WTIO30 FMEE 300123 RSMC / TROPICAL CYCLONE CENTER / LA REUNION TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN) 0.A WARNING NUMBER: 12/5/20172018 1.A TROPICAL CYCLONE 5 (CEBILE) 2.A POSITION 2018/01/30 AT 0000 UTC: WITHIN 20 NM RADIUS OF POINT 16.0 S / 80.4 E (SIXTEEN DECIMAL ZERO DEGREES SOUTH AND EIGHTY DECIMAL FOUR DEGREES EAST) MOVEMENT : SOUTH-WEST 4 KT 3.A DVORAK ANALYSIS: 5.0/5.5/W 0.5/24 H 4.A CENTRAL PRESSURE: 958 HPA 5.A MAX AVERAGE WIND SPEED (10 MN): 80 KT RADIUS OF MAXIMUM WINDS (RMW) :56 KM 6.A EXTENSION OF WIND BY QUADRANTS (KM): 28 KT NE: 200 SE: 310 SW: 300 NW: 180 34 KT NE: 140 SE: 160 SW: 160 NW: 130 48 KT NE: 100 SE: 100 SW: 100 NW: 90 64 KT NE: 80 SE: 80 SW: 80 NW: 70 7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1007 HPA / 1000 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP 1.B FORECASTS: 12H: 2018/01/30 12 UTC: 16.1 S / 79.5 E, MAX WIND=095 KT, INTENSE TROPICAL CYCLONE 24H: 2018/01/31 00 UTC: 16.0 S / 78.6 E, MAX WIND=105 KT, INTENSE TROPICAL CYCLONE 36H: 2018/01/31 12 UTC: 15.9 S / 78.1 E, MAX WIND=105 KT, INTENSE TROPICAL CYCLONE 48H: 2018/02/01 00 UTC: 16.2 S / 77.5 E, MAX WIND=100 KT, INTENSE TROPICAL CYCLONE 60H: 2018/02/01 12 UTC: 16.7 S / 77.2 E, MAX WIND=095 KT, INTENSE TROPICAL CYCLONE 72H: 2018/02/02 00 UTC: 17.3 S / 77.0 E, MAX WIND=090 KT, INTENSE TROPICAL CYCLONE 2.B LONGER-RANGE OUTLOOK : 96H: 2018/02/03 00 UTC: 18.6 S / 78.2 E, MAX WIND=070 KT, TROPICAL CYCLONE 120H: 2018/02/04 00 UTC: 21.0 S / 81.3 E, MAX WIND=055 KT, SEVERE TROPICAL STORM 2.C ADDITIONAL INFORMATION: T=5.0 CI=5.5 LATEST MICROWAVE IMAGERY (SSMI AT 2116Z AND SSMIS AT 22Z) DEPICT AN ERC IN ITS TERMINAL PHASE: THE TINY INNER-CORE HAS COLLAPSED WITH SOME REMNANTS STILL VISIBLE WITHIN A NEW 55-60 NM WIDE EYE. THE INTENSITY ASSESSMENT IS TRICKY AS CONVENTIONAL TECHNIQUE (DVORAK) IS NOT SUITED FOR THIS KIND OF SITUATION. THE MAX WINDS AT 80 KT IS EXTRAPOLATED FROM A SATCON AT 1623Z WITH 98 KT 1-MIN WINDS (OR 86 KT 10-MIN WINDS). INDEED, NOW THAT THE RADIUS OF MAX WINDS HAS SHIFTED IN THE OUTER WALL, THE SYSTEM IS LIKELY AT THE WEAKEST PART OF THE ERC CONCEPTUAL MODEL (CF SITKOWSKI ETAL. 2011) THE FORWARD MOTION, THAT IS STILL FLUCTUATING BETWEEN WEST-SOUTHWESTWARDS AND SOUTHWESTWARDS, HAS SLOW DOWN. CEBILE IS CAUGHT IN-BETWEEN TWO OPPOSITE STEERING FLOW WITH THE STR TO THE SOUTH-WEST AND A NER TO ITS NORTH-EAST. ALL THE NUMERICAL GUIDANCE SUGGEST A SLOW WESTWARDS MOTION SUGGESTING THAT THE STEERING FLOW FROM THE STR WILL PREVAIL FIRST. GIVEN THE CONTEXT, THE WESTWARD MOTION MAY RATHER BE CLOSE TO A DRIFT THAN ANYTHING ELSE. IN THE MIDDLE OF THE WEEK, THE SUBTROPICAL RIDGE WEAKENS TO ITS SOUTH-EAST AND THE NEAR EQUATORIAL RIDGE TO ITS NORTH-EAST IS EXPECTED TO TAKE THE LEAD ON THE STEERING FLOW ALLOWING THE SYSTEM TO TAKE A SOUTHEASTWARD TURN AND GRADUALLY ACCELERATE. MODELS ARE BECOMING SOMEWHAT IN BETTER AGREEMENT ON THE LOCALIZATION OF THE TURN BUT SIGNIFICANT DIFFERENCES IN THE FORWARD MOTION ARE STILL NOTED AMONG THE NUMERICAL GUIDANCE. OVERALL, THE CONFIDENCE REMAIN LOW IN THE FORECAST TRACK. THE CURRENT WEAKENING TREND DUE TO THE ERC IS LIKELY TEMPORARILY. AS THE SYSTEM WILL TRACK WESTWARDS, IT WILL MOVE THROUGH A NEAR PERFECT ENVIRONMENT IN TERM OF SHEAR, UPPER LEVEL DIVERGENCE AND OCEANIC CONTAIN (IT IS EXPECTED TO INCREASE UNDER THE SYSTEM AS LONG AS IT MOVE WEST OF 80E AND STAY NORTH OF 18S). IT SHOULD ALLOW THE INNER-CORE TO BE PROTECTED FROM ENVIRONMENTAL DRY MID-LEVEL AIR .... IF THE FORWARD MOTION REMAINS SUFFICIENT TO PREVENT A SELF-INDUCED OCEANIC COOLING. THIS IS THE CURRENT HYPOTHESIS OF THE CURRENT FORECAST ... BUT HERE TOO, SOME UNCERTAINTY EXISTS .... IF CEBILE DON'T SUFFER FROM SELF-INDUCED COLD SST, THIS SYSTEM HAS THE POTENTIAL TO MAINTAIN AT FAIRLY HIGH INTENSITY OVER THE NEXT FEW DAYS (WITH SOME UNPREDICTABLE FLUCTUATIONS LINKED TO OTHER POTENTIAL ERC) BEFORE LESS FAVORABLE ENVIRONMENTAL CONDITIONS LATER THIS WEEK WITH INCREASING WESTERLY SHEAR ASSOCIATED WITH AN APPROACHING UPPER LEVEL TROUGH.=