WDIO31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03B (THREE) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.3N 86.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 357 NM EAST-SOUTHEAST OF CHENNAI, INDIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 03B HAS BEEN SLOWLY TRACKING TO THE WEST
UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE TO THE NORTH. OVER THE
PAST 6 HOURS THE CIRCULATION HAS GAINED SPEED MOVING AT 09 KTS AND
THE ASSOCIATED CONVECTION HAS IMPROVED AS EVIDENCED BY THE COOLER
TEMPERATURES DEPICTED BY ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY. CONVECTIVE ACTIVITY IS DISPLACED WELL TO THE WEST DUE TO
HIGH (25-30 KTS) EASTERLY VERTICAL WIND SHEAR (VWS). ENVIRONMENTAL
CONDITIONS ARE MARGINALLY FAVORABLE FOR DEVELOPMENT WITH WARM SEA
SURFACE TEMPERATURES (28 C TO 29C), MOIST ATMOSPHERIC COLUMN AND
STRONG WESTWARD OUTFLOW, OFFSET BY HIGH VWS. THE INITIAL POSITION
IS PLACED WITH MEDIUM CONFIDENCE BASED THE ANIMATED EIR IMAGERY, AS
WELL AS EXTRAPOLATION FROM A 260813Z ATMS MICROWAVE PASS. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON A 260618Z OSCAT AND AGENCY FIXES.

INITIAL WIND RADII BASIS: A 260618Z OCEANSAT-3 SCATTEROMETER DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS D-PRINT: 29 KTS AT 261200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 03B IS A WEAK CIRCULATION THAT LACKS THE
INGREDIENTS TO UNDERGO ANY SIGNIFICANT DEVELOPMENT. THE
CYCLOGENESIS IS CURRENTLY BEING PUSHED TO THE WEST BY A SUBTROPICAL
RIDGE TO THE NORTH. AS THE STR BEGINS TO RETROGRADE WITHIN THE NEXT
FEW HOURS, IT WILL ALLOW TC 03B TO UNDERGO A NORTHWESTWARD TURN FOR 
THE
REMAINDER OF THE FORECAST PERIOD. THE DECREASING STRENGTH OF THE
RIDGE WILL PLAY A LARGE ROLE IN DETERMINING HOW NORTH THE SYSTEM
WILL PROGRESS UP THE COAST OF INDIA. PLENTY OF WARM WATER AND
STRONG DIVERGENCE ALOFT WILL LET THE CIRCULATION INCREASE UP TO 50
KTS STRENGTH BY TAU 36. THE CONTINUED EFFECTS OF HIGH VERTICAL WIND
SHEAR AND RELATIVELY DRIER AIR TO THE NORTH WILL CAUSE TC 03B TO
BEGIN WEAKENING JUST BEFORE LANDFALL. TC 03B WILL BEGIN ITS
DISSIPATION OVER WATER AROUND TAU 36 AND IS EXPECTED TO FULLY 
DISSIPATE OVER LAND
BY TAU 72. 

MODEL DISCUSSION: MODELS ARE IN GOOD AGREEMENT WITH A CROSS TRACK
SPREAD UNDER 70 NM THROUGH TAU 48. AFTERWARDS THERE IS A BIT OF
UNCERTAINTY DEPICTED AS THE SYSTEM WEAKENS AND THE STEERING
INFLUENCES REGRESS. NAVGEM KEEPS TC 03B MOVING INLAND SOUTH OF
NIDAMARRU, INDIA, WHILE GFS HAS A TRACK NORTH OF VISAKHAPATNAM,
INDIA. THE JTWC TRACK IS PLACED BETWEEN THE MULTI-MODEL CONSENSUS
AND GFS WITH CONSIDERATION GIVEN TO THE RETROGRADING STEERING
ELEMENTS AND THE WEAK NATURE OF THE SYSTEM CLOSER TO LANDFALL.
INTENSITY SPREAD IS AROUND 20 KTS, WITH ONLY HAFS-A DEPICTING
MAXIMUM INTENSITIES HIGHER THAN 50 KNOTS. THE JTWC FORECAST
INTENSITY IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH
CONFIDENCE DUE THE CURRENT AND FORECASTED ENVIRONMENTAL CONDITIONS.


FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH
NNNN