WDPN31 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (NALGAE) WARNING NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.2N 115.9E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 209 NM SOUTH-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A SYSTEM THAT
IS IN GRADUAL DECAY AS IT TRACKS DEEPER INTO THE COLD NORTHEASTERLY
WIND SURGE FUNNELING IN FROM THE TAIWAN STRAIT INTO THE SOUTH CHINA
SEA (SCS). THE SURGE IS EVIDENCED BY LOW LEVEL STRATOCUMULUS LINES
STREAMING IN CONTRA-FLOW WITH THE UPPER LEVEL CIRRI STREAKS CAUGHT
IN THE SOUTHWESTERLY JET STREAM THAT IS PROVIDING POLEWARD
VENTILATION TO THE ASSOCIATED CONVECTION. THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON AN IRREGULAR DIMPLE FEATURE,
REMNANT OF AN EYE, ADJUSTED FOR TILT DUE TO SHEAR. THE INITIAL
INTENSITY IS BASED ON THE CLOSELY-VALUED AGENCY AND AUTOMATED
DVORAK ESTIMATES AND REFLECTS THE WEAKENING TREND.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

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 SATCON: 65 KTS AT 010508Z
   CIMSS ADT: 57 KTS AT 010540Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TYPHOON NALGAE WILL CONTINUE ON ITS CURRENT
TRACK UNDER THE STEERING INFLUENCE OF THE STR TO THE EAST. AFTER
TAU 36, AN EXTENSION OF THE SECONDARY STR TO THE WEST-NORTHWEST
WILL ASSUME STEERING AND DRIVE THE SYSTEM WESTWARD INTO
SOUTHEASTERN CHINA JUST WEST OF HONG KONG MOMENTARILY BEFORE
EXITING BACK INTO THE SCS. THE UNFAVORABLE ENVIRONMENT, MAINLY DUE
TO THE COLD SURGE AND INCREASING VWS, WILL CONTINUE TO ERODE TY 26W
DOWN TO 40KTS 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 200NM BY TAU 72, LENDING AN OVERALL
MEDIUM CONFIDENCE TO THE JTWC TRACK FORECAST. 

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