Advisories

WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.0N 132.7E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 380 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM 22W (KROVANH) WITH A CONSOLIDATING LOW-LEVEL CIRCULATION
CENTER (LLCC) AND FRAGMENTED CONVECTIVE BANDING ALONG THE SOUTHERN
SEMICIRCLE. OVER THE PAST 6 HOURS, THE SYSTEM MADE A SOMEWHAT
UNEXPECTED JUMP TO THE SOUTHEAST, HENCE THE RELOCATED WARNING. THIS
WAS LIKELY DUE TO THE CIRCULATION PINCHING OFF ALONG THE EASTERN
PORTION OF THE PREVIOUSLY MUCH BROADER CIRCULATION. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE BRIEFLY
EXPOSED LOW-LEVEL CLOUDS IN ANIMATED EIR WRAPPING INTO THE CENTER.
THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGENCY DVORAK FIXES AND CIMSS INTENSITY ESTIMATES
LISTED BELOW. ENVIRONMENTAL ANALYSIS INDICATES THAT 22W IS IN A
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE
EQUATORWARD OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR,
SUBSIDENCE OVER THE WESTERN PERIPHERY, AND WARM (28-29 C) SEA
SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT WITH A
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST AND A NEAR
EQUATORIAL RIDGE (NER) TO THE SOUTHWEST. 


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 011220Z
   CIMSS AIDT: 40 KTS AT 011220Z
   CIMSS D-PRINT: 27 KTS AT 011220Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: SUBSIDENCE ALONG THE WESTERN PERIPHERY CAUSED BY
AN UPPER-LEVEL TROUGH

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 22W IS FORECAST TO CONTINUE TRACKING SLOWLY
OVER THE NEXT 12 HOURS AS THE SYSTEM REMAINS PLACED WITHIN THE
COMPETING STEERING PATTERN. AFTER TAU 12, THE NER TO THE SOUTHWEST
WILL WEAKEN AND MOVE OFF TO THE WEST, ALLOWING FOR THE STR TO
BECOME THE PRIMARY STEERING MECHANISM. THIS WILL CAUSE 22W TO TRACK
NORTHWESTWARD THROUGH TAU 60, TOWARD THE RYUKYU ISLANDS. AFTER TAU
60, AN UPPER-LEVEL TROUGH WILL BREAK DOWN THE STEERING RIDGE,
CAUSING THE SYSTEM TO BE PLACED WITHIN A WEAK STEERING ENVIRONMENT.
THE ACTUAL TRACK OF THE SYSTEM IS HIGHLY UNCERTAIN AFTER TAU 60,
BUT THE JTWC TRACK FORECAST CALLS FOR A SLOW EASTWARD MOVEMENT
THROUGH TAU 120 AS A BUILDING NER FAR TO THE SOUTH LOOSELY CONTROLS
THE STEERING. IN TERMS OF INTENSITY, 22W IS FORECAST TO MARGINALLY
INTENSIFY TO A PEAK OF 45 KTS AROUND TAU 60 AS THE BROAD VORTEX
ATTEMPTS TO FURTHER CONSOLIDATE AND THE UPPER-LEVEL TROUGH TO 
THE WEST FILLS. AFTER TAU 60, WESTERLY SHEAR AND DRY AIR IS
FORECAST TO INCREASE, CAUSING THE SYSTEM TO GRADUALLY WEAKEN THROUGH 
TAU 120. 

MODEL DISCUSSION: MODEL TRACK GUIDANCE REMAINS IN VERY POOR
AGREEMENT THROUGHOUT THE ENTIRE FORECAST PERIOD. THE VARIOUS
AI-BASED MODELS SHOW A MUCH SLOWER POLEWARD MOVEMENT, THAT TAKES
THE VORTEX CLOSER TO OKINAWA WITH A STALL AND SLOW EASTWARD TURN.
OTHER MODELS, SUCH AS THE GFS AND JGSM, SHOW A FASTER TRACK THROUGH
TAU 72, PLACING THE VORTEX JUST SOUTH OF KYUSHU. IF THE SYSTEM IS
FASTER, A TRACK AROUND THE STEERING RIDGE BEFORE THE TROUGH BREAKS
DOWN THE BREAK IS MORE LIKELY. THE JTWC TRACK FORECAST IS CURRENTLY
PLACED NEAR THE CONSENSUS THROUGH TAU 48, THEN CLOSER TO THE
EXPERIMENTAL GOOGLE DEEPMIND ENSEMBLE MEAN THROUGH TAU 120.
HOWEVER, CHANGES TO THE TRACK FORECAST ARE LIKELY ONCE THE FORWARD
MOTION OF 22W BECOMES MORE APPARENT. INTENSITY GUIDANCE GENERALLY
AGREES ON A STEADY INTENSITY THROUGH TAU 36 FOLLOWED BY SLIGHT
INTENSIFICATION THROUGH TAU 60. AFTER TAU 60, THE MODELS THAT SHOW
A FASTER POLEWARD TRACK WEAKEN THE SYSTEM MORE QUICKLY WHILE THE
GOOGLE DEEPMIND AND COAMPS-TC, WHICH ARE MUCH SLOWER, SHOW A STEADY
INTENSITY THROUGH TAU 120. THE JTWC INTENSITY FORECAST IS PLACED
NEAR THE CONSENSUS THROUGH TAU 72 AND THEN CLOSER TO THE GOOGLE
DEEPMIND THROUGH TAU 120 WITH LOW CONFIDENCE.

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