Advisories

WDPN31 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 22W (KROVANH) 
WARNING NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.7N 131.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 179 NM EAST-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: 
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION 22W (KROVANH) WITH A FULLY EXPOSED LOW-LEVEL CIRCULATION 
CENTER (LLCC) AND FLARING CONVECTION CONFINED TO THE SOUTHWESTERN 
QUADRANT. 22W HAS STALLED IN PLACE SINCE 061000Z, JUST SOUTHWEST OF 
MINAMI DAITO JIMA. PRESSURE READINGS FROM SURFACE OBSERVATIONS ON THE 
ISLAND HAVE DROPPED TO 990 MB AS THE CIRCULATION INCHES CLOSER. THE 
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED 
LLCC IN ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF 30 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND 
CIMSS INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL ANALYSIS 
INDICATES THAT 22W REMAINS IN A MARGINAL ENVIRONMENT CHARACTERIZED BY 
MODERATE POLEWARD OUTFLOW ALOFT, 15-20 KTS SOUTHEASTERLY VERTICAL WIND 
SHEAR, DRY AIR ENTRAINMENT, AND WARM (28-29 C) SEA SURFACE 
TEMPERATURES.

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

CURRENT STEERING MECHANISM: THE NORTHERN PERIPHERY OF AN ELONGATED
NEAR EQUATORIAL RIDGE (NER) POSITIONED TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 061140Z
   CIMSS AIDT: 36 KTS AT 061140Z
   CIMSS D-MINT: 28 KTS AT 060824Z
   CIMSS D-PRINT: 28 KTS AT 061140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE WEST


ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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: TD 22W IS FORECAST TO BEGIN TURNING NORTHEASTWARD 
WITHIN THE NEXT 6 HOURS AS THE PRIMARY STEERING MECHANISM TRANSITIONS 
TO THE SUBTROPICAL RIDGE CENTERED TO THE SOUTHEAST OF JAPAN. 22W WILL 
THEN TRACK GENERALLY NORTHWARD, ALONG THE WESTERN PERIPHERY OF THE 
RIDGE THROUGH TAU 48. FOLLOWING TAU 48, THE TRAJECTORY IS EXPECTED TO 
BECOME MORE NORTHEASTWARD WITH AN INCREASING SPEED OF ADVANCE AS THE 
SYSTEM TRACKS ALONG THE NORTHWESTERN EXTENT OF THE RIDGE. 22W IS 
FORECAST TO SKIRT  THE SOUTHERN COAST OF JAPAN AFTER TAU 60 WITH THE 
REMNANT VORTEX PASSING SOUTH OF KYOTO, AROUND TAU 72. IN TERMS OF 
INTENSITY, 22W IS FORECAST TO MAINTAIN ITS CURRENT INTENSITY OF 30 KTS 
THROUGH TAU 48 UNDER THE EFFECTS OF THE MARGINAL ENVIRONMENT. WHILE 
DRY AIR ENTRAINMENT IS EXPECTED TO WORSEN, POLEWARD OUTFLOW WILL 
IMPROVE DUE TO THE SYSTEM TAPPING INTO A JET STREAK EXTENDING OVER 
NORTHERN HONSHU. AFTER TAU 48, SOUTHEASTERLY SHEAR WILL GREATLY 
INCREASE, CAUSING 22W TO WEAKEN AS IT APPROACHES SOUTHERN JAPAN. 
DISSIPATION IS FORECAST TO OCCUR AT AROUND TAU 72, AS THE SHALLOW 
VORTEX ACCELERATES NORTHEASTWARD AND INTERACTS WITH THE MOUNTAINOUS 
TERRAIN OF THE SHIKOKU AND KANSAI REGIONS. 

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT 
THROUGH TAU 48 WITH A CROSS-TRACK SPREAD OF ABOUT 100 NM. THE ECMWF 
AND EC-AIFS MAKE UP THE WESTERNMOST TRACKERS WHILE THE GFS AND GEFS 
MEAN MAKE UP THE EASTERNMOST TRACKERS. AFTER TAU 48, THE ALONG-TRACK
SPREAD INCREASES SIGNIFICANTLY DUE TO VARYING TRACK SPEEDS AROUND THE 
RIDGE AXIS. THE GFS AND THE EXPERIMENTAL GOOGLE DEEPMIND ENSEMBLE MEAN 
ARE QUICKER TO ROUND THE RIDGE WHILE THE JGSM, NAVGEM, AND ECMWF ARE 
SLOWER. AT TAU 72 THE ALONG-TRACK SPREAD IS MEASURED TO BE OVER 350 
NM, CAUSING THERE TO BE LESS CONFIDENCE IN THE FORECAST TRACK PAST THE 
TAU 48 MARK. THE JTWC TRACK FORECAST IS SITUATED NEAR THE CONSENSUS 
THROUGH TAU 48 AND THEN CLOSER TO THEN GOOGLE DEEPMIND THROUGH TAU 72. 
INTENSITY GUIDANCE CONTINUES TO HAVE A SLIGHT SPLIT BETWEEN THE MODELS 
WITH THE PRIMARY OUTLIER BEING HAFS-A. THE REMAINDER OF THE GUIDANCE 
SHOWS A STEADY INTENSITY THROUGH TAU 48 FOLLOWED BY WEAKENING WHILE 
HAFS-A SHOWS A BRIEF PERIOD OF INTENSIFICATION FROM TAU 36 TO TAU 60 
WITH A PEAK INTENSITY OF AROUND 40 KTS. THE JTWC INTENSITY FORECAST 
REFLECTSTHE SAME PHILOSOPHY AS THE PREVIOUS WARNING, AND IS PLACED 
WITH MEDIUM CONFIDENCE.

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