WDPN31 PGTW 181500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (MITAG) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.1N 116.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 196 NM SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
OBSCURED LOW-LEVEL CIRCULATION (LLCC) ACCOMPANIED BY BUILDING
CONVECTION OVER THE CENTER. THE MID-LEVEL ROTATION PREVIOUSLY
OFFSET TO THE EAST HAS BECOME MORE VERTICALLY ALIGNED WITH THE
LLCC. ENVIRONMENTAL ANALYSIS INDICATES TROPICAL STORM (TS) 23W IS
IN A MARGINALLY FAVORABLE ENVIRONMENT, CHARACTERIZED BY WARM SEA
SURFACE TEMPERATURES (29-30 C) AND LOW VERTICAL WIND SHEAR (5-10
KTS), OFFSET BY DRY AIR ENTRAINMENT FROM THE WEST. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE OBSCURED
LLCC. HOWEVER, LOW-LEVEL CLOUD WRAPPING IS VISIBLE THROUGH THE
MID-LEVEL TURNING, LENDING SOME CONFIDENCE TO THE JTWC INITIAL
POSITION. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE INTENSITY ESTIMATES
LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: AN ELONGATED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS ADT: 39 KTS AT 181140Z
   CIMSS AIDT: 38 KTS AT 181140Z
   CIMSS D-PRINT: 26 KTS AT 181140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE WEST

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 23W IS FORECAST TO CONTINUE ITS
NORTHWESTWARD TRACK AS IT IS STEERED BY THE ELONGATED SOUTHWESTERN
PERIPHERY OF THE STR TO THE NORTHEAST. LANDFALL IS EXPECTED TO
OCCUR BETWEEN TAUS 24-36 IN EASTERN HONG KONG. AFTER LANDFALL, 23W
IS EXPECTED TO CURVE WESTWARD AS THE SYSTEM APPROACHES THE SOUTHERN
EXTENT OF THE STR. 23W HAS BECOME VERTICALLY ALIGNED WITH THE MOIST
MID LEVELS, WHICH CONTRIBUTED TO ITS SLIGHT INTENSIFICATION TO ITS
PEAK AT 35 KTS. 23W WILL MAINTAIN 35 KTS UNTIL LANDFALL; HOWEVER,
THE WESTERN SEMICIRCLE IS EXPECTED TO REMAIN WEAKER THAN THE
EASTERN SEMICIRCLE. AFTER LANDFALL, 23W WILL RAPIDLY WEAKEN AS
TERRAIN INTERACTION ERODES THE SYSTEM. DISSIPATION IS FORECAST TO
OCCUR NO LATER THAN TAU 48 OVER SOUTHERN CHINA.

MODEL DISCUSSION: DETERMINISTIC MODELS ARE IN GOOD AGREEMENT ON A
NORTHWEST FORECAST TRACK, WITH A 110NM CROSS-TRACK SPREAD AT TAU 48
BETWEEN JGSM TO THE NORTH AND NAVGEM TO THE SOUTH. AS A RESULT, THE
JTWC TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE, HEDGED
SLIGHTLY TO THE NORTH OF THE BULK OF CONSENSUS MEMBERS. THERE IS
MINIMAL ALONG-TRACK SPREAD BETWEEN MEMBERS, LENDING ADDITIONAL
CONFIDENCE TO THE JTWC TRACK FORECAST. RELIABLE INTENSITY GUIDANCE
IS ALSO IN GOOD AGREEMENT THAT 23W WILL MAINTAIN 35 KTS UNTIL
LANDFALL, WITH DISSIPATION IMMINENTLY FOLLOWING. THEREFORE, THE
JTWC INTENSITY FORECAST IS PLACED WITH HIGH CONFIDENCE.

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