WDIO31 PGTW 150900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07A (SEVEN) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.9N 67.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 619 NM SOUTHEAST OF MASIRAH ISLAND
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
JTWC HAS CONDUCTED A REANALYSIS OF THE PREVIOUS INTENSITY ESTIMATES
FOR TC 07A, RESULTING IN A SIGNIFICANT INCREASE IN THE INTENSITY IN
THE PRIOR POSITIONS, WHICH IS CARRIED FORWARD TO THIS FORECAST.
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN IRREGULAR
CENTRAL DENSE OVERCAST (CDO) FEATURE, WHICH IS BEGINNING TO WEAKEN
AND BECOME INCREASINGLY RAGGED. THE MOST RECENT MICROWAVE IMAGE
FROM 150223Z SHOWED A TITLED VORTEX, WITH THE LOW LEVEL CIRCULATION
CENTER (LLCC) POSITIONED SLIGHTLY WEST OF THE CYCLONICALLY CURVED
CONVECTIVE MASS DUE TO MODERATE SOUTH-SOUTHWESTERLY SHEAR.
EXTRAPOLATION OF THE LLCC IN THE MICROWAVE DATA AS WELL AS THE
AMBIGUITY ANALYSIS FROM A 150446Z ASCAT-B PASS PROVIDED HIGH
CONFIDENCE TO THE INITIAL POSITION. AS NOTED ABOVE, THE PREVIOUS
INTENSITY ESTIMATES HAVE BEEN INCREASED AND CARRIED THROUGH THIS
FORECAST, WITH THE INITIAL INTENSITY NOW SET AT 45 KNOTS, IN LINE
WITH THE MULTI-AGENCY CURRENT INTENSITY (CI) ESTIMATES OF T3.0 (45
KNOTS) AND CONFIRMED BY THE ASCAT-B PASS, WHICH SHOWED 40 KNOT WIND
BARBS IN THE NORTHERN HEMISPHERE OF THE SYSTEM, WHICH CONSIDERING
THE LOW-BIAS INHERENT IN ASCAT DATA AT THIS SPEED, EASILY SUPPORTS
A 45 KNOT INTENSITY. OF NOTE, DUE TO AN UPSTREAM OUTAGE, THERE ARE
NO OBJECTIVE INTENSITY ESTIMATES AVAILABLE AT PRESENT. THE SYSTEM
LIES IN A MARGINALLY FAVORABLE ENVIRONMENT, FOR NOW, WITH MODERATE
(15-20 KNOTS) VWS, GOOD POLEWARD OUTFLOW AND WARM SSTS. DRY AIR IN
THE 500MB-300MB LEVEL IS IMPINGING THE WESTERN PORTION OF THE
CIRCULATION AND BEGINNING TO ERODE CONVECTION ON THAT SIDE OF THE
SYSTEM.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) OVER CENTRAL INDIA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: UPPER-LEVEL DRY AIR INTRUSION ON THE WESTERN SIDE
OF THE SYSTEM. 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE INITIAL INTENSITY HAS BEEN
INCREASED BY 10 KNOTS AND THE FORECAST HAS BEEN LENGTHENED BY 12
HOURS. 

FORECAST DISCUSSION: AS MENTIONED ABOVE, THE INITIAL INTENSITY HAS
BEEN SET AT 45 KNOTS, UP 10 KNOTS FROM THE 150000Z FORECAST.
HOWEVER, THIS IS NOT REFLECTIVE OF AN INTENSIFICATION BUT RATHER AN
ADJUSTMENT IN THE PEAK INTENSITY FROM 24 HOURS AGO. THE ADJUSTED
INTENSITY TREND IS FLAT OVER THE PREVIOUS 12 HOURS. THE TRACK HAS
SHIFTED TO A BIT MORE OF A NORTHWESTWARD TRAJECTORY OVER THE PAST
SIX HOURS, AS THE SYSTEM IS A BIT STRONGER AND THUS BEING STEERED
BY A DEEPER LAYER OF THE DEEP STR TO THE EAST, THE PERIPHERY OF
WHICH IS ORIENTED A BIT MORE SOUTHEAST TO NORTHWEST. HENCE, THE
SYSTEM IS FORECAST TO CONTINUE ON A GENERALLY WEST-NORTHWEST PATH
FOR THE NEXT 12 HOURS. THE RIDGE IS ANTICIPATED TO BUILD IN TO THE
WEST, TO THE NORTH OF TC 07A, WHICH WILL RESULT IN A MORE WESTWARD
TRACK THROUGH TAU 24. THEN AS TC 07A WEAKENS, IT WILL TURN ONTO A
MORE SOUTHWESTWARD TRACK THROUGH THE END OF THE FORECAST. THE
SYSTEM HAS PEAKED IN INTENSITY SOME TIME AGO AND SHOULD NOW START
TO WEAKEN, AS ALREADY SEEN IN THE RAPID EROSION OF THE CDO OVER THE
PAST COUPLE OF HOURS. SHEAR IS EXPECTED TO INCREASE A BIT OVER THE
NEXT 12 HOURS, BUT THE REAL KILLER WILL BE THE MASS OF DRY AIR
CURRENTLY LURKING OUT TO THE WEST IN THE STRONG NORTHEASTERLY FLOW.
ONCE THE TC BEGINS TO INTERACT WITH THIS DRY AIR OVER THE NEXT 12
HOURS, IT WILL QUICKLY BECOME SMOTHERED IN AN AIR MASS
NON-CONDUCIVE TO TROPICAL CYCLONE DEVELOPMENT, AND RAPIDLY WEAKEN,
WITH DISSIPATION BELOW WARNING CRITERIA EXPECTED NO LATER THAN TAU
36. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN MODERATE
AGREEMENT, WITH A LARGE SPREAD OF 175NM AT TAU 36, THOUGH
ALL OF THE CONSENSUS GUIDANCE AGREES ON THE OVERALL SCENARIO. THE
JTWC FORECAST LIES CLOSE TO THE GFS AND GFS ENSEMBLE MEAN TRACKS
WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO MIXED, WITH THE
BULK OF THE MEMBERS SHOWING RAPID WEAKENING COMMENCING AFTER TAU 06
AND REACHING 30 KNOTS OR LESS BY TAU 36. THE ONLY EXCEPTION BEING
HWRF WHICH SHOWS A VERY SLOW WEAKENING TREND, HOLDING ONTO THE
SYSTEM AS A MINIMAL TS UNTIL TAU 96. THE JTWC FORECAST HAS BEEN
LENGTHENED BY 12 HOURS, AS A REFLECTION OF HIGHER INITIAL INTENSITY
TAKING A BIT LONGER TO WEAKEN BELOW WARNING CRITERIA, BUT OTHERWISE
REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND THE BULK OF THE
GUIDANCE. 

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