WDPN31 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (EIGHT) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.4N 150.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 317 NM EAST-NORTHEAST OF SAIPAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A DISORGANIZED
BUT CONSOLIDATING SYSTEM WITH THE MAIN CONVECTION, ALTHOUGH SHEARED
EASTWARD, ENCROACHING INTO BUT STILL PARTIALLY EXPOSING THE LOW
LEVEL CIRCULATION CENTER (LLCC). THE MSI LOOP ALSO SHOWS THE STEADY
INFLUX OF COOL DRY AIR FROM THE NORTH AS EVIDENCED BY A STREAM OF
STRATOCUMULUS STREAKS WRAPPING INTO THE LLCC. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC
AND CONCENTRIC WITH A MICROWAVE LLCC FEATURE IN THE 230521Z SSMIS
IMAGE. THE INITIAL INTENSITY IS ALSO HELD WITH HIGH CONFIDENCE
BASED ON THE DVORAK ESTIMATES OF T2.0 (30KTS) FROM PGTW AND RJTD AND
THE ADT OBJECTIVE DVORAK ESTIMATE. ANALYSIS INDICATES A MARGINAL
ENVIRONMENT WITH THE DRY AIR INTRUSION AND MODERATE VWS OFFSET BY
STRONG POLEWARD OUTFLOW AND VERY WARM SST.

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

CURRENT STEERING MECHANISM: QUASI STATIONARY (QS) IN A COL BETWEEN
THE LOW REFLECTIONS OF THE SUBTROPICAL RIDGE (STR) TO THE NORTHWEST
AND THE NEAR EQUATORIAL RIDGE TO THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 27 KTS AT 230530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: LOW LEVEL COOL DRY AIR INTRUSION FROM THE NORTH.

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: TD 08W WILL REMAIN QS OVER THE NEXT 24-36HRS.
AFTERWARD, THE NER WILL BUILD AND BECOME THE DOMINANT STEERING
MECHANISM AND SLOWLY DRIVE THE CYCLONE NORTH-NORTHEASTWARD. AFTER
TAU 72, AS THE SYSTEM DEEPENS, A SECONDARY DEEP-LAYERED STR TO THE
NORTHEAST WILL ASSUME STEERING AND DRIVE THE CYCLONE NORTHWESTWARD
TOWARD JAPAN. THE MARGINAL ENVIRONMENT WILL FUEL A WEAK
INTENSIFICATION TO 35KTS AND HOLD IT THERE DURING THE QS PHASE.
AFTERWARD, INCREASING POLEWARD OUTFLOW AND DIMINISHING DRY AIR
INTRUSION AT THE LOW LEVELS WILL PROMOTE A STEADY INTENSIFICATION
TO 55KTS BY TAU 120. WORTH MENTIONING AT THIS EARLY STAGE IS THAT
TD 08W WILL TRACK ALONG THE EASTERN BOUNDARY OF A GYRE THE INCLUDES
MULTIPLE VORTICES OVER A WIDE AREA BOUNDED BY JAPAN, TAIWAN, AND
THE PHILIPPINE ISLAND OF LUZON. THE WIND FIELD OF THIS SYSTEM IS
FORECAST TO BECOME VERY EXPANSIVE WITH SUBTROPICAL CHARACTERISTICS.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT
WITH A GRADUAL SPREAD TO 216NM BY TAU 72. AFTERWARD, THEY SPREAD
OUT SIGNIFICANTLY AND UNEVENLY TO 460NM BY TAU 120.  GIVEN THESE,
PLUS THE UNCERTAINTIES INHERENT WITH QS STORM MOTION, THERE IS LOW
CONFIDENCE IN THE WHOLE DURATION OF THE JTWC TRACK AND INTENSITY
FORECASTS. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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