Advisories

WDIO31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02B (ARNAB) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.9N 87.2E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 408 NM SOUTH OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TC 02B CONTINUES TO RAPIDLY INTENSIFY. DEEP CONVECTIVE BURSTS ALONG
THE EYEWALL HAVE OBSCURED THE PREVIOUSLY VISIBLE RAGGED EYE, WHILE
THE CENTRAL DENSE OVERCAST (CDO) CONTINUES TO CONSOLIDATE AND
TIGHTEN. A LARGE BANDING FEATURE PERSISTS ALONG THE WESTERN
PERIPHERY OF THE SYSTEM. TC 02B MAINTAINS MODERATE RADIAL OUTFLOW
ALOFT, STRONGEST TOWARD THE WEST, AS IT MOVES GENERALLY
WEST-NORTHWESTWARD OVER VERY WARM SEA SURFACE TEMPERATURES (SST) OF
29-30 DEGREES CELSIUS AND LOW VERTICAL WIND SHEAR (VWS). THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON VORTICAL
HOT TOWERS OUTLINING THE EYEWALL IN ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY. THE INITIAL INTENSITY HAS BEEN RAISED TO
80 KTS WITH LOW CONFIDENCE, BASED ON THE PGTW DVORAK ESTIMATE OF
T4.5. THIS ASSESSMENT IS HIGHER THAN MOST OF THE AVAILABLE CIMSS
OBJECTIVE INTENSITY ESTIMATES, WHICH RANGE FROM 52 TO 72 KTS, AND
MAY STILL BE LAGGING THE RAPID DEVELOPMENT OF THE COMPACT INNER
CORE. THE DVORAK EMBEDDED CENTER TECHNIQUE YIELDS A DATA T-NUMBER
OF 4.5-5.0, CORRESPONDING TO 77-90 KTS. THIS SUPPORTS THE CURRENT
ASSESSMENT BUT ALSO INDICATES THAT SUBSTANTIAL INTENSITY
UNCERTAINTY REMAINS DUE TO THE OBSCURED EYE AND THE SPREAD AMONG
AVAILABLE ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMPETING INFLUENCES FROM A SUBTROPICAL
RIDGE (STR) TO THE NORTHEAST AND A DEEP-LAYER TROUGH TO THE
SOUTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   DEMS: T3.0 - 45 KTS
   CIMSS ADT: 72 KTS AT 261200Z
   CIMSS AIDT: 52 KTS AT 261200Z
   CIMSS D-MINT: 66 KTS AT 261157Z
   CIMSS D-PRINT: 53 KTS AT 261200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 02B LIES BETWEEN TWO COMPETING STEERING
INFLUENCES. THE DEEP-LAYER TROUGH TO THE SOUTHWEST CONTRIBUTES A
SOUTHWARD COMPONENT TO THE STEERING FLOW, WHILE THE STR TO THE
NORTHEAST FAVORS A NORTHWESTWARD COMPONENT. THESE COMPETING
INFLUENCES HAVE PRODUCED AN UNSTEADY TRACK DURING THE PAST 24
HOURS, INCLUDING A SOUTHWESTWARD COMPONENT FOLLOWED BY THE MORE
RECENT NORTHWESTWARD MOTION. AS THE TROUGH SHIFTS EASTWARD TO A
POSITION SOUTH AND SOUTHEAST OF TC 02B, THE NET STEERING FLOW WILL
BECOME MORE WESTWARD THROUGH TAU 12. BY TAU 24, THE COMPETING
STEERING INFLUENCES WILL WEAKEN, CAUSING TC 02B TO SLOW TO AROUND 4
KTS. A BRIEF EQUATORWARD NUDGE REMAINS POSSIBLE DURING THIS PERIOD.
THEREAFTER, THE TROUGH WILL LIFT POLEWARD AND EAST OF THE SYSTEM,
ALLOWING THE STR TO BECOME THE DOMINANT STEERING INFLUENCE. TC 02B
WILL THEN TURN SHARPLY POLEWARD NEAR TAU 36 AND MAKE LANDFALL ALONG
THE CENTRAL COAST OF ANDHRA PRADESH. FROM TAU 48 TO TAU 72, THE
WEAKENING VORTEX WILL ACCELERATE NORTHWARD ALONG THE WESTERN
PERIPHERY OF THE STR. ENVIRONMENTAL CONDITIONS WILL REMAIN HIGHLY
FAVORABLE FOR THE NEXT 12 TO 18 HOURS, WITH LOW VWS AND SST NEAR
29-30 DEGREES CELSIUS. TC 02B WILL CONTINUE RAPID INTENSIFICATION
THROUGH TAU 12, THEN LEVEL OFF NEAR TAU 24. AFTER TAU 24, SLOWER
FORWARD MOTION MAY INCREASE THE POTENTIAL FOR UPWELLING OF COOLER
SUBSURFACE WATER. VWS WILL INCREASE TO 20-30 KTS BY TAU 36. THE
COMBINATION OF INCREASING VWS, LAND INTERACTION, AND POSSIBLE
UPWELLING WILL INITIATE STEADY TO RAPID WEAKENING PRIOR TO
LANDFALL. WEAKENING WILL ACCELERATE AFTER LANDFALL, AND TC 02B WILL
DISSIPATE BY TAU 72.

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT, WITH THE
PRIMARY UNCERTAINTY TIED TO THE INTERACTION BETWEEN TC 02B AND THE
DEEP-LAYER TROUGH. A SUBSET OF THE GUIDANCE DEPICTS A MORE
PRONOUNCED TEMPORARY WEST SOUTHWESTWARD DEFLECTION, WHILE THE AI
MODELS AND THE BULK OF THE DYNAMICAL GUIDANCE SHOW A GENERALLY
WESTWARD TRACK THROUGH TAU 24. THE LANDFALL ENVELOPE EXTENDS FROM
NEAR KAKINADA IN THE EAST TO JUST EAST OF GUNTUR IN THE WEST. THE
JTWC FORECAST TRACK IS PLACED NEAR THE CENTER OF THE GUIDANCE
ENVELOPE, CLOSE TO THE MULTI-MODEL CONSENSUS, THE AI-MODEL MEAN,
AND THE GOOGLE DEEPMIND SOLUTION. MEDIUM TRACK CONFIDENCE REFLECTS
UNCERTAINTY IN THE TIMING OF THE POLEWARD TURN AND THE RESULTING
LANDFALL LOCATION. THE JTWC INTENSITY FORECAST CALLS FOR RAPID
INTENSIFICATION THROUGH TAU 12, A PLATEAU NEAR TAU 24, AND STEADY
TO RAPID WEAKENING THEREAFTER. THIS FORECAST ALIGNS MOST CLOSELY
WITH THE GOOGLE DEEPMIND SOLUTION. SEVERAL RAPID INTENSIFICATION
AIDS DEPICT HIGHER PEAK INTENSITIES, WHILE HAFS-A AND COAMPS-TC
DEPICT PEAK INTENSITIES NEAR 90 KTS. THE SPREAD IN PEAK INTENSITY
GUIDANCE, THE UNCERTAIN CURRENT INTENSITY, AND THE TIMING OF LAND
INTERACTION SUPPORT LOW INTENSITY FORECAST CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: LOW//
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