WDPS31 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 30P (THIRTY) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.1S 155.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 717 NM NORTHEAST OF CAIRNS, AUSTRALIA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 30P WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) AND DEEP CONVECTION SLIGHTLY OFFSET TO THE WEST OF THE LLCC.
A PARTIAL 032308Z METOP-B ASCAT PASS REVEALED A SWATH OF 35 KNOT
WINDS CONFINED TO THE NORTHERN SEMICIRCLE OF THE SYSTEM. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
PARTIALLY EXPOSED LLCC IN ANIMATED MSI. THE INITIAL INTENSITY OF 35
KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED
ASCAT PASS AND AN EARLY DPRINT ESTIMATE OF 33 KTS AT 0401000Z.
ENVIRONMENTAL ANALYSIS INDICATES THAT 30P IS CURRENTLY IN A
FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE POLEWARD AND
EQUATORWARD OUTFLOW ALOFT, LOW (10-15 KTS) EASTERLY VERTICAL WIND
SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: 032308Z METOP-B ASCAT SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: A COMPETING STEERING ENVIRONMENT WITH A
SUBTROPICAL RIDGE (STR) CENTERED OVER CENTRAL AUSTRALIA AND A
NEAR-EQUATORIAL RIDGE (NER) POSITIONED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS D-PRINT: 33 KTS AT 040100Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 30P IS FORECAST TO REMAIN WITHIN A
COMPETING STEERING ENVIRONMENT THROUGHOUT THE ENTIRE 120-HOUR
FORECAST, CAUSING IT TO BE QUASI-STATIONARY WITHIN THE SOLOMON SEA.
THE RIDGING TO BOTH THE NORTH AND SOUTH OF THE SYSTEM IS EXPECTED
TO MAINTAIN CONTROL OVER THE SYSTEM THROUGHOUT THE FORECAST PERIOD,
CREATING VERY SLOW TRACK SPEEDS. THE ACTUAL TRACK DIRECTION OF 30P
WILL LIKELY BE HIGHLY ERRATIC DUE TO THE COMPETING STEERING. A
FAVORABLE ENVIRONMENT WITH WARM SEA SURFACE TEMPERATURES AND LOW
SHEAR WILL ALLOW FOR INTENSIFICATION THROUGH TAU 72 BEFORE THE
UPWELLING OF COOLER WATERS BEGINS TO TAKE A TOLL ON THE SYSTEM. AS
A RESULT, 30P IS FORECAST TO WEAKEN FROM TAU 72 THROUGH TAU 120 AS
IT REMAINS NEARLY STATIONARY WITHIN THE SOLOMON SEA. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN AGREEMENT ON
A VERY SLOW WESTWARD MOVEMENT THROUGH TAU 36. AFTER TAU 36, MODELS
BEGIN TO DIVERGE IN NEARLY ALL DIRECTIONS, CREATING A HIGH AMOUNT
OF UNCERTAINTY. IN LARGE, MODELS KEEP THE SYSTEM EAST OF PAPUA NEW
GUINEA THROUGHOUT THE ENTIRE FORECAST PERIOD, THOUGH AN EXACT
DIRECTION IS NEARLY IMPOSSIBLE TO PREDICT. INTENSITY GUIDANCE IS IN
BETTER AGREEMENT, WITH ALL MODELS SHOWING INTENSIFICATION THROUGH
TAU 72. HAFS-A AND HWRF ARE THE MOST AGGRESSIVE MODELS, SUGGESTING
A PEAK INTENSITY OF AROUND 110 KTS. THE JTWC INTENSITY FORECAST IS
PLACED QUITE A BIT LOWER, WITH A PEAK OF 80 KTS, DUE TO THE
EXPECTED UPWELLING EFFECTS ON THE SYSTEM. AFTER TAU 72, MODELS
AGREE ON WEAKENING THROUGH TAU 120. THE JTWC INTENSITY FORECAST IS
ASSESSED WITH OVERALL MEDIUM CONFIDENCE DUE TO UNCERTAINTY
REGARDING HOW MUCH OF AN EFFECT THE UPWELLING WILL HAVE ON THE
SYSTEM AND POTENTIAL FOR TRACK VARIATION. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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