WDXS32 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (HALIMA) WARNING 
NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.1S 81.7E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 946 NM SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
OVER THE PAST TWELVE HOURS, THE OVERALL STRUCTURE OF TC 22S HAS
BEGUN TO DETERIORATE SLIGHTLY, WITH THE DEEP CONVECTION NOW LIMITED
TO THE SOUTHERN SEMICIRCLE OF THE CIRCULATION. THE SYSTEM LIES
WITHIN AN AREA OF MODERATELY MOIST AIR, BUT IS COCOONED WITHIN A
DRY, STABLE AIRMASS. THE CIMSS VERTICAL WIND SHEAR (VWS) PRODUCT
AND HWRF SYNTHETIC SOUNDING INDICATE THE BULK SHEAR REMAINS LOW
(5-10 KNOTS), THE HWRF SOUNDING SHOWS THE MAXIMUM SHEAR IS CLOSER
TO 20-25 KNOTS IN THE MID-LEVELS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS THE CONVECTIVE DEBRIS IS BEING ELONGATED OFF TO
THE SOUTHEAST, INDICATIVE OF A SLIGHTLY INCREASED NORTHWESTERLY
SHEAR VECTOR IN THE MID TO UPPER-LEVELS AS INDICATED BY THE HWRF
SOUNDING. A 300122Z GMI 37GHZ MICROWAVE IMAGE SHOWS A LARGE REGION
OF EXPOSED LOW LEVEL BANDS WRAPPING INTO A SMALL MICROWAVE EYE-LIKE
FEATURE. THE INITIAL POSITION WAS PLACED PRIOR TO THE LATE RECEIPT
OF THE MICROWAVE IMAGERY, WITH MEDIUM CONFIDENCE, AND WILL BE
ADJUSTED SLIGHTLY TO THE SOUTHEAST POST FACTO. THE INITIAL
INTENSITY REMAINS AT A SOLID 45 KNOTS, WITH HIGH CONFIDENCE, BASED
ON THE HIGHER-END FMEE AND FIMP DVORAK CURRENT INTENSITY ESTIMATES
AND CONSISTENT WITH EARLIER SMAP AND SCATTEROMETER DATA.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING AND WEAK STEERING PATTERN. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   FMEE: T3.0 - 45 KTS
   FIMP: T3.0 - 45 KTS
   CIMSS ADT: 37 KTS AT 292115Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG EASTWARD
   OTHER FACTORS: SIGNIFICANT MID-LEVEL DRY AIR SURROUNDING THE
SYSTEM

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 22S REMAINS ENSCONCED WITHIN A COMPLEX AND
COMPETING STEERING ENVIRONMENT, CAUGHT BETWEEN STRONG RIDGES TO THE
NORTHWEST AND SOUTHEAST, AND A MID-LATITUDE TROUGH PASSING FAR TO
THE SOUTH. WITHOUT A DOMINANT STEERING MECHANISM, THE SYSTEM IS
WANDERING GENERALLY NORTHWARD. THIS GENERAL TRACK MOTION, WITH AN
EXPECTED GRADUAL TURN TO THE NORTHEAST, OVER THE NEXT 36 HOURS.
DURING THIS TIME FRAME, TC 22S IS EXPECTED TO REMAIN COCOONED
WITHIN A SMALL REGION OF RELATIVELY MOIST AIR, AND SHOULD BE ABLE
TO FIGHT OFF THE RELATIVELY LOW BULK SHEAR, ALLOWING IT TO MAINTAIN
INTENSITY FOR ANOTHER TWELVE HOURS, FOLLOWED BY VERY SLOW
WEAKENING. BY TAU 48, STRONG UPPER-LEVEL TROUGH WILL MOVE IN
RAPIDLY FROM THE WEST, SHUTTLING IN INCREASING SHEAR AND
SIGNIFICANTLY DRIER MID-LEVEL AIR MASS WHICH WILL OVERWHELM THE
SYSTEM AND LEAD TO A MORE RAPID WEAKENING. AFTER TAU 48, A STRONG
LOW-LEVEL RIDGE BUILDS IN TO THE SOUTH BEHIND THE AFOREMENTIONED
TROUGH, AND AS TC 22S RAPIDLY WEAKENS, THE TRACK WILL SHIFT SHARPLY
WESTWARD ALONG THE EQUATORWARD PERIPHERY OF THE RIDGE TO THE SOUTH.
TC 22S IS EXPECTED TO DISSIPATE AS A TROPICAL CYCLONE NO LATER THAN
TAU 72, BUT POTENTIALLY AS EARLY AS TAU 60.  

MODEL DISCUSSION: OVERALL, DETERMINISTIC TRACK GUIDANCE IS IN
RELATIVELY GOOD AGREEMENT ON THE SCENARIO BUT DIFFERS ON THE
EASTWARD PROGRESSION OF THE TRACK, AND THE TIMING AND EXTENT OF THE
TURN TO THE WEST. THE ECMWF AND GALWEM FOR INSTANCE TAKE THE SYSTEM
FURTHEST TO THE EAST BY TAU 48, THEN TURN THE SYSTEM WEST, BUT LAG
THE OTHER MODELS DUE TO THE FURTHER EAST TURNING POINT. MEANWHILE
THE NAVGEM, AND GFS ENSEMBLE DEPICT A MORE GRADUAL AND SHALLOW TURN
TO THE EAST AND A QUICKER TURN WEST, THUS LIE MUCH FURTHER WEST BY
TAU 72. THE JTWC FORECAST CLOSELY FOLLOWS THE GFS SOLUTION, ON THE
WESTERN SIDE OF THE ENVELOPE WITH MEDIUM CONFIDENCE. INTENSITY
GUIDANCE REMAINS MIXED, WITH HWRF STEADILY WEAKENING THE SYSTEM
THROUGH TAU 24 FOLLOWED BY INTENSIFICATION THROUGH TAU 120 AND THE
DECAY SHIPS INDICATING A PEAK INTENSITY OF 50 KNOTS AT TAU 24
FOLLOWED BY STEADY WEAKENING. THE JTWC FORECAST LIES CLOSE TO THE
CONSENSUS MEAN WITH MEDIUM CONFIDENCE.  

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
NNNN