Advisories

WDIO31 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01B (ONE) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.6N 84.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 359 NM SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: EASTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
QUASI-STATIONARY, PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC), WITH PERSISTENT DEEP CONVECTION SHEARED TO THE WEST. CLOUD
TOP TEMPERATURES REMAIN COLDER THAN -80 DEGREES CELSIUS, AND
CONVECTION CONTINUES TO FLARE ON THE UPSHEAR SIDE OF THE LLCC.
DESPITE MODERATE VERTICAL WIND SHEAR (VWS), DEEP CONVECTION HAS
REMAINED PERSISTENT NEAR THE LLCC WHILE THE PERIPHERAL CONVECTIVE
STRUCTURE CONTINUES TO IMPROVE. A 222315Z SSMIS PASS CONFIRMS THE
SHEARED NATURE OF THE SYSTEM, DEPICTING A COMPACT LLCC DISPLACED
RELATIVE TO THE DEEP CONVECTION. THE ENVIRONMENT REMAINS GENERALLY
FAVORABLE, CHARACTERIZED BY VERY WARM SEA SURFACE TEMPERATURES
(SST) OF 29-30 DEGREES CELSIUS, RICH DEEP-LAYER MOISTURE, AND
MODEST WESTWARD DIVERGENCE ALOFT, THOUGH THESE FAVORABLE FACTORS
ARE PARTIALLY OFFSET BY 20 KTS OF NORTHEASTERLY VWS AND INCREASING
LAND INTERACTION. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC. BASED ON THE
IMPROVING CONVECTIVE STRUCTURE OVER THE PAST SIX HOURS, THE INITIAL
INTENSITY HAS BEEN RAISED TO 40 KTS WITH MEDIUM CONFIDENCE. THIS
ASSESSMENT IS SUPPORTED BY THE ADT AND D-PRINT OBJECTIVE ESTIMATES
FROM CIMSS.

INITIAL WIND RADII BASIS: PERSISTENCE

CURRENT STEERING MECHANISM: A WEAK STEERING ENVIRONMENT DEFINED BY
A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) OVER NORTHWESTERN INDIA
AND A STR OVER THE FAR NORTHERN PORTION OF THE BAY OF BENGAL

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS ADT: 43 KTS AT 222330Z
   CIMSS AIDT: 35 KTS AT 222330Z
   CIMSS D-MINT: 38 KTS AT 221953Z
   CIMSS D-PRINT: 42 KTS AT 222330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: LAND INTERACTION

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 01B HAS BEEN QUASI-STATIONARY OVER THE PAST
SIX HOURS, LOCATED IN A WEAK STEERING ENVIRONMENT COMPRISED OF A
LOW- TO MID-LEVEL STR OVER NORTHWESTERN INDIA AND A SEPARATE STR
NEAR THE FAR NORTHERN PORTION OF THE BAY OF BENGAL. OVER THE NEXT
36 HOURS, THE COMBINATION OF BETA DRIFT AND A SLIGHTLY MORE
DOMINANT STR FAR TO THE NORTHEAST WILL DRIVE THE SYSTEM SLOWLY
NORTHWESTWARD AT 03-05 KTS. THE FORECAST CALLS FOR A LANDFALL NEAR
THE VIZIANAGARAM-SRIKAKULAM REGION WITHIN 24 HOURS. THE SYSTEM IS
LIKELY AT OR APPROACHING PEAK INTENSITY. WHILE TROPOSPHERIC
MOISTURE AND SST WILL REMAIN FAVORABLE, LAND INTERACTION WILL
INCREASE OVER THE NEXT 12 HOURS, AND VWS WILL PERSIST. IT IS
POSSIBLE THAT TC 01B WILL STRENGTHEN SLIGHTLY MORE, BUT THE LIMITED
TIME OVER WATER WILL CONSTRAIN SIGNIFICANT INTENSIFICATION. TC 01B
WILL WEAKEN BY TAU 24 AS IT TRACKS INLAND AND DISSIPATE BY TAU 36.
THE 30-KT INTENSITY AT TAU 36 REFLECTS THE ENHANCED SOUTHWESTERLY
FLOW OFF THE COAST, WHILE THE INLAND VORTEX WEAKENS AND BROADENS.

MODEL DISCUSSION: THE TRACK GUIDANCE ENVELOPE REMAINS WIDE, WITH
CROSS-TRACK SPREAD INCREASING FROM 60 NM AT TAU 12 TO 165 NM AT TAU
36, THOUGH A CORE CLUSTER OF MODEL SOLUTIONS EXISTS. GFS IS THE
SOLE EQUATORWARD OUTLIER, WHILE COAMPS-TC AND HAFS-A OCCUPY THE
POLEWARD SIDE OF THE ENVELOPE. A NOTABLE CHANGE FROM THE PREVIOUS
CYCLE IS A GENERAL POLEWARD SHIFT AMONG MANY MODELS AT TAU 36. THE
JTWC FORECAST TRACK IS PLACED BETWEEN THE CONSENSUS AND THE
EXPERIMENTAL GOOGLE DEEPMIND SOLUTION THROUGH TAU 36 WITH MEDIUM
CONFIDENCE. THE SPREAD AMONG THE INTENSITY GUIDANCE HAS INCREASED
TO 10 KTS THIS CYCLE, WHICH REMAINS RELATIVELY TIGHT. HAFS-A IS THE
STRONGEST SOLUTION, SHOWING A PEAK INTENSITY NEAR 45 KTS AT TAU 12,
WHILE GFS SHOWS IMMEDIATE WEAKENING. THE JTWC INTENSITY FORECAST IS
SET ALONG THE CENTER OF THE GUIDANCE ENVELOPE WITH HIGH CONFIDENCE,
ALIGNING CLOSELY WITH THE CONSENSUS AND DEEPMIND THROUGH TAU 36.

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