Advisories

WDPN31 PGTW 160300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 24W (TWENTYFOUR) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.0N 148.7E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 168 NM EAST OF SAIPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION 24W WITH A MUCH MORE DEFINED AND SYMMETRIC LOW-LEVEL
CIRCULATION CENTER (LLCC) THAT IS NOW PARTIALLY EXPOSED. CONVECTIVE
ACTIVITY REMAINS MOSTLY CONFINED TO THE SOUTHWESTERN PERIPHERY. A
TIMELY 152319Z METOP-C ASCAT BULLSEYE PASS REVEALED A DEFINED
CENTER WITH WINDS OF 25-30 KTS PRIMARILY LOCATED WITHIN THE
SOUTHEASTERN QUADRANT OF THE SYSTEM. THE INITIAL POSITION AND
INTENSITY ARE BOTH PLACED WITH HIGH CONFIDENCE BASED ON THE ASCAT
DATA. ENVIRONMENTAL ANALYSIS INDICATES THAT 24W REMAINS PLACED
WITHIN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE
OUTFLOW ALOFT, LOW (5-10 KTS) NORTHERLY VERTICAL WIND SHEAR, DRY
AIR ENTRAINMENT FROM THE NORTH, AND WARM (29-30 C) SEA SURFACE
TEMPERATURES.

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

CURRENT STEERING MECHANISM: THE NORTHWARD EXTENSION OF AN ELONGATED
NEAR EQUATORIAL RIDGE (NER) POSITIONED TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS SATCON: 33 KTS AT 152027Z
   CIMSS ADT: 34 KTS AT 160000Z
   CIMSS AIDT: 32 KTS AT 160000Z
   CIMSS D-MINT: 28 KTS AT 152026Z
   CIMSS D-PRINT: 38 KTS AT 160000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE NORTH

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 24W HAS NOW STARTED ON ITS NORTHWARD TRACK, 
PRIMARILY DRIVEN BY THE ELONGATED NER POSITIONED TO THE SOUTHEAST. 
THE SUBTROPICAL RIDGE (STR) THAT IS CURRENTLY TO THE NORTHEAST OF THE 
SYSTEM IS EXPECTED TO REORIENT EASTWARD AND WEAKEN AS AN UPPER-LEVEL 
TROUGH MOVES IN FROM THE WEST. AS A RESULT, A GENERALLY NORTHWARD 
TRACK IS EXPECTED TO PERSIST THROUGH TAU 24. THE SYSTEM WILL THEN 
BEGIN TO INTERACT WITH THE SOUTHWESTERN PERIPHERY OF THE STR NEAR TAU 
24, WHICH WILL DIRECT THE VORTEX NORTHWESTWARD THROUGH TAU 72. AFTER 
TAU 72, 24W IS FORECAST TO ROUND THE WESTERN EXTENT OF THE RIDGE WITH 
A NORTHWARD TURN THROUGH TAU 96. FOLLOWING TAU 96, THE SYSTEM WILL 
BEGIN TO ACCELERATE NORTHEASTWARD AS IT CONTINUES TO ROUND THE RIDGE 
AXIS, TRACKING CLOSE TO THE EASTERN COAST OF HONSHU. 24W IS CURRENTLY 
FORECAST TO STAY EAST OF HONSHU, HOWEVER, THERE IS STILL SOME 
UNCERTAINTY IN THE TIMING AND TRAJECTORY OF THE NORTHEASTWARD TURN 
AFTER TAU 96. IF 24W STAYS ON A NORTHWESTWARD TRACK FOR LONGER THAN 
ANTICIPATED, IT COULD GET CLOSER TO THE COAST AND IMPACT AREAS NEAR 
THE KANTO PLAIN REGION. IN TERMS OF INTENSITY, 24W IS FORECAST TO 
STEADILY INTENSIFY THROUGH TAU 60 AS THE VORTEX CONSOLIDATES AND 
POLEWARD OUTFLOW GREATLY IMPROVES. AFTER TAU 60, THE SYSTEM WILL 
BATTLE WITH DRY AIR ENTRAINMENT FROM THE WEST, CAUSING THE SYSTEM TO 
HALT THE INTENSIFICATION TREND. IF 24W IS ABLE TO CONSOLIDATE AND FORM 
A MORE COMPACT CORE, THEN FURTHER INTENSIFICATION COULD BE POSSIBLE. 
AFTER TAU 96, SOUTHERLY SHEAR IS EXPECTED TO INCREASE WHILE THE SYSTEM 
SIMULTANEOUSLY TAPS INTO A ROBUST POLEWARD OUTFLOW CHANNEL PROVIDED BY 
A STRONG JET STREAK OVER NORTHERN JAPAN. NOTABLY, THE HAFS-A MODEL 
SHOWS THE SYSTEM STRUGGLING TO CONSOLIDATE AND IS THEREFORE NEVER ABLE 
TO FULLY STAVE OFF THE DRY AIR. AS IT STANDS, 24W IS FORECAST TO 
MAINTAIN LOW TYPHOON-STRENGTH THROUGH THE REMAINDER OF THE FORECAST 
PERIOD AS IT PASSES BY JUST EAST OF HONSHU.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT 
THROUGH TAU 72 WITH THE VARIOUS AI-BASED MODELS MAKING UP THE EASTERN 
SIDE OF THE ENVELOPE WHILE THE PHYSICS-BASED MODELS ARE FURTHER WEST. 
SPECIFICALLY, THE EXPERIMENTAL GOOGLE DEEPMIND AND EC-AIFS ARE THE 
FURTHEST EAST, WHILE JGSM AND NAVGEM ARE THE FURTHEST WEST. AFTER TAU 
72, THE PRIMARY DIFFERENCE BETWEEN MODELS IS THE TRACK SPEED AROUND 
THE RIDGE. GOOGLE DEEPMIND IS THE FASTEST, SHOWING THE VORTEX 
NORTHEAST OF TOKYO AT TAU 120 WHILE THE JGSM BECOMES A SIGNIFICANT 
OUTLIER, SHOWING THE VORTEX SOUTHEAST OF YAKUSHIMA AT THE SAME TIME. 
THE JTWC TRACK FORECAST IS PLACED NEAR THE CONSENSUS THROUGH TAU 72 
AND THEN CLOSER TO THE VARIOUS AI-BASED MODELS THROUGH TAU 120 DUE TO 
THEIR STRONG PERFORMANCE IN THE RECURVING TRACK TYPE. INTENSITY 
GUIDANCE GENERALLY AGREES ON INTENSIFICATION THROUGH TAU 60 FOLLOWED 
BY A STEADY INTENSITY THROUGH TAU 120. HWRF IS NOW THE MOST AGGRESSIVE 
MODEL, SUGGESTING AN INTENSITY OF AROUND 85 KTS AT TAU 120, HOWEVER, 
IT ALSO DEPICTS A MUCH SLOWER TRACK AROUND THE RIDGE THAN THE BULK OF 
RELIABLE TRACK GUIDANCE SUGGESTS. OVERALL, THE JTWC INTENSITY FORECAST 
IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE.

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