Advisories

WDPN32 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (TWENTYTHREE) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.6N 135.2E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 436 NM SOUTHEAST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: 
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION 23W WITH A SMALL AND FULLY EXPOSED LOW-LEVEL CIRCULATION 
CENTER (LLCC). CONVECTIVE BURSTS ARE LOCALIZED TO THE SOUTHERN 
PERIPHERY, BUT QUICKLY DIE OFF UNDER THE EFFECTS OF NORTHERLY SHEAR. 
A 050254Z 89 GHZ AMSR3 MICROWAVE IMAGE REVEALED LOW-LEVEL CLOUDS 
TIGHTLY WRAPPING INTO THE CENTER WITH LITTLE TO NO ASSOCIATED 
CONVECTION. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED 
ON THE EXPOSED LLCC IN THE AMSR3 IMAGE AND ANIMATED MSI. THE INITIAL 
INTENSITY OF 25 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON EARLIER 
SCATTEROMETER DATA SHOWING 20-25 KTS WITHIN THE NORTHEASTERN QUADRANT 
AND PGTW FIX OF T1.0. ENVIRONMENTAL ANALYSIS INDICATES THAT 23W IS 
LOCATED WITHIN AN UNFAVORABLE ENVIRONMENT CHARACTERIZED BY WEAK 
OUTFLOW ALOFT, 10-15 KTS NORTHERLY SHEAR, AND WARM (28-29 C) SEA 
SURFACE TEMPERATURES. THE PRIMARY HINDERING FACTOR IS THAT 23W IS 
SMALL AND IS EMBEDDED WITHIN LOW-LEVEL SOUTHERLY FLOW, CAUSING 
INHERENT ASYMMETRY IN THE OVERALL STRUCTURE.

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

CURRENT STEERING MECHANISM: THE WESTERN FLANK OF A SUBTROPICAL RIDGE 
(STR) CENTERED TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   CIMSS SATCON: 35 KTS AT 050419Z
   CIMSS ADT: 27 KTS AT 050540Z
   CIMSS AIDT: 36 KTS AT 050540Z
   CIMSS D-MINT: 25 KTS AT 050552Z
   CIMSS D-PRINT: 24 KTS AT 050540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: EMBEDDED WITHIN LARGE-SCALE SOUTHERLY FLOW

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST HAS BEEN TRUNCATED TO 24 
HOURS

FORECAST DISCUSSION: TD 23W IS FORECAST TO TRACK NORTHWESTWARD, ALONG 
THE WESTERN PERIPHERY OF THE STR TO THE EAST THROUGHOUT THE SHORT 24 
HOUR FORECAST. THE SURROUNDING ENVIRONMENT IS DOMINATED BY THE 
LARGER-SCALE LOW-LEVEL CYCLONIC FLOW SOUTH OF JAPAN, PARTIALLY DUE TO 
TROPICAL STORM 22W, WHICH WILL HINDER ANY CHANCE FOR DEVELOPMENT OF 
THE MUCH SMALLER CIRCULATION. THE SYSTEM IS FORECAST TO WASH OUT 
WITHIN THE SURROUNDING WIND FIELD WITHIN THE NEXT 24 HOURS, SOUTHEAST 
OF KYUSHU. 

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT ON A
NORTHWESTWARD TRACK THROUGH TAU 24 WITH NO MAJOR OUTLIERS PRESENT.
SOME MODELS DO SHOW THE POTENTIAL FOR A TURN TO THE WEST ONCE THE
DISTANCE TO 22W SHRINKS. THE JTWC FORECAST CALLS FOR 23W TO DISSIPATE 
BEFORE THE REMNANT VORTICITY IS ABSORBED BY 22W. THE FORECAST IS 
PLACED NEAR THE CONSENSUS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS 
NOT VERY HELPFUL DUE TO THE ENHANCED SURROUNDING WINDS THAT ARE NOT 
ASSOCIATED WITH 23W. THE JTWC INTENSITY FORECAST CLOSELY FOLLOWS THE 
DECAY SHIPS GUIDANCE WITH HIGH CONFIDENCE.  

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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