WDPN31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 03W (GUCHOL) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.7N 134.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 387 NM NORTHWEST OF YAP
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
SOMEWHAT ASYMMETRIC CIRCULATION WITH FLARING DEEP CONVECTIVE BANDS
TO THE SOUTH WRAPPING UP INTO THE LOW LEVEL CIRCULATION CENTER
(LLCC). THE MOST RECENT IMAGERY SHOWS SOME DEVELOPING HOT TOWERS
MUCH CLOSER TO THE ASSESSED LLCC, WHICH ARE EXHIBITING SOME SIGNS
OF CYCLONIC CURVATURE.  EARLIER SCATTEROMETER DATA SHOWED THAT THE
LLCC REMAINS ELONGATED ALONG THE EAST-WEST AXIS BUT THE LATEST
SATELLITE IMAGERY SUGGESTS IT MAY BE SLOWLY CONSOLIDATING INTO A
MORE DEFINED AND DISCRETE CIRCULATION. LATE RECEIPT OF A 061710Z
AMSR2 89GHZ IMAGE SHOWED FRAGMENTED CONVECTIVE BANDS TO THE
SOUTHEAST OF THE CENTER, AND LOW LEVEL CLOUD BANDS TO THE
NORTHWEST, ANALYSIS OF WHICH SUGGESTS THE INITIAL POSITION COULD BE
SLIGHTLY FURTHER SOUTH THAN THE 18Z BEST TRACK POSITION. THE
INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE, AS ALL AGENCIES
ARE IN AGREEMENT ON A T2.5 DVORAK CURRENT INTENSITY (CI), SUPPORTED
BY THE ADT, SATCON AND THE CIMSS D-PRINT WHICH ARE ALSO ESTIMATING
A 35 KNOT INTENSITY. THE OVERALL ENVIRONMENT IS FAVORABLE FOR
DEVELOPMENT, WITH LOW VWS, WARM SSTS, AND HIGH OHC. OUTFLOW IS
STRONGEST TO THE EAST, INTO A STRONG TUTT-CELL LOCATED AT ROUGHLY
19N 150E, WITH WEAKER OUTFLOW EXTENDING EQUATORWARD. THE SYSTEM IS
TRAPPED BETWEEN A NEAR EQUATORIAL RIDGE (NER) SOUTH OF GUAM AND A
NARROW EXTENSION OF THE SUBTROPICAL RIDGE (STR) WHICH EXTENDS FROM
TAIWAN NORTHEAST TO A RIDGE CENTER NEAR 30N 175W.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: STR EXTENSION TO THE NORTH WITH A PUSH
FROM THE NER TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 35 KTS AT 061631Z
   CIMSS ADT: 35 KTS AT 061730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: OUTFLOW INTO A TUTT-CELL FAR TO THE
EAST-NORTHEAST. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: AS ALREADY NOTED IN THE BEST TRACK DATA, TS
03W LOOKS TO HAVE STARTED TO TURN ONTO A MORE WEST-NORTHWEST
COURSE, AS THE EXTENSION OF THE STR THAT LIES TO THE NORTH EXERTS
AN INCREASING INFLUENCE ON THE STEERING FLOW. NO SIGNIFICANT
CHANGE IS EXPECTED IN THE STRENGTH OR PLACEMENT OF THIS RIDGE
THROUGH THE NEXT 48 HOURS. THIS, COMBINED WITH THE GENERAL MOVEMENT
OF THE NER TOWARDS THE NORTHWEST, WILL RESULT IN A WEST-NORTHWEST
TRACK MOTION THROUGH THE FIRST 48 HOURS OF THE FORECAST. AROUND TAU
48, A MAJOR SHORTWAVE TROUGH AND ASSOCIATED JET MAX WILL PUSH OVER
JAPAN AND BREAK THE STR TO THE NORTH, WHILE SIMULTANEOUSLY BUILDING
A STR THAT DEVELOPS NEAR 160E. AS A RESULT, TS 03W WILL RAPIDLY
TURN POLEWARD BY TAU 72, AND THEN ACCELERATE NORTHEASTWARD ALONG
THE TIGHTENING GRADIENT ON THE WEST SIDE OF THE STR THROUGH THE
REMAINDER OF THE FORECAST PERIOD. IN TERMS OF INTENSITY, THE SYSTEM
IS EXPECTED TO QUICKLY CONSOLIDATE AND EMBARK ON A PERIOD OF
NEAR-RAPID INTENSIFICATION THROUGH THE NEXT 48 HOURS, AS IT
CONTINUES TO TAP INTO THE ROBUST OUTFLOW INTO THE TUTT CELL TO THE
EAST AND TAKES ADVANTAGE OF THE ZESTY OCEAN WATERS AND LOW SHEAR
ENVIRONMENT. AFTER PEAKING NEAR 85 KNOTS AT TAU 48, A COMBINATION
OF INCREASING NORTHWESTERLY SHEAR, COOLER SSTS AND A DECREASE IN
OUTFLOW ALOFT, WILL COMBINE TO SLOWLY WEAKEN THE SYSTEM THROUGH THE
REMAINDER OF THE FORECAST PERIOD. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD AGREEMENT
ON THE OVERALL RECURVE SCENARIO, BUT SHOWS INCREASED UNCERTAINTY IN
THE LATER FORECAST TAUS. THROUGH THE FIRST 48 HOURS, ALL CONSENSUS
MEMBERS LIE WITHIN A TIGHTLY CONFINED ENVELOPE OF 70NM, LENDING
HIGH CONFIDENCE TO THE FORECAST TRACK IN THIS TIMEFRAME. MODEL
SPREAD INCREASES AFTER TAU 72 WITH JGSM MARKING THE WESTERN
OUTLIER, WHILE THE GFS, NAVGEM AND COAMPS-TC MARKING THE EASTERN
EDGE OF THE ENVELOPE. THE REMAINDER OF THE GUIDANCE INCLUDING THE
EUROPEAN MODELS LIE CLOSE TO THE CONSENSUS MEAN. THE JTWC TRACK
DEPARTS TO THE EAST OF THE MEAN AND CLOSELY TRACKS THE
CONGLOMERATION OF THE US MODELS AFTER TAU 72, THOUGH CONFIDENCE
REMAINS MEDIUM DUE TO THE LARGE AND INCREASING MODEL SPREAD.
INTENSITY GUIDANCE IS IN GENERAL AGREEMENT ON THE INTENSIFICATION
TREND, AND SEVERAL RAPID INTENSIFICATION (RI) AIDS HAVE BEEN
TRIGGERED. THE JTWC FORECAST FOLLOWS THE RIPA AID THROUGH TAU 48,
THEN GENERALLY LIES ABOUT FIVE KNOTS HIGHER THAN THE CONSENSUS
THROUGH THE REMAINDER OF THE FORECAST. UNCERTAINTY SURROUNDING THE
TIMING OF THE LLCC CONSOLIDATION AND SUBSEQUENT INTENSIFICATION
RESULTS IN MEDIUM CONFIDENCE IN THE INTENSITY FORECAST. 

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