Tropical Storm CEMPAKA Advisory 7月21日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 10W (CEMPAKA)
WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 22.8N 109.5E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 262 NM WEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: N/A
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY, RADAR
ANIMATION, AND SURFACE REPORTS CONFIRM THAT THE LOW LEVEL
CIRCULATION CENTER (LLCC) REMAINS INTACT. DEEP CONVECTION IS
PERSISTING OVER THE CORE AND ALONG THE COASTLINE TO THE SOUTH. THE
INTENSITY ASSESSMENT IS BASED ON SURFACE PRESSURE REPORTS. THE SYSTEM
EXISTS UNDER A FAVORABLE UPPER LEVEL ENVIRONMENT LOW VERTICAL WIND
SHEAR AND UNIMPEDED OUTFLOW.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: A WEAK LOW TO MID-LEVEL RIDGE OVER
EASTERN CHINA.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: NO CURRENT ESTIMATE
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 5-10 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: LOW
   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: THE FORECASTING ISSUE WITH TD 10W REMAINS HOW
MUCH OF THE CORE WILL BE LEFT WHEN AND IF IT MAKES IT TO THE COAST.
ONCE OUT TO SEA IN THE GULF OF TONKIN, THE SYSTEM WILL RE-GENERATE IN
THE VERY WARM 30-31C WATERS AND FAVORABLE UPPER LEVEL ENVIRONMENT,
BUT WILL AGAIN RUN INTO THE RUGGED TERRAIN OF HAINAN ISLAND. IF IT
MAKES IT ACROSS HAINAN ISLAND, IT WILL ENCOUNTER VISCIOUS WIND
SHEAR DUE TO THE NEAR GALE FORCE GRADIENT FLOW OVER THE SOUTH CHINA
SEA UNDERNEATH NORTHEASTERLY UPPER LEVEL WINDS ASSOCIATED WITH
OUTFLOW FROM TY 09W. THE SURVIVAL OF THE SYSTEM TURNS ON A NUMBER
OF NUANCES SUCH AS EXACTLY WHERE IT ENTERS THE GULF OF TONKIN AND
HOW MUCH TIME IT SPENDS OVER THE GULF OF TONKIN, AS WELL AS HOW MUCH
OF IT IS LEFT WHEN IT ENTERS THE SOUTH CHINA SEA. THERE IS INCREASING
CONVICTION THAT THE SYSTEM WILL NOT SURVIVE VERY FAR POLEWARD OF THE
20TH LATITUDE.
MODEL DISCUSSION: MODEL GUIDANCE HAS BEEN REMARKABLY CONSISTENT AND
ACCURATE IN PREDICTING THE CYCLONIC LOOP ON THE OVERLAND TRACK.
THERE IS CONSIDERABLE VARIABILITY IN ALONG-TRACK SPEED OF ADVANCE.
THE JTWC FORECAST STAYS CLOSE TO THE MULTI-MODEL CONSENSUS.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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