WDPN31 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (LAN) WARNING NR 
032//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 36.2N 134.8E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 175 NM NORTHEAST OF IWAKUNI, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
DETERIORATING AND ASYMMETRIC WEB OF CONVECTIVE BANDS WITH 
THE A LOW LEVEL CIRCULATION CENTER THAT IS DECOUPLED FROM THE UPPER 
LEVEL CIRCULATION CENTER. WITHOUT THE LUXURY OF NEW MICROWAVE 
IMAGERY, ANIMATED RADAR IMAGERY WAS THE PRIMARY LOCALIZING TOOL. A 
LARGE DONUT-LIKE STRUCTURE IS STILL EVIDENT AS THE CIRCULATION 
EMERGES BACK OVER OPEN WATER. A 150848Z PARTIAL SOIL MOISTURE ACTIVE 
PASSIVE (SMAP) PASS REVEALED THE LEADING EDGE OF THE CIRCULATION HAS 
WEAKENED TO AROUND 45 KTS WITH A MAJORITY OF THE PRIMARY WIND FIELD 
AT 35-40 KTS. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE 
BASED ON THE LACK OF MICROWAVE DATA AND THE AMORPHOUS, BROAD 
STRUCTURE EVIDENT IN RADAR IMAGERY. THE INITIAL INTENSITY OF 45 KTS 
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE MAJORITY OF INTENSITY 
ESTIMATES SUCH AS PGTW DVORAK ESTIMATE, CIMSS, AIDT AND DPRINT 
SUPPORTING 45KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 33 KTS AT 151130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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: HAVING RECENTLY ENTERED THE WARM WATERS OF THE
SEA OF JAPAN, TS 07W (LAN) IS FORECAST TO PROCEED GENERALLY
POLEWARD. AS 07W TRACKS NORTHWARD, STEADILY IMPROVING OUTFLOW ALOFT
WILL FIGHT TO OVERCOME GRADUALLY INCREASING VERTICAL WIND SHEAR
VALUES. THE RESULT OF THIS BATTLE WILL ALMOST CERTAINLY BE
ANTICLIMACTIC, 07W WILL LIKELY ONLY MAINTAIN MOST OF ITS INTENSITY
THROUGH TAU 24. THE CURRENT JTWC FORECAST PHILOSOPHY IS ONE OF 
GRADUAL DECLINE DUE TO THE INCREASING SHEAR VALUES BEYOND TAU 36. AS 
THE SYSTEM PASSES THE 44TH PARALLEL, 07W WILL BEGIN TO INTERACT WITH 
A STRONG BAROCLINIC ZONE AS IT FURTHER INCREASES ITS POLEWARD TRACK 
SPEED, THEREBY INITIATING EXTRA-TROPICAL TRANSITION (ETT). BY TAU 
120, NOW WELL INTO THE SEA OF OKHOTSK, 07W WILL LOSE ITS LAST 
REMAINING TROPICAL CHARACTERISTICS AND COMPLETE ETT JUST BEFORE ITS 
EVENTUAL DISSIPATION.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT, WITH ALL
MEMBERS FOLLOWING THE JTWC TRACK FORECAST AND MULTI-MODEL CONSENSUS
WITH MINIMAL VARIABILITY THROUGH TAU 72. FOR THIS REASON THE JTWC
TRACK FORECAST IS PLACED WITH OVERALL MEDIUM CONFIDENCE. RELIABLE
MODEL INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH ALL MEMBERS
SHOWING GRADUAL DECLINE THROUGH TAU 24 AND AFTER THAT SHARPER
DECLINE THROUGH THE FORECAST PERIOD. FOR THIS REASON THE JTWC
INTENSITY FORECAST IS PLACED WITH OVERALL MEDIUM CONFIDENCE AS
WELL.

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