WDPN31 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (PENHA) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 8.0N 129.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 237 NM NORTHWEST OF SONSOROL
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 02W (PENHA) HAS SLOWLY CONSOLIDATED OVER THE
PAST SIX HOURS WITH DEEP CONVECTION STILL SHEARED TO THE NORTHWEST
ALTHOUGH VERTICAL ALIGNMENT HAS IMPROVED AS DEPICTED BY ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI). CLOUD TOP TEMPERATURES
CONTINUE TO COOL WHILE THE ENVIRONMENT IS MARGINALLY FAVORABLE WITH
WARM (28 C TO 29 C) SEA SURFACE TEMPERATURES (SST), MODERATE (15-20
KTS) VERTICAL WIND SHEAR, AND MODERATE POLEWARD OUTFLOW. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON ANIMATED
MSI IMAGERY OF THE PARTIALLY EXPOSED LLCC CONSISTENT WITH THE
POSITION DEPICTED BY THE 050041Z METOP-B ASCAT PASS. THE INITIAL
INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
OBJECTIVE AND SUBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE CENTERED SOUTHEAST OF
TAIWAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 37 KTS AT 041800Z
   CIMSS ADT: 32 KTS AT 050100Z
   CIMSS AIDT: 34 KTS AT 050100Z
   CIMSS D-MINT: 30 KTS AT 042007Z
   CIMSS D-PRINT: 32 KTS AT 050100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: THE SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST
OF TAIWAN WILL CONTINUE PUSHING TS PENHA NORTHWESTWARD. AS THE
CIRCULATION APPROACHES THE EASTERN COAST OF MINDANAO BETWEEN TAU 12
AND TAU 24, THE SYSTEM IS FORECAST TO INTENSIFY SLIGHTLY AND
CONTINUE TO IMPROVE IN VERTICAL STRUCTURE. VERTICAL WIND SHEAR HAS
DROPPED TO 15-20 KTS AND IS EXPECTED TO REMAIN WITHIN THAT RANGE OR
BELOW AS THE CENTER PASSES OVER MINDANAO AND BACK INTO THE SULU
SEA. A DECREASE IN UPPER LEVEL STEERING INFLUENCE WILL SLOW THE
NORTHWESTWARD PROGRESS OF TS PENHA AS THE SYSTEM TRACKS OVER THE
SULU SEA TOWARDS PALAWAN. A WEAK STEERING GRADIENT, WEAKENED
VERTICAL STRUCTURE FOLLOWING LANDFALL, COOLING SEA SURFACE
TEMPERATURES (27 C TO 28 C) AND SIGNIFICANTLY DRIER AIR FROM THE
WEST WILL IMPEDE FURTHER DEVELOPMENT. STEADY WEAKENING IS FORECAST
UNTIL THE CIRCULATION IS BROKEN DOWN BY NORTHERLY, LOW-LEVEL FLOW,
BECOMING FULLY ENGULFED IN THE COLD SURGE BOUNDARY OVER THE WESTERN
PHILIPPINES BY TAU 72.

MODEL DISCUSSION: CROSS TRACK GUIDANCE IS SPREAD UP TO 120 NM BY
TAU 36 WITH MODELS STRUGGLING TO RESOLVE THE WEAKENED STEERING
PATTERN AND EFFECTS OF LANDFALL OVER MINDANAO. NAVGEM IS DEPICTING
A TRACK THAT BRINGS THE CIRCULATION SOUTH OF ARACELI, PHILIPPINES
WHILE GALWEM PRESENTS A TRACK NORTH OF LINAPACAN ISLAND. THE JTWC
FORECAST TRACK IS PLACED JUST SOUTH OF THE MULTI MODEL CONSENSUS
ACCOUNTING FOR THE UNLIKELINESS OF THE SYSTEM TO OVERCOME STRONG
NORTHERLY FLOW. INTENSITY GUIDANCE IS SPREAD UP TO 10 KTS WITH THE
MODELS SHOWING STRONG AGREEMENT ON A WEAK INTENSITY BETWEEN 25-35
KTS AS TS PENHA TRACKS ACROSS THE SULU SEA. THE JTWC FORECAST
INTENSITY REFLECTS VALUES CLOSE TO THE MULTI MODEL CONSENSUS WITH
MEDIUM CONFIDENCE ACCOUNTING FOR SOME UNCERTAINTY IN THE TIMING OF
THE INFLUENCE OF THE COLD SURGE FLOW. 

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