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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