WDIO31 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02B (TWO) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.6N 91.3E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 798 NM SOUTH-SOUTHEAST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES THAT TC
02B HAS CONSOLIDATED QUICKLY WITH TIGHTLY-CURVED BANDING WRAPPING
INTO A SMALL CENTRAL DENSE OVERCAST (CDO) FEATURE OBSCURING THE
LOW-LEVEL CIRCULATION CENTER. HOWEVER, A 070654Z AMSR2 89GHZ
MICROWAVE IMAGE DEPICTS A COMPACT CORE OF WELL-ORGANIZED DEEP
CONVECTION SURROUNDING A WEAK MICROWAVE EYE FEATURE, WHICH SUPPORTS
THE INITIAL POSITION WITH HIGH CONFIDENCE. DESPITE SOME PRESSURE
OVER THE EASTERN SEMICIRCLE DUE TO EASTERLY VERTICAL WIND SHEAR
(VWS), POLEWARD AND WESTWARD OUTFLOW IS VIGOROUS ALLOWING THE
SYSTEM TO MAINTAIN THE SMALL CDO. THE INITIAL INTENSITY OF 40 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE AND IS HEDGED ABOVE THE PGTW AND
DEMS DVORAK ESTIMATES BASED ON THE CONVECTIVE STRUCTURE AND
DEVELOPING MICROWAVE EYE FEATURE. ADDITIONAL WINDSPEED DATA IS
AVAILABLE BUT APPEARS TO BE TOO HIGH: A 070342Z ASCAT-C UHR IMAGE
SHOWS MAXIMUM 45-55 KNOT WINDS WHILE A 070652Z AMSR2 WINDSPEED
IMAGE SHOWS MAXIMUM 50-58 KNOT WINDS. THIS DATA IS DISCOUNTED SINCE
IT IS INCONSISTENT WITH THE CONVECTIVE STRUCTURE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE NORTHEAST AND EAST 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   DEMS: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 02B IS EXPECTED TO CONTINUE TRACKING
NORTHWESTWARD ALONG THE PERIPHERY OF THE STR THROUGH TAU 48. DUE TO
THE COMPACT CORE AND GENERALLY FAVORABLE CONDITIONS, TC 02B WILL
INTENSIFY AT A CLIMATOLOGICAL RATE THROUGH TAU 48 REACHING A PEAK
INTENSITY OF 75 KNOTS. AFTER TAU 48, THE STR IS FORECAST TO REALIGN
IN RESPONSE TO AN APPROACHING MIDLATITUDE SHORTWAVE TROUGH, WHICH
WILL DEEPEN OVER EASTERN INDIA, ALLOWING THE SYSTEM TO TURN
POLEWARD. GRADUAL WEAKENING IS ANTICIPATED AS UPPER-LEVEL EASTERLY
FLOW INCREASES AND POLEWARD OUTFLOW WEAKENS. AFTER TAU 72, THE
SYSTEM WILL RECURVE NORTH-NORTHEASTWARD AND WEAKEN STEADILY AS IT
ENCOUNTERS MIDLATITUDE WESTERLIES AND ENTRAINS DRY AIR.    

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH TRACKS THE
SYSTEM INTO THE STR AND INTO CENTRAL INDIA, NUMERICAL MODEL
GUIDANCE IS IN FAIR AGREEMENT SUPPORTING THE RECURVE SCENARIO THUS
OVERALL CONFIDENCE IS MEDIUM THROUGH THE FORECAST PERIOD. BASED ON
THE EXCELLENT CONVECTIVE STRUCTURE, FAVORABLE ENVIRONMENTAL
CONDITIONS AND TRIGGERING OF THE RAPID INTENSITY GUIDANCE, THE JTWC
INTENSITY FORECAST IS PLACED HIGHER THAN HWRF AND THE INTENSITY
CONSENSUS (ICNW) WHICH PEAK THE SYSTEM AT 60 KNOTS. OVERALL, THERE
IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST.


FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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