WDIO31 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07A (SEVEN) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.1N 66.5E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 581 NM SOUTHEAST OF MASIRAH ISLAND
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) DISPLACED TO
THE SOUTHWEST OF A RAGGED CENTRAL DENSE OVERCAST (CDO) FEATURE WITH
EMBEDDED OVERSHOOTING TOPS WITH CLOUD TEMPERATURES AS LOW AS -80C.
A 15118Z SSMIS 91GHZ MICROWAVE IMAGE REVEALED THE TILTED NATURE OF
THE VORTEX, WITH LOW-LEVEL BANDING FEATURES WRAPPING INTO A DEFINED
LLCC SOUTHWEST OF THE CYCLONICALLY CURVED CONVECTION WITHIN THE CDO
AND SIGNIFICANT DRY AIR TO THE ENTRENCHED TO THE WEST AND A TONGUE
OF DRY AIR ENTRAINING ALL THE WAY INTO THE EASTERN SIDE OF THE
SYSTEM. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED
ON THE AFOREMENTIONED MICROWAVE IMAGE. THE INITIAL INTENSITY IS OF
40 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON A BLEND OF
DVORAK CURRENT INTENSITY ESTIMATES OF T3.0 FROM PGTW AND KNES, AND
THE SLIGHTLY LOWER OBJECTIVE ESTIMATES CLOSER TO 35 KNOTS. THE
SYSTEM IS MOVING INTO A MORE MARGINAL ENVIRONMENT IN WHICH GOOD
POLEWARD OUTFLOW AND WARM SSTS ARE BEING OFFSET BY STEADILY
INCREASING SHEAR, NOW APPROACHING 18 KNOTS ACCORDING TO THE LATEST
CIMSS ANALYSIS AND SIGNIFICANT DRY AIR ENTRAINMENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEST-NORTHWEST PERIPHERY OF THE
DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED OVER CENTRAL INDIA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS ADT: 33 KTS AT 1245Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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: NO SIGNIFICANT CHANGES ARE EXPECTED IN THE
OVERALL FORECAST. TC 07A WILL CONTINUE TO TRACK TOWARDS THE
WEST-NORTHWEST THROUGH THE EARLY PHASE OF THE FORECAST, ALONG THE
WESTERN SIDE OF THE DEEP-LAYER STR OVER INDIA, WHICH IS ORIENTED IN
A NORTHWEST-SOUTHEAST DIRECTION. THE SYSTEM IS NOW FIRMLY
ESTABLISHED ON A WEAKENING TREND, WITH A SIGNIFICANTLY TILTED
VORTEX WHICH WILL LIKELY DECOUPLE IN THE NEXT 12 HOURS. THE SYSTEM
SHOULD MAINTAIN INTENSITY FOR THE FIRST 12 HOURS OF THE FORECAST,
TAKING TIME TO SPIN DOWN. AFTER TAU 12, THE SYSTEM IS FORECAST TO
QUICKLY WEAKEN UNDER THE COMBINED STRESSES OF INCREASING
SOUTHWESTERLY SHEAR AND DRY AIR INTRUSION FROM THE WEST. AS THE
SYSTEM WEAKENS BELOW 35 KNOTS BY THE END OF THE FORECAST PERIOD, IT
WILL GRADUALLY TURN TO A MORE WEST-SOUTHWESTWARD TRACK AS IT COMES
UNDER THE STEERING INFLUENCE OF THE STRONG NORTHEASTERLY FLOW
ALREADY FIRMLY IN PLACE OVER THE WESTERN PORTION OF THE NORTH
ARABIAN SEA. THE REMNANT CIRCULATION IS EXPECTED TO LINGER FOR SOME
TIME AND WILL TRACK GENERALLY TOWARDS SOCOTRA ISLAND WHILE
REMAINING WELL BELOW WARNING CRITERIA. 

MODEL DISCUSSION: THE BULK OF THE DETERMINISTIC TRACK GUIDANCE IS
IN GOOD AGREEMENT, WITH ALL CONSENSUS MEMBERS SAVE FOR NAVGEM AND
COTC CONFINED TO A 55NM WIDE ENVELOPE THROUGH TAU 36. THE NAVGEM
AND COTC KEEP THE SYSTEM ON A NORTHWESTWARD TRACK THROUGH THE
FORECAST PERIOD AND BEYOND. NOTABLY, THE ECMWF INTERMEDIATE RUN
LIES WITHIN THE TIGHT ENVELOPE THROUGH THE FORECAST PERIOD, BUT
THEN DIVERGES TO THE NORTH TOWARDS THE OMANI COAST AFTER THE END OF
THE FORECAST WHILE THE REST OF THE GUIDANCE TURNS THE REMNANTS OF
THE CIRCULATION TOWARDS SOCOTRA. THE JTWC FORECAST REMAINS
CONSISTENT WITH THE PREVIOUS FORECAST AND LIES AMONGST THE TIGHTLY
PACKED MODEL ENVELOPE WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS
IN GOOD AGREEMENT THAT THE SYSTEM WILL HOLD INTENSITY THROUGH TAU
12 AND THEN RAPIDLY WEAKEN BELOW 35 KNOTS BETWEEN TAU 24 AND TAU
36. THE HWRF IS THE ONLY EXCEPTION, WHICH HOLDS ONTO THE SYSTEM
NEAR 35 KNOTS UNTIL TAU 96. THE JTWC FORECAST CALLS FOR THE SYSTEM
TO DISSIPATE BY TAU 36, BUT IT IS POSSIBLE THE SYSTEM COULD
DISSIPATE AS EARLY AS TAU 24.   

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