Advisories

WDPN31 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.2N 127.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 24 NM SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 22W (KROVANH) WITH A LOOSELY-DEFINED AND EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC) THAT RECONSOLIDATED JUST WEST OF OKINAWA
OVER THE PAST 12 HOURS. DEEP CONVECTION HAS RECENTLY STARTED TO
FORM SOUTH OF THE CENTER AFTER 050600Z. THE STRONGEST WINDS ARE
ASSOCIATED WITH THE NORTHERLY WINDS ALONG THE WESTERN PERIPHERY AND
ARE DISPLACED QUITE A WAYS FROM THE ACTUAL LLCC. THE MID-LEVEL
CIRCULATION REMAINS DISPLACED TO THE NORTH, WEST OF AMAMI OSHIMA,
WHERE PERSISTENT CONVECTIVE ACTIVITY IS LOCATED. A 050254Z AMSR3 89
GHZ MICROWAVE IMAGE REVEALED THE EXPOSED LOW-LEVEL CLOUDS WRAPPING
INTO THE CENTER WITH THE PERSISTENT CONVECTION DISPLACED OVER 100
NM TO THE NORTH. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE AMSR3 IMAGE AND ANIMATED MSI. THE INITIAL
INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AGENCY DVORAK AND CIMSS INTENSITY ESTIMATES LISTED BELOW.
ENVIRONMENTAL ANALYSIS INDICATES THAT 22W IS LOCATED WITHIN A
MARGINAL ENVIRONMENT CHARACTERIZED BY STRONG POELWARD OUTLFOW
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: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: THE SOUTHEASTERN FLANK OF A SUBTROPICAL
RIDGE (STR) POSITIONED OVER EASTERN CHINA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 38 KTS AT 050515Z
   CIMSS ADT: 33 KTS AT 050540Z
   CIMSS AIDT: 36 KTS AT 050540Z
   CIMSS D-MINT: 30 KTS AT 050535Z
   CIMSS D-PRINT: 32 KTS AT 050540Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE TRACK HAS BEEN SHIFTED TO THE
WEST AND SLOWER AFTER TAU 72. 

FORECAST DISCUSSION: TS 22W IS FORECAST TO TRACK EAST-SOUTHEASTWARD
AS A NEAR EQUATORIAL RIDGE (NER) BUILDS TO THE SOUTH. THIS
TRAJECTORY IS EXPECTED TO PERSIST THROUGH TAU 24, WHERE THE SYSTEM
WILL BEGIN TO INTERACT WITH THE STR POSITIONED TO THE SOUTHEAST OF
JAPAN. AFTER TAU 24, 22W WILL BEGIN TO TURN POLEWARD AS IT TRACKS
ALONG THE WESTERN PERIPHERY OF THE STR THROUGH TAU 96. 22W WILL
APPROACH SOUTHERN KYUSHU AND THEN TURN SHARPLY NORTHEASTWARD ONCE
IT BEGINS TO INTERACT WITH A STRONG UPPER-LEVEL TROUGH THAT DIGS IN
OVER THE SEA OF JAPAN. IN TERMS OF INTENSITY, 22W IS FORECAST TO
MAINTAIN AN INTENSITY OF AROUND 35 KTS THROUGH TAU 36 UNDER THE
EFFECTS OF THE MARGINAL ENVIRONMENT. AFTER TAU 36, DRY AIR
ENTRAINMENT FROM THE WEST ALONG WITH A SHALLOWING VORTEX WILL
CAUSE 22W TO WEAKEN. AROUND TAU 72, THE SYSTEM WILL BEGIN TO TAP
INTO A STRONG POLEWARD OUTFLOW CHANNEL, HOWEVER SOUTH-SOUTHWESTERLY
VERTICAL WIND SHEAR WILL GREATLY INCREASE, PREVENTING ANY
REDEVELOPMENT. AROUND TAU 96, THE CIRCULATION WILL LIKELY START TO
STRETCH AS IT INTERACTS WITH THE HOSTILE UPPER-LEVEL WINDS, WHICH
COULD LEAD TO A SLIGHTLY EARLIER DISSIPATION THAN IS DEPICTED IN
THE CURRENT FORECAST.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN POOR AGREEMENT,
PARTICULARLY AFTER TAU 72. THE CROSS-TRACK SPREAD AT TAU 72 IS
MEASURED TO BE ABOUT 205 NM. THE GFS AND GEFS MEAN ARE FAR EASTERN
OUTLIERS THIS RUN. AFTER TAU 72, SOME MODELS SHOW A QUICK TURN TO
THE NORTHEAST WHILE OTHERS SHOW A SLOWER MOVEMENT, KEEPING THE
SYSTEM SOUTH OF JAPAN THROUGH TAU 120. THE JTWC TRACK FORECAST IS
PLACED NEAR THE MODIFIED CONSENSUS (REMOVING THE GFS) THROUGH TAU
72 AND THEN CLOSER TO THE EXPERIMENTAL GOOGLE DEEPMIND ENSEMBLE
MEAN AND ECMWF DETERMINISTIC TRACKER THROUGH TAU 120. INTENSITY
GUIDANCE GENERALLY AGREES ON GRADUAL WEAKENING THROUGH TAU 36
FOLLOWED BY A STEADY INTENSITY THROUGH THE REMAINDER OF THE
FORECAST PERIOD. THE GOOGLE DEEPMIND DOES SHOW A SLIGHT
INTENSIFICATION AROUND TAU 96 TO 40 KTS BEFORE WEAKENING AGAIN. THE
JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE MULTI-MODEL
CONSENSUS WITH MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW CONFIDENCE
THEREAFTER. 

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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