WDPN31 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (FOUR) WARNING 
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.7N 146.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 261 NM EAST-SOUTHEAST OF CHICHI JIMA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH
TROPICAL DEPRESSION (TD) 04W. THE INITIAL POSITION IS THEREFORE
PLACED WITH HIGH CONFIDENCE. RECENT FLARE UP OF CENTRAL CONVECTION
WAS QUICKLY SHEARED OFF TO THE NORTH BY A 15-20 KTS PREDOMINANTLY
SOUTHERLY VERTICAL WIND SHEAR (VWS). ADDITIONAL ENVIRONMENTAL
ANALYSIS REVEALS MARGINALLY FAVORABLE ENVIRONMENT, CHARACTERIZED BY
WARM (28-29 C) SEA SURFACE TEMPERATURES (SST), DEEP MOISTURE ACROSS
THE ATMOSPHERIC COLUMN, STRONG POLEWARD OUTFLOW ALOFT, OFFSET BY
THE IMPACTS OF THE TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL
LOCATED TO THE SOUTHWEST OF THE LLCC, AS WELL AS DRY AIR ENTERING
THE CORE OF THE VORTEX. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON COMBINATION OF AGENCY FIXES AND
OBJECTIVE ESTIMATES LISTED BELOW.

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

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 32 KTS AT 020530Z
   CIMSS AIDT: 35 KTS AT 020530Z
   CIMSS D-PRINT: 32 KTS AT 020530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT, AS WELL AS TUTT CELL
ASSOCIATED SHEAR

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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: TD 04W IS FORECAST TO INITIALLY TRACK
NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A STR TO THE
NORTHEAST. AROUND TAU 48 THE RIDGE WILL BEGIN TO REORIENT,
RESULTING IN STRENGTHENING OF TWO RIDGING AREAS THAT ARE SOUTH AND
EAST OF THE SYSTEM. THIS WILL LEAD TO TD 04W TRACKING NORTH AND 
EVENTUALLY NORTHEAST THROUGHOUT TAU 96. AFTER THAT, FURTHER
STRENGTHENING OF THE RIDGE TO THE EAST WILL CAUSE THE SYSTEM TO BEGIN
TURNING NORTHWARD AGAIN. INTENSITY IS FORECAST TO STEADILY INCREASE
THROUGHOUT TAU 72, WHILE THE SYSTEM DISTANCES ITSELF FROM THE TUTT
CELL. PEAK INTENSITY IS EXPECTED TO REACH 60 KTS AROUND THAT TIME.
AFTERWARD HOWEVER, IMPACTS FROM CONTINUOUS DRY AIR ENTRAINMENT, AS
WELL AS COOLING SST WILL RESULT IN WEAKENING, AS THE SYSTEM TRACKS
POLEWARD. FINALLY, MODELS SUGGEST AN UPPER-LEVEL TROUGH INTERACTION
TOWARD THE END OF THE FORECAST PERIOD, RESULTING IN A DRASTIC
INCREASE IN VWS.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN FAIR
AGREEMENT THROUGH TAU 96 WITH ALL MODELS SUGGESTING AN S-SHAPED
TRACK PATTERN, AS WITNESSED BY A CROSS-TRACK SPREAD OF 110 NM AT
TAU 72. AFTER THAT, UNCERTAINTY INCREASES, AS MODELS DO NOT AGREE
ON THE DOMINANT STEERING PATTERN AND THEREFORE TIMELINE AND EXTENT
OF THE INTERACTION WITH THE UPPER-LEVEL TROUGH PASSING FROM THE
WEST. DETERMINISTIC GFS SUGGESTS A NORTHWESTWARD TURN BY TAU 120,
WHILE NAVGEM AND ECWMF ENSEMBLE ARE PLACING THE TRACK TURNING
NORTHEASTWARD. MAJORITY OF THE MODELS ARE LEANING TOWARD THE NORTH OR
NORTHEASTWARD TRACK AND JTWC FORECAST IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS. INTENSITY GUIDANCE IS IN FAIR AGREEMENT
THROUGHOUT THE FORECAST PERIOD, WITH NEARLY ALL CONSENSUS MEMBERS
AGREEING ON THE TIMELINE OF INTENSIFICATION AND WEAKENING. PEAK
INTENSITY SPREAD HOWEVER IS ASSESSED AT 30 KTS, WITH COAMPS-TC
GOING AS HIGH AS 75 KTS AND STATISTICAL-DYNAMICAL MODELS ON THE
LOWER END OF THE SPECTRUM, PREDICTING PEAK INTENSITY OF 45-50 KTS.
ONCE AGAIN, JTWC FORECAST IS PLACED CLOSE TO THE MULTI-MODEL AVERAGE.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
NNNN