WDPN32 PGTW 222100
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: 14.5N 146.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 58 NM SOUTHEAST OF SAIPAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTION FLARING OVER THE NORTHEAST PERIPHERY OF AN ASYMMETRIC
LOW LEVEL CIRCULATION CENTER (LLCC). HAVING CLOUD TOP TEMPERATURES
COLDER THAN -85 DEGREES CELSIUS, VORTICAL HOT TOWERS ARE ROTATING
ABOUT A MID-LEVEL CENTER THAT IS DISPLACED NORTH OF THE LLCC. THIS
TILT IN THE FORMATIVE VORTEX INDICATES THE PRESENCE OF SOUTHERLY
SHEAR ALOFT. A FORTUITOUS 221147Z ASCAT-C PASS REVEALED A SWATH OF
30 KT WINDS IN THE NE QUADRANT AND MUCH WEAKER 5-15 KT WINDS IN THE
SOUTHERN SEMICIRCLE. A RECENT OBSERVATION FROM SAIPAN INTERNATIONAL
AIRPORT NOTED A WIND GUST OF 38 KTS. THE ENVIRONMENT IS MARGINALLY
FAVORABLE FOR DEVELOPMENT, CHARACTERIZED BY WARM SEA SURFACE
TEMPERATURE (SST) OFFSET BY MODEST VERTICAL WIND SHEAR (VWS) AND
DRY AIR IN THE 400-200 MB LAYER AS DEPICTED IN THE 221200Z GUAM
SOUNDING. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE PARTIALLY EXPOSED LLCC IN THE SHORTWAVE IR IMAGERY AND
RADAR IMAGERY FROM PGUA. THE INITIAL INTENSITY IS SET AT 30 KTS
WITH MEDIUM CONFIDENCE, WHICH IS HIGHER THAN THE SUBJECTIVE DVORAK
ESTIMATES OF T1.0-1.5 BUT STILL COULD BE CONSERVATIVE GIVEN THE
IMPROVEMENT IN STRUCTURE SINCE THE ASCAT PASS.

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

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A LOW- TO
MID-LEVEL RIDGE CENTERED OVER THE CENTRAL NORTH PACIFIC

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS D-PRINT: 21 KTS AT 221900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: DRY AIR ALOFT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   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: TROPICAL DEPRESSION 08W WILL TRACK TOWARDS THE
WEST-NORTHWEST THROUGH TAU 60 UNDER THE INFLUENCE OF A STR. THE
VORTEX WILL ROUND THE STR AXIS AT TAU 72 AND THEN ACCELERATE
TOWARDS THE NORTHEAST AND INTO THE MID-LATITUDE WESTERLIES. THE
INTENSITY FORECAST IS QUITE UNCERTAIN. WHILE THE ENVIRONMENT OF LOW
TO MODERATE SOUTHEASTERLY VWS AND WARM SST WILL BE FAVORABLE FOR
DEVELOPMENT THROUGH TAU 36, SLOW INTENSIFICATION IS FORECAST DUE TO
THE PRESENT STRUCTURE OF THE CIRCULATION. ONCE 08W BECOMES A
MODERATE TROPICAL STORM, INTERACTION WITH LARGER, MORE POTENT
CIRCULATION OF 07W APPEARS PROBABLE. THE PROXIMITY OF 08W TO 07W
WILL DICTATE WHETHER THIS SYSTEM WILL WASH OUT AND DISSIPATE BY TAU
96 OR MAINTAIN INTENSITY AS IT ROUNDS THE RIDGE. THE FORECAST LEANS
TOWARDS THE LATTER SOLUTION AND ALLOWS THE DISCRETE SYSTEM TO
UNDERGO EXTRATROPICAL TRANSITION BEGINNING AT TAU 96.

MODEL DISCUSSION: MOST OF THE RELIABLE GUIDANCE IS TIGHTLY
CLUSTERED THROUGH TAU 72, AND THE JTWC TRACK FORECAST IS LARGELY
CENTERED WITHIN THIS CLUSTER WITH HIGH CONFIDENCE. CROSS-TRACK
SPREAD REMAINS LOW AT TAU 96 AND TAU 120, BUT THE ALONG-TRACK
SPREAD INCREASES SIGNIFICANTLY. THE FORECAST IS HEDGED BETWEEN THE
FASTER ECMWF AND SLOWER GFS SOLUTIONS AT THE END OF THE FORECAST
PERIOD WITH LOW CONFIDENCE. THERE IS A CHANCE THAT THE SYSTEM WILL
BE ABSORBED INTO THE CIRCULATION OF 07W AFTER TAU 72, SO THE TRACK
FORECAST IS SET WITH MEDIUM CONFIDENCE FOR THE NEAR TERM AND WITH
LOW CONFIDENCE BEYOND 72 HOURS. MODELS GENERALLY SHOW DEVELOPMENT
FOR THE FIRST THREE DAYS, AND THE INTENSITY FORECAST IS SET CLOSE
TO THE CONSENSUS WITH MEDIUM CONFIDENCE. BECAUSE THE CURRENT JTWC
FORECAST CALLS FOR 08W TO SURVIVE THE INTERACTION WITH 07W, THE
INTENSITY PREDICTION HEDGES ON THE HIGHER SIDE OF THE GUIDANCE
AFTER TAU 72 WITH LOW CONFIDENCE. THE FORECAST PEAK OF 45 KTS IS
BELOW THE 55 KT PEAK OF THE EXPERIMENTAL GOOGLE DEEPMIND AND ABOVE
GFS AND HAFS-A.

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