WDPS31 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03P (THREE) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.4S 156.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 183 NM WEST OF HONIARA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A 042005 SSMIS
MICROWAVE PASS DEPICT AN ORGANIZING TROPICAL CYCLONE JUST SOUTHWEST
OF THE SOLOMON ISLANDS WITH CURVED DEEP CONVECTIVE BANDING
EXPANDING AROUND THE WESTERN SEMICIRCLE DURING THE PAST SIX HOURS,
WITH MORE FRAGMENTED BANDING OVER AND NORTHEAST OF THE SOLOMON
ISLANDS. THE LOW-LEVEL CIRCULATION CENTER (LLCC) IS SOMEWHAT
ELONGATED NORTHWEST TO SOUTHEAST AND PARTIALLY OBSCURED BY THE DEEP
CONVECTION. ROBUST UPPER-LEVEL OUTFLOW IS OBSERVED, PARTICULARLY
POLEWARD INTO A STRONG JET STREAK TO THE SOUTH NEAR NEW CALEDONIA.
THE INITIAL INTENSITY IS SET AT 35 KT BASED ON AGENCY DVORAK
ESTIMATES OF T2.5.

INITIAL WIND RADII BASIS: OTHER 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   ABRF: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: CYCLONE 03P IS CURRENTLY TRACKING AROUND THE
NORTHWESTERN PERIPHERY OF A DEEP-LAYER RIDGE EAST OF VANUATU. A
MID-LATITUDE TROUGH SOUTH OF NEW CALEDONIA IS CURRENTLY ERODING THE
WESTERN SIDE OF THIS RIDGE, WHICH IS FORECAST TO CAUSE 03P TO TURN
SOUTH OR SOUTH-SOUTHWESTWARD INTO THE CORAL SEA IN THE SHORT TERM.
THIS TROUGH WILL QUICKLY EXIT EASTWARD, ALLOWING A NEW RIDGE TO
BUILD IN OVER SOUTHERN QUEENSLAND IN 24-48 HOURS. NUMERICAL MODEL
GUIDANCE EXPECTS CYCLONE 03P TO TRACK TOWARDS THE NORTHERN
PERIPHERY OF THIS RIDGE WITH A GENERALLY SOUTHWESTWARD MOTION
DURING THE 24-120 HOUR PERIOD. ENVIRONMENTAL CONDITIONS ARE
FAVORABLE FOR INTENSIFICATION THROUGH 72 HOURS, PERHAPS AT A RAPID
RATE AT TIMES. SEA SURFACE TEMPERATURES ARE WARM AT 28-29 DEGREES
CELSIUS, VERTICAL SHEAR IS LOW, AND THE UPPER-LEVEL JET STREAK TO
THE SOUTH OF THE STORM IS BOOSTING UPPER-LEVEL DIVERGENCE AND THUS
CONVECTIVE ORGANIZATION IN THE SHORT TERM. UNTIL AN INNER CORE
CONVECTIVE STRUCTURE HAS FORMED, THE PACE OF INTENSIFICATION IS
SUBJECT TO SOME UNCERTAINTY. THE JTWC FORECAST BRINGS 03P TO A PEAK
INTENSITY OF 100 KT IN 72 HOURS, CLOSE TO THE MAXIMUM INTENSITY
PREDICTED BY HAFS-A AND HWRF. THEREAFTER, THE POLEWARD MOTION IS
FORECAST TO BRING 03P INTO A ZONE OF ELEVATED BACKGROUND WESTERLY
SHEAR EXCEEDING 30 KT IN MAGNITUDE. COUPLED WITH A PREEXISTING DRY
AIR MASS OVER THE CORAL SEA, THIS SHEAR WOULD DISRUPT THE CYCLONE'S
INNER CORE, LEADING TO WEAKENING. BEYOND 96 HOURS, SEA SURFACE
TEMPERATURE WILL ALSO BEGIN COOLING BELOW 28 DEGREES CELSIUS,
CONTRIBUTING TO A LESS FAVORABLE ENVIRONMENT. NUMERICAL MODELS ARE
IN GOOD AGREEMENT ON THIS ENVIRONMENTAL EVOLUTION AND SUBSEQUENT
WEAKENING OF 03P DURING THE 72-120 HOUR PERIOD. THE JTWC FORECAST
FOLLOWS SUIT, SHOWING WEAKENING TO 75 KT BY 120 HOURS AS THE
CYCLONE DRAWS WITHIN 250 NM OF QUEENSLAND.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT ON TRACK
THROUGH 72 HOURS, BUT SPREAD INCREASES DURING THE 72-120 HOUR
PERIOD DUE TO DISAGREEMENT IN HOW QUICKLY 03P WILL MOVE POLEWARD
AND HOW LONG THE DEEP-LAYER RIDGE OVER QUEENSLAND WILL REMAIN
ENTRENCHED. THE JTWC FORECAST IS CLOSE TO THE MULTI-MODEL
CONSENSUS. THE JTWC INTENSITY FORECAST IS SIMILAR TO A BLEND OF THE
HAFS, HWRF, GFS, AND SHIPS MODELS WHICH ARE IN GOOD AGREEMENT
THROUGH 72 HOURS BUT EXHIBIT INCREASING SPREAD THROUGH 120 HOURS,
IN PART DUE TO THE AFOREMENTIONED TRACK UNCERTAINTY.

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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