING THE
SYSTEM TO RECURVE NORTH TOWARDS SHANGHAI BY TAU 120. CURRENT
ASSESSMENT OF THE GLOBAL MODEL FIELDS SUGGESTS THE ECMWF SOLUTION
MAY BE THE BETTER OPTION, AT LEAST FOR THE MOMENT IF FOR NO OTHER
REASON THAN ITS CONSISTENCY OVER THE PAST 48 HOURS WHEREAS THE GFS
HAS BEEN EXHIBITING GIGANTIC SWINGS FROM RUN TO RUN. THE JTWC
FORECAST TAKES THE SYSTEM INLAND SOUTH OF SHANGHAI AROUND TAU 96
THEN TRACKS NORTHWARD ACROSS EASTERN CHINA THROUGH TAU 120. IN
TERMS OF INTENSITY, THE SYSTEM WILL CONTINUE TO STRUGGLE FOR THE
NEXT 48 HOURS AS IT CONTINUES TO BE CONSTRAINED BY VORTEX TILT AND
MODERATE SHEAR. BY AROUND TAU 48, THE SHEAR IS EXPECTED TO BACK OFF
SIGNIFICANTLY, WHICH SHOULD ALLOW THE VORTEX TO SYMMETRIZE AND
START A PERIOD OF RAPID INTENSIFICATION AS THE SYSTEM PASSES SOUTH
OF OKINAWA AND INTO THE EAST CHINA SEA. LAND INTERACTION WILL LEAD
TO RAPID WEAKENING AFTER LANDFALL. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE HAS
COME INTO MUCH BETTER AGREEMENT WITH THIS RUN, WITH EVEN THE GFS
GIVING UP ON THE ERRATIC TRACK THAT IT WAS DEPICTING OVER THE PAST
36 HOURS. ALL CONSENSUS MEMBERS NOW AGREE ON A WEST-NORTHWEST TRACK
THROUGH TAU 48 BUT DO SHOW SOME DIVERGENCE AFTER THIS POINT AS
DESCRIBED ABOVE. THE HAFS-A AND COAMPS-TC, WHILE NOT MEMBERS OF THE
TRACK CONSENSUS, SHOULD BE NOTED AS BEING SOUTHWARD OUTLIERS,
TAKING THE SYSTEM OVER NORTHERN TAIWAN OR JUST NORTHEAST OF TAIWAN
BY THE END OF THE FORECAST. THE GFS TRACKS JUST NORTH OF MIYAKOJIMA
WHILE THE ECMWF HAS SHIFTED A BIT SOUTH AND NOW KEEPS THE TRACK
SOUTH OF OKINAWA BY ABOUT 25NM. THE RESULT IS A TIGHTENING OF THE
GUIDANCE ENVELOPE THOUGH TAU 48. AFTER THIS POINT TWO GROUPS
EMERGE, WITH THE NAVGEM, GFS AND UKMET ENSEMBLE TRACKING THE SYSTEM
INTO CHINA NEAR WENZHOU WHILE THE ECMWF, ECENS, AND GEFS TURN THE
SYSTEM POLEWARD TOWARDS SHANGHAI. THE JTWC FORECAST LIES CLOSE TO
THE CONSENSUS MEAN AND THE ECMWF TRACK WITH MEDIUM CONFIDENCE.
INTENSITY GUIDANCE IS FOR THE MOST PART IN GOOD AGREEMENT ON A SLOW
INTENSIFICATION TREND TO TAU 48 FOLLOWED BY A SHARP INTENSIFICATION
PERIOD THROUGH TAU 72 AND THEN RAPID WEAKENING AFTER LANDFALL. THE
JTWC FORECAST IS CONSISTENT WITH THE INTENSITY CONSENSUS MEAN AND
THE COAMPS-TC FORECAST. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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