Advisories

WDPN31 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 24W (TWENTYFOUR) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.9N 148.9E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 266 NM EAST-NORTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 
CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) CURRENTLY FULLY 
OBSCURED BY PERSISTENT CONVECTION TO THE SOUTHWEST. WHILE THE LLCC 
REMAINS ELONGATED ALONG THE NORTHEAST-SOUTHWEST AXIS, A RECENT 
151025Z METOP-B ASCAT PASS REVEALED TIGHTENING CURVATURE TUCKING 
UNDER DEVELOPING DEEP CONVECTION. A BROAD AREA OF DRY AIR TO THE 
NORTH AND NORTHWEST IS SLOWING DOWN DEVELOPMENT, WHILE OTHER 
ENVIRONMENTAL PARAMETERS ARE FAVORABLE FOR INTENSIFICATION - SEA 
SURFACE TEMPERATURES (SST) ARE WARM (29-30 C) AND POLEWARD UPPER-
LEVEL OUTFLOW IS STRONG, DRIVEN BY AN UPPER-LEVEL LOW TO THE 
NORTHEAST. ADDITIONALLY, VERTICAL WIND SHEAR (VWS) IS LOW (10-15 KTS) 
OVER THE LLCC. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE 
BASED ON THE AFOREMENTIONED ASCAT PASS. THE INITIAL INTENSITY OF 25 
KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE SAME PASS SHOWING A 
BROAD AREA OF 20-25 KTS WIND BARBS, AS WELL AS LIMITED AGENCY AND 
OBJECTIVE ESTIMATES LISTED BELOW.

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

CURRENT STEERING MECHANISM: SOUTHEASTERN EXTENSION OF A RIDGE
CENTERED TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T1.5 - 25 KTS
   CIMSS D-PRINT: 21 KTS AT 151200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 24W IS FORECAST TO SLOWLY TRACK NORTHWARD, 
DRIVEN PRIMARILY BY WEAK INFLUENCE FROM THE NORTH-SOUTH ORIENTED 
RIDGING TO THE EAST OF THE SYSTEM. WITHIN THE NEXT 24-36 HOURS, THIS 
EXTENSION WILL RECEDE, WHILE THE SUBTROPICAL RIDGE (STR) CENTERED TO 
THE NORTH-NORTHEAST ASSUMES PRIMARY STEERING. AS A RESULT, TD 24W 
WILL BEGIN TURNING NORTHWESTWARD WHILE SLOWLY INTENSIFYING. A PEAK 
INTENSITY OF 70-75 KTS IS EXPECTED TO BE ATTAINED BETWEEN TAUS 96 AND 
120. AROUND THE SAME TIME, THE SYSTEM WILL TURN NORTHWARD AND BEGIN 
ITS RECURVATURE AROUND THE AXIS OF THE STR. INTENSIFICATION IS 
EXPECTED TO BE GRADUAL, AS A RESULT OF GENERALLY FAVORABLE 
ENVIRONMENTAL PARAMETERS. THE MAIN HINDRANCES TO SIGNIFICANT 
DEVELOPMENT ARE THE POTENTIAL FOR CONTINUOUS DRY-AIR ENTRAINMENT AND 
THE INITIAL LACK OF WIND FIELD SYMMETRY. A STRONG POLEWARD OUTFLOW 
CHANNEL IS EXPECTED TO REMAIN IN PLACE UNTIL AT LEAST TAU 48. AFTER 
THAT, THE SYSTEM WILL BEGIN TO DISTANCE ITSELF FROM THE FAVORABLE 
EXHAUST MECHANISM. AROUND TAU 96, HOWEVER, ANOTHER POLEWARD CHANNEL 
WILL OPEN AS THE SYSTEM APPROACHES THE BAROCLINIC ZONE AND THE 
ASSOCIATED JET STREAM.

MODEL DISCUSSION: NUMERICAL WEATHER PREDICTION GUIDANCE IS IN FAIRLY 
GOOD AGREEMENT WITH REGARD TO THE TRACK ACROSS THE DETERMINISTIC AND 
ENSEMBLE GUIDANCE. ALL AVAILABLE MODELS AGREE ON THE GENERAL S-SHAPED 
TRACK. HOWEVER, THE TIMELINE OF THE STR TRANSITIONS DIFFERS BETWEEN 
THE PREDICTION SUITES. AS A RESULT, THE CROSS-TRACK SPREAD AROUND TAU 
96 IS CURRENTLY ESTIMATED AT 280 NM, AND THE OFFICIAL JTWC PREDICTION 
IS ASSESSED WITH LOW LONG-TERM CONFIDENCE AND PLACED TO THE EAST OF 
THE MULTI-MODEL CONSENSUS. NAVGEM OFFERS THE WESTERNMOST PREDICTION, 
WHILE ENSEMBLE AND EXPERIMENTAL AI GUIDANCE ARE FORECASTING TRACK 
PLACEMENT FARTHER EAST AND A SHARPER RECURVATURE. SIMILARLY, 
INTENSITY PREDICTION CONFIDENCE DECREASES WITH TIME AS WITNESSED BY A 
45-80 KTS PEAK INTENSITY SPREAD. CONCURRENTLY, ALL CONSENSUS MEMBERS 
CONSISTENTLY ESTIMATE THE MAXIMUM WIND SPEEDS TO BE ATTAINED BETWEEN 
TAUS 96 AND 120.

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