WDPN31 PGTW 032100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (TWENTYFOUR) WARNING 
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.0N 134.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 830 NM EAST-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM 24W WITH A CENTRAL DENSE OVERCAST (CDO) OBSCURING THE
LOW-LEVEL CIRCULATION CENTER (LLCC). CONVECTIVE BANDING IS
BEGINNING TO FORM ALONG THE WESTERN PERIPHERY OF THE CDO, TIGHTLY
WRAPPING INTO THE CENTER. THE COLD CLOUD TOPS CURRENTLY ARE AROUND
-80C NEAR THE MOST AGGRESSIVE CONVECTIVE BURSTS. ENVIRONMENTAL
ANALYSIS INDICATES THAT 24W IS IN A FAVORABLE ENVIRONMENT FOR
INTENSIFICATION CHARACTERIZED BY MODERATE POLEWARD OUTFLOW ALOFT,
LOW (10-15 KTS) VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE
TEMPERATURES. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE
BASED ON THE COMPLETELY OBSCURED LLCC IN THE ANIMATED EIR SATELLITE
IMAGERY. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 43 KTS AT 031730Z 
   CIMSS ADT: 39 KTS AT 031800Z
   CIMSS AIDT: 35 KTS AT 031800Z
   CIMSS DPRINT: 39 KTS AT 031800Z 

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: QUICKER INTENSIFICATION THROUGH TAU
24 THAN PREVIOUSLY FORECASTED.

FORECAST DISCUSSION: 24W IS FORECAST TO CONTINUE TRACKING
NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR THROUGH
TAU 48. NEAR TAU 48, AN UPPER-LEVEL TROUGH WILL BREAK DOWN THE
RIDGE AND CAUSE THE STEERING PATTERN TO WEAKEN. ADDITIONALLY, A
COLD-SURGE FLOWING THROUGH THE TAIWAN STRAIT AND INTO THE SOUTH
CHINA SEA WILL INHIBIT MUCH OF THE NORTHWARD TRACK CAUSING 24W TO
DRIFT SLOWLY WESTWARD THROUGH TAU 96. AFTER TAU 96, A RIDGE
EXTENDING FROM SOUTHERN CHINA WILL BUILD AND EXTEND OVER TO
SOUTHERN TAIWAN, CAUSING 24W TO CONTINUE ITS WESTWARD TRACK THROUGH
THE REMAINDER OF THE FORECAST PERIOD. REGARDING INTENSITY, 24W IS
FORECAST TO CONTINUE INTENSIFYING OVER THE NEXT 48 HOURS DUE TO THE
IMPROVING POLEWARD OUTFLOW THROUGH THAT TIME. AFTER TAU 48,
INTENSIFICATION IS EXPECTED TO HALT IN RESPONSE TO THE INTERACTION
WITH THE COLD SURGE BRINGING IN DRY AIR AND SEA SURFACE
TEMPERATURES SLIGHTLY DECREASING NORTH OF THE PHILIPPINES. A
GRADUAL WEAKENING TREND IS FORECAST FOR THE REMAINDER OF THE
FORECAST PERIOD AS 24W TRACKS JUST NORTH OF THE PHILLIPES THROUGH
THE LUZON STRAIT, POSSIBLY INTERACTING WITH NORTHERN LUZON.    

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
CONCERNING THE TRACK OF 24W THROUGH TAU 72. HOWEVER, AFTER TAU 72
GUIDANCE BEGINS TO DIVERGE DUE TO DIFFERING PLACEMENTS OF THE
EXTENSION OF THE RIDGE OVER SOUTHERN CHINA AROUND TAU 84-96. MODELS
RANGE FROM A TRACK SOUTHWESTWARD INTO LUZON AFTER TAU 72 (ECMWF)
AND WEST NORTHWESTWARD THROUGH THE LUZON STRAIT. THE JTWC TRACK
FORECAST IS PLACED CLOSE TO CONSENSUS, WHICH MORE CLOSELY
REPRESENTS THE LATTER SCENARIO. INTENSITY GUIDANCE IS BEGINING TO
BECOME LESS CONFIDENT DUE TO THE FACT THAT SOME RAPID
INTENSIFICATION (RI) AIDS ARE STARTING TO APPEAR. COAMPS-TC
ENSEMBLE GUIDANCE ALSO SUGGESTS A MODERATE CHANCE OF RI FROM TAU 12
TO TAU 60. THE JTWC INTENSITY FORECAST IS ALSO PLACED CLOSE TO
CONSENSUS, WITH RI FORECAST FROM TAU 12 TO 36 (50 TO 80 KTS). 
ADDITIONALLY, THE POSSIBILITY OF LAND INTERACTION WITH
NORTHERN LUZON WILL CAUSE MAJOR CHANGES IN THE INTENSITY FORECAST
IF IT BECOMES MORE LIKELY.  

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