WDPN31 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (FOUR) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.0N 147.4E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 735 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION (TD) 04W WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) AND WEAKENED CENTRAL CONVECTION. THE LARGE BAND OF
FLARING CONVECTION ALONG THE EASTERN PERIPHERY PERSISTS. A 012315Z
GMI 89 GHZ MICROWAVE IMAGE REVEALS THE DEFINED LOW-LEVEL CLOUDS
WRAPPING INTO THE LLCC. THE SYSTEM CONTINUES TO FEEL THE EFFECTS OF
THE TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL CENTERED TO THE
SOUTHWEST, APPARENT BY THE CONVECTION STRUGGLING TO FORM OVER THE
CIRCULATION CENTER. ENVIRONMENTAL ANALYSIS INDICATES THAT 04W IS IN
A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD
OUTFLOW ALOFT, MODERATE (15-20 KTS) SOUTHERLY VERTICAL WIND SHEAR,
DRY AIR WITHIN THE SOUTHERN SEMICIRCLE, AND WARM (28-29 C) SEA
SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC IN THE ANIMATED MSI
AND SHORT EXTRAPOLATION FROM THE MENTIONED GMI MICROWAVE IMAGE. THE
INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED
ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED
BELOW.

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

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF AN ELONGATED
SUBTROPICAL RIDGE (STR) CENTERED 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 020010Z
   CIMSS AIDT: 34 KTS AT 020010Z
   CIMSS DPRINT: 31 KTS AT 020010Z
   CIMSS DMINT: 29 KTS AT 012313Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: PRESSURE FROM THE TUTT CELL AND DRY AIR
ENTRAINMENT

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 CONTINUE TRACKING
NORTH-NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE THROUGH TAU 48. NEAR TAU 48, RIDGING TO THE WEST WILL BUILD
AND PULL THE VORTEX TOWARD THE NORTHEAST THROUGH THE REMAINDER OF
THE FORECAST PERIOD. REGARDING INTENSITY, 04W IS FORECAST TO
MARGINALLY INTENSIFY OVER THE NEXT 24 HOURS AS THE TUTT CELL
CONTINUES TO AFFECT THE VORTEX, HINDERING DEVELOPMENT. AFTER TAU
24, THE SYSTEM WILL HAVE SUFFICIENTLY DISTANCED ITSELF FROM THE
TUTT CELL WHICH WILL ALLOW FOR FURTHER INTENSIFICATION AS SHEAR
DROPS TO AROUND 5-10 KTS. A PEAK INTENSITY OF 55 KTS IS FORECAST TO
OCCUR NEAR TAU 72-96. AFTER TAU 96, SEA SURFACE TEMPERATURES WILL
BEGIN TO COOL, HALTING ANY FURTHER INTENSIFICATION. BY TAU 120, SEA
TEMPERATURES ARE EXPECTED TO DROP TO AROUND 25 C, WHICH WILL
INITIATE A WEAKENING TREND. ADDITIONALLY, AN UPPER-LEVEL TROUGH
WILL PROPAGATE EASTWARD AND BEGIN INTERACTING WITH THE SYSTEM
AROUND TAU 120, CAUSING SHEAR TO DRAMATICALLY INCREASE IN THE
EXTENDED FORECAST. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 72 WITH A 120 NM CROSS-TRACK SPREAD AT TAU
72. AFTERWARD, MODELS SIGNIFICANTLY DIVERGE DUE TO DIFFERING
INTERACTIONS WITH THE UPPER-LEVEL TROUGH. GFS DETERMINISTIC HAS THE
SYSTEM TURN NORTHWESTWARD VICE NORTHEASTWARD AFTER TAU 96 AS THE
VORTEX GETS CAUGHT UNDERNEATH RIDGING TO THE NORTH. HOWEVER, THE 
MAJORITY OF ENSEMBLE MEMBERS SHOW THE NORTHEASTWARD TRACK.
THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL
CONSENSUS THROUGH TAU 96 AND THEN SLIGHTLY TO THE EAST THROUGH TAU
120. INTENSITY GUIDANCE IS IN MODERATE AGREEMENT WITH HAFS-A AND
GFS BEING THE LEAST AGGRESSIVE WHILE COAMPS-TC (GFS BASED) IS THE
MOST AGGRESSIVE MODEL WITH A PEAK INTENSITY OF 80 KTS AT TAU 84.
THE JTWC INTENSITY FORECAST IS PLACED IN LINE WITH THE CONSENSUS
THROUGHOUT THE FORECAST PERIOD WITH MEDIUM CONFIDENCE.

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