WDPN31 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING NR 
026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.9N 114.9E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 93 NM SOUTH-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A RAPIDLY
WEAKENING SYSTEM WITH THE CENTRAL CONVECTION SHEARED 30+ NM
NORTHEASTWARD AND PARTLY EXPOSING A RAGGED LOW-LEVEL CIRCULATION
(LLC) AS IT TRACKED DEEPER INTO THE COLD NORTHEASTERLY WIND SURGE
THAT IS FUNNELING IN FROM THE TAIWAN STRAIT INTO THE SOUTH CHINA
SEA (SCS). THE SURGE IS EVIDENCED BY LOW LEVEL STRATOCUMULUS LINES
STREAMING SOUTHWESTWARD IN CONTRA-FLOW WITH THE UPPER-LEVEL CIRRI
STREAKS CAUGHT IN THE SOUTHWESTERLY JET STREAM THAT IS PROVIDING
STRONG POLEWARD OUTFLOW TO THE WEAKENING CONVECTION. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTLY
EXPOSED LLC IN THE MSI LOOP.  THE INITIAL INTENSITY IS BASED ON
AGENCY AND AUTOMATED DVORAK ESTIMATES THAT REFLECT THE WEAKENING
TREND.

INITIAL WIND RADII BASIS: PERSISTENCE AND SYNOPTIC OBSERVATIONS.

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
(STR) POSITIONED TO THE NORTHEAST. 


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 41 KTS AT 020230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL STORM NALGAE WILL CONTINUE ON ITS 
CURRENT TRACK UNDER THE STR TO THE NORTHEAST UP TO TAU 12. AFTERWARD, 
IT WILL TURN MORE NORTHWESTWARD AS AN EXTENSION OF A SECONDARY STR TO 
THE WEST-NORTHWEST ASSUMES STEERING AND DRIVES THE SYSTEM WESTWARD. 
THE UNFAVORABLE ENVIRONMENT, MAINLY DUE TO THE COLD SURGE, COOLING 
SST, AND INCREASING VWS, WILL CONTINUE TO RAPIDLY WEAKEN THE SYSTEM 
TO DISSIPATION BY TAU 36, POSSIBLY SOONER.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT UP TO TAU
24 THEN SPREAD OUT TO OVER 110NM BY TAU 36 AS THE MODELS LOSE THE
VORTEX, LENDING AN OVERALL MEDIUM CONFIDENCE TO THE JTWC TRACK
FORECAST. 

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