WDPN31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 22W (KROVANH) 
WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.5N 128.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 64 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: 
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION 22W (KROVANH) WITH A LOOSELY-DEFINED LOW-LEVEL CIRCULATION 
CENTER (LLCC) THAT IS PARTIALLY OBSCURED BY FLARING CONVECTION TO THE 
SOUTH. THE CONVECTION THAT WAS PREVIOUSLY DISPLACED FAR TO THE NORTH 
HAS SHIFTED SOUTHWARD AND IS NOW CLOSER TO THE LLCC. A 051036Z F16 
SSMIS 91 GHZ MICROWAVE IMAGE REVEALED AN ILL-DEFINED LLCC WITH 
CONVECTIVE ACTIVITY LOCATED ABOUT 50 NM TO THE NORTHEAST OF KADENA 
AB. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON 
THE SSMIS IMAGE AND 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 IS LOCATED WITHIN A MARGINAL ENVIRONMENT 
CHARACTERIZED BY STRONG POLEWARD OUTFLOW ALOFT, LOW TO MODERATE (15-
20 KTS) VERTICAL WIND SHEAR, SIGNIFICANT DRY AIR ENTRAINMENT, AND 
WARM (29-30 C) SEA SURFACE TEMPERATURES.

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

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 35 KTS AT 051036Z
   CIMSS ADT: 30 KTS AT 051140Z
   CIMSS AIDT: 35 KTS AT 051140Z
   CIMSS D-MINT: 29 KTS AT 051035Z
   CIMSS D-PRINT: 30 KTS AT 051140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT FROM THE WEST

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 TRACK EAST-SOUTHEASTWARD
THROUGH TAU 24 UNDER THE STEERING INFLUENCE OF THE NER TO THE SOUTH. 
AFTER TAU 24, 22W WILL BEGIN TO TURN POLEWARD AS IT TRACKS ALONG THE 
WESTERN PERIPHERY OF THE STR POSITIONED SOUTHEAST OF JAPAN THROUGH 
TAU 72. 22W WILL THEN APPROACH SOUTHEASTERN KYUSHU AND TURN 
NORTHEASTWARD ONCE IT BEGINS TO ROUND THE STR AXIS. IN TERMS OF 
INTENSITY, 22W IS FORECAST TO MAINTAIN AN INTENSITY OF AROUND 30 KTS 
THROUGH TAU 36 UNDER THE EFFECTS OF THE MARGINAL ENVIRONMENT. AFTER 
TAU 36, DRY AIR ENTRAINMENT FROM THE WEST ALONG WITH DECREASING OCEAN 
HEAT CONTENT WILL CAUSE THE SYSTEM TO WEAKEN. AROUND TAU 72, THE 
SYSTEM WILL BEGIN TO TAP INTO A STRONG POLEWARD OUTFLOW CHANNEL, 
HOWEVER SOUTHWESTERLY VERTICAL WIND SHEAR WILL ALSO GREATLY INCREASE,
PREVENTING ANY CHANCES FOR INTENSIFICATION. AROUND TAU 96, THE
CIRCULATION WILL LIKELY BECOME EXTREMELY STRETCHED AS IT INTERACTS 
WITH THE HOSTILE UPPER-LEVEL WINDS. AS A RESULT, 22W IS FORECAST TO
DISSIPATE OVER WATER SOUTH OF SHIKOKU NEAR TAU 96 WITH A SHALLOW AND 
ELONGATED VORTEX.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT 
THROUGH TAU 72 WITH ALL MODELS AGREEING ON THE POLEWARD TURN. THE GFS 
REMAINS THE EASTERNMOST TRACKER AND THE EC-AIFS REMAINS THE 
WESTERNMOST. THE CROSS-TRACK SPREAD AT TAU 72 IS MEASURED TO BE
ABOUT 230 NM. AFTER TAU 72, MODELS BEGIN TO DIVERGE DUE TO A LARGE
VARIATION IN HOW QUICKLY THE VORTEX ROUNDS THE RIDGE AXIS. AT TAU 96 
THE JGSM IS AMONG THE FASTEST, AND SHOWS THE CENTER LOCATED SOUTHEAST 
OF KYOTO, WHILE THE EC-AIFS SHOWS THE CENTER LOCATED SOUTH OF SASEBO 
AT THE SAME TIME. THE JTWC TRACK FORECAST IS PLACED SLIGHTLY TO THE 
WEST AND SLOWER THAN THE CONSENSUS THROUGH TAU 72 AND THEN NEAR THE 
EXPERIMENTAL GOOGLE DEEPMIND ENSEMBLE MEAN THROUGH TAU 96. THE 
INTENSITY GUIDANCE GENERALLY SHOWS A STEADY DECLINE AFTER TAU 36. THE 
JTWC INTENSITY FORECAST IS PLACED NEAR THE CONSENSUS THROUGHOUT THE 
FORECAST PERIOD WITH OVERALL MEDIUM CONFIDENCE.

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