WDPN32 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (CEMPAKA) WARNING
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 20.9N 113.1E
INITIAL INTENSITY: 45 KTS
GEOGRAPHIC REFERENCE: 104 NM SOUTHWEST OF HONG KONG
MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 02 KTS
SIGNIFICANT WAVE HEIGHT: 16 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE FIRST FEW FRAMES OF ANIMATED MULTISPECTRAL SATELLITE IMAGERY
DEPICTS A MASS OF PERSISTENT DEEP CONVECTION WITH OVERSHOOTING TOPS
OVER A DEVELOPING LOW LEVEL CIRCULATION CENTER (LLCC). ANIMATED
RADAR AND A 182352Z GPM PASS REVEALS A WELL DEFINED SPIRAL BANDING
STRUCTURE UNDER THE CLOUD TOPS. SINCE THE ANALYSIS TIME, CEMPAKA
HAS CONTINUED TO IMPROVE ITS CONVECTIVE STRUCTURE. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED
GPM DATA AND AGENCY FIXES. THE INITIAL INTENSITY OF 45 KNOTS IS
BASED ON THE HIGH END OF THE AGENCY FIX RANGE OF T2.0 TO T3.0,
ACCOUNTING FOR THE WELL DEFINED CENTER IN THE 37 GHZ DATA AND THE
SMALL SIZE OF THE SYSTEM.
INITIAL WIND RADII BASIS: MEASUREMENT OF MICROWAVE IMAGERY DATA AND
PERSISTENCE
CURRENT STEERING MECHANISM: WEAK EXTENSION OF THE STR TO THE NORTH
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 0-5 KTS
SST: 30-31 CELSIUS
OUTFLOW: STRONG EQUATORWARD
OTHER FACTORS: COMPACT SIZE MAY ALLOW FOR FASTER THAN
CLIMATOLOGICAL INTENSIFICATION RATE
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
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: TS CEMPAKA IS FORECAST TO CONTINUE A GENERALLY
WEST-NORTHWESTWARD TRACK OVER THE NEXT 24-36 HOURS UNDER THE
CURRENT STEERING INFLUENCE BEFORE THE TRACK SHIFTS TO WESTWARD
THROUGH 72. A COMPLEX FLOW PATTERN AFTER THAT TIME INTRODUCES
INCREASING UNCERTAINTY AS WESTERLY FLOW BUILDS TO THE SOUTH AND
MOST GUIDANCE CALLS FOR A SLOW TURN BACK TO THE SOUTHEAST. HOWEVER,
THE SPEED AND DEGREE OF THIS TURN IS HIGHLY VARIABLE AND GUIDANCE
HAS YET TO LOCK ON TO A CLEAR SOLUTION. THE FORECAST CALLS FOR A
RELATIVELY TIGHT TURN, BUT AN ALTERNATE SCENARIO MAY SEE A SLOWER
TURN WEST OF THE LEIZHOU PENINSULA. THE FORECAST INTENSITY IS
PLACED ABOVE THE CONSENSUS MEAN TO ACCOUNT FOR THE COMPACT SIZE OF
THE LLCC, AND NOTING THE RAPID CONSOLIDATION THAT HAS ALREADY
OCCURRED. THE POTENTIAL FOR RAPID INTENSIFICATION IS HIGH. THE PEAK
INTENSITY IS RAISED TO 60 KNOTS, HOWEVER, CEMPAKA MAY REACH TYPHOON
STATUS PRIOR TO LANDFALL GIVEN THE HIGH SST AND OTHER FAVORABLE
FACTORS.
MODEL DISCUSSION: MODEL GUIDANCE GENERALLY AGREES ON AN EVENTUAL
TURN BACK TO THE SOUTHEAST, BUT THERE IS SIGNIFICANT SPREAD IN THE
TIMING. INTENSITY IS TIGHTLY TIED TO THE DEGREE TO WHICH 10W TRACKS
OVER LAND, AND MAY SHIFT HIGHER IF THE TRACK IS MORE COASTAL.
GUIDANCE CALLS FOR STRENGTHENING AS 10W RE-EMERGES OVER WATER.
