WDPN31 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (FIVE) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 7.3N 146.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 379 NM SOUTH-SOUTHEAST OF HAGATNA, GUAM
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP
CONVECTION CONFINED TO THE WESTERN PERIPHERY OF A LOW-LEVEL
CIRCULATION THAT IS CURRENTLY NEARLY FULLY EXPOSED DUE TO
PERSISTENT WESTERLY VERTICAL WIND SHEAR AND INTRUSION OF RELATIVELY
DRIER AIR FROM THE SURROUNDING ENVIRONMENT. ASCAT SCATTEROMETER
DATA FROM 052344Z (METOP-B) AND 060015Z (METOP-C) SHOW ASSOCIATED
NEAR-SURFACE WIND SPEEDS OF 30 TO 35 KNOTS CONFINED TO THE
NORTHEASTERN QUADRANT OF THE CIRCULATION, WITH LOWER WIND SPEEDS
NEAR AND TO THE SOUTH OF THE CIRCULATION CENTER. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE WITHIN THE AREA OF
TIGHTEST TURNING EVIDENT IN THE EASTERN PORTION OF THE SOMEWHAT
ELONGATED LOW-LEVEL CIRCULATION DEPICTED IN SCATTEROMETER DATA AND
ANIMATED MULTISPECTRAL SATELLITE IMAGERY. THE INITIAL INTENSITY OF
35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE SCATTEROMETER
DATA SHOWING A SOLID AREA OF 30- TO 35-KNOT WINDS NORTHEAST OF THE
CIRCULATION CENTER.

INITIAL WIND RADII BASIS: 052344Z METOP-B ASCAT SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 31 KTS AT 052050Z
   CIMSS AIDT: 31 KTS AT 052050Z
   CIMSS D-MINT: 30 KTS AT 052112Z
   CIMSS D-PRINT: 25 KTS AT 052200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: INTRUSION OF RELATIVELY DRIER AIR FROM THE
SURROUNDING ENVIRONMENT

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE SYSTEM CENTER HAS BEEN RELOCATED
APPROXIMATELY 60 NM TO THE SOUTHWEST OF THE PREVIOUS POSITION
ASSESSMENT AND ANTICIPATED SIX HOUR FORECAST POSITION. AS A RESULT,
THE CURRENT FORECAST TRACK LIES TO THE SOUTH OF THE PREVIOUS
FORECAST TRACK, ALTHOUGH THE DISTANCE CLOSES A BIT BY TAU 120.  THE
INTENSITY FORECAST IS CONSISTENT WITH THE PREVIOUS WARNING.

FORECAST DISCUSSION: TD 05W IS EXPECTED TO TRACK GENERALLY WESTWARD
OVER THE NEXT 36 HOURS UNDER THE CONTINUOUS STEERING INFLUENCE OF
THE STR TO THE NORTHEAST. THEREAFTER, A SHORTWAVE TROUGH PASSING TO
THE NORTH OF THE SYSTEM WILL WEAKEN AND MODIFY THE ORIENTATION OF
THE STEERING RIDGE SLIGHTLY, DEFLECTING 05W TOWARD A
WEST-NORTHWESTWARD TRACK. THE SYSTEM IS EXPECTED TO STRUGGLE EARLY
IN THE FORECAST PERIOD DUE SUSTAINED, BUT ONLY MODERATE, WESTERLY
VERTICAL WIND SHEAR, ENTRAINMENT OF DRIER AIR FROM THE SURROUNDING
ENVIRONMENT, AND A DISORGANIZED LOW-LEVEL CIRCULATION.
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO TEMPORARILY IMPROVE BY TAU
24 AS THE CIRCULATION BECOMES MORE ORGANIZED AND POLEWARD OUTFLOW
ALOFT INCREASES AHEAD OF A SHORTWAVE TROUGH PASSING TO THE NORTH.
INCREASING VERTICAL WIND SHEAR AND CONVERGENT FLOW ALOFT WILL 
CONTRIBUTE TO SLOW WEAKENING AFTER TAU 72. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN AGREEMENT
REGARDING THE OVERALL TRACK SCENARIO, WITH MOST AVAILABLE CONSENSUS
AND EXPERIMENTAL AI MODELS FAIRLY EVENLY SPREAD IN AN ENVELOPE
AROUND THE CURRENT FORECAST TRACK. FORWARD TRACK SPEEDS ARE VERY
EVEN ACROSS MODEL SOLUTIONS, SUGGESTING THAT UNCERTAINTY LIES
MAINLY IN THE CROSS-TRACK DIRECTION, CORRESPONDING TO SUBTLE
DIFFERENCES IN THE ORIENTATION OF THE STEERING RIDGE BUT NOT ITS
MAGNITUDE. INTENSITY GUIDANCE IS ALSO IN GOOD GENERAL AGREEMENT
REGARDING SLOW INTENSIFICATION THROUGH THE MIDDLE OF THE FORECAST
PERIOD FOLLOWED BY WEAKENING. A FEW RAPID INTENSIFICATION (RI) AIDS
ARE AVAILABLE IN THE LATEST GUIDANCE PACKAGE, INDICATIVE OF
ELEVATED RI PROBABILITIES THAT ARE INCONSISTENT WITH CURRENTLY
ASSESSED MARGINAL ENVIRONMENTAL CONDITIONS.

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