WDIO31 PGTW 310900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (ASNA)       
WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.3N 64.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 382 NM EAST-NORTHEAST OF MASIRAH ISLAND
   MOVEMENT PAST 6 HOURS: WESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE INITIAL POSITION OF TC 02A (ASNA) IS PLACED WITH HIGH CONFIDENCE 
BASED ON A 310458Z ASCAT-C BULLSEYE PASS SHOWING A BROAD, SYMMETRIC 
LOW LEVEL CIRCULATION CENTER (LLCC) THAT HAS BEEN PROGRESSING WESTWARD 
AT A CLIMATOLOGICALLY SLOW PACE SINCE ITS DEPARTURE FROM THE NORTHWEST 
COAST OF INDIA TWO DAYS AGO. AS REVEALED BY MULTISPECTRAL SATELLITE 
IMAGERY (MSI), DEEP-LAYERED CONVECTION IS PRESENT IN A SMALL PORTION 
NORTHWEST OF THE LLCC AND MODERATELY SHALLOW BANDING CAN BE SEEN 
WRAPPING AROUND THE SOUTH, EAST, AND NORTHERN FLANKS. THE SOUTHEASTERN 
PERIPHERY IS SHOWING EARLY SIGNS OF DECAY BY THE RECENT INTRUSION OF 
DRY AIR FROM THE WEST, WHICH IS PARTIALLY EXPOSING THE LLCC. 
TRANSVERSE BANDING IS EVIDENT IN AN EQUATORWARD OUTFLOW CHANNEL, 
CONFIRMING THE PRESENCE OF MODERATE UPPER-LEVEL WINDS WITHIN THE 
TROPICAL EASTERLY JET (TEJ), WITH WEAK EXHAUST POLEWARD.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMBINED INFLUENCE OF STRONG RIDGING OVER 
THE SAUDI PENINSULA AND BROAD CYCLONIC INFLUENCE OF A LOW PRESSURE 
CENTER OVER INDIA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS SATCON: 40 KTS AT 310456Z
   CIMSS ADT: 31 KTS AT 310600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 02A (ASNA) IS EXPECTED TO CONTINUE IN ITS
WESTWARD TRACK AND TURN TOWARDS THE WEST-SOUTHWEST AFTER TAU 12. AS 
THE SYSTEM INCHES CLOSER TO THE SAUDI PENINSULA, DRY AIR FROM THE WEST 
WILL QUICKLY CHOKE OFF THE NECESSARY SUPPLY OF MOISTURE THAT ALLOWED 
THIS SYSTEM TO INITIALLY THRIVE. A GFS MODEL-DERIVED RELATIVE HUMIDITY 
CROSS SECTION OF TC 02A SHOWS MID-LEVEL DRY AIR HAS ALREADY BEGUN TO 
INTRUDE INTO THE CORE, WHICH IS DISPLAYED IN THE MSI BY THE EXPOSURE 
OF LOW-TO-MID LEVEL BANDING WRAPPING AROUND THE MAJORITY OF THE LLCC. 
INCREASING VERTICAL WIND SHEAR (15-20 KTS) WILL ALSO CONTRIBUTE TO THE 
DISSIPATION OF THE SYSTEM BY TAU 48.

MODEL DISCUSSION: GLOBAL MODEL GUIDANCE HAS REMAINED IN GOOD
AGREEMENT REGARDING THE WESTWARD TRACK AND THE TURN TOWARDS THE
SOUTHWEST, WITH THE GFS MAINTAINING A SOUTHWESTWARD TRACK AND THE
ECMWF PUSHING THE TRACK SLIGHTLY MORE SOUTHWARD. THE INTENSITY
GUIDANCE IS ALSO IN GOOD AGREEMENT AS TO THE INTENSITY STEADILY
DROPPING OFF AFTER PEAKING AT TAU 12, MOST NOTABLY DUE TO THE
ENTRAINMENT OF DRY AIR INTO THE CORE OF THE STORM.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: HIGH//
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