WDPN31 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 29W (TWENTYNINE) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.8N 125.2E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 276 NM EAST-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
CONSOLIDATING SYSTEM WITH PERSISTENT DEEP CONVECTION OBSCURING THE
LOW-LEVEL CIRCULATION CENTER (LLCC). A 101827Z GMI 89GHZ MICROWAVE
IMAGE REVEALS SHALLOW BANDING WRAPPING INTO LOW-LEVEL CIRCULATION
POSITIONED ALONG THE SOUTHEASTERN EDGE OF A CURVED CONVECTIVE BAND
ON THE WESTERN PERIPHERY. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON AN EARLIER 101320Z ASCAT-C, WHICH SHOWS
AN ELONGATED BUT DEFINED CENTER WITH 20-25 KNOT WINDS OVER THE
NORTHWESTERN PERIPHERY. THE INITIAL INTENSITY OF 25 KTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON THE PGTW, RJTD DVORAK ESTIMATES AND
ASCAT DATA. ENVIRONMENTAL ANALYSIS OF 29W SHOWS THAT CONDITIONS ARE 
FAVORABLE FOR DEVELOPMENT WITH WARM (28-29C) SEA SURFACE TEMPERATURES 
(SSTS), LOW (5-10 KNOTS) VERTICAL WIND SHEAR (VWS), AND WEAK RADIAL 
OUTFLOW.

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

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE POSITIONED TO THE
EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 29W IS TRACKING NORTHEASTWARD ALONG THE
WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE
EAST, AND WILL CONTINUE TRACKING THROUGH TAU 24. AFTER TAU 24, THE
SYSTEM WILL PASS THE STR AXIS AND THEN BEGIN TO TRACK
EAST-NORTHEASTWARD THROUGH TAU 36. DURING THIS TIMEFRAME THE
ENVIRONMENTAL CONDITIONS ARE FORECAST TO REMAIN FAVORABLE,
CHARACTERIZED BY WARM (28-29C) SEA SURFACE TEMPERATURES (SSTS),
MODERATE RADIAL DIVERGENCE ALOFT AND LOW (5-10 KNOTS) VERTICAL WIND
SHEAR (VWS), WHICH WILL ALLOW TD 29W TO REACH A POTENTIAL MAXIMUM
INTENSITY OF 50 KNOTS BY TAU 36. HOWEVER, BY TAU 48, STRONG
NORTHEASTERLY FLOW ASSOCIATED WITH A HIGH PRESSURE SYSTEM TO THE
NORTHWEST WILL INCREASE VWS AND ADVECT A DRY STABLE AIR MASS
AROUND THE SYSTEM. AS A RESULT THE SYSTEM WILL QUICKLY BECOME
SIGNIFICANTLY INFLUENCED BY A MORE HOSTILE ENVIRONMENT AND BEGIN
DISSIPATING. BETWEEN TAU 48 AND TAU 72 TD 29W WILL SUCCUMB TO THE
UNFAVORABLE ENVIRONMENT FACTORS BEFORE DISSIPATING AS THE SYSTEM
MEANDERS SOUTHEASTWARD.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT THROUGH
TAU 36. PAST TAU 36 MODEL TRACK GUIDANCE BECOMES MORE UNCERTAIN
WITH A LARGER SPREAD. THE GFS REMAINS ON THE NORTHERN EDGE OF
GUIDANCE WHILE THE ECMWF IS ON THE SOUTHERN EDGE OF THE GUIDANCE
ENVELOPE. THUS, THE JTWC FORECAST FOLLOWS A BLEND OF BOTH SOLUTIONS
AND FOLLOWS CLOSE TO THE MULTI-MODEL CONSENSUS. INTENSITY GUIDANCE
IS MIXED, WITH THE HWRF AND COAMPS-TC MEMBERS SHOWING A FAIRLY
QUICK INTENSIFICATION TO AROUND TAU 36, WITH A PEAK INTENSITY BETWEEN 
45-50 KNOTS. WHILE GFS SHOWS A GRADUAL INTENSIFICATION BETWEEN 35-40
KNOTS. THEREFORE, THE JTWC FORECAST LIES CLOSE TO THE MULTI-MODEL
CONSENSUS THROUGH TAU 24, AND THEN CROSSES HIGHER THAN THE MEAN
THEREAFTER, FOLLOWING MOST CLOSELY TO THE HWRF AND COAMPS-TC
GUIDANCE.   


FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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