Tropical Storm EIGHT Advisory 7月7日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (EIGHT)
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 19.2N 108.0E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 160 NM SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A RAGGED
DEEP CONVECTIVE STRUCTURE BEGINNING TO LOCALIZE AROUND A LOW-LEVEL
CIRCULATION CENTER (LLCC) WITH DEEP CONVECTIVE BURSTS OVER MAINLY
THE WESTERN AND SOUTHERN SEMICIRCLES. A PARTIAL 071144Z SSMIS 91GHZ
MICROWAVE IMAGE INDICATES FRAGMENTED, FORMATIVE BANDING PRIMARILY
OVER THE WESTERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH
LOW CONFIDENCE BASED ON THE EIR LOOP AND THE PARTIAL MICROWAVE
IMAGE. THE INITIAL INTENSITY OF 25 KTS IS ASSESSED WITH LOW
CONFIDENCE BASED ON MULTIPLE AGENCY DVORAK ESTIMATES OF T1.0,
CONSISTENT WITH THE OVERALL STRUCTURE. THE ENVIRONMENTAL ANALYSIS
IS MARGINALLY FAVORABLE DUE TO THE STRONG UPPER-LEVEL EASTERLY
OUTFLOW, WHICH IS PREDOMINATELY OFFSET BY THE MODERATE TO HIGH
VERTICAL WIND SHEAR.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL
WIND RADII).
CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTHEAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T1.0 - 25 KTS
   RJTD: T1.0 - 25 KTS
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.
FORECAST DISCUSSION: TD 08W IS FORECAST TO TRACK AROUND THE
SOUTHWEST PERIPHERY OF THE DEEP-LAYERED STR TOWARD VIETNAM
THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE SYSTEM AT
CURRENT IS DISORGANIZED BUT WILL CONSOLIDATE AROUND THE LLCC AS
THE STRONG VWS WILL BEGIN TO DECREASE TO 10-15KTS WITHIN THE NEXT
12 HOURS. ONCE THE VWS DECREASES THE STRONG OUTFLOW WILL HELP THE
INTENSITY REACH A PEAK OF 30 KTS BEFORE MAKING LANDFALL SOUTH OF
HANOI, VIETNAM, JUST AFTER TAU 12. THEREAFTER, THE SYSTEM WILL
MAKE LANDFALL AND BEGIN DISSIPATION OVER THE RUGGED TERRAIN OVER
VIETNAM AND LAOS.
MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
ON THE FORECAST TO MAKE LANDFALL JUST SOUTH OF HANOI, VIETNAM,
WITH A VERY SMALL CROSS-TRACK SPREAD OF ONLY 46NM THROUGH TAU 24.
THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL
CONSENSUS, BUT SLIGHTLY EQUATORWARD TOWARD THE BULK OF THE MODEL
SOLUTIONS, WHICH ARE ON THE SOUTHERN EDGE OF THE AIDS ENVELOPE.
AFUM AND EEMN REMAIN THE TWO MOST SIGNIFICANT POLEWARD OUTLIERS
FROM CONSENSUS.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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