WDIO31 PGTW 121500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03A (THREE) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.0N 65.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 185 NM SOUTH-SOUTHWEST OF KARACHI,
PAKISTAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), UNDER CIRRUS BLOWOFF
EMANATING FROM DEEP CONVECTIVE ACTIVITY SHEARED TO THE WEST. TC 03A
HAS PEAKED, WITH THE EARLIER POINT SOURCE ALOFT WHICH HAD ALLOWED
FOR A MESOSCALE REDUCTION IN THE SHEAR, HAVING DISSIPATED, REPLACED
BY THE SEASONAL STRONG TROPICAL EASTERLY JET (TEJ) ASSOCIATED FLOW
PATTERN. A 121200Z F16 SSMIS 91GHZ MICROWAVE IMAGE REVEALED THE
LLCC, DEVOID OF ANY SIGNIFICANT CONVECTION, AND LENT HIGH
CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY REMAINS
SET AT 35 KNOTS BASED IN LARGE PART ON THE CIMSS ADT ESTIMATE, ABOVE
THE SUBJECTIVE DVORAK INTENSITY ESTIMATES. THE ENVIRONMENT HAS
BECOME EVER MORE HOSTILE, WITH SHEAR DRAMATICALLY INCREASING TO
ROUGHLY 30 KNOTS, MORE THAN SUFFICIENT TO OFFSET ANY DOWNSTREAM
DIVERGENCE ALOFT AND THE WARM SSTS, AND THE FIRST HINTS OF A NOSE
OF MID-LEVEL DRY AIR PUNCHING IN FROM THE EAST. THE SYSTEM LIES IN
A WEAK STEERING PATTERN AND IS DRIFTING RATHER AIMLESSLY TO THE
NORTH.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING PATTERN IN A COL REGION
BETWEEN A SUBTROPICAL RIDGE (STR) OVER THE SAUDI PENINSULA, AN
EXTENSION OF THE STR EXTENDING FROM CENTRAL CHINA TO AFGHANISTAN
AND A NEAR EQUATORIAL RIDGE (NER) CENTERED SOUTHWEST OF SOUTHERN
INDIA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
   DEMS: T1.5 - 25 KTS
   CIMSS ADT: 35 KTS AT 121215Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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: TRAPPED BETWEEN A SERIES OF LOW TO MID-LEVEL
RIDGES DESCRIBED ABOVE, TC 03A WILL EXHIBIT ERRATIC MOVEMENT
THROUGH THE DURATION OF THE FORECAST. MEAN MOTION IS EXPECTED TO BE
NORTH-NORTHWESTWARD AS THE RIDGE EXTENSION TO THE NORTH RECEDES AND
WEAKENS, AND THE NER PUSHES NORTH TO 10N, MOVING TC 03A NORTHWARD
AS WELL. BUT SIGNIFICANT DEPARTURES FROM THIS FORECAST ARE POSSIBLE
DUE TO THE LACK OF A STRONG STEERING MECHANISM. NOW THAT THE SYSTEM
HAS LOST THE PROTECTION OF THE UPPER-LEVEL POINT SOURCE AND IS
EXPOSED TO THE FULL FORCE OF THE TEJ WINDS ALOFT, IT IS FORECAST TO
SLOWLY SUCCUMB TO THE INFLUENCE OF MODERATE TO HIGH VWS AND AN
INFLUX OF MID-LEVEL DRY AIR PUSHING SOUTH OUT OF PAKISTAN. HOWEVER,
DUE TO THE STRONG LOW-LEVEL SOUTHWESTERLY MONSOONAL FLOW ALONG THE
SOUTHERN FLANK OF THE SYSTEM FEEDING STRONG VORTICITY INTO THE
CIRCULATION, IT WILL TAKE SOME TIME FOR THE SYSTEM TO SPIN DOWN
BELOW GALE FORCE, EXPECTED TO OCCUR NO LATER THAN TAU 36,
POTENTIALLY AS EARLY AS TAU 24. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN GENERAL AGREEMENT ON A SLOW
DRIFT TO THE NORTHWEST THROUGH THE FORECAST PERIOD, WITH GFS TAKING
THE SYSTEM FURTHEST TO THE WEST WHILE THE ECMWF FURTHEST EAST. THE
JTWC FORECAST CLOSELY TRACKS THE ECMWF WITH LOW CONFIDENCE DUE TO
THE VAGARIES ASSOCIATED WITH WEAK STEERING PATTERNS. INTENSITY
GUIDANCE IS IN RELATIVELY GOOD AGREEMENT, WITH ALL BUT THE
COAMPS-TC INDICATING A NEAR-TERM INTENSIFICATION TO 40 KNOTS
FOLLOWED BY SLOW BUT STEADY WEAKENING. THE JTWC FORECAST LIES BELOW
THE GUIDANCE THROUGH TAU 24 AND LIES ALONG THE CONSENSUS MEAN
THEREAFTER. CONFIDENCE IN THE INTENSITY FORECAST IS MEDIUM. 

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