WDPN31 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 33W (KOTO) WARNING NR 
026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.7N 111.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 206 NM EAST-SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED AND SHALLOW LOW LEVEL CIRCULATION CENTER (LLCC) AND
ISOLATED WEAK CONVECTION LOCATED ALONG A CONVERGENT FEEDER BAND WELL
TO THE SOUTHEAST. WATER VAPOR IMAGERY, A 302325Z SSMIS 91GHZ
MICROWAVE IMAGE AND HIGH-RESOLUTION MODEL CROSS-SECTIONS CONFIRM
THE PRESENCE OF A LAYER OF VERY DRY MID-LEVEL AIR PUSHING IN OVER
TOP OF THE SHALLOW VORTEX FROM THE NORTHWEST. OUTFLOW ALOFT IS WEAK
TO NON-EXISTENT DUE TO THE LACK OF CONVECTION AND THE SHALLOWNESS
OF THE VORTEX, WHICH LOOKS TO BE RESTRICTED TO BELOW 600MB. THE
INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
EXPOSED LLCC IN THE MSI. THE INITIAL INTENSITY IS ASSESSED WITH
HIGH CONFIDENCE BASED ON A BLEND OF THE SUBJECTIVE AND OBJECTIVE
INTENSITY ESTIMATES NOTED BELOW. THE ENVIRONMENT CONTINUES TO
DETERIORATE AS THE WEDGE OF DRY AIR EXPANDS VERTICALLY AND
CONTINUES TO ENVELOPE TS 33W, WHILE SSTS REMAIN MARGINAL AT BEST,
HOVERING AROUND 25-26C.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK AND COMPETING STEERING PATTERN,
PARTICULARLY IN THE LOW- TO MID-LEVELS. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS ADT: 33 KTS AT 010030Z
   CIMSS AIDT: 32 KTS AT 010030Z
   CIMSS D-MINT: 33 KTS AT 302325Z
   CIMSS D-PRINT: 28 KTS AT 010030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 5-10 KTS
   SST: 25-27 CELSIUS
   OUTFLOW: WEAK RADIAL
   OTHER FACTORS: DRY MID-LEVEL AIR OVERLAYING THE SHALLOW VORTEX. 

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: TS 33W HAS BEEN RELATIVELY QUASI-STATIONARY
OVER THE PAST SIX HOURS, WITH AN OVERALL DRIFT TOWARDS THE
SOUTHWEST. THE SYSTEM IS STILL STUCK IN A WEAK STEERING PATTERN,
WHILE THE OVERALL PATTERN IS SIMILAR THROUGH THE ENTIRE
COLUMN (DEEP-LAYER RIDGING OVER THE PHILIPPINE SEA AND OVER
SOUTHERN MYANMAR) THE RIDGE PATTERN IS MUCH WEAKER IN THE
LOWER-LEVELS. WITH THIS IN MIND, TS 33W WILL CONTINUE TO DRIFT
SLOWLY TOWARDS THE SOUTHWEST OVER THE NEXT 12-24, BEFORE EVENTUALLY
PICKING UP SOME SPEED AFTER TAU 24 AS IT THE RIDGE BUILDS OVER
INDOCHINA. THE SYSTEM IS LIKELY TO SKIRT THE COAST OF SOUTHEASTERN
VIETNAM, BUT IT STILL FORECAST TO REMAIN OFFSHORE IN THIS FORECAST.
AS ADDITIONAL DRY AIR MOVES IN FROM THE NORTHWEST AND THE SYSTEM
MOVES OVER EVEN COOLER WATERS, TS 33W STANDS NO CHANCE OF
REINTENSIFYING. BUT IT WILL TAKE SOME TIME TO SPIN DOWN AND
DISSIPATE, LIKE TO STAIR-STEP DOWNWARDS IN INTENSITY THROUGH THE
FORECAST PERIOD. THE FORECAST CALLS FOR DISSIPATION AT TAU 72, BUT
IN REALITY, THE SYSTEM WILL MORE THAN LIKELY WEAKEN BELOW 25 KNOTS
BY TAU 60 AND POTENTIALLY AS EARLY AS TAU 48. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE CONTINUES TO TREND
TOWARDS BETTER AGREEMENT NOW THAT THE SYSTEM APPEARS TO HAVE TURNED
TOWARDS THE SOUTHWEST. EVEN THE NAVGEM, WHICH HAD BEEN A DIE-HARD
HOLDOUT TAKING THE SYSTEM INTO CAMBODIA, HAS JOINED THE REST OF THE
CONSENSUS GROUP AND IN FACT HAS SHIFTED OVER TO THE EASTERN SIDE OF
THE ENVELOPE. THE JTWC FORECAST IS POSITIONED CLOSE TO THE ECMWF
TRACKER, WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD
AGREEMENT THAT THE SYSTEM WILL SLOWLY WEAKEN TO DISSIPATION BY TAU
60. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM//
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