WDPN32 PGTW 270900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.5N 139.7E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 203 NM NORTH-NORTHEAST OF YAP
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A BROAD
CIRCULATION WITH FRAGMENTED AND DISORGANIZED CONVECTION FIRING OFF,
BUT UNABLE TO PERSIST AT THIS TIME. A 262353Z ASCAT-C SCATTEROMETER
PASS REVEALED A BROAD LOW LEVEL CIRCULATION CENTER (LLCC) WITH
20-25 KNOTS WINDS PRESENT IN ALL QUADRANTS, BUT WITH A RADIUS OF
MAXIMUM WINDS (RMW) OF ABOUT 80NM. SUBSEQUENT AMSR2 WINDSPEED
PRODUCTS INDICATED A SIMILAR ARRANGEMENT, WITH AN RMW OF ABOUT 70NM
AND 25-30 KNOT WINDS LIMITED TO THE NORTHEAST QUADRANT. A 270613Z
SSMIS COLOR ENHANCED 91GHZ MICROWAVE IMAGE REVEALED WELL DEFINED
LOW-LEVEL BANDS BUT ONLY FRAGMENTED AREAS OF MODERATE CONVECTION.
THE MICROWAVE IMAGERY AND ANIMATED MSI PROVIDED MEDIUM CONFIDENCE
IN THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED WITH
HIGH CONFIDENCE BASED ON A T1.5 DVORAK ESTIMATE FROM RJTD AND A
T1.0 FROM PGTW AS WELL AS THE AFOREMENTIONED, AMSR2 AND
SCATTEROMETER DATA. THE SYSTEM IS CURRENTLY TRACKING NORTHWESTWARD
ALONG THE SOUTHWEST PERIPHERY OF A LOW TO MID-LEVEL NEAR-EQUATORIAL
RIDGE (NER) CENTERED TO THE EAST OF THE MARIANAS. OVERALL, THE
ENVIRONMENT IS CURRENTLY CHARACTERIZED AS MARGINALLY FAVORABLE,
WITH VERY WARM (30-31C) SSTS AND MODERATE EQUATORWARD OUTFLOW. THE
PRIMARY LIMITING FACTORS AT PRESENT ARE THE BROAD NATURE OF THE LLC
AND THE NORTHERLY FLOW EMANATING FROM TY 05W PUSHING DOWN FROM THE
NORTH. HOWEVER, THE SYSTEM LIES RIGHT UNDER THE INFLECTION POINT
WHERE THE OUTFLOW FROM TY 05W SPLITS, AND THEREFORE SHEAR HAS
LESSENED A BIT.

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

CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A LOW TO
MID-LEVEL NEAR-EQUATORIAL RIDGE (NER) TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   RJTD: T1.5 - 25 KTS

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

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TD 06W (SIX) IS EXPECTED TO MOVE TOWARDS THE
WEST-NORTHWEST FOR THE NEXT 24 HOURS UNDER THE INFLUENCE OF THE LOW
TO MID-LEVEL FLOW ASSOCIATED WITH THE NER CENTERED EAST OF THE
MARIANAS. AROUND TAU 24, THE SYSTEM IS EXPECTED TO TURN MORE
POLEWARD AS THE NER TO THE EAST STRENGTHENS AND MOVES WEST AND
ALIGNS TO A MORE NORTH-SOUTH AXIS. BY AROUND TAU 72, THE NER
WEAKENS AND BEGINS TO SLIDE SOUTHWESTWARD, AND TD 06W RUNS SMACK
INTO THE VERY STRONG SUBTROPICAL RIDGE (STR) CENTERED NEAR TOKYO.
THIS WILL FORCE THE SYSTEM TO TURN LEFT ONTO A MORE
WEST-NORTHWESTWARD TRACK FROM TAU 72 THROUGH TO THE END OF THE
FORECAST PERIOD AS THE PRIMARY STEERING INFLUENCE SHIFTS TO THE STR
TO THE NORTH. THROUGH THE NEXT 36 HOURS, TD 06W WILL SLOWLY BUT
STEADILY CONSOLIDATE, AND THE RMW WILL STEADILY REDUCE. DUE TO THE
MARGINAL OUTFLOW ENVIRONMENT AND MODEST AMOUNTS OF NORTHERLY SHEAR,
THE SYSTEM WILL INTENSIFY AT A SLOW RATE, REACHING 40 KNOTS BY TAU
36. AROUND TAU 48 HOWEVER, THE ENVIRONMENT WILL RAPIDLY BECOME MORE
FAVORABLE. AS EARLY AS TAU 24, A TUTT-CELL BEGINS TO DEVELOP
BETWEEN TWO VERY STRONG UPPER-LEVEL ANTICYCLONES, IN THE VICINITY
25N 140E. BUT THROUGH THE FIRST 36 HOURS OF THE FORECAST, THE TUTT
IS IN AN UNFAVORABLE POSITION FOR TD 06W. BETWEEN TAU 48 AND 72 THE
TUTT MOVES INTO A HIGHLY FAVORABLE POSITION TO THE NORTHWEST OF TD
06W, AND THE SYSTEM WILL TAP INTO THE VERY STRONG POLEWARD OUTFLOW
CHANNEL INTO THE EASTERN SIDE OF THE STRONG TUTT-CELL, SUPPORTING
EXPLOSIVE INTENSIFICATION AFTER TAU 48, TO A PEAK OF AT LEAST 115
KNOTS, THOUGH A THE POTENTIAL FOR A MUCH HIGHER PEAK CANNOT BE
RULED OUT, IN THE TAUS BETWEEN THE FORECAST POINTS. AFTER TAU 96,
THE SYSTEM MOVES INTO AN AREA OF SLIGHTLY LESS UPPER-LEVEL OUTFLOW
AND WILL LIKELY MAINTAIN INTENSITY AFTER PASSING VERY CLOSE TO OR
OVER THE ISLAND OF OKINAWA AND MOVING INTO THE EAST CHINA SEA. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD
AGREEMENT, WITH THE CONSENSUS MEMBERS CONTAINED WITHIN A 100NM
ENVELOPE AT TAU 72 WHICH GRADUALLY EXPANDS TO JUST 150NM BY TAU
120. AVAILABLE ENSEMBLE GUIDANCE IS ALSO CONSTRAINED TO A FAIRLY
TIGHT, THOUGH SLIGHTLY LARGER THAN THE DETERMINISTIC, ENVELOPE
CENTERED ON OKINAWA. THE JTWC FORECAST LIES WEST AND SOUTH OF THE
CONSENSUS MEAN THROUGH THE FIRST 24 HOURS, THEN CLOSELY TRACKS THE
GFS AND CONSENSUS MEAN THROUGH THE REMAINDER OF THE FORECAST.
CONFIDENCE IN THE FIRST 72 HOURS OF THE TRACK IS MEDIUM DUE TO THE
FACT THAT THE BROAD NATURE OF THE LLC INDUCES UNCERTAINTY IN THE
INITIAL POSITION AND THUS THE FIRST STAGES OF THE FORECAST.
CONFIDENCE REMAINS MEDIUM IN THE LONG-RANGE TRACK FOR THE SAME
REASON. INTENSITY GUIDANCE IS IN GOOD AGREEMENT BUT IS INTENSIFYING
THE SYSTEM TOO FAST IN THE FIRST 48 HOURS AND NOT ENOUGH IN THE
LATER TAUS. THE JTWC FORECAST LIES 5-10 KNOTS BELOW THE CONSENSUS
MEAN THROUGH TAU 48, THEN GOES WELL ABOVE THE MEAN AFTER TAU 72.
THE FORECAST MOST CLOSELY FOLLOWS THE HWRF AND CTR1 SOLUTION AFTER
TAU 48, AND PEAKS 30 KNOTS HIGHER THAN THE CONSENSUS MEAN, WHICH IS
BEING HELD TOO LOW BY THE HAFS-A AND GFS MESOSCALE GUIDANCE.
ADDITIONALLY, THE COAMPS-TC ENSEMBLE RAPID INTENSIFICATION (RI)
PROBABILITY GUIDANCE, SHOWS A 50 PERCENT PROBABILITY OF RI BETWEEN
TAU 54 AND TAU 90, PROVIDING ADDITIONAL CONFIDENCE IN THE FORECAST
ABOVE THE CONSENSUS MEAN, BUT CONFIDENCE REMAINS LOW IN THE LATER
TAUS DUE TO THE UNCERTAINTY IN THE EARLY PORTION OF THE FORECAST
AND HOW LONG IT TAKES THE SYSTEM TO ORGANIZE AND REACH TROPICAL
STORM STRENGTH. 

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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