Advisories

WDPN32 PGTW 250300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (CHAMPI) WARNING NR 
043//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.0N 124.7E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 356 NM SOUTHWEST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS 
TROPICAL STORM (TS) 29W AS A FULLY EXPOSED, SHALLOW, AND RAGGED
CIRCULATION, OVERWHELMED BY HIGH VERTICAL WIND SHEAR (VWS) AND DRY 
AIR. THE 242141Z WSFM MICROWAVE IMAGERY CONFIRMS THE SYSTEM IS SHALLOW 
AND ELONGATED, AND INDEED, 29W IS A SHELL OF ITS FORMER SELF. 
ENVIRONMENTAL ANALYSIS REVEALS A HOSTILE ENVIRONMENT, CHARACTERIZED BY 
HIGH (30-35 KTS) VWS, COLD (25-26 C) SEA SURFACE TEMPERATURES (SST), 
SIGNIFICANT DRY AIR ELIMINATING ANY CONVECTION, NEGLIGIBLY OFFSET BY 
THE STRONG POLEWARD OUTFLOW PROVIDED BY THE UPPER-LEVEL JET. THE 
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE 
RAGGED, FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER. THE INITIAL 
INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE 
AGENCY DVORAK FIXES AND CIMSS AUTOMATED INTENSITY ESTIMATES LISTED 
BELOW.

INITIAL WIND RADII BASIS: SURFACE OBSERVATIONS

CURRENT STEERING MECHANISM: WESTERN FLANK OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED SOUTHEAST OF HONSHU


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 51 KTS AT 250040Z
   CIMSS AIDT: 40 KTS AT 250040Z
   CIMSS D-MINT: 57 KTS AT 242243Z
   CIMSS D-PRINT: 54 KTS AT 240010Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 30-35 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: DRY AIR

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 29W (CHAMPI) IS FORECAST TO CONTINUE TRACKING 
POLEWARD AS IT ROUNDS THE NORTHWESTERN PERIPHERY OF THE STEERING STR 
FOR THE DURATION OF THE FORECAST PERIOD. HAS BEGUN TO TRANSITION INTO 
AN EXTRATROPICAL CYCLONE AS IT APPROACHES THE FRINGES OF THE UPPER 
LEVEL JET: EXHIBITING TEMPERATURE ADVECTION, VORTEX ASYMMETRY, AND NO 
DEEP CONVECTION. TRANSITION IS EXPECTED TO BE COMPLETE NO LATER THAN 
TAU 24, BUT LIKELY MUCH SOONER. THE ENVIRONMENT IS EXPECTED TO 
BECOMING INCREASINGLY HOSTILE AS 29W TRACKS POLEWARD, WITH SSTS 
CONTINUOUSLY DROPPING, VWS INCREASING AS PROXIMITY TO THE UPPER-LEVEL 
JET DECREASES, AND CONTINUED COPIOUS AMOUNTS OF DRY AIR INUNDATING THE 
SYSTEM. THE DEGRADING ENVIRONMENT IS EXPECTED TO WEAKEN THE SYSTEM 
THROUGH TAU 36. BETWEEN TAU 12-36, IT IS POSSIBLE THAT 29W WILL 
DEGRADE INTO A TROUGH AND THEREFORE DISSIPATE PRIOR TO COMPLETING 
EXTRATROPICAL TRANSITION.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN GOOD 
AGREEMENT THROUGH TAU 36, WITH THE EXCEPTION OF GALWEM AND HAFS-A, 
WHICH ARE FARTHER POLEWARD THAN THE BULK OF GUIDANCE. DISCOUNTING 
THOSE MODEL SOLUTIONS, THE JTWC TRACK FORECAST IS PLACED WITH HIGH 
CONFIDENCE NEAR THE MULTI-MODEL CONSENSUS. RELIABLE INTENSITY AIDS ARE 
IN STRONG AGREEMENT IN A STEADY WEAKENING THROUGH TAU 36. AS A RESULT, 
THE JTWC INTENSITY FORECAST IS ASSESSED WITH HIGH CONFIDENCE. 

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