Tropical Storm CHAMPI Advisory 6月21日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING
NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 11.2N 147.4E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 210 NM SOUTHEAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 9 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTIVE
BURSTS OVER THE CENTER AND PERSISTENT CONVECTIVE BANDING DISPLACED
OVER THE EASTERN AND NORTHERN SEMICIRCLES. A 202341Z MHS 89GHZ
MICROWAVE IMAGE INDICATES FRAGMENTED, FORMATIVE BANDING PRIMARILY
OVER THE NORTHERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE MSI AND LOW-LEVEL CLOUD LINES OVER
THE SOUTHERN QUADRANT WRAPPING INTO THE EASTERN QUADRANT. THE
INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE PGTW DVORAK ESTIMATE OF T2.0, CONSISTENT WITH THE
OVERALL STRUCTURE. THE UPPER-LEVEL ENVIRONMENT IS MARGINALLY
FAVORABLE DUE TO THE WEAK POLEWARD OUTFLOW INTO A NARROW, WEAK
TUTT POSITIONED TO THE NORTH. THIS IS OFFSET SOMEWHAT BY WARM
SST VALUES AND LOW 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 NORTH.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THIS IS THE FIRST PROGNOSTIC REASONING
MESSAGE AND SETS THE FORECAST PHILOSOPHY.
FORECAST DISCUSSION: TD 06W IS FORECAST TO TRACK AROUND THE
SOUTHWEST PERIPHERY OF THE DEEP-LAYERED STR THEN POLEWARD THROUGH
THE REMAINDER OF THE FORECAST PERIOD. THE SYSTEM SHOULD SLOW
SLIGHTLY AS IT ROUNDS THE STR THEN ACCELERATE AS IT APPROACHES A
SHORTWAVE TROUGH EXPECTED TO DIG SOUTH OF HONSHU. DUE TO THE WEAK
OUTFLOW AND FORMATIVE LOW-LEVEL CONVECTIVE STRUCTURE, THE SYSTEM
WILL INTENSIFY SLOWLY AS IT APPROACHES GUAM WITH A SLIGHT INCREASE
IN INTENSITY TO 35 KNOTS BY TAU 24 THEN GRADUAL INTENSIFICATION TO
A PEAK OF 45 KNOTS BY TAU 72. AFTER TAU 72, THE SYSTEM WILL WEAKEN
DUE TO INCREASING NORTHERLY VERTICAL WIND SHEAR ASSOCIATED WITH THE
UPPER-LEVEL STR TO THE NORTHWEST AND A TUTT CELL FORECAST TO TRACK
SOUTHEAST OF HONSHU BY TAU 72.
MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE, IN GENERAL, SUPPORTS
THE FORECAST TRACK JUST SOUTH OF GUAM WITH A SPREAD OF 62NM AT TAU
24. THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL
CONSENSUS BUT SLIGHTLY POLEWARD TOWARD THE ECMF AND EEMN SOLUTIONS,
WHICH ARE ON THE NORTHERN EDGE OF THE AIDS ENVELOPE. THE PRIMARY
REASON FOR THIS ADJUSTMENT IS THAT THE ECMF AND EEMN INITIALIZED
THE SYSTEM CENTER BETTER THAN GFS, WHICH WAS A BIT FURTHER SOUTH.
AFTER TAU 24, THE BULK OF THE GUIDANCE REMAINS IN CLOSE AGREEMENT
WITH THE JTWC FORECAST TRACK WITH THE EXCEPTION OF THE UKMO ENSEMBLE
MEAN AND THE GFS TRACKERS, WHICH DIVERGE SIGNIFICANTLY ON THE WESTERN
AND EASTERN SIDES OF THE AIDS ENVELOPE.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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