WDXS32 PGTW 270300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (HALIMA) 
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.6S 75.9E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 776 NM SOUTH-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
MEDIUM-SIZED SYSTEM, WITH FLARING CONVECTION ON THE WESTERN AND
EASTERN SIDES OF THE LOW-LEVEL CIRCULATION (LLC). DRY AIR
ENTRAINMENT ON THE NORTHERN SECTOR IS WEAKENING THE SYSTEM AS IT
CONTINUES TRACKING SOUTHEAST, AS EVIDENCED BY THE MIMIC-TOTAL
PRECIPITABLE WATER (TPW) LOOP AND THE EIR LOOP. THE INITIAL POSITION 
IS PLACED WITH HIGH CONFIDENCE BASED ON A LARGE MICROWAVE EYE FEATURE
IN BOTH THE 262324Z SSMIS 37GHZ AND 91GHZ IMAGES. THE INITIAL
INTENSITY IS SET WITH HIGH CONFIDENCE BASED ON AN OVERALL
ASSESSMENT FROM MULTIPLE AGENCIES AND AUTOMATED DVORAK ESTIMATES
(SHOWN BELOW), WHICH CONTINUE SHOWING THE DETERIORATING TREND. OVER
THE LAST TWELVE HOURS, LITTLE HAS HELPED ENHANCE TC HALIMA WITHIN
THE ENVIRONMENT, WITH WARM SST AND STRONG POLEWARD OUTFLOW OFFSET
BY INCREASING VERTICAL WIND SHEAR. THE CYCLONE IS TRACKING ALONG
THE SOUTHWEST PERIPHERY OF A DEEP-LAYERED NER TO THE NORTHEAST.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE (NER) TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   FMEE: T4.0 - 65 KTS
   FIMP: T3.5 - 55 KTS
   CIMSS SATCON: 55 KTS AT 270015Z
   CIMSS ADT: 51 KTS AT 270015Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC HALIMA WILL CONTINUE TO TRACK SOUTHEASTWARD
UNDER THE STEERING INFLUENCE OF THE NER. AFTER TAU 24, THE SYSTEM
WILL TRACK MORE EASTWARD AS THE NER EXTENDS WESTWARD AND IMPEDE THE
OVERALL SPEED OF MOTION FOR TC 22S. NEARING TAU 48, A SUBTROPICAL
RIDGE TO THE SOUTHWEST WILL ASSUME STEERING AS IT BUILDS AND DRIVES
A SHALLOWER AND WEAKER TC HALIMA NORTHWARD, THEN NORTHWESTWARD BY
TAU 60. THE INCREASING VWS WILL BE RESPONSIBLE FOR THE GRADUAL
WEAKENING OF THE SYSTEM, DESPITE POLEWARD VENTING AWAY FROM THE
SYSTEM. A SLIGHT COOLING TO THE SSTS AND INCREASED DRY AIR
INTRUSION BY TAU 60 WILL CONTRIBUTE TO FURTHER WEAKENING, WHICH
WILL ENHANCE DISSIPATION THROUGH TAU 96.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL FAIR AGREEMENT UP
TO TAU 48. BY TAU 96, A BIFURCATION SETS UP WITHIN THE
DETERMINISTIC AND ENSEMBLE MODELS. GFS (AVNI, AEMI) AND ECMWF (ECM2,
EEM2) TURN THE SYSTEM EQUATORWARD AS THE NER REMAINS THE MAIN
STEERING MECHANISM, AND UKMET (EGRI, UEMI) TURNS IT POLEWARD WITH
THE STEERING FROM THE STR TO THE SOUTH. THE DETERMINISTIC NAVGEM
AND AFUM INDICATE A POLEWARD VORTEX TRAJECTORY. BECAUSE OF THIS,
THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECAST
UP TO TAU 48, THEN LOW CONFIDENCE AFTERWARD. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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