WDPN31 PGTW 280300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (JANGMI) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.7N 135.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 232 NM NORTHWEST OF YAP
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
BROAD CIRCULATION FIELD, WITH A RECENT CLEARING OF CENTRAL
CONVECTION REVEALING A LIKELY LOW LEVEL CENTER. MICROWAVE IMAGERY
OVER THE SYSTEM CENTER HAS REMAINED ELUSIVE, HOWEVER THE 280029Z
METOP-B ASCAT PASS ARRIVED AT THE END OF THE FORECAST CYCLE AND
PROVIDED EXCELLENT COVERAGE THAT CONFIRMS THE PRESENCE OF AN
ILL-DEFINED 100NM DIAMETER CENTER, CHARACTERIZED BY 20 TO 25 KNOT 
WINDS, WITH A FEW HIGHER VALUES UNDERNEATH CONVECTIVE POCKETS.  THE
ANALYZED CENTER WAS BASED ON THE PARTIALLY EXPOSED LLCC SCENE, AND
ALIGNS WELL WITH THE AREA OF TIGHTEST TURNING IN THE ASCAT DATA.
THE INITIAL INTENSITY WAS ASSESSED AT 30 KTS BASED ON THE RANGE OF
AGENCY AND OBJECTIVE ESTIMATES, AND ALIGNS WITH THE HIGH END OF THE
ASCAT DATA, UNDERSCORING THAT 06W HAS BEEN TAKING ITS TIME TO
CONSOLIDATE DESPITE VERY FAVORABLE VERTICAL WIND SHEAR OF 5 TO 10
KNOTS, 29 DEGREE SST, AND HIGH OHC. ADDITIONALLY, MID-LEVEL
RELATIVE HUMIDITY VALUES AND UPPER LEVEL OUTFLOW ARE VERY
SUPPORTIVE FOR DEVELOPMENT ONCE THE CORE VORTEX BECOMES BETTER
ESTABLISHED.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL RIDGING TO THE EAST
AND SOUTHEAST


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 30 KTS AT 271900Z
   CIMSS ADT: 33 KTS AT 272030Z
   CIMSS AIDT: 36 KTS AT 272030Z
   CIMSS D-MINT: 23 KTS AT 271920Z
   CIMSS D-PRINT: 26 KTS AT 272320Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: AS 06W DEEPENS, A BUILDING DEEP LAYER RIDGE TO 
THE EAST WILL BECOME THE DOMINANT STEERING MECHANISM, RESULTING IN A 
NORTHWESTWARD TO NORTH-NORTHWESTWARD MOTION OVER THE FIRST 72 HOURS. 
THE CENTRAL CORE SHOULD BECOME BETTER ALIGNED OVER THE NEXT 24 TO 36 
HOURS, AFTER WHICH CONTINUED FAVORABLE CONDITIONS SHOULD ALLOW FOR A 
MORE RAPID INTENSIFICATION TREND UP TO A PEAK OF APPROXIMATELY 95 
KNOTS. AFTER TAU 72, A SHORT-WAVE TROUGH PASSING OVER JAPAN SHOULD 
WEAKEN THE RIDGE AND ALLOW JANGMI TO BEGIN TO ROUND THE AXIS
OF THE SUBTROPICAL RIDGE. AT APPROXIMATELY THE SAME TIME, THE SYSTEM 
IS EXPECTED TO ENTER COOLER WATERS, THE EFFECTS OF WHICH WILL BE 
FURTHER AMPLIFIED BY UPWELLING, INITIATING A WEAKENING TREND THAT 
SHOULD CONTINUE THROUGH THE REMAINDER OF THE FORECAST, DESPITE THE 
INCREASE OF POLEWARD OUTFLOW. EVEN IF 06W AVOIDS A DIRECT LANDFALL ON 
THE RYUKYU ISLANDS, THE SIGNIFICANT GALE AND STORM FORCE WIND RADII 
WILL GENERATE IMPACTS FAR FROM THE CENTER. 

MODEL DISCUSSION: THE LATEST ROUND OF MULTI-MODEL CONSENSUS AID SPREAD 
IS 160 NM AT TAU 72, WHICH IS FAIRLY EVENLY DISTRIBUTED. BY CPA TO 
OKINAWA, SPREAD IS APPROXIMATELY 190 NM. MOST NOTABLY, PHYSICS-BASED 
MODELS ARE PRIMARILY ON THE WESTERN SIDE OF THE ENVELOPE, WHEREAS THE 
GROWING NUMBER OF EXPERIMENTAL AI MODEL AIDS HAVE CONSISTENTLY FAVORED 
THE EASTERN SIDE OF THE ENVELOPE, WITH A FASTER ALONG-TRACK SPEED 
AFTER TAU 72. THE JTWC TRACK WAS HELD CLOSE TO THE PRIOR FORECAST, AND 
EAST OF THE CONSENSUS IN DEFERENCE TO THE PERSISTENCE OF THE AI 
GUIDANCE. RELIABLE INTENSITY AIDS HAVE BEEN CONSISTENT WITH PEAK 
ESTIMATES AROUND 90 TO 95 KNOTS, WITH HIGH RESOLUTION COUPLED MODELS 
ACCOUNTING FOR THE DROP IN SST LATE IN THE FORECAST. 


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