Tropical Storm CEMPAKA Advisory Wed Jul 21

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (CEMPAKA) WARNING
NR
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 21.9N 110.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 185 NM WEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 0 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM
CONTINUED TO TRACK DEEPER INLAND CHINA AS IT RAPIDLY DECAYED, AS
EVIDENCED BY COLLAPSING CONVECTIVE CLOUD TOPS. THE INITIAL POSITION
IS PLACED WITH MEDIUM CONFIDENCE BASED ON A BROAD LOW LEVEL
CIRCULATION FEATURE IN A CMA COMPOSITE RADAR LOOP AND TRIANGULATED
FROM NEARBY SURFACE WIND OBSERVATIONS. THE INITIAL INTENSITY OF 35
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON NEARBY SURFACE
OBSERVATIONS INCLUDING ONE FROM YANGCHUN CITY 15NM TO THE NE
(SE15G20KTS, 1000MB) AND SUPPORTED BY A DVORAK ESTIMATE FROM RCTP.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: NO CURRENT ESTIMATE
   RCTP: T2.5 - 35 KTS
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: WEAK RADIAL
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TS 10W WILL TRACK FURTHER INLAND AND GENERALLY
WESTWARD UNDER A LOW REFLECTION OF THE STR. AFTER TAU 36, AS
SECONDARY STR TO THE WEST WILL ASSUME STEERING AND DRIVE THE
CYCLONE SOUTHWARD INTO THE GULF OF TONKIN (GOT) AND INTO HAINAN BY
TAU 72. AFTERWARD, THE SYSTEM WILL DRIFT EAST-NORTHEASTWARD WITH AN
AMPLIFIED MONSOON FLOW IN THE SOUTH CHINA SEA. THE RUGGED TERRAIN
AND INCREASED VERTICAL WIND SHEAR WILL CONTINUE TO ERODE THE SYSTEM
DOWN TO 25KTS BY TAU 24. HOWEVER, AFTER IT EXITS BACK ONTO WATER IN
THE GOT, IT WILL REGAIN TS INTENSITY MOMENTARILY UNTIL IT BECOMES
EXPOSED TO HIGH VWS IN THE SCS ASSOCIATED WITH THE SOUTHWEST
MONSOON. THERE IS A DISTINCT POSSIBILITY THAT TS CEMPAKA WILL
DISSIPATE OVER LAND IN THE NEXT 36HRS.
MODEL DISCUSSION: NUMERICAL MODELS HAVE BECOME MORE SPREAD OUT WITH
UKMET, ECMF, AND JGSM KEEPING THE VORTEX OVER LAND, AND THE
REMAINDER MAINTAINING AN ANTI-CLOCKWISE LOOPING MOTION. IN VIEW OF
THESE, PLUS THE POSSIBILITY OF EARLY DISSIPATION OVER LAND, THERE
IS LOW CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECAST.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
NNNN
NNNN