WDPN31 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 31W (KALMAEGI) WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.6N 123.2E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 272 NM SOUTH-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERTICALLY
TILTED CONVECTIVE STRUCTURE REVEALING LOW-LEVEL BANDING ALONG THE
EASTERN AND NORTHEASTERN PERIPHERY OF TYPHOON (TY) 31W. THE TILT IS
DUE TO THE STRONG NORTHEASTERLY UPPER-LEVEL FLOW, WHICH IS ALSO
ACTING AS A DIFFLUENT OUTFLOW CHANNEL. RADAR IMAGERY IS NO LONGER
AVAILABLE FOR THIS REGION, BUT LOCAL SURFACE OBSERVATIONS SUPPORT
THE POSITION OF THE LOW-LEVEL CIRCULATION CENTER. THE LOWEST
REPORTED MEAN SEA-LEVEL PRESSURE IS 987MB. THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON THE AFOREMENTIONED MSI AND
OBSERVATIONAL DATA. THE INITIAL INTENSITY OF 70 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON THE AIDT AND DPRINT INTENSITIES
BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS AIDT: 78 KTS AT 032300Z
   CIMSS D-PRINT: 52 KTS AT 032300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 31W WILL REMAIN UNDER THE STEERING
INFLUENCE OF THE WEAKENING SUBTROPICAL RIDGE TO THE NORTH. AFTER
THE RIDGE WEAKENS BETWEEN TAU 0-24, IT WILL BE REPLACED BY A
BUILDING RIDGE OVER THE GULF OF TONKIN THAT WILL ALLOW TY 31W TO
CONTINUE TO TRACK WEST-NORTHWESTWARD. TY 31W IS ANTICIPATED TO MAKE
LANDFALL BETWEEN TAU 48-72, AND REMAIN OVER LAND THROUGH THE END OF
THE FORECAST PERIOD. THE SYSTEM WILL STAGNATE IN A MARGINAL
ENVIRONMENT FOR THE NEXT 12 HOURS WHILE INTERACTING WITH THE
TOPOGRAPHY OF THE PHILIPPINE ISLANDS. AFTER TRACKING INTO THE SOUTH
CHINA SEA, THE SYSTEM WILL GRADUALLY INTENSIFY AS VERTICAL WIND
SHEAR WEAKENS FAVORABLY, ALLOWING THE SYSTEM TO REACH A PEAK
INTENSITY OF 100KTS AT TAU 48 WHILE OTHER ENVIRONMENTAL FACTORS
REMAIN FAVORABLE. THE FINAL WEAKENING PHASE TY 31W WILL BE
INITIATED BY TOPOGRAPHIC INTERACTION AFTER LANDFALL BETWEEN TAU
48-72, ULTIMATELY LEADING TO DISSIPATION.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD
AGREEMENT THAT TY 31W WILL REMAIN ON A WEST-NORTHWESTWARD TRACK
UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO THE NORTH.
EXCLUDING THE OUTLIER OF NAVGEM, THE CROSS-TRACK SPREAD IS
APPROXIMATELY 50NM AT LANDFALL CONTRIBUTING TO HIGH CONFIDENCE IN
THE LONG-TERM FORECAST. THE INTENSITY GUIDANCE HAS LOWERED SLIGHTLY
SINCE PREVIOUS RUNS, AND THE SPREAD IS FROM 80-100KTS. JTWC REMAINS
ON THE HIGHER END KEEPING CONSISTENCY WITH PREVIOUS FORECASTS, BUT
WATCHING FOR FURTHER TRENDS.

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