WDPN31 PGTW 231500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 26W (TWENTYSIX) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.9N 134.4E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 834 NM EAST-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION 26W WITH TWO DISTINCT CONVECTIVE BANDS WRAPPING AROUND
THE NORTHERN AND WESTERN PERIPHERIES OF THE CIRCULATION. 231127Z
AND 231217Z ASCAT PASSES SHOWED SWATHS OF 25 KNOT WINDS WITHIN THE
NORTHWESTERN AND SOUTHWESTERN QUADRANTS WITH WEAKER WINDS ALONG THE
EASTERN SIDE. ENVIRONMENTAL ANALYSIS INDICATES THAT 26W IS IN A
FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE POLEWARD AND
EQUATORWARD OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND
WARM (29-30 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION AND
INTENSITY ARE BOTH PLACED WITH MEDIUM CONFIDENCE BASED ON THE TWO
AFOREMENTIONED PARTIAL ASCAT PASSES. AGENCY DVORAK FIXES OF T1.0-1.5
FURTHER SUPPORT THE INITIAL INTENSITY ASSESSMENT.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A LARGE
SUBTROPICAL RIDGE CENTERED FAR TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS D-MINT: 20 KTS AT 231037Z
   CIMSS D-PRINT: 20 KTS AT 231200Z

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: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 26W IS FORECAST TO TRACK GENERALLY
NORTHWESTWARD THROUGHOUT THE ENTIRE FORECAST PERIOD. THE SYSTEM
WILL TRACK ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE, WHICH WILL PROPAGATE WESTWARD, FOLLOWING 26W. AN INITIAL
LANDFALL IS FORECAST TO OCCUR AROUND TAU 60, NEAR LEGAZPI. 26W WILL
THEN EMERGE WITHIN THE SOUTH CHINA SEA AND CONTINUE NORTHWESTWARD,
AND TRACK SOUTH OF HAINAN NEAR THE END OF THE FORECAST PERIOD.
REGARDING INTENSITY, 26W IS FORECAST TO STEADILY INTENSIFY OVER THE
NEXT 48 HOURS TO AROUND 55 KTS BEFORE MAKING THE FIRST LANDFALL.
INTERACTION WITH CENTRAL PHILIPPINES WILL BRIEFLY DETERIORATE THE
SYSTEM. THEN AFTER TAU 72, CONDITIONS IN THE SOUTH CHINA SEA WILL
BE CONDUCIVE WITH LOW SHEAR, ALLOWING FOR 26W TO REINTENSIFY.
CONDITIONS WITHIN THE SOUTHERN GULF OF TONKIN ARE EXPECTED TO BE
HIGHLY FAVORABLE WITH VERY WARM SEA SURFACE TEMPERATURES, WHICH
WILL ALLOW 26W TO INTENSIFY TO TYPHOON INTENSITY NEAR THE END OF
THE FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 60 WITH A 75 NM CROSS TRACK SPREAD AT THAT
TIME. AFTER LANDFALL IN THE PHILIPPINES ALONG-TRACK SPREAD BETWEEN
MODELS RAPIDLY INCREASES. AT TAU 96 THERE IS AROUND 440 NM OF
ALONG-TRACK SPREAD WITH JGSM BEING THE SLOWEST MEMBER, WHILE GFS IS
THE FASTEST. THE JTWC TRACK FORECAST IS MORE IN LINE WITH THE GFS
AND AI MODEL DEPICTION WITH HIGH CONFIDENCE THROUGH TAU 72 AND
MEDIUM CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS IN GOOD
AGREEMENT ON INTENSIFICATION THROUGH TAU 48, BRIEF WEAKENING
THROUGH TAU 72, AND REINTENSIFICATION AFTERWARD. THE JTWC INTENSITY
FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH OVERALL
MEDIUM CONFIDENCE.

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