WDPN31 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (AERE) WARNING 
NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.0N 127.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 217 NM SOUTH-SOUTHWEST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RECENT
FLARE OF DEEP CONVECTION SHEARING SOUTHEASTWARD FROM THE LOW-LEVEL
CIRCULATION CENTER. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON 032241Z SSMIS 37 GHZ IMAGERY, A 032330Z PGTW
SATELLITE FIX AND ASSESSMENT OF A PARTIALLY-EXPOSED LOW-LEVEL
CIRCULATION CENTER EVIDENT IN MSI. THE INITIAL INTENSITY OF 30 KTS
IS ASSESSED WITH HIGH CONFIDENCE BASED ON A CONSENSUS OF SUBJECTIVE
DVORAK CURRENT INTENSITY AND AUTOMATED SATELLITE INTENSITY
ESTIMATES. ANIMATED WATER VAPOR IMAGERY AND ATMOSPHERIC MOTION
VECTOR DATA INDICATES THAT AN UPPER-LEVEL TROUGH REMAINS ENTRENCHED
OVER THE SYSTEM, INDUCING STRONG NORTHWESTERLY VERTICAL WIND SHEAR.
A RECENT FLARE OF DEEP CONVECTION OBSERVED OVER THE EASTERN AND
SOUTHERN PERIPHERIES OF THE CIRCULATION IS WANING DUE TO THE
PERSISTENT SHEAR.

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

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE TO THE
EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS ADT: 27 KTS AT 032040Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: UPPER-LEVEL TROUGH OVER THE LOW-LEVEL CIRCULATION

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 05W WILL TURN EASTWARD AS IT ROUNDS THE
NORTHWESTERN PERIPHERY OF THE CURRENT SUBTROPICAL STEERING RIDGE
OVER THE NEXT 24 TO 36 HOURS. THE SUBTROPICAL RIDGE WILL REMAIN THE
DOMINANT STEERING MECHANISM FOR ABOUT 72 HOURS, BY WHICH TIME TD
05W IS EXPECTED TO BEGIN MERGING WITH A DEVELOPING SHORTWAVE TROUGH
AND SLOW SIGNIFICANTLY OFF THE EAST COAST OF HONSHU. THE OFFSETTING
INFLUENCES OF PERSISTENT VERTICAL WIND SHEAR AND FAVORABLE
DIFFLUENCE ALOFT WILL ENABLE TD 05W TO MAINTAIN INTENSITY PRIOR TO
LANDFALL IN KYUSHU IN APPROXIMATELY 24 HOURS. WEAKENING IS
ANTICIPATED AFTER LANDFALL. HOWEVER, THE WEAKENING TREND WILL
REVERSE AS THE SYSTEM REEMERGES OVER WATER AND MERGES WITH THE
AFOREMENTIONED SHORTWAVE TROUGH, WHICH IS EXPECTED TO REMAIN CUT
OFF FROM THE PRIMARY MIDLATITUDE WESTERLY FLOW PATTERN. FAVORABLE
BAROCLINIC INTERACTION BETWEEN TD 05W AND THE TROUGH IS EXPECTED TO
YIELD A GALE FORCE SUBTROPICAL LOW.

MODEL DISCUSSION: NUMERICAL MODELS REMAIN IN GOOD AGREEMENT WITH
THE CURRENT FORECAST SCENARIO THROUGH TAU 120. SOME SPREAD REMAINS
IN THE ORIENTATION AND SPEED OF THE TRACK AS THE SYSTEM ROUNDS THE
RIDGE AXIS, AND THE NAVGEM AND ECMWF DETERMINISTIC MODEL TRACKERS
LOSE THE VORTEX BY TAU 48 DUE TO MORE PRONOUNCED DISSIPATION OVER
LAND. OVERALL, CONFIDENCE IN THE TRACK FORECAST IS MEDIUM. WITH
INTENSITY CHANGE CONSTRAINED TO A NARROW RANGE BY OFFSETTING
INFLUENCES THROUGH TAU 72, INTENSITY FORECAST CONFIDENCE
IS HIGH IN THE NEAR-TERM. INTENSITY DURING AND AFTER SUBTROPICAL
TRANSITION WILL DEPEND ON THE EXACT NATURE OF THE INTERACTION
BETWEEN TD 05W AND THE DEVELOPING SHORTWAVE TROUGH, AND SPREAD IN
THE INTENSITY GUIDANCE INCREASES DURING THAT PERIOD, SO INTENSITY
FORECAST CONFIDENCE FOR TAU 72 TO 120 IS MEDIUM.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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