WDPN31 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 11W (KIROGI) 
WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.6N 134.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 193 NM SOUTHEAST OF IWAKUNI, JAPAN
   MOVEMENT PAST 6 HOURS: WESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AVAILABLE METEOROLOGICAL DATA SUPPORTS A RESUMPTION OF TROPICAL
CYCLONE WARNINGS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY DEPICTS FLARING CONVECTION WHICH BLOSSOMED AFTER THE 0600Z,
BUT WHICH HAS ALREADY BEGUN TO RAPIDLY WEAKEN BY THE 1200Z HOUR.
THE PREVIOUS EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WAS
TRACKED WESTWARD AND TUCKED UNDER THE CONVECTIVE ENVELOPE. THE
INITIAL POSITION WAS ASSESSED WITH HIGH CONFIDENCE BASED ON
AMBIGUITY ANALYSIS OF A 041130Z ASCAT-B BULLSEYE PASS AND A
MICROWAVE EYE FEATURE IN A 041110Z GPM 37GHZ MICROWAVE IMAGE,
HOWEVER UNLIKELY THAT MIGHT APPEAR AT FIRST BLUSH. THE AMBIGUITIES
INDICATED THE SYSTEM HAS BECOME MUCH BETTER ORGANIZED AND
SYMMETRICAL IN JUST THE LAST 12 HOURS. THE INITIAL INTENSITY IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE ASCAT-B WIND FIELD,
WHICH SHOWED 25 KNOT WINDS SURROUNDING THREE QUARTERS OF THE LLCC
AND 30 KNOT WINDS, WITH SOME HIGHER READINGS UNDER THE STRONGEST
CONVECTION, COVERING A LARGE PORTION OF THE WESTERN SIDE OF THE
CIRCULATION. THE ENVIRONMENT IS MARGINAL AT BEST, WITH WARM SSTS,
MODERATE TO HIGH VERTICAL WIND SHEAR AND STRONG DUAL CHANNEL
OUTFLOW. THE SYSTEM IS POSITIONED IN A UNIQUE SPOT ON NORTHWEST
SIDE OF A STRONG TROPICAL UPPER-TROPOSPHERIC TROUGH (TUTT) CELL, AT
THE INFLECTION POINT WHERE THE EASTERLY FLOW SPLITS BOTH POLEWARD
AND EQUATORWARD, GENERATING A DUAL CHANNEL OUTFLOW REGIME WHICH HAS
ALLOWED FOR THE UPTICK IN INTENSITY AND ORGANIZATION.

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

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A SHALLOW
SUBTROPICAL RIDGE TO THE NORTH. 

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

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE DUAL-CHANNEL
   OTHER FACTORS: MID-LEVEL DRY AIR TO THE EAST ASSOCIATED WITH THE
TUTT-CELL.

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE UPON RESUMPTION OF WARNINGS AND ESTABLISHES THE NEW
FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 11W (KIROGI) WILL
CONTINUE TO TRACK WESTWARD FOR THE NEXT 12 HOURS OR SO, BEFORE
TURNING SHARPLY NORTHWARD AND MOVING INTO THE BUNGO CHANNEL BY TAU
24 AND CONTINUING NORTHEASTWARD OVER NORTHERN SHIKOKU ISLAND BY THE
END OF THE FORECAST PERIOD. THE AFOREMENTIONED TUTT CELL IS MOVING
NORTHWARD AND OVER THE NEXT 12 TO 24 HOURS, THE TWO SYSTEMS WILL
ALIGN AS THEY MOVE NORTH THEN NORTHEAST ALONG THE WESTERN SIDE OF A
DEEP SUBTROPICAL RIDGE TO THE EAST. THE GENERAL MARGINAL
CONDITIONS WILL NOT SUPPORT INTENSIFICATION AND IN FACT, CONDITIONS
BECOME INCREASINGLY HOSTILE OVER THE NEXT 12 HOURS. THE SYSTEM WILL
STEADILY WEAKEN AS IT MOVES DIRECTLY UNDER THE TUTT CELL AND
IS TORN APART BY THE FRICTIONAL EFFECTS OF THE RUGGED TERRAIN OF
KYUSHU AND SHIKOKU. DISSIPATION BELOW 20 KNOTS IS EXPECTED NO LATER
THAN TAU 36, BUT POTENTIALLY COULD OCCUR WITHIN THE NEXT 24 HOURS. 

MODEL DISCUSSION: THE MINIMAL TRACK GUIDANCE AVAILABLE IS IN
MODERATE AGREEMENT ON THE OVERALL TRACK SCENARIO, THOUGH THE ECMWF
MODEL TAKES THE SYSTEM STRAIGHT INTO KYUSHU BY TAU 12. THE HAFS-A
MODEL TRACKS THE SYSTEM TO THE KYUSHU COAST THEN DOES A 180 AND
RAPIDLY TRACKS THE SYSTEM TO A RENDEZVOUS AND MERGER WITH INVEST
99W NOW DEVELOPING IN THE PHILIPPINE SEA. THE REMAINDER OF THE
GUIDANCE PACKAGE SUPPORTS THE SHARP TURN NORTHEASTWARD AFTER TAU
12, THOUGH CROSS-TRACK SPREAD IS LARGE, LEADING TO MEDIUM
CONFIDENCE IN THE FORECAST TRACK. THERE IS NO RELIABLE INTENSITY
GUIDANCE AVAILABLE BUT BASED ON THE ENVIRONMENTAL ANALYSIS ABOVE,
THERE IS STILL MEDIUM CONFIDENCE IN THE JTWC FORECAST. 

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