WDPN31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (TWENTYFIVE) 
WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.2N 119.5E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 686 NM EAST-NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 9 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAGGED,
DECAYING LOW-LEVEL CIRCULATION DEVOID OF ANY SIGNIFICANT DEEP
CONVECTION. MSI ALSO SHOWS STRATOCUMULUS BANDS WRAPPING INTO A
WEAKLY-DEFINED CENTER WITH A STRATOCUMULUS FIELD WEST AND SOUTHWEST
OF THE SYSTEM. A 220600Z GFS SOUNDING THROUGH THE CENTER INDICATES
A STABLE LOWER LAYER WITH AN INVERSION NEAR 850MB, WHICH MAKES
SENSE CONSIDERING THE STABLE CLOUD TYPE ADVECTING INTO THE SYSTEM'S
CORE. ADDITIONALLY, A PARTIAL 220224Z ASCAT-C IMAGE SHOWS EXTENSIVE
NORTHERLY WINDS OF 10-20 KNOTS OVER THE WESTERN AND SOUTHWESTERN
QUADRANTS WITH NO WESTERLY OR NORTHWESTERLY FLOW WRAPPING INTO THE
SYSTEM. A SHIP REPORT 42NM SSW AT 220300Z DID INDICATE NORTH-
NORTHWESTERLY SURFACE WINDS AT 23 KNOTS, HOWEVER, THE SLP VALUE
OF 1011MB IS UNIMPRESSIVE AND ALSO HIGHLIGHTS THE WEAK NATURE
OF THE SYSTEM AND ENVIRONMENT. UPPER-LEVEL CONDITIONS ARE
MARGINALLY FAVORABLE WITH LOW VERTICAL WIND SHEAR AND WEAK OUTFLOW,
HOWEVER, THE LOW-LEVEL ENVIRONMENT IS MARGINAL WITH STABLE
CONDITIONS SO OVERALL CONDITIONS ARE ASSESSED AS MARGINAL.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: LOW-LEVEL SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTH AND NORTHWEST.  

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   KNES: T1.5 - 25 KTS
   CIMSS SATCON: 41 KTS AT 220456Z
   CIMSS ADT: 31 KTS AT 220540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: DUE TO THE SIGNIFICANT WEAKENING
EVIDENT IN SATELLITE IMAGERY, THE FORECAST DURATION HAS BEEN
SHORTENED TO 48 HOURS. 

FORECAST DISCUSSION: TD 25 IS FORECAST TO TRACK WESTWARD THROUGH
TAU 12 BUT IS EXPECTED TO TURN SOUTHWESTWARD AS IT TRACKS WITHIN
THE GENERAL LOW-LEVEL NORTHEASTERLY SURGE FLOW. TD 25W IS
STRUGGLING BUT IS EXPECTED TO MAINTAIN TD STRENGTH THROUGH TAU 24
WITH A STEADY WEAKENING TREND AND EVENTUAL DISSIPATION AFTER TAU
24.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
WITH A 70 TO 90NM SPREAD IN SOLUTIONS FROM TAU 36 TO TAU 48,
THEREFORE, THERE IS MEDIUM CONFIDENCE IN THE JTWC FORECAST TRACK.
RELIABLE INTENSITY GUIDANCE RANGES FROM A PEAK OF 25-30 KNOTS OVER
THE NEXT 24-36 HOURS THEN STEADY WEAKENING. EVEN THE 220000Z
COAMPS-TC ENSEMBLE SUPPORTS THE GRADUAL WEAKENING TREND WITH A HIGH
PROBABILITY OF TD TO DISTURBANCE STRENGTH WITHIN THE NEXT 48 TO 72
HOURS.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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