South Indian: TC 05S(DARIAN) forecast to intensify//Remnants of TC 07A//Invest 98B// 1812utc

JTWC IS ISSUING 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 05S(DARIAN). 3HOURLY SATELLITE BULLETINS WERE DISCONTINUED ON THE REMNANTS OF TC 07A AT 18/0815UTC.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP CONVECTION EXPANDING OVER AN INCREASINGLY TIGHTLY-WRAPPED LOW LEVEL CIRCULATION. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON RECENT MULTI-AGENCY SATELLITE FIXES AND A 180343Z METOP-B ASCAT PASS. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE SAME DATASETS. TC 05S HAS CONSOLIDATED INTO A TROPICAL CYCLONE WITH THE ENVIRONMENTAL SUPPORT OF STRONG POLEWARD OUTFLOW AND LOW VERTICAL WIND SHEAR.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TC 05S WILL TURN TOWARD AND CONTINUE ON A SOUTHEASTWARD TRAJECTORY FOR THE NEXT 48 HOURS UNDER THE STEERING INFLUENCE OF NEAR-EQUATORIAL RIDGING SITUATED TO THE NORTHEAST. AFTER TAU 48, THE NEAR-EQUATORIAL STEERING RIDGE IS EXPECTED TO WEAKEN AND REORIENT AS A SUBTROPICAL RIDGE CONCURRENTLY BUILDS TO THE SOUTH OF THE SYSTEM, STEERING TC 05S ON A WESTWARD TO SOUTH-WESTWARD TRAJECTORY FOR THE REMAINDER OF THE FORECAST PERIOD. FAVORABLY LOW VERTICAL WIND SHEAR (VWS) AND STRONG POLEWARD OUTFLOW WILL SUPPORT STEADY INTENSIFICATION IN THE NEAR-TERM. THE MAGNITUDE OF INTENSIFICATION SHOULD BE LIMITED, HOWEVER, AS ALONG-TRACK SEA SURFACE TEMPERATURES ARE ONLY MARGINALLY FAVORABLE AND VWS IS EXPECTED TO INCREASE DUE TO SHIFTING UPPER-LEVEL WINDS BY TAU 36. INCREASING SHEAR AND A SLIGHTLY LESS FAVORABLE OUTFLOW PATTERN WILL DRIVE WEAKENING AFTER TAU 36, BUT THE PATTERN WILL AGAIN IMPROVE LATE IN THE FORECAST PERIOD TO SUPPORT POSSIBLE REINTENSIFICATION BY TAU 120.

MODEL DISCUSSION: AVAILABLE NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT REGARDING THE GENERAL FORECAST SCENARIO, INCLUDING A TRACK TO THE SOUTHEAST THROUGH TAU 48 FOLLOWED BY A TURN TO THE WEST-SOUTHWEST CONTINUING THROUGH TAU 120. SOLUTIONS VARY REGARDING THE EXACT ORIENTATION OF THE TRACK, WHICH IS NOT SURPRISING GIVEN THE COMPLEXITY OF CHANGES IN THE STEERING PATTERN THAT ARE ANTICIPATED. DESPITE NOTED SPREAD, MODEL SOLUTIONS ARE FAIRLY EVENLY DISTRIBUTED AROUND THE TRACK CONSENSUS, WHICH HAS BEEN STEADY OVER THE PAST SEVERAL MODEL CYCLES. CONSIDERING THESE FACTORS, OVERALL CONFIDENCE IN THE TRACK FORECAST IS MEDIUM. INTENSITY FORECAST GUIDANCE IS ALSO IN GOOD AGREEMENT WITH RESPECT TO THE GENERAL TREND - UPWARD IN THE NEAR TERM, FOLLOWED BY WEAKENING AFTER TAU 36 AND THE POSSIBILITY OF SLOW REINTENSIFICATION BY TAU 120. A FEW MODELS, INCLUDING THE COAMPS-TC ENSEMBLE AND A STATISTICAL-DYNAMICAL RAPID INTENSIFICATION AID, INDICATE THE POSSIBILITY OF MORE PRONOUNCED INTENSIFICATION IN THE NEAR-TERM, BUT THE HWRF AND SHIPS SOLUTIONS ARE MORE MUTED. GIVEN THE ENVIRONMENTAL FACTORS NOTED ABOVE, RAPID INTENSIFICATION DOES NOT SEEM LIKELY AT THIS POINT. CONFIDENCE IN THE INTENSITY FORECAST IS MEDIUM.

THE LOW LEVEL CIRCULATION HAS BEEN GETTING BETTER DEFINED.