WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING NR 
023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.8N 115.6E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 169 NM SOUTH-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM
CONTINUED TO GRADUALLY DECAY AND UNRAVEL 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 CENTRAL CONVECTION HAS BECOME MORE
ASYMMETRIC AND IS TOTALLY OBSCURING THE LOW LEVEL CIRCULATION
(LLC). THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON
A BROAD AND PIXELATED MICROWAVE LLC FEATURE IN THE 011130Z AMSU-B
IMAGE AND EXTRAPOLATED FROM THE CURRENT STORM MOTION. THE INITIAL 
INTENSITY IS BASED ON THE PGTW, RJTD, AND ADT DVORAK ESTIMATES THAT 
REFLECT THE WEAKENING TREND.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 57 KTS AT 010840Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: MEDIUM
   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 TURN MORE
NORTHWESTWARD AS AN EXTENSION OF A SECONDARY STR TO THE
WEST-NORTHWEST ASSUMES STEERING AND BY TAU 24, DRIVES THE SYSTEM
WESTWARD INTO SOUTHEASTERN CHINA JUST WEST OF HONG KONG. THE
UNFAVORABLE ENVIRONMENT, MAINLY DUE TO THE COLD SURGE, COOLING SST,
AND INCREASING VWS, WILL CONTINUE TO ERODE TY 26W DOWN TO 35KTS BY 
TAU 36 PRIOR TO LANDFALL. AFTERWARD, THE ADDITION OF LAND INTERACTION 
WILL RAPIDLY WEAKEN THE SYSTEM TO DISSIPATION BY TAU 72, POSSIBLY 
SOONER.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT UP TO TAU
36 THEN SPREAD OUT TO OVER 230NM BY TAU 72 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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